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-rw-r--r--.github/ISSUE_TEMPLATE/bug_report.yml2
-rw-r--r--CHANGELOG.md3
-rw-r--r--clippy_lints/src/casts/cast_enum_constructor.rs21
-rw-r--r--clippy_lints/src/casts/mod.rs21
-rw-r--r--clippy_lints/src/collapsible_if.rs4
-rw-r--r--clippy_lints/src/doc.rs15
-rw-r--r--clippy_lints/src/lib.register_all.rs4
-rw-r--r--clippy_lints/src/lib.register_complexity.rs1
-rw-r--r--clippy_lints/src/lib.register_lints.rs3
-rw-r--r--clippy_lints/src/lib.register_nursery.rs1
-rw-r--r--clippy_lints/src/lib.register_pedantic.rs1
-rw-r--r--clippy_lints/src/lib.register_perf.rs1
-rw-r--r--clippy_lints/src/lib.register_restriction.rs1
-rw-r--r--clippy_lints/src/lib.register_style.rs1
-rw-r--r--clippy_lints/src/lib.register_suspicious.rs1
-rw-r--r--clippy_lints/src/lib.rs1
-rw-r--r--clippy_lints/src/macro_use.rs3
-rw-r--r--clippy_lints/src/matches/match_same_arms.rs396
-rw-r--r--clippy_lints/src/methods/map_flatten.rs118
-rw-r--r--clippy_lints/src/methods/mod.rs81
-rw-r--r--clippy_lints/src/methods/or_then_unwrap.rs68
-rw-r--r--clippy_lints/src/methods/unnecessary_join.rs41
-rw-r--r--clippy_lints/src/methods/unnecessary_lazy_eval.rs29
-rw-r--r--clippy_lints/src/methods/unnecessary_to_owned.rs46
-rw-r--r--clippy_lints/src/missing_doc.rs21
-rw-r--r--clippy_lints/src/mutable_debug_assertion.rs4
-rw-r--r--clippy_lints/src/ptr.rs2
-rw-r--r--clippy_lints/src/ranges.rs2
-rw-r--r--clippy_lints/src/single_component_path_imports.rs18
-rw-r--r--clippy_lints/src/transmute/mod.rs3
-rw-r--r--clippy_lints/src/transmute/transmute_undefined_repr.rs98
-rw-r--r--clippy_lints/src/try_err.rs2
-rw-r--r--clippy_lints/src/utils/internal_lints/metadata_collector.rs3
-rw-r--r--clippy_lints/src/write.rs9
-rw-r--r--clippy_utils/src/diagnostics.rs86
-rw-r--r--clippy_utils/src/sugg.rs2
-rw-r--r--tests/ui/cast_enum_constructor.rs17
-rw-r--r--tests/ui/cast_enum_constructor.stderr16
-rw-r--r--tests/ui/map_flatten.rs74
-rw-r--r--tests/ui/map_flatten.stderr125
-rw-r--r--tests/ui/map_flatten_fixable.fixed (renamed from tests/ui/map_flatten.fixed)0
-rw-r--r--tests/ui/map_flatten_fixable.rs31
-rw-r--r--tests/ui/map_flatten_fixable.stderr80
-rw-r--r--tests/ui/match_same_arms.stderr165
-rw-r--r--tests/ui/match_same_arms2.rs53
-rw-r--r--tests/ui/match_same_arms2.stderr228
-rw-r--r--tests/ui/or_then_unwrap.fixed52
-rw-r--r--tests/ui/or_then_unwrap.rs52
-rw-r--r--tests/ui/or_then_unwrap.stderr22
-rw-r--r--tests/ui/ptr_arg.rs7
-rw-r--r--tests/ui/single_component_path_imports_macro.fixed20
-rw-r--r--tests/ui/single_component_path_imports_macro.rs4
-rw-r--r--tests/ui/single_component_path_imports_macro.stderr10
-rw-r--r--tests/ui/temporary_assignment.rs1
-rw-r--r--tests/ui/temporary_assignment.stderr8
-rw-r--r--tests/ui/transmute_undefined_repr.rs55
-rw-r--r--tests/ui/transmute_undefined_repr.stderr34
-rw-r--r--tests/ui/transmutes_expressible_as_ptr_casts.stderr4
-rw-r--r--tests/ui/unnecessary_join.fixed35
-rw-r--r--tests/ui/unnecessary_join.rs37
-rw-r--r--tests/ui/unnecessary_join.stderr20
-rw-r--r--tests/ui/unnecessary_lazy_eval.fixed8
-rw-r--r--tests/ui/unnecessary_lazy_eval.rs8
-rw-r--r--tests/ui/unnecessary_lazy_eval.stderr145
-rw-r--r--tests/ui/unnecessary_lazy_eval_unfixable.stderr12
-rw-r--r--tests/ui/unnecessary_to_owned.fixed48
-rw-r--r--tests/ui/unnecessary_to_owned.rs48
-rw-r--r--tests/ui/unnecessary_to_owned.stderr8
68 files changed, 1982 insertions, 558 deletions
diff --git a/.github/ISSUE_TEMPLATE/bug_report.yml b/.github/ISSUE_TEMPLATE/bug_report.yml
index 68877efc9e1..b6f70a7f183 100644
--- a/.github/ISSUE_TEMPLATE/bug_report.yml
+++ b/.github/ISSUE_TEMPLATE/bug_report.yml
@@ -18,7 +18,7 @@ body:
     id: reproducer
     attributes:
       label: Reproducer
-      description: Please provide the code and steps to repoduce the bug
+      description: Please provide the code and steps to reproduce the bug
       value: |
         I tried this code:
 
diff --git a/CHANGELOG.md b/CHANGELOG.md
index 2bc393d6042..88f71931d92 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -3069,6 +3069,7 @@ Released 2018-09-13
 [`bytes_nth`]: https://rust-lang.github.io/rust-clippy/master/index.html#bytes_nth
 [`cargo_common_metadata`]: https://rust-lang.github.io/rust-clippy/master/index.html#cargo_common_metadata
 [`case_sensitive_file_extension_comparisons`]: https://rust-lang.github.io/rust-clippy/master/index.html#case_sensitive_file_extension_comparisons
+[`cast_enum_constructor`]: https://rust-lang.github.io/rust-clippy/master/index.html#cast_enum_constructor
 [`cast_enum_truncation`]: https://rust-lang.github.io/rust-clippy/master/index.html#cast_enum_truncation
 [`cast_lossless`]: https://rust-lang.github.io/rust-clippy/master/index.html#cast_lossless
 [`cast_possible_truncation`]: https://rust-lang.github.io/rust-clippy/master/index.html#cast_possible_truncation
@@ -3366,6 +3367,7 @@ Released 2018-09-13
 [`option_map_unit_fn`]: https://rust-lang.github.io/rust-clippy/master/index.html#option_map_unit_fn
 [`option_option`]: https://rust-lang.github.io/rust-clippy/master/index.html#option_option
 [`or_fun_call`]: https://rust-lang.github.io/rust-clippy/master/index.html#or_fun_call
+[`or_then_unwrap`]: https://rust-lang.github.io/rust-clippy/master/index.html#or_then_unwrap
 [`out_of_bounds_indexing`]: https://rust-lang.github.io/rust-clippy/master/index.html#out_of_bounds_indexing
 [`overflow_check_conditional`]: https://rust-lang.github.io/rust-clippy/master/index.html#overflow_check_conditional
 [`panic`]: https://rust-lang.github.io/rust-clippy/master/index.html#panic
@@ -3506,6 +3508,7 @@ Released 2018-09-13
 [`unnecessary_filter_map`]: https://rust-lang.github.io/rust-clippy/master/index.html#unnecessary_filter_map
 [`unnecessary_find_map`]: https://rust-lang.github.io/rust-clippy/master/index.html#unnecessary_find_map
 [`unnecessary_fold`]: https://rust-lang.github.io/rust-clippy/master/index.html#unnecessary_fold
+[`unnecessary_join`]: https://rust-lang.github.io/rust-clippy/master/index.html#unnecessary_join
 [`unnecessary_lazy_evaluations`]: https://rust-lang.github.io/rust-clippy/master/index.html#unnecessary_lazy_evaluations
 [`unnecessary_mut_passed`]: https://rust-lang.github.io/rust-clippy/master/index.html#unnecessary_mut_passed
 [`unnecessary_operation`]: https://rust-lang.github.io/rust-clippy/master/index.html#unnecessary_operation
diff --git a/clippy_lints/src/casts/cast_enum_constructor.rs b/clippy_lints/src/casts/cast_enum_constructor.rs
new file mode 100644
index 00000000000..1973692e105
--- /dev/null
+++ b/clippy_lints/src/casts/cast_enum_constructor.rs
@@ -0,0 +1,21 @@
+use clippy_utils::diagnostics::span_lint;
+use rustc_hir::def::{CtorKind, CtorOf, DefKind, Res};
+use rustc_hir::{Expr, ExprKind};
+use rustc_lint::LateContext;
+use rustc_middle::ty::{self, Ty};
+
+use super::CAST_ENUM_CONSTRUCTOR;
+
+pub(super) fn check(cx: &LateContext<'_>, expr: &Expr<'_>, cast_expr: &Expr<'_>, cast_from: Ty<'_>) {
+    if matches!(cast_from.kind(), ty::FnDef(..))
+        && let ExprKind::Path(path) = &cast_expr.kind
+        && let Res::Def(DefKind::Ctor(CtorOf::Variant, CtorKind::Fn), _) = cx.qpath_res(path, cast_expr.hir_id)
+    {
+        span_lint(
+            cx,
+            CAST_ENUM_CONSTRUCTOR,
+            expr.span,
+            "cast of an enum tuple constructor to an integer",
+        );
+    }
+}
diff --git a/clippy_lints/src/casts/mod.rs b/clippy_lints/src/casts/mod.rs
index 6a0eabd089d..be59145afa0 100644
--- a/clippy_lints/src/casts/mod.rs
+++ b/clippy_lints/src/casts/mod.rs
@@ -1,3 +1,4 @@
+mod cast_enum_constructor;
 mod cast_lossless;
 mod cast_possible_truncation;
 mod cast_possible_wrap;
@@ -454,6 +455,24 @@ declare_clippy_lint! {
     "casting using `as` between raw pointers to slices of types with different sizes"
 }
 
+declare_clippy_lint! {
+    /// ### What it does
+    /// Checks for casts from an enum tuple constructor to an integer.
+    ///
+    /// ### Why is this bad?
+    /// The cast is easily confused with casting a c-like enum value to an integer.
+    ///
+    /// ### Example
+    /// ```rust
+    /// enum E { X(i32) };
+    /// let _ = E::X as usize;
+    /// ```
+    #[clippy::version = "1.61.0"]
+    pub CAST_ENUM_CONSTRUCTOR,
+    suspicious,
+    "casts from an enum tuple constructor to an integer"
+}
+
 pub struct Casts {
     msrv: Option<RustcVersion>,
 }
@@ -481,6 +500,7 @@ impl_lint_pass!(Casts => [
     CHAR_LIT_AS_U8,
     PTR_AS_PTR,
     CAST_ENUM_TRUNCATION,
+    CAST_ENUM_CONSTRUCTOR
 ]);
 
 impl<'tcx> LateLintPass<'tcx> for Casts {
@@ -518,6 +538,7 @@ impl<'tcx> LateLintPass<'tcx> for Casts {
                     cast_sign_loss::check(cx, expr, cast_expr, cast_from, cast_to);
                 }
                 cast_lossless::check(cx, expr, cast_expr, cast_from, cast_to, &self.msrv);
+                cast_enum_constructor::check(cx, expr, cast_expr, cast_from);
             }
         }
 
diff --git a/clippy_lints/src/collapsible_if.rs b/clippy_lints/src/collapsible_if.rs
index f03f34e5a4b..eae2723a7da 100644
--- a/clippy_lints/src/collapsible_if.rs
+++ b/clippy_lints/src/collapsible_if.rs
@@ -42,7 +42,7 @@ declare_clippy_lint! {
     ///
     /// Should be written:
     ///
-    /// ```rust.ignore
+    /// ```rust,ignore
     /// if x && y {
     ///     …
     /// }
@@ -76,7 +76,7 @@ declare_clippy_lint! {
     ///
     /// Should be written:
     ///
-    /// ```rust.ignore
+    /// ```rust,ignore
     /// if x {
     ///     …
     /// } else if y {
diff --git a/clippy_lints/src/doc.rs b/clippy_lints/src/doc.rs
index 16173580fd4..703aa458f44 100644
--- a/clippy_lints/src/doc.rs
+++ b/clippy_lints/src/doc.rs
@@ -637,12 +637,6 @@ fn check_code(cx: &LateContext<'_>, text: &str, edition: Edition, span: Span) {
                 loop {
                     match parser.parse_item(ForceCollect::No) {
                         Ok(Some(item)) => match &item.kind {
-                            // Tests with one of these items are ignored
-                            ItemKind::Static(..)
-                            | ItemKind::Const(..)
-                            | ItemKind::ExternCrate(..)
-                            | ItemKind::ForeignMod(..) => return false,
-                            // We found a main function ...
                             ItemKind::Fn(box Fn {
                                 sig, body: Some(block), ..
                             }) if item.ident.name == sym::main => {
@@ -661,8 +655,13 @@ fn check_code(cx: &LateContext<'_>, text: &str, edition: Edition, span: Span) {
                                     return false;
                                 }
                             },
-                            // Another function was found; this case is ignored too
-                            ItemKind::Fn(..) => return false,
+                            // Tests with one of these items are ignored
+                            ItemKind::Static(..)
+                            | ItemKind::Const(..)
+                            | ItemKind::ExternCrate(..)
+                            | ItemKind::ForeignMod(..)
+                            // Another function was found; this case is ignored
+                            | ItemKind::Fn(..) => return false,
                             _ => {},
                         },
                         Ok(None) => break,
diff --git a/clippy_lints/src/lib.register_all.rs b/clippy_lints/src/lib.register_all.rs
index 23bca5a0eab..132a4662676 100644
--- a/clippy_lints/src/lib.register_all.rs
+++ b/clippy_lints/src/lib.register_all.rs
@@ -23,6 +23,7 @@ store.register_group(true, "clippy::all", Some("clippy_all"), vec![
     LintId::of(bool_assert_comparison::BOOL_ASSERT_COMPARISON),
     LintId::of(booleans::LOGIC_BUG),
     LintId::of(booleans::NONMINIMAL_BOOL),
+    LintId::of(casts::CAST_ENUM_CONSTRUCTOR),
     LintId::of(casts::CAST_ENUM_TRUNCATION),
     LintId::of(casts::CAST_REF_TO_MUT),
     LintId::of(casts::CAST_SLICE_DIFFERENT_SIZES),
@@ -166,7 +167,6 @@ store.register_group(true, "clippy::all", Some("clippy_all"), vec![
     LintId::of(methods::ITER_NTH_ZERO),
     LintId::of(methods::ITER_OVEREAGER_CLONED),
     LintId::of(methods::ITER_SKIP_NEXT),
-    LintId::of(methods::ITER_WITH_DRAIN),
     LintId::of(methods::MANUAL_FILTER_MAP),
     LintId::of(methods::MANUAL_FIND_MAP),
     LintId::of(methods::MANUAL_SATURATING_ARITHMETIC),
@@ -182,6 +182,7 @@ store.register_group(true, "clippy::all", Some("clippy_all"), vec![
     LintId::of(methods::OPTION_FILTER_MAP),
     LintId::of(methods::OPTION_MAP_OR_NONE),
     LintId::of(methods::OR_FUN_CALL),
+    LintId::of(methods::OR_THEN_UNWRAP),
     LintId::of(methods::RESULT_MAP_OR_INTO_OPTION),
     LintId::of(methods::SEARCH_IS_SOME),
     LintId::of(methods::SHOULD_IMPLEMENT_TRAIT),
@@ -290,7 +291,6 @@ store.register_group(true, "clippy::all", Some("clippy_all"), vec![
     LintId::of(transmute::UNSOUND_COLLECTION_TRANSMUTE),
     LintId::of(transmute::WRONG_TRANSMUTE),
     LintId::of(transmuting_null::TRANSMUTING_NULL),
-    LintId::of(try_err::TRY_ERR),
     LintId::of(types::BORROWED_BOX),
     LintId::of(types::BOX_COLLECTION),
     LintId::of(types::REDUNDANT_ALLOCATION),
diff --git a/clippy_lints/src/lib.register_complexity.rs b/clippy_lints/src/lib.register_complexity.rs
index 68d6c6ce5f7..a2ce69065f9 100644
--- a/clippy_lints/src/lib.register_complexity.rs
+++ b/clippy_lints/src/lib.register_complexity.rs
@@ -47,6 +47,7 @@ store.register_group(true, "clippy::complexity", Some("clippy_complexity"), vec!
     LintId::of(methods::NEEDLESS_SPLITN),
     LintId::of(methods::OPTION_AS_REF_DEREF),
     LintId::of(methods::OPTION_FILTER_MAP),
+    LintId::of(methods::OR_THEN_UNWRAP),
     LintId::of(methods::SEARCH_IS_SOME),
     LintId::of(methods::SKIP_WHILE_NEXT),
     LintId::of(methods::UNNECESSARY_FILTER_MAP),
diff --git a/clippy_lints/src/lib.register_lints.rs b/clippy_lints/src/lib.register_lints.rs
index 1a45763a869..21f1ef562b5 100644
--- a/clippy_lints/src/lib.register_lints.rs
+++ b/clippy_lints/src/lib.register_lints.rs
@@ -70,6 +70,7 @@ store.register_lints(&[
     cargo::REDUNDANT_FEATURE_NAMES,
     cargo::WILDCARD_DEPENDENCIES,
     case_sensitive_file_extension_comparisons::CASE_SENSITIVE_FILE_EXTENSION_COMPARISONS,
+    casts::CAST_ENUM_CONSTRUCTOR,
     casts::CAST_ENUM_TRUNCATION,
     casts::CAST_LOSSLESS,
     casts::CAST_POSSIBLE_TRUNCATION,
@@ -319,6 +320,7 @@ store.register_lints(&[
     methods::OPTION_FILTER_MAP,
     methods::OPTION_MAP_OR_NONE,
     methods::OR_FUN_CALL,
+    methods::OR_THEN_UNWRAP,
     methods::RESULT_MAP_OR_INTO_OPTION,
     methods::SEARCH_IS_SOME,
     methods::SHOULD_IMPLEMENT_TRAIT,
@@ -332,6 +334,7 @@ store.register_lints(&[
     methods::UNNECESSARY_FILTER_MAP,
     methods::UNNECESSARY_FIND_MAP,
     methods::UNNECESSARY_FOLD,
+    methods::UNNECESSARY_JOIN,
     methods::UNNECESSARY_LAZY_EVALUATIONS,
     methods::UNNECESSARY_TO_OWNED,
     methods::UNWRAP_OR_ELSE_DEFAULT,
diff --git a/clippy_lints/src/lib.register_nursery.rs b/clippy_lints/src/lib.register_nursery.rs
index 8d4dde42bbe..c2fc67afba5 100644
--- a/clippy_lints/src/lib.register_nursery.rs
+++ b/clippy_lints/src/lib.register_nursery.rs
@@ -13,6 +13,7 @@ store.register_group(true, "clippy::nursery", Some("clippy_nursery"), vec![
     LintId::of(future_not_send::FUTURE_NOT_SEND),
     LintId::of(index_refutable_slice::INDEX_REFUTABLE_SLICE),
     LintId::of(let_if_seq::USELESS_LET_IF_SEQ),
+    LintId::of(methods::ITER_WITH_DRAIN),
     LintId::of(missing_const_for_fn::MISSING_CONST_FOR_FN),
     LintId::of(mutable_debug_assertion::DEBUG_ASSERT_WITH_MUT_CALL),
     LintId::of(mutex_atomic::MUTEX_ATOMIC),
diff --git a/clippy_lints/src/lib.register_pedantic.rs b/clippy_lints/src/lib.register_pedantic.rs
index 00d30513181..eb6534cb8ca 100644
--- a/clippy_lints/src/lib.register_pedantic.rs
+++ b/clippy_lints/src/lib.register_pedantic.rs
@@ -63,6 +63,7 @@ store.register_group(true, "clippy::pedantic", Some("clippy_pedantic"), vec![
     LintId::of(methods::IMPLICIT_CLONE),
     LintId::of(methods::INEFFICIENT_TO_STRING),
     LintId::of(methods::MAP_UNWRAP_OR),
+    LintId::of(methods::UNNECESSARY_JOIN),
     LintId::of(misc::FLOAT_CMP),
     LintId::of(misc::USED_UNDERSCORE_BINDING),
     LintId::of(mut_mut::MUT_MUT),
diff --git a/clippy_lints/src/lib.register_perf.rs b/clippy_lints/src/lib.register_perf.rs
index 6e9c0ee33a1..f2f5c988d8f 100644
--- a/clippy_lints/src/lib.register_perf.rs
+++ b/clippy_lints/src/lib.register_perf.rs
@@ -16,7 +16,6 @@ store.register_group(true, "clippy::perf", Some("clippy_perf"), vec![
     LintId::of(methods::EXTEND_WITH_DRAIN),
     LintId::of(methods::ITER_NTH),
     LintId::of(methods::ITER_OVEREAGER_CLONED),
-    LintId::of(methods::ITER_WITH_DRAIN),
     LintId::of(methods::MANUAL_STR_REPEAT),
     LintId::of(methods::OR_FUN_CALL),
     LintId::of(methods::SINGLE_CHAR_PATTERN),
diff --git a/clippy_lints/src/lib.register_restriction.rs b/clippy_lints/src/lib.register_restriction.rs
index 4e30fc38197..6ab139b2fb6 100644
--- a/clippy_lints/src/lib.register_restriction.rs
+++ b/clippy_lints/src/lib.register_restriction.rs
@@ -62,6 +62,7 @@ store.register_group(true, "clippy::restriction", Some("clippy_restriction"), ve
     LintId::of(strings::STRING_SLICE),
     LintId::of(strings::STRING_TO_STRING),
     LintId::of(strings::STR_TO_STRING),
+    LintId::of(try_err::TRY_ERR),
     LintId::of(types::RC_BUFFER),
     LintId::of(types::RC_MUTEX),
     LintId::of(undocumented_unsafe_blocks::UNDOCUMENTED_UNSAFE_BLOCKS),
diff --git a/clippy_lints/src/lib.register_style.rs b/clippy_lints/src/lib.register_style.rs
index 05211476ff2..dcf399cf956 100644
--- a/clippy_lints/src/lib.register_style.rs
+++ b/clippy_lints/src/lib.register_style.rs
@@ -105,7 +105,6 @@ store.register_group(true, "clippy::style", Some("clippy_style"), vec![
     LintId::of(single_component_path_imports::SINGLE_COMPONENT_PATH_IMPORTS),
     LintId::of(tabs_in_doc_comments::TABS_IN_DOC_COMMENTS),
     LintId::of(to_digit_is_some::TO_DIGIT_IS_SOME),
-    LintId::of(try_err::TRY_ERR),
     LintId::of(unsafe_removed_from_name::UNSAFE_REMOVED_FROM_NAME),
     LintId::of(unused_unit::UNUSED_UNIT),
     LintId::of(upper_case_acronyms::UPPER_CASE_ACRONYMS),
diff --git a/clippy_lints/src/lib.register_suspicious.rs b/clippy_lints/src/lib.register_suspicious.rs
index 465baa82581..fa3a88e1368 100644
--- a/clippy_lints/src/lib.register_suspicious.rs
+++ b/clippy_lints/src/lib.register_suspicious.rs
@@ -7,6 +7,7 @@ store.register_group(true, "clippy::suspicious", Some("clippy_suspicious"), vec!
     LintId::of(attrs::BLANKET_CLIPPY_RESTRICTION_LINTS),
     LintId::of(await_holding_invalid::AWAIT_HOLDING_LOCK),
     LintId::of(await_holding_invalid::AWAIT_HOLDING_REFCELL_REF),
+    LintId::of(casts::CAST_ENUM_CONSTRUCTOR),
     LintId::of(casts::CAST_ENUM_TRUNCATION),
     LintId::of(eval_order_dependence::EVAL_ORDER_DEPENDENCE),
     LintId::of(float_equality_without_abs::FLOAT_EQUALITY_WITHOUT_ABS),
diff --git a/clippy_lints/src/lib.rs b/clippy_lints/src/lib.rs
index 504235d0d1e..f2a07999144 100644
--- a/clippy_lints/src/lib.rs
+++ b/clippy_lints/src/lib.rs
@@ -23,6 +23,7 @@
 
 // FIXME: switch to something more ergonomic here, once available.
 // (Currently there is no way to opt into sysroot crates without `extern crate`.)
+extern crate rustc_arena;
 extern crate rustc_ast;
 extern crate rustc_ast_pretty;
 extern crate rustc_attr;
diff --git a/clippy_lints/src/macro_use.rs b/clippy_lints/src/macro_use.rs
index ca1ccb93bf3..76c5cfadc2c 100644
--- a/clippy_lints/src/macro_use.rs
+++ b/clippy_lints/src/macro_use.rs
@@ -35,7 +35,8 @@ struct PathAndSpan {
     span: Span,
 }
 
-/// `MacroRefData` includes the name of the macro.
+/// `MacroRefData` includes the name of the macro
+/// and the path from `SourceMap::span_to_filename`.
 #[derive(Debug, Clone)]
 pub struct MacroRefData {
     name: String,
diff --git a/clippy_lints/src/matches/match_same_arms.rs b/clippy_lints/src/matches/match_same_arms.rs
index d11dda57e6f..b8591fe0db0 100644
--- a/clippy_lints/src/matches/match_same_arms.rs
+++ b/clippy_lints/src/matches/match_same_arms.rs
@@ -1,19 +1,66 @@
 use clippy_utils::diagnostics::span_lint_and_then;
 use clippy_utils::source::snippet;
 use clippy_utils::{path_to_local, search_same, SpanlessEq, SpanlessHash};
-use rustc_hir::{Arm, Expr, HirId, HirIdMap, HirIdSet, Pat, PatKind};
+use core::cmp::Ordering;
+use core::iter;
+use core::slice;
+use rustc_arena::DroplessArena;
+use rustc_ast::ast::LitKind;
+use rustc_errors::Applicability;
+use rustc_hir::def_id::DefId;
+use rustc_hir::{Arm, Expr, ExprKind, HirId, HirIdMap, HirIdSet, Pat, PatKind, RangeEnd};
 use rustc_lint::LateContext;
+use rustc_middle::ty;
+use rustc_span::Symbol;
 use std::collections::hash_map::Entry;
 
 use super::MATCH_SAME_ARMS;
 
-pub(crate) fn check<'tcx>(cx: &LateContext<'tcx>, arms: &'tcx [Arm<'_>]) {
+#[allow(clippy::too_many_lines)]
+pub(super) fn check<'tcx>(cx: &LateContext<'tcx>, arms: &'tcx [Arm<'_>]) {
     let hash = |&(_, arm): &(usize, &Arm<'_>)| -> u64 {
         let mut h = SpanlessHash::new(cx);
         h.hash_expr(arm.body);
         h.finish()
     };
 
+    let arena = DroplessArena::default();
+    let normalized_pats: Vec<_> = arms
+        .iter()
+        .map(|a| NormalizedPat::from_pat(cx, &arena, a.pat))
+        .collect();
+
+    // The furthast forwards a pattern can move without semantic changes
+    let forwards_blocking_idxs: Vec<_> = normalized_pats
+        .iter()
+        .enumerate()
+        .map(|(i, pat)| {
+            normalized_pats[i + 1..]
+                .iter()
+                .enumerate()
+                .find_map(|(j, other)| pat.has_overlapping_values(other).then(|| i + 1 + j))
+                .unwrap_or(normalized_pats.len())
+        })
+        .collect();
+
+    // The furthast backwards a pattern can move without semantic changes
+    let backwards_blocking_idxs: Vec<_> = normalized_pats
+        .iter()
+        .enumerate()
+        .map(|(i, pat)| {
+            normalized_pats[..i]
+                .iter()
+                .enumerate()
+                .rev()
+                .zip(forwards_blocking_idxs[..i].iter().copied().rev())
+                .skip_while(|&(_, forward_block)| forward_block > i)
+                .find_map(|((j, other), forward_block)| {
+                    (forward_block == i || pat.has_overlapping_values(other)).then(|| j)
+                })
+                .unwrap_or(0)
+        })
+        .collect();
+
     let eq = |&(lindex, lhs): &(usize, &Arm<'_>), &(rindex, rhs): &(usize, &Arm<'_>)| -> bool {
         let min_index = usize::min(lindex, rindex);
         let max_index = usize::max(lindex, rindex);
@@ -42,53 +89,316 @@ pub(crate) fn check<'tcx>(cx: &LateContext<'tcx>, arms: &'tcx [Arm<'_>]) {
             }
         };
         // Arms with a guard are ignored, those can’t always be merged together
-        // This is also the case for arms in-between each there is an arm with a guard
-        (min_index..=max_index).all(|index| arms[index].guard.is_none())
-            && SpanlessEq::new(cx)
-                .expr_fallback(eq_fallback)
-                .eq_expr(lhs.body, rhs.body)
-            // these checks could be removed to allow unused bindings
-            && bindings_eq(lhs.pat, local_map.keys().copied().collect())
-            && bindings_eq(rhs.pat, local_map.values().copied().collect())
+        // If both arms overlap with an arm in between then these can't be merged either.
+        !(backwards_blocking_idxs[max_index] > min_index && forwards_blocking_idxs[min_index] < max_index)
+                && lhs.guard.is_none()
+                && rhs.guard.is_none()
+                && SpanlessEq::new(cx)
+                    .expr_fallback(eq_fallback)
+                    .eq_expr(lhs.body, rhs.body)
+                // these checks could be removed to allow unused bindings
+                && bindings_eq(lhs.pat, local_map.keys().copied().collect())
+                && bindings_eq(rhs.pat, local_map.values().copied().collect())
     };
 
     let indexed_arms: Vec<(usize, &Arm<'_>)> = arms.iter().enumerate().collect();
-    for (&(_, i), &(_, j)) in search_same(&indexed_arms, hash, eq) {
-        span_lint_and_then(
-            cx,
-            MATCH_SAME_ARMS,
-            j.body.span,
-            "this `match` has identical arm bodies",
-            |diag| {
-                diag.span_note(i.body.span, "same as this");
-
-                // Note: this does not use `span_suggestion` on purpose:
-                // there is no clean way
-                // to remove the other arm. Building a span and suggest to replace it to ""
-                // makes an even more confusing error message. Also in order not to make up a
-                // span for the whole pattern, the suggestion is only shown when there is only
-                // one pattern. The user should know about `|` if they are already using it…
-
-                let lhs = snippet(cx, i.pat.span, "<pat1>");
-                let rhs = snippet(cx, j.pat.span, "<pat2>");
-
-                if let PatKind::Wild = j.pat.kind {
-                    // if the last arm is _, then i could be integrated into _
-                    // note that i.pat cannot be _, because that would mean that we're
-                    // hiding all the subsequent arms, and rust won't compile
-                    diag.span_note(
-                        i.body.span,
-                        &format!(
-                            "`{}` has the same arm body as the `_` wildcard, consider removing it",
-                            lhs
-                        ),
-                    );
+    for (&(i, arm1), &(j, arm2)) in search_same(&indexed_arms, hash, eq) {
+        if matches!(arm2.pat.kind, PatKind::Wild) {
+            span_lint_and_then(
+                cx,
+                MATCH_SAME_ARMS,
+                arm1.span,
+                "this match arm has an identical body to the `_` wildcard arm",
+                |diag| {
+                    diag.span_suggestion(
+                        arm1.span,
+                        "try removing the arm",
+                        String::new(),
+                        Applicability::MaybeIncorrect,
+                    )
+                    .help("or try changing either arm body")
+                    .span_note(arm2.span, "`_` wildcard arm here");
+                },
+            );
+        } else {
+            let back_block = backwards_blocking_idxs[j];
+            let (keep_arm, move_arm) = if back_block < i || (back_block == 0 && forwards_blocking_idxs[i] <= j) {
+                (arm1, arm2)
+            } else {
+                (arm2, arm1)
+            };
+
+            span_lint_and_then(
+                cx,
+                MATCH_SAME_ARMS,
+                keep_arm.span,
+                "this match arm has an identical body to another arm",
+                |diag| {
+                    let move_pat_snip = snippet(cx, move_arm.pat.span, "<pat2>");
+                    let keep_pat_snip = snippet(cx, keep_arm.pat.span, "<pat1>");
+
+                    diag.span_suggestion(
+                        keep_arm.pat.span,
+                        "try merging the arm patterns",
+                        format!("{} | {}", keep_pat_snip, move_pat_snip),
+                        Applicability::MaybeIncorrect,
+                    )
+                    .help("or try changing either arm body")
+                    .span_note(move_arm.span, "other arm here");
+                },
+            );
+        }
+    }
+}
+
+#[derive(Clone, Copy)]
+enum NormalizedPat<'a> {
+    Wild,
+    Struct(Option<DefId>, &'a [(Symbol, Self)]),
+    Tuple(Option<DefId>, &'a [Self]),
+    Or(&'a [Self]),
+    Path(Option<DefId>),
+    LitStr(Symbol),
+    LitBytes(&'a [u8]),
+    LitInt(u128),
+    LitBool(bool),
+    Range(PatRange),
+    /// A slice pattern. If the second value is `None`, then this matches an exact size. Otherwise
+    /// the first value contains everything before the `..` wildcard pattern, and the second value
+    /// contains everything afterwards. Note that either side, or both sides, may contain zero
+    /// patterns.
+    Slice(&'a [Self], Option<&'a [Self]>),
+}
+
+#[derive(Clone, Copy)]
+struct PatRange {
+    start: u128,
+    end: u128,
+    bounds: RangeEnd,
+}
+impl PatRange {
+    fn contains(&self, x: u128) -> bool {
+        x >= self.start
+            && match self.bounds {
+                RangeEnd::Included => x <= self.end,
+                RangeEnd::Excluded => x < self.end,
+            }
+    }
+
+    fn overlaps(&self, other: &Self) -> bool {
+        // Note: Empty ranges are impossible, so this is correct even though it would return true if an
+        // empty exclusive range were to reside within an inclusive range.
+        (match self.bounds {
+            RangeEnd::Included => self.end >= other.start,
+            RangeEnd::Excluded => self.end > other.start,
+        } && match other.bounds {
+            RangeEnd::Included => self.start <= other.end,
+            RangeEnd::Excluded => self.start < other.end,
+        })
+    }
+}
+
+/// Iterates over the pairs of fields with matching names.
+fn iter_matching_struct_fields<'a>(
+    left: &'a [(Symbol, NormalizedPat<'a>)],
+    right: &'a [(Symbol, NormalizedPat<'a>)],
+) -> impl Iterator<Item = (&'a NormalizedPat<'a>, &'a NormalizedPat<'a>)> + 'a {
+    struct Iter<'a>(
+        slice::Iter<'a, (Symbol, NormalizedPat<'a>)>,
+        slice::Iter<'a, (Symbol, NormalizedPat<'a>)>,
+    );
+    impl<'a> Iterator for Iter<'a> {
+        type Item = (&'a NormalizedPat<'a>, &'a NormalizedPat<'a>);
+        fn next(&mut self) -> Option<Self::Item> {
+            // Note: all the fields in each slice are sorted by symbol value.
+            let mut left = self.0.next()?;
+            let mut right = self.1.next()?;
+            loop {
+                match left.0.cmp(&right.0) {
+                    Ordering::Equal => return Some((&left.1, &right.1)),
+                    Ordering::Less => left = self.0.next()?,
+                    Ordering::Greater => right = self.1.next()?,
+                }
+            }
+        }
+    }
+    Iter(left.iter(), right.iter())
+}
+
+#[allow(clippy::similar_names)]
+impl<'a> NormalizedPat<'a> {
+    #[allow(clippy::too_many_lines)]
+    fn from_pat(cx: &LateContext<'_>, arena: &'a DroplessArena, pat: &'a Pat<'_>) -> Self {
+        match pat.kind {
+            PatKind::Wild | PatKind::Binding(.., None) => Self::Wild,
+            PatKind::Binding(.., Some(pat)) | PatKind::Box(pat) | PatKind::Ref(pat, _) => {
+                Self::from_pat(cx, arena, pat)
+            },
+            PatKind::Struct(ref path, fields, _) => {
+                let fields =
+                    arena.alloc_from_iter(fields.iter().map(|f| (f.ident.name, Self::from_pat(cx, arena, f.pat))));
+                fields.sort_by_key(|&(name, _)| name);
+                Self::Struct(cx.qpath_res(path, pat.hir_id).opt_def_id(), fields)
+            },
+            PatKind::TupleStruct(ref path, pats, wild_idx) => {
+                let adt = match cx.typeck_results().pat_ty(pat).ty_adt_def() {
+                    Some(x) => x,
+                    None => return Self::Wild,
+                };
+                let (var_id, variant) = if adt.is_enum() {
+                    match cx.qpath_res(path, pat.hir_id).opt_def_id() {
+                        Some(x) => (Some(x), adt.variant_with_ctor_id(x)),
+                        None => return Self::Wild,
+                    }
                 } else {
-                    diag.span_help(i.pat.span, &format!("consider refactoring into `{} | {}`", lhs, rhs,))
-                        .help("...or consider changing the match arm bodies");
+                    (None, adt.non_enum_variant())
+                };
+                let (front, back) = match wild_idx {
+                    Some(i) => pats.split_at(i),
+                    None => (pats, [].as_slice()),
+                };
+                let pats = arena.alloc_from_iter(
+                    front
+                        .iter()
+                        .map(|pat| Self::from_pat(cx, arena, pat))
+                        .chain(iter::repeat_with(|| Self::Wild).take(variant.fields.len() - pats.len()))
+                        .chain(back.iter().map(|pat| Self::from_pat(cx, arena, pat))),
+                );
+                Self::Tuple(var_id, pats)
+            },
+            PatKind::Or(pats) => Self::Or(arena.alloc_from_iter(pats.iter().map(|pat| Self::from_pat(cx, arena, pat)))),
+            PatKind::Path(ref path) => Self::Path(cx.qpath_res(path, pat.hir_id).opt_def_id()),
+            PatKind::Tuple(pats, wild_idx) => {
+                let field_count = match cx.typeck_results().pat_ty(pat).kind() {
+                    ty::Tuple(subs) => subs.len(),
+                    _ => return Self::Wild,
+                };
+                let (front, back) = match wild_idx {
+                    Some(i) => pats.split_at(i),
+                    None => (pats, [].as_slice()),
+                };
+                let pats = arena.alloc_from_iter(
+                    front
+                        .iter()
+                        .map(|pat| Self::from_pat(cx, arena, pat))
+                        .chain(iter::repeat_with(|| Self::Wild).take(field_count - pats.len()))
+                        .chain(back.iter().map(|pat| Self::from_pat(cx, arena, pat))),
+                );
+                Self::Tuple(None, pats)
+            },
+            PatKind::Lit(e) => match &e.kind {
+                // TODO: Handle negative integers. They're currently treated as a wild match.
+                ExprKind::Lit(lit) => match lit.node {
+                    LitKind::Str(sym, _) => Self::LitStr(sym),
+                    LitKind::ByteStr(ref bytes) => Self::LitBytes(&**bytes),
+                    LitKind::Byte(val) => Self::LitInt(val.into()),
+                    LitKind::Char(val) => Self::LitInt(val.into()),
+                    LitKind::Int(val, _) => Self::LitInt(val),
+                    LitKind::Bool(val) => Self::LitBool(val),
+                    LitKind::Float(..) | LitKind::Err(_) => Self::Wild,
+                },
+                _ => Self::Wild,
+            },
+            PatKind::Range(start, end, bounds) => {
+                // TODO: Handle negative integers. They're currently treated as a wild match.
+                let start = match start {
+                    None => 0,
+                    Some(e) => match &e.kind {
+                        ExprKind::Lit(lit) => match lit.node {
+                            LitKind::Int(val, _) => val,
+                            LitKind::Char(val) => val.into(),
+                            LitKind::Byte(val) => val.into(),
+                            _ => return Self::Wild,
+                        },
+                        _ => return Self::Wild,
+                    },
+                };
+                let (end, bounds) = match end {
+                    None => (u128::MAX, RangeEnd::Included),
+                    Some(e) => match &e.kind {
+                        ExprKind::Lit(lit) => match lit.node {
+                            LitKind::Int(val, _) => (val, bounds),
+                            LitKind::Char(val) => (val.into(), bounds),
+                            LitKind::Byte(val) => (val.into(), bounds),
+                            _ => return Self::Wild,
+                        },
+                        _ => return Self::Wild,
+                    },
+                };
+                Self::Range(PatRange { start, end, bounds })
+            },
+            PatKind::Slice(front, wild_pat, back) => Self::Slice(
+                arena.alloc_from_iter(front.iter().map(|pat| Self::from_pat(cx, arena, pat))),
+                wild_pat.map(|_| &*arena.alloc_from_iter(back.iter().map(|pat| Self::from_pat(cx, arena, pat)))),
+            ),
+        }
+    }
+
+    /// Checks if two patterns overlap in the values they can match assuming they are for the same
+    /// type.
+    fn has_overlapping_values(&self, other: &Self) -> bool {
+        match (*self, *other) {
+            (Self::Wild, _) | (_, Self::Wild) => true,
+            (Self::Or(pats), ref other) | (ref other, Self::Or(pats)) => {
+                pats.iter().any(|pat| pat.has_overlapping_values(other))
+            },
+            (Self::Struct(lpath, lfields), Self::Struct(rpath, rfields)) => {
+                if lpath != rpath {
+                    return false;
+                }
+                iter_matching_struct_fields(lfields, rfields).all(|(lpat, rpat)| lpat.has_overlapping_values(rpat))
+            },
+            (Self::Tuple(lpath, lpats), Self::Tuple(rpath, rpats)) => {
+                if lpath != rpath {
+                    return false;
                 }
+                lpats
+                    .iter()
+                    .zip(rpats.iter())
+                    .all(|(lpat, rpat)| lpat.has_overlapping_values(rpat))
+            },
+            (Self::Path(x), Self::Path(y)) => x == y,
+            (Self::LitStr(x), Self::LitStr(y)) => x == y,
+            (Self::LitBytes(x), Self::LitBytes(y)) => x == y,
+            (Self::LitInt(x), Self::LitInt(y)) => x == y,
+            (Self::LitBool(x), Self::LitBool(y)) => x == y,
+            (Self::Range(ref x), Self::Range(ref y)) => x.overlaps(y),
+            (Self::Range(ref range), Self::LitInt(x)) | (Self::LitInt(x), Self::Range(ref range)) => range.contains(x),
+            (Self::Slice(lpats, None), Self::Slice(rpats, None)) => {
+                lpats.len() == rpats.len() && lpats.iter().zip(rpats.iter()).all(|(x, y)| x.has_overlapping_values(y))
             },
-        );
+            (Self::Slice(pats, None), Self::Slice(front, Some(back)))
+            | (Self::Slice(front, Some(back)), Self::Slice(pats, None)) => {
+                // Here `pats` is an exact size match. If the combined lengths of `front` and `back` are greater
+                // then the minium length required will be greater than the length of `pats`.
+                if pats.len() < front.len() + back.len() {
+                    return false;
+                }
+                pats[..front.len()]
+                    .iter()
+                    .zip(front.iter())
+                    .chain(pats[pats.len() - back.len()..].iter().zip(back.iter()))
+                    .all(|(x, y)| x.has_overlapping_values(y))
+            },
+            (Self::Slice(lfront, Some(lback)), Self::Slice(rfront, Some(rback))) => lfront
+                .iter()
+                .zip(rfront.iter())
+                .chain(lback.iter().rev().zip(rback.iter().rev()))
+                .all(|(x, y)| x.has_overlapping_values(y)),
+
+            // Enums can mix unit variants with tuple/struct variants. These can never overlap.
+            (Self::Path(_), Self::Tuple(..) | Self::Struct(..))
+            | (Self::Tuple(..) | Self::Struct(..), Self::Path(_)) => false,
+
+            // Tuples can be matched like a struct.
+            (Self::Tuple(x, _), Self::Struct(y, _)) | (Self::Struct(x, _), Self::Tuple(y, _)) => {
+                // TODO: check fields here.
+                x == y
+            },
+
+            // TODO: Lit* with Path, Range with Path, LitBytes with Slice
+            _ => true,
+        }
     }
 }
 
diff --git a/clippy_lints/src/methods/map_flatten.rs b/clippy_lints/src/methods/map_flatten.rs
index e1212c31cfb..f447940ea3b 100644
--- a/clippy_lints/src/methods/map_flatten.rs
+++ b/clippy_lints/src/methods/map_flatten.rs
@@ -1,83 +1,73 @@
-use clippy_utils::diagnostics::span_lint_and_sugg;
+use clippy_utils::diagnostics::span_lint_and_sugg_for_edges;
 use clippy_utils::is_trait_method;
-use clippy_utils::source::snippet;
+use clippy_utils::source::snippet_with_applicability;
 use clippy_utils::ty::is_type_diagnostic_item;
 use rustc_errors::Applicability;
-use rustc_hir as hir;
+use rustc_hir::Expr;
 use rustc_lint::LateContext;
 use rustc_middle::ty;
-use rustc_span::symbol::sym;
+use rustc_span::{symbol::sym, Span};
 
 use super::MAP_FLATTEN;
 
 /// lint use of `map().flatten()` for `Iterators` and 'Options'
-pub(super) fn check<'tcx>(
-    cx: &LateContext<'tcx>,
-    expr: &'tcx hir::Expr<'_>,
-    recv: &'tcx hir::Expr<'_>,
-    map_arg: &'tcx hir::Expr<'_>,
-) {
-    // lint if caller of `.map().flatten()` is an Iterator
-    if is_trait_method(cx, expr, sym::Iterator) {
-        let map_closure_ty = cx.typeck_results().expr_ty(map_arg);
-        let is_map_to_option = match map_closure_ty.kind() {
-            ty::Closure(_, _) | ty::FnDef(_, _) | ty::FnPtr(_) => {
-                let map_closure_sig = match map_closure_ty.kind() {
-                    ty::Closure(_, substs) => substs.as_closure().sig(),
-                    _ => map_closure_ty.fn_sig(cx.tcx),
-                };
-                let map_closure_return_ty = cx.tcx.erase_late_bound_regions(map_closure_sig.output());
-                is_type_diagnostic_item(cx, map_closure_return_ty, sym::Option)
-            },
-            _ => false,
-        };
-
-        let method_to_use = if is_map_to_option {
-            // `(...).map(...)` has type `impl Iterator<Item=Option<...>>
-            "filter_map"
-        } else {
-            // `(...).map(...)` has type `impl Iterator<Item=impl Iterator<...>>
-            "flat_map"
-        };
-        let func_snippet = snippet(cx, map_arg.span, "..");
-        let hint = format!(".{0}({1})", method_to_use, func_snippet);
-        span_lint_and_sugg(
+pub(super) fn check(cx: &LateContext<'_>, expr: &Expr<'_>, recv: &Expr<'_>, map_arg: &Expr<'_>, map_span: Span) {
+    if let Some((caller_ty_name, method_to_use)) = try_get_caller_ty_name_and_method_name(cx, expr, recv, map_arg) {
+        let mut applicability = Applicability::MachineApplicable;
+        let help_msgs = [
+            &format!("try replacing `map` with `{}`", method_to_use),
+            "and remove the `.flatten()`",
+        ];
+        let closure_snippet = snippet_with_applicability(cx, map_arg.span, "..", &mut applicability);
+        span_lint_and_sugg_for_edges(
             cx,
             MAP_FLATTEN,
-            expr.span.with_lo(recv.span.hi()),
-            "called `map(..).flatten()` on an `Iterator`",
-            &format!("try using `{}` instead", method_to_use),
-            hint,
-            Applicability::MachineApplicable,
+            expr.span.with_lo(map_span.lo()),
+            &format!("called `map(..).flatten()` on `{}`", caller_ty_name),
+            &help_msgs,
+            format!("{}({})", method_to_use, closure_snippet),
+            applicability,
         );
     }
+}
 
-    // lint if caller of `.map().flatten()` is an Option or Result
-    let caller_type = match cx.typeck_results().expr_ty(recv).kind() {
-        ty::Adt(adt, _) => {
+fn try_get_caller_ty_name_and_method_name(
+    cx: &LateContext<'_>,
+    expr: &Expr<'_>,
+    caller_expr: &Expr<'_>,
+    map_arg: &Expr<'_>,
+) -> Option<(&'static str, &'static str)> {
+    if is_trait_method(cx, expr, sym::Iterator) {
+        if is_map_to_option(cx, map_arg) {
+            // `(...).map(...)` has type `impl Iterator<Item=Option<...>>
+            Some(("Iterator", "filter_map"))
+        } else {
+            // `(...).map(...)` has type `impl Iterator<Item=impl Iterator<...>>
+            Some(("Iterator", "flat_map"))
+        }
+    } else {
+        if let ty::Adt(adt, _) = cx.typeck_results().expr_ty(caller_expr).kind() {
             if cx.tcx.is_diagnostic_item(sym::Option, adt.did()) {
-                "Option"
+                return Some(("Option", "and_then"));
             } else if cx.tcx.is_diagnostic_item(sym::Result, adt.did()) {
-                "Result"
-            } else {
-                return;
+                return Some(("Result", "and_then"));
             }
-        },
-        _ => {
-            return;
-        },
-    };
+        }
+        None
+    }
+}
 
-    let func_snippet = snippet(cx, map_arg.span, "..");
-    let hint = format!(".and_then({})", func_snippet);
-    let lint_info = format!("called `map(..).flatten()` on an `{}`", caller_type);
-    span_lint_and_sugg(
-        cx,
-        MAP_FLATTEN,
-        expr.span.with_lo(recv.span.hi()),
-        &lint_info,
-        "try using `and_then` instead",
-        hint,
-        Applicability::MachineApplicable,
-    );
+fn is_map_to_option(cx: &LateContext<'_>, map_arg: &Expr<'_>) -> bool {
+    let map_closure_ty = cx.typeck_results().expr_ty(map_arg);
+    match map_closure_ty.kind() {
+        ty::Closure(_, _) | ty::FnDef(_, _) | ty::FnPtr(_) => {
+            let map_closure_sig = match map_closure_ty.kind() {
+                ty::Closure(_, substs) => substs.as_closure().sig(),
+                _ => map_closure_ty.fn_sig(cx.tcx),
+            };
+            let map_closure_return_ty = cx.tcx.erase_late_bound_regions(map_closure_sig.output());
+            is_type_diagnostic_item(cx, map_closure_return_ty, sym::Option)
+        },
+        _ => false,
+    }
 }
diff --git a/clippy_lints/src/methods/mod.rs b/clippy_lints/src/methods/mod.rs
index 5edd22cd14c..9d4e1fa3994 100644
--- a/clippy_lints/src/methods/mod.rs
+++ b/clippy_lints/src/methods/mod.rs
@@ -45,6 +45,7 @@ mod option_as_ref_deref;
 mod option_map_or_none;
 mod option_map_unwrap_or;
 mod or_fun_call;
+mod or_then_unwrap;
 mod search_is_some;
 mod single_char_add_str;
 mod single_char_insert_string;
@@ -59,6 +60,7 @@ mod uninit_assumed_init;
 mod unnecessary_filter_map;
 mod unnecessary_fold;
 mod unnecessary_iter_cloned;
+mod unnecessary_join;
 mod unnecessary_lazy_eval;
 mod unnecessary_to_owned;
 mod unwrap_or_else_default;
@@ -780,6 +782,42 @@ declare_clippy_lint! {
 
 declare_clippy_lint! {
     /// ### What it does
+    /// Checks for `.or(…).unwrap()` calls to Options and Results.
+    ///
+    /// ### Why is this bad?
+    /// You should use `.unwrap_or(…)` instead for clarity.
+    ///
+    /// ### Example
+    /// ```rust
+    /// # let fallback = "fallback";
+    /// // Result
+    /// # type Error = &'static str;
+    /// # let result: Result<&str, Error> = Err("error");
+    /// let value = result.or::<Error>(Ok(fallback)).unwrap();
+    ///
+    /// // Option
+    /// # let option: Option<&str> = None;
+    /// let value = option.or(Some(fallback)).unwrap();
+    /// ```
+    /// Use instead:
+    /// ```rust
+    /// # let fallback = "fallback";
+    /// // Result
+    /// # let result: Result<&str, &str> = Err("error");
+    /// let value = result.unwrap_or(fallback);
+    ///
+    /// // Option
+    /// # let option: Option<&str> = None;
+    /// let value = option.unwrap_or(fallback);
+    /// ```
+    #[clippy::version = "1.61.0"]
+    pub OR_THEN_UNWRAP,
+    complexity,
+    "checks for `.or(…).unwrap()` calls to Options and Results."
+}
+
+declare_clippy_lint! {
+    /// ### What it does
     /// Checks for calls to `.expect(&format!(...))`, `.expect(foo(..))`,
     /// etc., and suggests to use `unwrap_or_else` instead
     ///
@@ -1140,7 +1178,7 @@ declare_clippy_lint! {
     /// ```
     #[clippy::version = "1.61.0"]
     pub ITER_WITH_DRAIN,
-    perf,
+    nursery,
     "replace `.drain(..)` with `.into_iter()`"
 }
 
@@ -2012,6 +2050,35 @@ declare_clippy_lint! {
     "unnecessary calls to `to_owned`-like functions"
 }
 
+declare_clippy_lint! {
+    /// ### What it does
+    /// Checks for use of `.collect::<Vec<String>>().join("")` on iterators.
+    ///
+    /// ### Why is this bad?
+    /// `.collect::<String>()` is more concise and usually more performant
+    ///
+    /// ### Example
+    /// ```rust
+    /// let vector = vec!["hello",  "world"];
+    /// let output = vector.iter().map(|item| item.to_uppercase()).collect::<Vec<String>>().join("");
+    /// println!("{}", output);
+    /// ```
+    /// The correct use would be:
+    /// ```rust
+    /// let vector = vec!["hello",  "world"];
+    /// let output = vector.iter().map(|item| item.to_uppercase()).collect::<String>();
+    /// println!("{}", output);
+    /// ```
+    /// ### Known problems
+    /// While `.collect::<String>()` is more performant in most cases, there are cases where
+    /// using `.collect::<String>()` over `.collect::<Vec<String>>().join("")`
+    /// will prevent loop unrolling and will result in a negative performance impact.
+    #[clippy::version = "1.61.0"]
+    pub UNNECESSARY_JOIN,
+    pedantic,
+    "using `.collect::<Vec<String>>().join(\"\")` on an iterator"
+}
+
 pub struct Methods {
     avoid_breaking_exported_api: bool,
     msrv: Option<RustcVersion>,
@@ -2039,6 +2106,7 @@ impl_lint_pass!(Methods => [
     OPTION_MAP_OR_NONE,
     BIND_INSTEAD_OF_MAP,
     OR_FUN_CALL,
+    OR_THEN_UNWRAP,
     EXPECT_FUN_CALL,
     CHARS_NEXT_CMP,
     CHARS_LAST_CMP,
@@ -2096,6 +2164,7 @@ impl_lint_pass!(Methods => [
     MANUAL_SPLIT_ONCE,
     NEEDLESS_SPLITN,
     UNNECESSARY_TO_OWNED,
+    UNNECESSARY_JOIN,
 ]);
 
 /// Extracts a method call name, args, and `Span` of the method name.
@@ -2377,7 +2446,7 @@ fn check_methods<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>, msrv: Optio
                 flat_map_option::check(cx, expr, arg, span);
             },
             (name @ "flatten", args @ []) => match method_call(recv) {
-                Some(("map", [recv, map_arg], _)) => map_flatten::check(cx, expr, recv, map_arg),
+                Some(("map", [recv, map_arg], map_span)) => map_flatten::check(cx, expr, recv, map_arg, map_span),
                 Some(("cloned", [recv2], _)) => iter_overeager_cloned::check(cx, expr, recv2, name, args),
                 _ => {},
             },
@@ -2391,6 +2460,11 @@ fn check_methods<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>, msrv: Optio
             ("is_file", []) => filetype_is_file::check(cx, expr, recv),
             ("is_none", []) => check_is_some_is_none(cx, expr, recv, false),
             ("is_some", []) => check_is_some_is_none(cx, expr, recv, true),
+            ("join", [join_arg]) => {
+                if let Some(("collect", _, span)) = method_call(recv) {
+                    unnecessary_join::check(cx, expr, recv, join_arg, span);
+                }
+            },
             ("last", args @ []) | ("skip", args @ [_]) => {
                 if let Some((name2, [recv2, args2 @ ..], _span2)) = method_call(recv) {
                     if let ("cloned", []) = (name2, args2) {
@@ -2474,6 +2548,9 @@ fn check_methods<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>, msrv: Optio
                     Some(("get_mut", [recv, get_arg], _)) => {
                         get_unwrap::check(cx, expr, recv, get_arg, true);
                     },
+                    Some(("or", [recv, or_arg], or_span)) => {
+                        or_then_unwrap::check(cx, expr, recv, or_arg, or_span);
+                    },
                     _ => {},
                 }
                 unwrap_used::check(cx, expr, recv);
diff --git a/clippy_lints/src/methods/or_then_unwrap.rs b/clippy_lints/src/methods/or_then_unwrap.rs
new file mode 100644
index 00000000000..be5768c3545
--- /dev/null
+++ b/clippy_lints/src/methods/or_then_unwrap.rs
@@ -0,0 +1,68 @@
+use clippy_utils::source::snippet_with_applicability;
+use clippy_utils::ty::is_type_diagnostic_item;
+use clippy_utils::{diagnostics::span_lint_and_sugg, is_lang_ctor};
+use rustc_errors::Applicability;
+use rustc_hir::{lang_items::LangItem, Expr, ExprKind};
+use rustc_lint::LateContext;
+use rustc_span::{sym, Span};
+
+use super::OR_THEN_UNWRAP;
+
+pub(super) fn check<'tcx>(
+    cx: &LateContext<'tcx>,
+    unwrap_expr: &Expr<'_>,
+    recv: &'tcx Expr<'tcx>,
+    or_arg: &'tcx Expr<'_>,
+    or_span: Span,
+) {
+    let ty = cx.typeck_results().expr_ty(recv); // get type of x (we later check if it's Option or Result)
+    let title;
+    let or_arg_content: Span;
+
+    if is_type_diagnostic_item(cx, ty, sym::Option) {
+        title = "found `.or(Some(…)).unwrap()`";
+        if let Some(content) = get_content_if_ctor_matches(cx, or_arg, LangItem::OptionSome) {
+            or_arg_content = content;
+        } else {
+            return;
+        }
+    } else if is_type_diagnostic_item(cx, ty, sym::Result) {
+        title = "found `.or(Ok(…)).unwrap()`";
+        if let Some(content) = get_content_if_ctor_matches(cx, or_arg, LangItem::ResultOk) {
+            or_arg_content = content;
+        } else {
+            return;
+        }
+    } else {
+        // Someone has implemented a struct with .or(...).unwrap() chaining,
+        // but it's not an Option or a Result, so bail
+        return;
+    }
+
+    let mut applicability = Applicability::MachineApplicable;
+    let suggestion = format!(
+        "unwrap_or({})",
+        snippet_with_applicability(cx, or_arg_content, "..", &mut applicability)
+    );
+
+    span_lint_and_sugg(
+        cx,
+        OR_THEN_UNWRAP,
+        unwrap_expr.span.with_lo(or_span.lo()),
+        title,
+        "try this",
+        suggestion,
+        applicability,
+    );
+}
+
+fn get_content_if_ctor_matches(cx: &LateContext<'_>, expr: &Expr<'_>, item: LangItem) -> Option<Span> {
+    if let ExprKind::Call(some_expr, [arg]) = expr.kind
+        && let ExprKind::Path(qpath) = &some_expr.kind
+        && is_lang_ctor(cx, qpath, item)
+    {
+        Some(arg.span)
+    } else {
+        None
+    }
+}
diff --git a/clippy_lints/src/methods/unnecessary_join.rs b/clippy_lints/src/methods/unnecessary_join.rs
new file mode 100644
index 00000000000..973b8a7e6bf
--- /dev/null
+++ b/clippy_lints/src/methods/unnecessary_join.rs
@@ -0,0 +1,41 @@
+use clippy_utils::{diagnostics::span_lint_and_sugg, ty::is_type_diagnostic_item};
+use rustc_ast::ast::LitKind;
+use rustc_errors::Applicability;
+use rustc_hir::{Expr, ExprKind};
+use rustc_lint::LateContext;
+use rustc_middle::ty::{Ref, Slice};
+use rustc_span::{sym, Span};
+
+use super::UNNECESSARY_JOIN;
+
+pub(super) fn check<'tcx>(
+    cx: &LateContext<'tcx>,
+    expr: &'tcx Expr<'tcx>,
+    join_self_arg: &'tcx Expr<'tcx>,
+    join_arg: &'tcx Expr<'tcx>,
+    span: Span,
+) {
+    let applicability = Applicability::MachineApplicable;
+    let collect_output_adjusted_type = cx.typeck_results().expr_ty_adjusted(join_self_arg);
+    if_chain! {
+        // the turbofish for collect is ::<Vec<String>>
+        if let Ref(_, ref_type, _) = collect_output_adjusted_type.kind();
+        if let Slice(slice) = ref_type.kind();
+        if is_type_diagnostic_item(cx, *slice, sym::String);
+        // the argument for join is ""
+        if let ExprKind::Lit(spanned) = &join_arg.kind;
+        if let LitKind::Str(symbol, _) = spanned.node;
+        if symbol.is_empty();
+        then {
+            span_lint_and_sugg(
+                cx,
+                UNNECESSARY_JOIN,
+                span.with_hi(expr.span.hi()),
+                r#"called `.collect<Vec<String>>().join("")` on an iterator"#,
+                "try using",
+                "collect::<String>()".to_owned(),
+                applicability,
+            );
+        }
+    }
+}
diff --git a/clippy_lints/src/methods/unnecessary_lazy_eval.rs b/clippy_lints/src/methods/unnecessary_lazy_eval.rs
index 1e2765263c8..2369be70812 100644
--- a/clippy_lints/src/methods/unnecessary_lazy_eval.rs
+++ b/clippy_lints/src/methods/unnecessary_lazy_eval.rs
@@ -1,4 +1,4 @@
-use clippy_utils::diagnostics::span_lint_and_sugg;
+use clippy_utils::diagnostics::span_lint_and_then;
 use clippy_utils::source::snippet;
 use clippy_utils::ty::is_type_diagnostic_item;
 use clippy_utils::{eager_or_lazy, usage};
@@ -48,20 +48,19 @@ pub(super) fn check<'tcx>(
                     Applicability::MaybeIncorrect
                 };
 
-                span_lint_and_sugg(
-                    cx,
-                    UNNECESSARY_LAZY_EVALUATIONS,
-                    expr.span,
-                    msg,
-                    &format!("use `{}` instead", simplify_using),
-                    format!(
-                        "{0}.{1}({2})",
-                        snippet(cx, recv.span, ".."),
-                        simplify_using,
-                        snippet(cx, body_expr.span, ".."),
-                    ),
-                    applicability,
-                );
+                // This is a duplicate of what's happening in clippy_lints::methods::method_call,
+                // which isn't ideal, We want to get the method call span,
+                // but prefer to avoid changing the signature of the function itself.
+                if let hir::ExprKind::MethodCall(_, _, span) = expr.kind {
+                    span_lint_and_then(cx, UNNECESSARY_LAZY_EVALUATIONS, expr.span, msg, |diag| {
+                        diag.span_suggestion(
+                            span,
+                            &format!("use `{}(..)` instead", simplify_using),
+                            format!("{}({})", simplify_using, snippet(cx, body_expr.span, "..")),
+                            applicability,
+                        );
+                    });
+                }
             }
         }
     }
diff --git a/clippy_lints/src/methods/unnecessary_to_owned.rs b/clippy_lints/src/methods/unnecessary_to_owned.rs
index 7916fb8e3b4..1555758fc4a 100644
--- a/clippy_lints/src/methods/unnecessary_to_owned.rs
+++ b/clippy_lints/src/methods/unnecessary_to_owned.rs
@@ -2,7 +2,9 @@ use super::implicit_clone::is_clone_like;
 use super::unnecessary_iter_cloned::{self, is_into_iter};
 use clippy_utils::diagnostics::span_lint_and_sugg;
 use clippy_utils::source::snippet_opt;
-use clippy_utils::ty::{get_associated_type, get_iterator_item_ty, implements_trait, is_copy, peel_mid_ty_refs};
+use clippy_utils::ty::{
+    contains_ty, get_associated_type, get_iterator_item_ty, implements_trait, is_copy, peel_mid_ty_refs,
+};
 use clippy_utils::{fn_def_id, get_parent_expr, is_diag_item_method, is_diag_trait_item};
 use rustc_errors::Applicability;
 use rustc_hir::{def_id::DefId, BorrowKind, Expr, ExprKind};
@@ -114,7 +116,12 @@ fn check_addr_of_expr(
                     parent.span,
                     &format!("unnecessary use of `{}`", method_name),
                     "use",
-                    format!("{:&>width$}{}", "", receiver_snippet, width = n_target_refs - n_receiver_refs),
+                    format!(
+                        "{:&>width$}{}",
+                        "",
+                        receiver_snippet,
+                        width = n_target_refs - n_receiver_refs
+                    ),
                     Applicability::MachineApplicable,
                 );
                 return true;
@@ -182,20 +189,10 @@ fn check_into_iter_call_arg(cx: &LateContext<'_>, expr: &Expr<'_>, method_name:
         if let Some(item_ty) = get_iterator_item_ty(cx, parent_ty);
         if let Some(receiver_snippet) = snippet_opt(cx, receiver.span);
         then {
-            if unnecessary_iter_cloned::check_for_loop_iter(
-                cx,
-                parent,
-                method_name,
-                receiver,
-                true,
-            ) {
+            if unnecessary_iter_cloned::check_for_loop_iter(cx, parent, method_name, receiver, true) {
                 return true;
             }
-            let cloned_or_copied = if is_copy(cx, item_ty) {
-                "copied"
-            } else {
-                "cloned"
-            };
+            let cloned_or_copied = if is_copy(cx, item_ty) { "copied" } else { "cloned" };
             // The next suggestion may be incorrect because the removal of the `to_owned`-like
             // function could cause the iterator to hold a reference to a resource that is used
             // mutably. See https://github.com/rust-lang/rust-clippy/issues/8148.
@@ -243,10 +240,11 @@ fn check_other_call_arg<'tcx>(
         if if trait_predicate.def_id() == deref_trait_id {
             if let [projection_predicate] = projection_predicates[..] {
                 let normalized_ty =
-                    cx.tcx.subst_and_normalize_erasing_regions(call_substs, cx.param_env, projection_predicate.term);
+                    cx.tcx
+                        .subst_and_normalize_erasing_regions(call_substs, cx.param_env, projection_predicate.term);
                 implements_trait(cx, receiver_ty, deref_trait_id, &[])
-                    && get_associated_type(cx, receiver_ty, deref_trait_id,
-                    "Target").map_or(false, |ty| ty::Term::Ty(ty) == normalized_ty)
+                    && get_associated_type(cx, receiver_ty, deref_trait_id, "Target")
+                        .map_or(false, |ty| ty::Term::Ty(ty) == normalized_ty)
             } else {
                 false
             }
@@ -254,7 +252,7 @@ fn check_other_call_arg<'tcx>(
             let composed_substs = compose_substs(
                 cx,
                 &trait_predicate.trait_ref.substs.iter().skip(1).collect::<Vec<_>>()[..],
-                call_substs
+                call_substs,
             );
             implements_trait(cx, receiver_ty, as_ref_trait_id, &composed_substs)
         } else {
@@ -264,6 +262,12 @@ fn check_other_call_arg<'tcx>(
         // `Target = T`.
         if n_refs > 0 || is_copy(cx, receiver_ty) || trait_predicate.def_id() != deref_trait_id;
         let n_refs = max(n_refs, if is_copy(cx, receiver_ty) { 0 } else { 1 });
+        // If the trait is `AsRef` and the input type variable `T` occurs in the output type, then
+        // `T` must not be instantiated with a reference
+        // (https://github.com/rust-lang/rust-clippy/issues/8507).
+        if (n_refs == 0 && !receiver_ty.is_ref())
+            || trait_predicate.def_id() != as_ref_trait_id
+            || !contains_ty(fn_sig.output(), input);
         if let Some(receiver_snippet) = snippet_opt(cx, receiver.span);
         then {
             span_lint_and_sugg(
@@ -339,11 +343,7 @@ fn get_input_traits_and_projections<'tcx>(
                 if let Some(arg) = substs.iter().next();
                 if let GenericArgKind::Type(arg_ty) = arg.unpack();
                 if arg_ty == input;
-                then {
-                    true
-                } else {
-                    false
-                }
+                then { true } else { false }
             }
         };
         match predicate.kind().skip_binder() {
diff --git a/clippy_lints/src/missing_doc.rs b/clippy_lints/src/missing_doc.rs
index fc0483a929a..db6aab0671b 100644
--- a/clippy_lints/src/missing_doc.rs
+++ b/clippy_lints/src/missing_doc.rs
@@ -7,7 +7,8 @@
 
 use clippy_utils::attrs::is_doc_hidden;
 use clippy_utils::diagnostics::span_lint;
-use rustc_ast::ast;
+use if_chain::if_chain;
+use rustc_ast::ast::{self, MetaItem, MetaItemKind};
 use rustc_hir as hir;
 use rustc_lint::{LateContext, LateLintPass, LintContext};
 use rustc_middle::ty;
@@ -57,6 +58,20 @@ impl MissingDoc {
         *self.doc_hidden_stack.last().expect("empty doc_hidden_stack")
     }
 
+    fn has_include(meta: Option<MetaItem>) -> bool {
+        if_chain! {
+            if let Some(meta) = meta;
+            if let MetaItemKind::List(list) = meta.kind;
+            if let Some(meta) = list.get(0);
+            if let Some(name) = meta.ident();
+            then {
+                name.name == sym::include
+            } else {
+                false
+            }
+        }
+    }
+
     fn check_missing_docs_attrs(
         &self,
         cx: &LateContext<'_>,
@@ -80,7 +95,9 @@ impl MissingDoc {
             return;
         }
 
-        let has_doc = attrs.iter().any(|a| a.doc_str().is_some());
+        let has_doc = attrs
+            .iter()
+            .any(|a| a.doc_str().is_some() || Self::has_include(a.meta()));
         if !has_doc {
             span_lint(
                 cx,
diff --git a/clippy_lints/src/mutable_debug_assertion.rs b/clippy_lints/src/mutable_debug_assertion.rs
index cd1bc202370..4ba68c8eacd 100644
--- a/clippy_lints/src/mutable_debug_assertion.rs
+++ b/clippy_lints/src/mutable_debug_assertion.rs
@@ -92,10 +92,6 @@ impl<'a, 'tcx> Visitor<'tcx> for MutArgVisitor<'a, 'tcx> {
                 self.found = true;
                 return;
             },
-            ExprKind::If(..) => {
-                self.found = true;
-                return;
-            },
             ExprKind::Path(_) => {
                 if let Some(adj) = self.cx.typeck_results().adjustments().get(expr.hir_id) {
                     if adj
diff --git a/clippy_lints/src/ptr.rs b/clippy_lints/src/ptr.rs
index 9c776437d7f..ba1997e70e1 100644
--- a/clippy_lints/src/ptr.rs
+++ b/clippy_lints/src/ptr.rs
@@ -436,7 +436,7 @@ fn check_fn_args<'cx, 'tcx: 'cx>(
                             DerefTy::Path,
                             None,
                         ),
-                        Some(sym::Cow) => {
+                        Some(sym::Cow) if mutability == Mutability::Not => {
                             let ty_name = name.args
                                 .and_then(|args| {
                                     args.args.iter().find_map(|a| match a {
diff --git a/clippy_lints/src/ranges.rs b/clippy_lints/src/ranges.rs
index be7610f365c..e213c208794 100644
--- a/clippy_lints/src/ranges.rs
+++ b/clippy_lints/src/ranges.rs
@@ -330,7 +330,7 @@ fn check_range_zip_with_len(cx: &LateContext<'_>, path: &PathSegment<'_>, args:
         // `.iter()` and `.len()` called on same `Path`
         if let ExprKind::Path(QPath::Resolved(_, iter_path)) = iter_args[0].kind;
         if let ExprKind::Path(QPath::Resolved(_, len_path)) = len_args[0].kind;
-        if SpanlessEq::new(cx).eq_path_segments(&iter_path.segments, &len_path.segments);
+        if SpanlessEq::new(cx).eq_path_segments(iter_path.segments, len_path.segments);
         then {
             span_lint(cx,
                 RANGE_ZIP_WITH_LEN,
diff --git a/clippy_lints/src/single_component_path_imports.rs b/clippy_lints/src/single_component_path_imports.rs
index 961cdb317e7..66b79513032 100644
--- a/clippy_lints/src/single_component_path_imports.rs
+++ b/clippy_lints/src/single_component_path_imports.rs
@@ -1,5 +1,5 @@
 use clippy_utils::diagnostics::{span_lint_and_help, span_lint_and_sugg};
-use rustc_ast::{ptr::P, Crate, Item, ItemKind, MacroDef, ModKind, UseTreeKind, VisibilityKind};
+use rustc_ast::{ptr::P, Crate, Item, ItemKind, MacroDef, ModKind, UseTreeKind};
 use rustc_errors::Applicability;
 use rustc_lint::{EarlyContext, EarlyLintPass, LintContext};
 use rustc_session::{declare_lint_pass, declare_tool_lint};
@@ -76,14 +76,13 @@ fn check_mod(cx: &EarlyContext<'_>, items: &[P<Item>]) {
         );
     }
 
-    for single_use in &single_use_usages {
-        if !imports_reused_with_self.contains(&single_use.0) {
-            let can_suggest = single_use.2;
+    for (name, span, can_suggest) in single_use_usages {
+        if !imports_reused_with_self.contains(&name) {
             if can_suggest {
                 span_lint_and_sugg(
                     cx,
                     SINGLE_COMPONENT_PATH_IMPORTS,
-                    single_use.1,
+                    span,
                     "this import is redundant",
                     "remove it entirely",
                     String::new(),
@@ -93,7 +92,7 @@ fn check_mod(cx: &EarlyContext<'_>, items: &[P<Item>]) {
                 span_lint_and_help(
                     cx,
                     SINGLE_COMPONENT_PATH_IMPORTS,
-                    single_use.1,
+                    span,
                     "this import is redundant",
                     None,
                     "remove this import",
@@ -124,14 +123,11 @@ fn track_uses(
         ItemKind::Use(use_tree) => {
             let segments = &use_tree.prefix.segments;
 
-            let should_report =
-                |name: &Symbol| !macros.contains(name) || matches!(item.vis.kind, VisibilityKind::Inherited);
-
             // keep track of `use some_module;` usages
             if segments.len() == 1 {
                 if let UseTreeKind::Simple(None, _, _) = use_tree.kind {
                     let name = segments[0].ident.name;
-                    if should_report(&name) {
+                    if !macros.contains(&name) {
                         single_use_usages.push((name, item.span, true));
                     }
                 }
@@ -146,7 +142,7 @@ fn track_uses(
                         if segments.len() == 1 {
                             if let UseTreeKind::Simple(None, _, _) = tree.0.kind {
                                 let name = segments[0].ident.name;
-                                if should_report(&name) {
+                                if !macros.contains(&name) {
                                     single_use_usages.push((name, tree.0.span, false));
                                 }
                             }
diff --git a/clippy_lints/src/transmute/mod.rs b/clippy_lints/src/transmute/mod.rs
index 23cb9d40dfd..02569bd3a47 100644
--- a/clippy_lints/src/transmute/mod.rs
+++ b/clippy_lints/src/transmute/mod.rs
@@ -415,7 +415,8 @@ impl<'tcx> LateLintPass<'tcx> for Transmute {
                 // And see https://github.com/rust-lang/rust/issues/51911 for dereferencing raw pointers.
                 let const_context = in_constant(cx, e.hir_id);
 
-                let from_ty = cx.typeck_results().expr_ty(arg);
+                let from_ty = cx.typeck_results().expr_ty_adjusted(arg);
+                // Adjustments for `to_ty` happen after the call to `transmute`, so don't use them.
                 let to_ty = cx.typeck_results().expr_ty(e);
 
                 // If useless_transmute is triggered, the other lints can be skipped.
diff --git a/clippy_lints/src/transmute/transmute_undefined_repr.rs b/clippy_lints/src/transmute/transmute_undefined_repr.rs
index 6edff224092..f5e21267a89 100644
--- a/clippy_lints/src/transmute/transmute_undefined_repr.rs
+++ b/clippy_lints/src/transmute/transmute_undefined_repr.rs
@@ -3,8 +3,8 @@ use clippy_utils::diagnostics::span_lint_and_then;
 use clippy_utils::ty::is_c_void;
 use rustc_hir::Expr;
 use rustc_lint::LateContext;
-use rustc_middle::ty::subst::Subst;
-use rustc_middle::ty::{self, Ty, TypeAndMut};
+use rustc_middle::ty::subst::{Subst, SubstsRef};
+use rustc_middle::ty::{self, IntTy, Ty, TypeAndMut, UintTy};
 use rustc_span::Span;
 
 #[allow(clippy::too_many_lines)]
@@ -23,7 +23,8 @@ pub(super) fn check<'tcx>(
                 unsized_ty,
                 to_ty: to_sub_ty,
             } => match reduce_ty(cx, to_sub_ty) {
-                ReducedTy::IntArray | ReducedTy::TypeErasure => break,
+                ReducedTy::TypeErasure => break,
+                ReducedTy::UnorderedFields(ty) if is_size_pair(ty) => break,
                 ReducedTy::Ref(to_sub_ty) => {
                     from_ty = unsized_ty;
                     to_ty = to_sub_ty;
@@ -48,7 +49,8 @@ pub(super) fn check<'tcx>(
                 unsized_ty,
                 from_ty: from_sub_ty,
             } => match reduce_ty(cx, from_sub_ty) {
-                ReducedTy::IntArray | ReducedTy::TypeErasure => break,
+                ReducedTy::TypeErasure => break,
+                ReducedTy::UnorderedFields(ty) if is_size_pair(ty) => break,
                 ReducedTy::Ref(from_sub_ty) => {
                     from_ty = from_sub_ty;
                     to_ty = unsized_ty;
@@ -123,9 +125,19 @@ pub(super) fn check<'tcx>(
                 from_ty: from_sub_ty,
                 to_ty: to_sub_ty,
             } => match (reduce_ty(cx, from_sub_ty), reduce_ty(cx, to_sub_ty)) {
-                (ReducedTy::IntArray | ReducedTy::TypeErasure, _)
-                | (_, ReducedTy::IntArray | ReducedTy::TypeErasure) => return false,
+                (ReducedTy::TypeErasure, _) | (_, ReducedTy::TypeErasure) => return false,
                 (ReducedTy::UnorderedFields(from_ty), ReducedTy::UnorderedFields(to_ty)) if from_ty != to_ty => {
+                    let same_adt_did = if let (ty::Adt(from_def, from_subs), ty::Adt(to_def, to_subs))
+                        = (from_ty.kind(), to_ty.kind())
+                        && from_def == to_def
+                    {
+                        if same_except_params(from_subs, to_subs) {
+                            return false;
+                        }
+                        Some(from_def.did())
+                    } else {
+                        None
+                    };
                     span_lint_and_then(
                         cx,
                         TRANSMUTE_UNDEFINED_REPR,
@@ -135,21 +147,17 @@ pub(super) fn check<'tcx>(
                             from_ty_orig, to_ty_orig
                         ),
                         |diag| {
-                            if_chain! {
-                                if let (Some(from_def), Some(to_def)) = (from_ty.ty_adt_def(), to_ty.ty_adt_def());
-                                if from_def == to_def;
-                                then {
-                                    diag.note(&format!(
-                                        "two instances of the same generic type (`{}`) may have different layouts",
-                                        cx.tcx.item_name(from_def.did())
-                                    ));
-                                } else {
-                                    if from_ty_orig.peel_refs() != from_ty {
-                                        diag.note(&format!("the contained type `{}` has an undefined layout", from_ty));
-                                    }
-                                    if to_ty_orig.peel_refs() != to_ty {
-                                        diag.note(&format!("the contained type `{}` has an undefined layout", to_ty));
-                                    }
+                            if let Some(same_adt_did) = same_adt_did {
+                                diag.note(&format!(
+                                    "two instances of the same generic type (`{}`) may have different layouts",
+                                    cx.tcx.item_name(same_adt_did)
+                                ));
+                            } else {
+                                if from_ty_orig.peel_refs() != from_ty {
+                                    diag.note(&format!("the contained type `{}` has an undefined layout", from_ty));
+                                }
+                                if to_ty_orig.peel_refs() != to_ty {
+                                    diag.note(&format!("the contained type `{}` has an undefined layout", to_ty));
                                 }
                             }
                         },
@@ -196,10 +204,13 @@ pub(super) fn check<'tcx>(
                     continue;
                 },
                 (
-                    ReducedTy::OrderedFields(_) | ReducedTy::Ref(_) | ReducedTy::Other(_),
-                    ReducedTy::OrderedFields(_) | ReducedTy::Ref(_) | ReducedTy::Other(_),
+                    ReducedTy::OrderedFields(_) | ReducedTy::Ref(_) | ReducedTy::Other(_) | ReducedTy::Param,
+                    ReducedTy::OrderedFields(_) | ReducedTy::Ref(_) | ReducedTy::Other(_) | ReducedTy::Param,
                 )
-                | (ReducedTy::UnorderedFields(_), ReducedTy::UnorderedFields(_)) => break,
+                | (
+                    ReducedTy::UnorderedFields(_) | ReducedTy::Param,
+                    ReducedTy::UnorderedFields(_) | ReducedTy::Param,
+                ) => break,
             },
         }
     }
@@ -263,9 +274,8 @@ enum ReducedTy<'tcx> {
     UnorderedFields(Ty<'tcx>),
     /// The type is a reference to the contained type.
     Ref(Ty<'tcx>),
-    /// The type is an array of a primitive integer type. These can be used as storage for a value
-    /// of another type.
-    IntArray,
+    /// The type is a generic parameter.
+    Param,
     /// Any other type.
     Other(Ty<'tcx>),
 }
@@ -275,17 +285,18 @@ fn reduce_ty<'tcx>(cx: &LateContext<'tcx>, mut ty: Ty<'tcx>) -> ReducedTy<'tcx>
     loop {
         ty = cx.tcx.try_normalize_erasing_regions(cx.param_env, ty).unwrap_or(ty);
         return match *ty.kind() {
-            ty::Array(sub_ty, _) if matches!(sub_ty.kind(), ty::Int(_) | ty::Uint(_)) => ReducedTy::IntArray,
+            ty::Array(sub_ty, _) if matches!(sub_ty.kind(), ty::Int(_) | ty::Uint(_)) => ReducedTy::TypeErasure,
             ty::Array(sub_ty, _) | ty::Slice(sub_ty) => {
                 ty = sub_ty;
                 continue;
             },
             ty::Tuple(args) if args.is_empty() => ReducedTy::TypeErasure,
             ty::Tuple(args) => {
-                let Some(sized_ty) = args.iter().find(|&ty| !is_zero_sized_ty(cx, ty)) else {
+                let mut iter = args.iter();
+                let Some(sized_ty) = iter.find(|&ty| !is_zero_sized_ty(cx, ty)) else {
                     return ReducedTy::OrderedFields(ty);
                 };
-                if args.iter().all(|ty| is_zero_sized_ty(cx, ty)) {
+                if iter.all(|ty| is_zero_sized_ty(cx, ty)) {
                     ty = sized_ty;
                     continue;
                 }
@@ -313,9 +324,12 @@ fn reduce_ty<'tcx>(cx: &LateContext<'tcx>, mut ty: Ty<'tcx>) -> ReducedTy<'tcx>
             ty::Adt(def, _) if def.is_enum() && (def.variants().is_empty() || is_c_void(cx, ty)) => {
                 ReducedTy::TypeErasure
             },
+            // TODO: Check if the conversion to or from at least one of a union's fields is valid.
+            ty::Adt(def, _) if def.is_union() => ReducedTy::TypeErasure,
             ty::Foreign(_) => ReducedTy::TypeErasure,
             ty::Ref(_, ty, _) => ReducedTy::Ref(ty),
             ty::RawPtr(ty) => ReducedTy::Ref(ty.ty),
+            ty::Param(_) => ReducedTy::Param,
             _ => ReducedTy::Other(ty),
         };
     }
@@ -332,3 +346,27 @@ fn is_zero_sized_ty<'tcx>(cx: &LateContext<'tcx>, ty: Ty<'tcx>) -> bool {
         }
     }
 }
+
+fn is_size_pair(ty: Ty<'_>) -> bool {
+    if let ty::Tuple(tys) = *ty.kind()
+        && let [ty1, ty2] = &**tys
+    {
+        matches!(ty1.kind(), ty::Int(IntTy::Isize) | ty::Uint(UintTy::Usize))
+            && matches!(ty2.kind(), ty::Int(IntTy::Isize) | ty::Uint(UintTy::Usize))
+    } else {
+        false
+    }
+}
+
+fn same_except_params(subs1: SubstsRef<'_>, subs2: SubstsRef<'_>) -> bool {
+    // TODO: check const parameters as well. Currently this will consider `Array<5>` the same as
+    // `Array<6>`
+    for (ty1, ty2) in subs1.types().zip(subs2.types()).filter(|(ty1, ty2)| ty1 != ty2) {
+        match (ty1.kind(), ty2.kind()) {
+            (ty::Param(_), _) | (_, ty::Param(_)) => (),
+            (ty::Adt(adt1, subs1), ty::Adt(adt2, subs2)) if adt1 == adt2 && same_except_params(subs1, subs2) => (),
+            _ => return false,
+        }
+    }
+    true
+}
diff --git a/clippy_lints/src/try_err.rs b/clippy_lints/src/try_err.rs
index 80d6f3c6336..e108f7be12e 100644
--- a/clippy_lints/src/try_err.rs
+++ b/clippy_lints/src/try_err.rs
@@ -43,7 +43,7 @@ declare_clippy_lint! {
     /// ```
     #[clippy::version = "1.38.0"]
     pub TRY_ERR,
-    style,
+    restriction,
     "return errors explicitly rather than hiding them behind a `?`"
 }
 
diff --git a/clippy_lints/src/utils/internal_lints/metadata_collector.rs b/clippy_lints/src/utils/internal_lints/metadata_collector.rs
index a617422bbeb..b3fad6ce7b6 100644
--- a/clippy_lints/src/utils/internal_lints/metadata_collector.rs
+++ b/clippy_lints/src/utils/internal_lints/metadata_collector.rs
@@ -85,7 +85,7 @@ macro_rules! CONFIGURATION_VALUE_TEMPLATE {
     };
 }
 
-const LINT_EMISSION_FUNCTIONS: [&[&str]; 7] = [
+const LINT_EMISSION_FUNCTIONS: [&[&str]; 8] = [
     &["clippy_utils", "diagnostics", "span_lint"],
     &["clippy_utils", "diagnostics", "span_lint_and_help"],
     &["clippy_utils", "diagnostics", "span_lint_and_note"],
@@ -93,6 +93,7 @@ const LINT_EMISSION_FUNCTIONS: [&[&str]; 7] = [
     &["clippy_utils", "diagnostics", "span_lint_and_sugg"],
     &["clippy_utils", "diagnostics", "span_lint_and_then"],
     &["clippy_utils", "diagnostics", "span_lint_hir_and_then"],
+    &["clippy_utils", "diagnostics", "span_lint_and_sugg_for_edges"],
 ];
 const SUGGESTION_DIAGNOSTIC_BUILDER_METHODS: [(&str, bool); 9] = [
     ("span_suggestion", false),
diff --git a/clippy_lints/src/write.rs b/clippy_lints/src/write.rs
index 532bd810a2e..f3d818cc348 100644
--- a/clippy_lints/src/write.rs
+++ b/clippy_lints/src/write.rs
@@ -581,14 +581,19 @@ impl Write {
             };
 
             let replacement: String = match lit.token.kind {
-                LitKind::Integer | LitKind::Float | LitKind::Err => continue,
                 LitKind::StrRaw(_) | LitKind::ByteStrRaw(_) if matches!(fmtstr.style, StrStyle::Raw(_)) => {
                     lit.token.symbol.as_str().replace('{', "{{").replace('}', "}}")
                 },
                 LitKind::Str | LitKind::ByteStr if matches!(fmtstr.style, StrStyle::Cooked) => {
                     lit.token.symbol.as_str().replace('{', "{{").replace('}', "}}")
                 },
-                LitKind::StrRaw(_) | LitKind::Str | LitKind::ByteStrRaw(_) | LitKind::ByteStr => continue,
+                LitKind::StrRaw(_)
+                | LitKind::Str
+                | LitKind::ByteStrRaw(_)
+                | LitKind::ByteStr
+                | LitKind::Integer
+                | LitKind::Float
+                | LitKind::Err => continue,
                 LitKind::Byte | LitKind::Char => match lit.token.symbol.as_str() {
                     "\"" if matches!(fmtstr.style, StrStyle::Cooked) => "\\\"",
                     "\"" if matches!(fmtstr.style, StrStyle::Raw(0)) => continue,
diff --git a/clippy_utils/src/diagnostics.rs b/clippy_utils/src/diagnostics.rs
index a927788e6a4..625a53899df 100644
--- a/clippy_utils/src/diagnostics.rs
+++ b/clippy_utils/src/diagnostics.rs
@@ -8,7 +8,7 @@
 //! Thank you!
 //! ~The `INTERNAL_METADATA_COLLECTOR` lint
 
-use rustc_errors::{Applicability, Diagnostic};
+use rustc_errors::{emitter::MAX_SUGGESTION_HIGHLIGHT_LINES, Applicability, Diagnostic};
 use rustc_hir::HirId;
 use rustc_lint::{LateContext, Lint, LintContext};
 use rustc_span::source_map::{MultiSpan, Span};
@@ -213,6 +213,90 @@ pub fn span_lint_and_sugg<'a, T: LintContext>(
     });
 }
 
+/// Like [`span_lint_and_sugg`] with a focus on the edges. The output will either
+/// emit single span or multispan suggestion depending on the number of its lines.
+///
+/// If the given suggestion string has more lines than the maximum display length defined by
+/// [`MAX_SUGGESTION_HIGHLIGHT_LINES`][`rustc_errors::emitter::MAX_SUGGESTION_HIGHLIGHT_LINES`],
+/// this function will split the suggestion and span to showcase the change for the top and
+/// bottom edge of the code. For normal suggestions, in one display window, the help message
+/// will be combined with a colon.
+///
+/// Multipart suggestions like the one being created here currently cannot be
+/// applied by rustfix (See [rustfix#141](https://github.com/rust-lang/rustfix/issues/141)).
+/// Testing rustfix with this lint emission function might require a file with
+/// suggestions that can be fixed and those that can't. See
+/// [clippy#8520](https://github.com/rust-lang/rust-clippy/pull/8520/files) for
+/// an example and of this.
+///
+/// # Example for a long suggestion
+///
+/// ```text
+/// error: called `map(..).flatten()` on `Option`
+///   --> $DIR/map_flatten.rs:8:10
+///    |
+/// LL |           .map(|x| {
+///    |  __________^
+/// LL | |             if x <= 5 {
+/// LL | |                 Some(x)
+/// LL | |             } else {
+/// ...  |
+/// LL | |         })
+/// LL | |         .flatten();
+///    | |__________________^
+///    |
+///   = note: `-D clippy::map-flatten` implied by `-D warnings`
+/// help: try replacing `map` with `and_then`
+///    |
+/// LL ~         .and_then(|x| {
+/// LL +             if x <= 5 {
+/// LL +                 Some(x)
+///    |
+/// help: and remove the `.flatten()`
+///    |
+/// LL +                 None
+/// LL +             }
+/// LL ~         });
+///    |
+/// ```
+pub fn span_lint_and_sugg_for_edges(
+    cx: &LateContext<'_>,
+    lint: &'static Lint,
+    sp: Span,
+    msg: &str,
+    helps: &[&str; 2],
+    sugg: String,
+    applicability: Applicability,
+) {
+    span_lint_and_then(cx, lint, sp, msg, |diag| {
+        let sugg_lines_count = sugg.lines().count();
+        if sugg_lines_count > MAX_SUGGESTION_HIGHLIGHT_LINES {
+            let sm = cx.sess().source_map();
+            if let (Ok(line_upper), Ok(line_bottom)) = (sm.lookup_line(sp.lo()), sm.lookup_line(sp.hi())) {
+                let split_idx = MAX_SUGGESTION_HIGHLIGHT_LINES / 2;
+                let span_upper = sm.span_until_char(sp.with_hi(line_upper.sf.lines[line_upper.line + split_idx]), '\n');
+                let span_bottom = sp.with_lo(line_bottom.sf.lines[line_bottom.line - split_idx]);
+
+                let sugg_lines_vec = sugg.lines().collect::<Vec<&str>>();
+                let sugg_upper = sugg_lines_vec[..split_idx].join("\n");
+                let sugg_bottom = sugg_lines_vec[sugg_lines_count - split_idx..].join("\n");
+
+                diag.span_suggestion(span_upper, helps[0], sugg_upper, applicability);
+                diag.span_suggestion(span_bottom, helps[1], sugg_bottom, applicability);
+
+                return;
+            }
+        }
+        diag.span_suggestion_with_style(
+            sp,
+            &helps.join(", "),
+            sugg,
+            applicability,
+            rustc_errors::SuggestionStyle::ShowAlways,
+        );
+    });
+}
+
 /// Create a suggestion made from several `span → replacement`.
 ///
 /// Note: in the JSON format (used by `compiletest_rs`), the help message will
diff --git a/clippy_utils/src/sugg.rs b/clippy_utils/src/sugg.rs
index 63c442e7008..1fc9979f3dd 100644
--- a/clippy_utils/src/sugg.rs
+++ b/clippy_utils/src/sugg.rs
@@ -808,7 +808,7 @@ pub fn deref_closure_args<'tcx>(cx: &LateContext<'_>, closure: &'tcx hir::Expr<'
             closure_arg_is_type_annotated_double_ref,
             next_pos: closure.span.lo(),
             suggestion_start: String::new(),
-            applicability: Applicability::MaybeIncorrect,
+            applicability: Applicability::MachineApplicable,
         };
 
         let fn_def_id = cx.tcx.hir().local_def_id(closure.hir_id);
diff --git a/tests/ui/cast_enum_constructor.rs b/tests/ui/cast_enum_constructor.rs
new file mode 100644
index 00000000000..0193454ad14
--- /dev/null
+++ b/tests/ui/cast_enum_constructor.rs
@@ -0,0 +1,17 @@
+#![warn(clippy::cast_enum_constructor)]
+#![allow(clippy::fn_to_numeric_cast)]
+
+fn main() {
+    enum Foo {
+        Y(u32),
+    }
+
+    enum Bar {
+        X,
+    }
+
+    let _ = Foo::Y as usize;
+    let _ = Foo::Y as isize;
+    let _ = Foo::Y as fn(u32) -> Foo;
+    let _ = Bar::X as usize;
+}
diff --git a/tests/ui/cast_enum_constructor.stderr b/tests/ui/cast_enum_constructor.stderr
new file mode 100644
index 00000000000..710909dd26f
--- /dev/null
+++ b/tests/ui/cast_enum_constructor.stderr
@@ -0,0 +1,16 @@
+error: cast of an enum tuple constructor to an integer
+  --> $DIR/cast_enum_constructor.rs:13:13
+   |
+LL |     let _ = Foo::Y as usize;
+   |             ^^^^^^^^^^^^^^^
+   |
+   = note: `-D clippy::cast-enum-constructor` implied by `-D warnings`
+
+error: cast of an enum tuple constructor to an integer
+  --> $DIR/cast_enum_constructor.rs:14:13
+   |
+LL |     let _ = Foo::Y as isize;
+   |             ^^^^^^^^^^^^^^^
+
+error: aborting due to 2 previous errors
+
diff --git a/tests/ui/map_flatten.rs b/tests/ui/map_flatten.rs
index aa1f76e335a..7d47ee09dc1 100644
--- a/tests/ui/map_flatten.rs
+++ b/tests/ui/map_flatten.rs
@@ -1,31 +1,55 @@
-// run-rustfix
-
-#![warn(clippy::all, clippy::pedantic)]
-#![allow(clippy::let_underscore_drop)]
-#![allow(clippy::missing_docs_in_private_items)]
-#![allow(clippy::map_identity)]
-#![allow(clippy::redundant_closure)]
-#![allow(clippy::unnecessary_wraps)]
+#![warn(clippy::map_flatten)]
 #![feature(result_flattening)]
 
-fn main() {
-    // mapping to Option on Iterator
-    fn option_id(x: i8) -> Option<i8> {
-        Some(x)
-    }
-    let option_id_ref: fn(i8) -> Option<i8> = option_id;
-    let option_id_closure = |x| Some(x);
-    let _: Vec<_> = vec![5_i8; 6].into_iter().map(option_id).flatten().collect();
-    let _: Vec<_> = vec![5_i8; 6].into_iter().map(option_id_ref).flatten().collect();
-    let _: Vec<_> = vec![5_i8; 6].into_iter().map(option_id_closure).flatten().collect();
-    let _: Vec<_> = vec![5_i8; 6].into_iter().map(|x| x.checked_add(1)).flatten().collect();
+// issue #8506, multi-line
+#[rustfmt::skip]
+fn long_span() {
+    let _: Option<i32> = Some(1)
+        .map(|x| {
+            if x <= 5 {
+                Some(x)
+            } else {
+                None
+            }
+        })
+        .flatten();
 
-    // mapping to Iterator on Iterator
-    let _: Vec<_> = vec![5_i8; 6].into_iter().map(|x| 0..x).flatten().collect();
+    let _: Result<i32, i32> = Ok(1)
+        .map(|x| {
+            if x == 1 {
+                Ok(x)
+            } else {
+                Err(0)
+            }
+        })
+        .flatten();
 
-    // mapping to Option on Option
-    let _: Option<_> = (Some(Some(1))).map(|x| x).flatten();
+    let result: Result<i32, i32> = Ok(2);
+    fn do_something() { }
+    let _: Result<i32, i32> = result
+        .map(|res| {
+            if res > 0 {
+                do_something();
+                Ok(res)
+            } else {
+                Err(0)
+            }
+        })
+        .flatten();
+        
+    let _: Vec<_> = vec![5_i8; 6]
+        .into_iter()
+        .map(|some_value| {
+            if some_value > 3 {
+                Some(some_value)
+            } else {
+                None
+            }
+        })
+        .flatten()
+        .collect();
+}
 
-    // mapping to Result on Result
-    let _: Result<_, &str> = (Ok(Ok(1))).map(|x| x).flatten();
+fn main() {
+    long_span();
 }
diff --git a/tests/ui/map_flatten.stderr b/tests/ui/map_flatten.stderr
index bcd2047e6fa..c9c60df838f 100644
--- a/tests/ui/map_flatten.stderr
+++ b/tests/ui/map_flatten.stderr
@@ -1,46 +1,107 @@
-error: called `map(..).flatten()` on an `Iterator`
-  --> $DIR/map_flatten.rs:18:46
+error: called `map(..).flatten()` on `Option`
+  --> $DIR/map_flatten.rs:8:10
    |
-LL |     let _: Vec<_> = vec![5_i8; 6].into_iter().map(option_id).flatten().collect();
-   |                                              ^^^^^^^^^^^^^^^^^^^^^^^^^ help: try using `filter_map` instead: `.filter_map(option_id)`
+LL |           .map(|x| {
+   |  __________^
+LL | |             if x <= 5 {
+LL | |                 Some(x)
+LL | |             } else {
+...  |
+LL | |         })
+LL | |         .flatten();
+   | |__________________^
    |
    = note: `-D clippy::map-flatten` implied by `-D warnings`
-
-error: called `map(..).flatten()` on an `Iterator`
-  --> $DIR/map_flatten.rs:19:46
+help: try replacing `map` with `and_then`
    |
-LL |     let _: Vec<_> = vec![5_i8; 6].into_iter().map(option_id_ref).flatten().collect();
-   |                                              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try using `filter_map` instead: `.filter_map(option_id_ref)`
-
-error: called `map(..).flatten()` on an `Iterator`
-  --> $DIR/map_flatten.rs:20:46
+LL ~         .and_then(|x| {
+LL +             if x <= 5 {
+LL +                 Some(x)
    |
-LL |     let _: Vec<_> = vec![5_i8; 6].into_iter().map(option_id_closure).flatten().collect();
-   |                                              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try using `filter_map` instead: `.filter_map(option_id_closure)`
-
-error: called `map(..).flatten()` on an `Iterator`
-  --> $DIR/map_flatten.rs:21:46
+help: and remove the `.flatten()`
+   |
+LL +                 None
+LL +             }
+LL ~         });
    |
-LL |     let _: Vec<_> = vec![5_i8; 6].into_iter().map(|x| x.checked_add(1)).flatten().collect();
-   |                                              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try using `filter_map` instead: `.filter_map(|x| x.checked_add(1))`
 
-error: called `map(..).flatten()` on an `Iterator`
-  --> $DIR/map_flatten.rs:24:46
+error: called `map(..).flatten()` on `Result`
+  --> $DIR/map_flatten.rs:18:10
+   |
+LL |           .map(|x| {
+   |  __________^
+LL | |             if x == 1 {
+LL | |                 Ok(x)
+LL | |             } else {
+...  |
+LL | |         })
+LL | |         .flatten();
+   | |__________________^
+   |
+help: try replacing `map` with `and_then`
+   |
+LL ~         .and_then(|x| {
+LL +             if x == 1 {
+LL +                 Ok(x)
+   |
+help: and remove the `.flatten()`
+   |
+LL +                 Err(0)
+LL +             }
+LL ~         });
    |
-LL |     let _: Vec<_> = vec![5_i8; 6].into_iter().map(|x| 0..x).flatten().collect();
-   |                                              ^^^^^^^^^^^^^^^^^^^^^^^^ help: try using `flat_map` instead: `.flat_map(|x| 0..x)`
 
-error: called `map(..).flatten()` on an `Option`
-  --> $DIR/map_flatten.rs:27:39
+error: called `map(..).flatten()` on `Result`
+  --> $DIR/map_flatten.rs:30:10
+   |
+LL |           .map(|res| {
+   |  __________^
+LL | |             if res > 0 {
+LL | |                 do_something();
+LL | |                 Ok(res)
+...  |
+LL | |         })
+LL | |         .flatten();
+   | |__________________^
+   |
+help: try replacing `map` with `and_then`
+   |
+LL ~         .and_then(|res| {
+LL +             if res > 0 {
+LL +                 do_something();
+   |
+help: and remove the `.flatten()`
+   |
+LL +                 Err(0)
+LL +             }
+LL ~         });
    |
-LL |     let _: Option<_> = (Some(Some(1))).map(|x| x).flatten();
-   |                                       ^^^^^^^^^^^^^^^^^^^^^ help: try using `and_then` instead: `.and_then(|x| x)`
 
-error: called `map(..).flatten()` on an `Result`
-  --> $DIR/map_flatten.rs:30:41
+error: called `map(..).flatten()` on `Iterator`
+  --> $DIR/map_flatten.rs:42:10
+   |
+LL |           .map(|some_value| {
+   |  __________^
+LL | |             if some_value > 3 {
+LL | |                 Some(some_value)
+LL | |             } else {
+...  |
+LL | |         })
+LL | |         .flatten()
+   | |__________________^
+   |
+help: try replacing `map` with `filter_map`
+   |
+LL ~         .filter_map(|some_value| {
+LL +             if some_value > 3 {
+LL +                 Some(some_value)
+   |
+help: and remove the `.flatten()`
+   |
+LL +                 None
+LL +             }
+LL +         })
    |
-LL |     let _: Result<_, &str> = (Ok(Ok(1))).map(|x| x).flatten();
-   |                                         ^^^^^^^^^^^^^^^^^^^^^ help: try using `and_then` instead: `.and_then(|x| x)`
 
-error: aborting due to 7 previous errors
+error: aborting due to 4 previous errors
 
diff --git a/tests/ui/map_flatten.fixed b/tests/ui/map_flatten_fixable.fixed
index fec3a95edd6..fec3a95edd6 100644
--- a/tests/ui/map_flatten.fixed
+++ b/tests/ui/map_flatten_fixable.fixed
diff --git a/tests/ui/map_flatten_fixable.rs b/tests/ui/map_flatten_fixable.rs
new file mode 100644
index 00000000000..aa1f76e335a
--- /dev/null
+++ b/tests/ui/map_flatten_fixable.rs
@@ -0,0 +1,31 @@
+// run-rustfix
+
+#![warn(clippy::all, clippy::pedantic)]
+#![allow(clippy::let_underscore_drop)]
+#![allow(clippy::missing_docs_in_private_items)]
+#![allow(clippy::map_identity)]
+#![allow(clippy::redundant_closure)]
+#![allow(clippy::unnecessary_wraps)]
+#![feature(result_flattening)]
+
+fn main() {
+    // mapping to Option on Iterator
+    fn option_id(x: i8) -> Option<i8> {
+        Some(x)
+    }
+    let option_id_ref: fn(i8) -> Option<i8> = option_id;
+    let option_id_closure = |x| Some(x);
+    let _: Vec<_> = vec![5_i8; 6].into_iter().map(option_id).flatten().collect();
+    let _: Vec<_> = vec![5_i8; 6].into_iter().map(option_id_ref).flatten().collect();
+    let _: Vec<_> = vec![5_i8; 6].into_iter().map(option_id_closure).flatten().collect();
+    let _: Vec<_> = vec![5_i8; 6].into_iter().map(|x| x.checked_add(1)).flatten().collect();
+
+    // mapping to Iterator on Iterator
+    let _: Vec<_> = vec![5_i8; 6].into_iter().map(|x| 0..x).flatten().collect();
+
+    // mapping to Option on Option
+    let _: Option<_> = (Some(Some(1))).map(|x| x).flatten();
+
+    // mapping to Result on Result
+    let _: Result<_, &str> = (Ok(Ok(1))).map(|x| x).flatten();
+}
diff --git a/tests/ui/map_flatten_fixable.stderr b/tests/ui/map_flatten_fixable.stderr
new file mode 100644
index 00000000000..c91c73846b6
--- /dev/null
+++ b/tests/ui/map_flatten_fixable.stderr
@@ -0,0 +1,80 @@
+error: called `map(..).flatten()` on `Iterator`
+  --> $DIR/map_flatten_fixable.rs:18:47
+   |
+LL |     let _: Vec<_> = vec![5_i8; 6].into_iter().map(option_id).flatten().collect();
+   |                                               ^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: `-D clippy::map-flatten` implied by `-D warnings`
+help: try replacing `map` with `filter_map`, and remove the `.flatten()`
+   |
+LL |     let _: Vec<_> = vec![5_i8; 6].into_iter().filter_map(option_id).collect();
+   |                                               ~~~~~~~~~~~~~~~~~~~~~
+
+error: called `map(..).flatten()` on `Iterator`
+  --> $DIR/map_flatten_fixable.rs:19:47
+   |
+LL |     let _: Vec<_> = vec![5_i8; 6].into_iter().map(option_id_ref).flatten().collect();
+   |                                               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+help: try replacing `map` with `filter_map`, and remove the `.flatten()`
+   |
+LL |     let _: Vec<_> = vec![5_i8; 6].into_iter().filter_map(option_id_ref).collect();
+   |                                               ~~~~~~~~~~~~~~~~~~~~~~~~~
+
+error: called `map(..).flatten()` on `Iterator`
+  --> $DIR/map_flatten_fixable.rs:20:47
+   |
+LL |     let _: Vec<_> = vec![5_i8; 6].into_iter().map(option_id_closure).flatten().collect();
+   |                                               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+help: try replacing `map` with `filter_map`, and remove the `.flatten()`
+   |
+LL |     let _: Vec<_> = vec![5_i8; 6].into_iter().filter_map(option_id_closure).collect();
+   |                                               ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+error: called `map(..).flatten()` on `Iterator`
+  --> $DIR/map_flatten_fixable.rs:21:47
+   |
+LL |     let _: Vec<_> = vec![5_i8; 6].into_iter().map(|x| x.checked_add(1)).flatten().collect();
+   |                                               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+help: try replacing `map` with `filter_map`, and remove the `.flatten()`
+   |
+LL |     let _: Vec<_> = vec![5_i8; 6].into_iter().filter_map(|x| x.checked_add(1)).collect();
+   |                                               ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+error: called `map(..).flatten()` on `Iterator`
+  --> $DIR/map_flatten_fixable.rs:24:47
+   |
+LL |     let _: Vec<_> = vec![5_i8; 6].into_iter().map(|x| 0..x).flatten().collect();
+   |                                               ^^^^^^^^^^^^^^^^^^^^^^^
+   |
+help: try replacing `map` with `flat_map`, and remove the `.flatten()`
+   |
+LL |     let _: Vec<_> = vec![5_i8; 6].into_iter().flat_map(|x| 0..x).collect();
+   |                                               ~~~~~~~~~~~~~~~~~~
+
+error: called `map(..).flatten()` on `Option`
+  --> $DIR/map_flatten_fixable.rs:27:40
+   |
+LL |     let _: Option<_> = (Some(Some(1))).map(|x| x).flatten();
+   |                                        ^^^^^^^^^^^^^^^^^^^^
+   |
+help: try replacing `map` with `and_then`, and remove the `.flatten()`
+   |
+LL |     let _: Option<_> = (Some(Some(1))).and_then(|x| x);
+   |                                        ~~~~~~~~~~~~~~~
+
+error: called `map(..).flatten()` on `Result`
+  --> $DIR/map_flatten_fixable.rs:30:42
+   |
+LL |     let _: Result<_, &str> = (Ok(Ok(1))).map(|x| x).flatten();
+   |                                          ^^^^^^^^^^^^^^^^^^^^
+   |
+help: try replacing `map` with `and_then`, and remove the `.flatten()`
+   |
+LL |     let _: Result<_, &str> = (Ok(Ok(1))).and_then(|x| x);
+   |                                          ~~~~~~~~~~~~~~~
+
+error: aborting due to 7 previous errors
+
diff --git a/tests/ui/match_same_arms.stderr b/tests/ui/match_same_arms.stderr
index 7752a8a6ff2..b6d04263b37 100644
--- a/tests/ui/match_same_arms.stderr
+++ b/tests/ui/match_same_arms.stderr
@@ -1,128 +1,121 @@
-error: this `match` has identical arm bodies
-  --> $DIR/match_same_arms.rs:13:14
+error: this match arm has an identical body to the `_` wildcard arm
+  --> $DIR/match_same_arms.rs:11:9
    |
-LL |         _ => 0, //~ ERROR match arms have same body
-   |              ^
+LL |         Abc::A => 0,
+   |         ^^^^^^^^^^^ help: try removing the arm
    |
    = note: `-D clippy::match-same-arms` implied by `-D warnings`
-note: same as this
-  --> $DIR/match_same_arms.rs:11:19
+   = help: or try changing either arm body
+note: `_` wildcard arm here
+  --> $DIR/match_same_arms.rs:13:9
    |
-LL |         Abc::A => 0,
-   |                   ^
-note: `Abc::A` has the same arm body as the `_` wildcard, consider removing it
-  --> $DIR/match_same_arms.rs:11:19
-   |
-LL |         Abc::A => 0,
-   |                   ^
+LL |         _ => 0, //~ ERROR match arms have same body
+   |         ^^^^^^
 
-error: this `match` has identical arm bodies
-  --> $DIR/match_same_arms.rs:18:20
-   |
-LL |         (.., 3) => 42, //~ ERROR match arms have same body
-   |                    ^^
-   |
-note: same as this
-  --> $DIR/match_same_arms.rs:17:23
-   |
-LL |         (1, .., 3) => 42,
-   |                       ^^
-help: consider refactoring into `(1, .., 3) | (.., 3)`
+error: this match arm has an identical body to another arm
   --> $DIR/match_same_arms.rs:17:9
    |
 LL |         (1, .., 3) => 42,
-   |         ^^^^^^^^^^
-   = help: ...or consider changing the match arm bodies
+   |         ----------^^^^^^
+   |         |
+   |         help: try merging the arm patterns: `(1, .., 3) | (.., 3)`
+   |
+   = help: or try changing either arm body
+note: other arm here
+  --> $DIR/match_same_arms.rs:18:9
+   |
+LL |         (.., 3) => 42, //~ ERROR match arms have same body
+   |         ^^^^^^^^^^^^^
 
-error: this `match` has identical arm bodies
-  --> $DIR/match_same_arms.rs:24:15
+error: this match arm has an identical body to another arm
+  --> $DIR/match_same_arms.rs:24:9
    |
 LL |         51 => 1, //~ ERROR match arms have same body
-   |               ^
+   |         --^^^^^
+   |         |
+   |         help: try merging the arm patterns: `51 | 42`
    |
-note: same as this
-  --> $DIR/match_same_arms.rs:23:15
-   |
-LL |         42 => 1,
-   |               ^
-help: consider refactoring into `42 | 51`
+   = help: or try changing either arm body
+note: other arm here
   --> $DIR/match_same_arms.rs:23:9
    |
 LL |         42 => 1,
-   |         ^^
-   = help: ...or consider changing the match arm bodies
+   |         ^^^^^^^
 
-error: this `match` has identical arm bodies
-  --> $DIR/match_same_arms.rs:26:15
-   |
-LL |         52 => 2, //~ ERROR match arms have same body
-   |               ^
-   |
-note: same as this
-  --> $DIR/match_same_arms.rs:25:15
-   |
-LL |         41 => 2,
-   |               ^
-help: consider refactoring into `41 | 52`
+error: this match arm has an identical body to another arm
   --> $DIR/match_same_arms.rs:25:9
    |
 LL |         41 => 2,
-   |         ^^
-   = help: ...or consider changing the match arm bodies
+   |         --^^^^^
+   |         |
+   |         help: try merging the arm patterns: `41 | 52`
+   |
+   = help: or try changing either arm body
+note: other arm here
+  --> $DIR/match_same_arms.rs:26:9
+   |
+LL |         52 => 2, //~ ERROR match arms have same body
+   |         ^^^^^^^
 
-error: this `match` has identical arm bodies
-  --> $DIR/match_same_arms.rs:32:14
+error: this match arm has an identical body to another arm
+  --> $DIR/match_same_arms.rs:32:9
    |
 LL |         2 => 2, //~ ERROR 2nd matched arms have same body
-   |              ^
-   |
-note: same as this
-  --> $DIR/match_same_arms.rs:31:14
+   |         -^^^^^
+   |         |
+   |         help: try merging the arm patterns: `2 | 1`
    |
-LL |         1 => 2,
-   |              ^
-help: consider refactoring into `1 | 2`
+   = help: or try changing either arm body
+note: other arm here
   --> $DIR/match_same_arms.rs:31:9
    |
 LL |         1 => 2,
-   |         ^
-   = help: ...or consider changing the match arm bodies
+   |         ^^^^^^
 
-error: this `match` has identical arm bodies
-  --> $DIR/match_same_arms.rs:33:14
+error: this match arm has an identical body to another arm
+  --> $DIR/match_same_arms.rs:33:9
    |
 LL |         3 => 2, //~ ERROR 3rd matched arms have same body
-   |              ^
-   |
-note: same as this
-  --> $DIR/match_same_arms.rs:31:14
+   |         -^^^^^
+   |         |
+   |         help: try merging the arm patterns: `3 | 1`
    |
-LL |         1 => 2,
-   |              ^
-help: consider refactoring into `1 | 3`
+   = help: or try changing either arm body
+note: other arm here
   --> $DIR/match_same_arms.rs:31:9
    |
 LL |         1 => 2,
-   |         ^
-   = help: ...or consider changing the match arm bodies
+   |         ^^^^^^
 
-error: this `match` has identical arm bodies
-  --> $DIR/match_same_arms.rs:50:55
+error: this match arm has an identical body to another arm
+  --> $DIR/match_same_arms.rs:32:9
    |
-LL |                 CommandInfo::External { name, .. } => name.to_string(),
-   |                                                       ^^^^^^^^^^^^^^^^
+LL |         2 => 2, //~ ERROR 2nd matched arms have same body
+   |         -^^^^^
+   |         |
+   |         help: try merging the arm patterns: `2 | 3`
    |
-note: same as this
-  --> $DIR/match_same_arms.rs:49:54
+   = help: or try changing either arm body
+note: other arm here
+  --> $DIR/match_same_arms.rs:33:9
    |
-LL |                 CommandInfo::BuiltIn { name, .. } => name.to_string(),
-   |                                                      ^^^^^^^^^^^^^^^^
-help: consider refactoring into `CommandInfo::BuiltIn { name, .. } | CommandInfo::External { name, .. }`
+LL |         3 => 2, //~ ERROR 3rd matched arms have same body
+   |         ^^^^^^
+
+error: this match arm has an identical body to another arm
+  --> $DIR/match_same_arms.rs:50:17
+   |
+LL |                 CommandInfo::External { name, .. } => name.to_string(),
+   |                 ----------------------------------^^^^^^^^^^^^^^^^^^^^
+   |                 |
+   |                 help: try merging the arm patterns: `CommandInfo::External { name, .. } | CommandInfo::BuiltIn { name, .. }`
+   |
+   = help: or try changing either arm body
+note: other arm here
   --> $DIR/match_same_arms.rs:49:17
    |
 LL |                 CommandInfo::BuiltIn { name, .. } => name.to_string(),
-   |                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-   = help: ...or consider changing the match arm bodies
+   |                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
-error: aborting due to 7 previous errors
+error: aborting due to 8 previous errors
 
diff --git a/tests/ui/match_same_arms2.rs b/tests/ui/match_same_arms2.rs
index 67e1d518483..dbfeb4379d5 100644
--- a/tests/ui/match_same_arms2.rs
+++ b/tests/ui/match_same_arms2.rs
@@ -174,4 +174,57 @@ fn main() {
         Some(2) => 2,
         _ => 1,
     };
+
+    enum Foo {
+        X(u32),
+        Y(u32),
+        Z(u32),
+    }
+
+    // Don't lint. `Foo::X(0)` and `Foo::Z(_)` overlap with the arm in between.
+    let _ = match Foo::X(0) {
+        Foo::X(0) => 1,
+        Foo::X(_) | Foo::Y(_) | Foo::Z(0) => 2,
+        Foo::Z(_) => 1,
+        _ => 0,
+    };
+
+    // Suggest moving `Foo::Z(_)` up.
+    let _ = match Foo::X(0) {
+        Foo::X(0) => 1,
+        Foo::X(_) | Foo::Y(_) => 2,
+        Foo::Z(_) => 1,
+        _ => 0,
+    };
+
+    // Suggest moving `Foo::X(0)` down.
+    let _ = match Foo::X(0) {
+        Foo::X(0) => 1,
+        Foo::Y(_) | Foo::Z(0) => 2,
+        Foo::Z(_) => 1,
+        _ => 0,
+    };
+
+    // Don't lint.
+    let _ = match 0 {
+        -2 => 1,
+        -5..=50 => 2,
+        -150..=88 => 1,
+        _ => 3,
+    };
+
+    struct Bar {
+        x: u32,
+        y: u32,
+        z: u32,
+    }
+
+    // Lint.
+    let _ = match None {
+        Some(Bar { x: 0, y: 5, .. }) => 1,
+        Some(Bar { y: 10, z: 0, .. }) => 2,
+        None => 50,
+        Some(Bar { y: 0, x: 5, .. }) => 1,
+        _ => 200,
+    };
 }
diff --git a/tests/ui/match_same_arms2.stderr b/tests/ui/match_same_arms2.stderr
index e1ed12f9370..14a672ba2fe 100644
--- a/tests/ui/match_same_arms2.stderr
+++ b/tests/ui/match_same_arms2.stderr
@@ -1,175 +1,138 @@
-error: this `match` has identical arm bodies
-  --> $DIR/match_same_arms2.rs:20:14
+error: this match arm has an identical body to the `_` wildcard arm
+  --> $DIR/match_same_arms2.rs:11:9
    |
-LL |           _ => {
-   |  ______________^
-LL | |             //~ ERROR match arms have same body
+LL | /         42 => {
 LL | |             foo();
 LL | |             let mut a = 42 + [23].len() as i32;
+LL | |             if true {
 ...  |
 LL | |             a
 LL | |         },
-   | |_________^
+   | |_________^ help: try removing the arm
    |
    = note: `-D clippy::match-same-arms` implied by `-D warnings`
-note: same as this
-  --> $DIR/match_same_arms2.rs:11:15
+   = help: or try changing either arm body
+note: `_` wildcard arm here
+  --> $DIR/match_same_arms2.rs:20:9
    |
-LL |           42 => {
-   |  _______________^
-LL | |             foo();
-LL | |             let mut a = 42 + [23].len() as i32;
-LL | |             if true {
-...  |
-LL | |             a
-LL | |         },
-   | |_________^
-note: `42` has the same arm body as the `_` wildcard, consider removing it
-  --> $DIR/match_same_arms2.rs:11:15
-   |
-LL |           42 => {
-   |  _______________^
+LL | /         _ => {
+LL | |             //~ ERROR match arms have same body
 LL | |             foo();
 LL | |             let mut a = 42 + [23].len() as i32;
-LL | |             if true {
 ...  |
 LL | |             a
 LL | |         },
    | |_________^
 
-error: this `match` has identical arm bodies
-  --> $DIR/match_same_arms2.rs:34:15
+error: this match arm has an identical body to another arm
+  --> $DIR/match_same_arms2.rs:34:9
    |
 LL |         51 => foo(), //~ ERROR match arms have same body
-   |               ^^^^^
+   |         --^^^^^^^^^
+   |         |
+   |         help: try merging the arm patterns: `51 | 42`
    |
-note: same as this
-  --> $DIR/match_same_arms2.rs:33:15
-   |
-LL |         42 => foo(),
-   |               ^^^^^
-help: consider refactoring into `42 | 51`
+   = help: or try changing either arm body
+note: other arm here
   --> $DIR/match_same_arms2.rs:33:9
    |
 LL |         42 => foo(),
-   |         ^^
-   = help: ...or consider changing the match arm bodies
+   |         ^^^^^^^^^^^
 
-error: this `match` has identical arm bodies
-  --> $DIR/match_same_arms2.rs:40:17
+error: this match arm has an identical body to another arm
+  --> $DIR/match_same_arms2.rs:40:9
    |
 LL |         None => 24, //~ ERROR match arms have same body
-   |                 ^^
+   |         ----^^^^^^
+   |         |
+   |         help: try merging the arm patterns: `None | Some(_)`
    |
-note: same as this
-  --> $DIR/match_same_arms2.rs:39:20
-   |
-LL |         Some(_) => 24,
-   |                    ^^
-help: consider refactoring into `Some(_) | None`
+   = help: or try changing either arm body
+note: other arm here
   --> $DIR/match_same_arms2.rs:39:9
    |
 LL |         Some(_) => 24,
-   |         ^^^^^^^
-   = help: ...or consider changing the match arm bodies
+   |         ^^^^^^^^^^^^^
 
-error: this `match` has identical arm bodies
-  --> $DIR/match_same_arms2.rs:62:28
+error: this match arm has an identical body to another arm
+  --> $DIR/match_same_arms2.rs:62:9
    |
 LL |         (None, Some(a)) => bar(a), //~ ERROR match arms have same body
-   |                            ^^^^^^
-   |
-note: same as this
-  --> $DIR/match_same_arms2.rs:61:28
+   |         ---------------^^^^^^^^^^
+   |         |
+   |         help: try merging the arm patterns: `(None, Some(a)) | (Some(a), None)`
    |
-LL |         (Some(a), None) => bar(a),
-   |                            ^^^^^^
-help: consider refactoring into `(Some(a), None) | (None, Some(a))`
+   = help: or try changing either arm body
+note: other arm here
   --> $DIR/match_same_arms2.rs:61:9
    |
 LL |         (Some(a), None) => bar(a),
-   |         ^^^^^^^^^^^^^^^
-   = help: ...or consider changing the match arm bodies
+   |         ^^^^^^^^^^^^^^^^^^^^^^^^^
 
-error: this `match` has identical arm bodies
-  --> $DIR/match_same_arms2.rs:68:26
-   |
-LL |         (.., Some(a)) => bar(a), //~ ERROR match arms have same body
-   |                          ^^^^^^
-   |
-note: same as this
-  --> $DIR/match_same_arms2.rs:67:26
-   |
-LL |         (Some(a), ..) => bar(a),
-   |                          ^^^^^^
-help: consider refactoring into `(Some(a), ..) | (.., Some(a))`
+error: this match arm has an identical body to another arm
   --> $DIR/match_same_arms2.rs:67:9
    |
 LL |         (Some(a), ..) => bar(a),
-   |         ^^^^^^^^^^^^^
-   = help: ...or consider changing the match arm bodies
-
-error: this `match` has identical arm bodies
-  --> $DIR/match_same_arms2.rs:102:29
-   |
-LL |         (Ok(_), Some(x)) => println!("ok {}", x),
-   |                             ^^^^^^^^^^^^^^^^^^^^
+   |         -------------^^^^^^^^^^
+   |         |
+   |         help: try merging the arm patterns: `(Some(a), ..) | (.., Some(a))`
    |
-note: same as this
-  --> $DIR/match_same_arms2.rs:101:29
+   = help: or try changing either arm body
+note: other arm here
+  --> $DIR/match_same_arms2.rs:68:9
    |
-LL |         (Ok(x), Some(_)) => println!("ok {}", x),
-   |                             ^^^^^^^^^^^^^^^^^^^^
-help: consider refactoring into `(Ok(x), Some(_)) | (Ok(_), Some(x))`
+LL |         (.., Some(a)) => bar(a), //~ ERROR match arms have same body
+   |         ^^^^^^^^^^^^^^^^^^^^^^^
+
+error: this match arm has an identical body to another arm
   --> $DIR/match_same_arms2.rs:101:9
    |
 LL |         (Ok(x), Some(_)) => println!("ok {}", x),
-   |         ^^^^^^^^^^^^^^^^
-   = help: ...or consider changing the match arm bodies
-   = note: this error originates in the macro `println` (in Nightly builds, run with -Z macro-backtrace for more info)
+   |         ----------------^^^^^^^^^^^^^^^^^^^^^^^^
+   |         |
+   |         help: try merging the arm patterns: `(Ok(x), Some(_)) | (Ok(_), Some(x))`
+   |
+   = help: or try changing either arm body
+note: other arm here
+  --> $DIR/match_same_arms2.rs:102:9
+   |
+LL |         (Ok(_), Some(x)) => println!("ok {}", x),
+   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
-error: this `match` has identical arm bodies
-  --> $DIR/match_same_arms2.rs:117:18
+error: this match arm has an identical body to another arm
+  --> $DIR/match_same_arms2.rs:117:9
    |
 LL |         Ok(_) => println!("ok"),
-   |                  ^^^^^^^^^^^^^^
-   |
-note: same as this
-  --> $DIR/match_same_arms2.rs:116:18
+   |         -----^^^^^^^^^^^^^^^^^^
+   |         |
+   |         help: try merging the arm patterns: `Ok(_) | Ok(3)`
    |
-LL |         Ok(3) => println!("ok"),
-   |                  ^^^^^^^^^^^^^^
-help: consider refactoring into `Ok(3) | Ok(_)`
+   = help: or try changing either arm body
+note: other arm here
   --> $DIR/match_same_arms2.rs:116:9
    |
 LL |         Ok(3) => println!("ok"),
-   |         ^^^^^
-   = help: ...or consider changing the match arm bodies
-   = note: this error originates in the macro `println` (in Nightly builds, run with -Z macro-backtrace for more info)
+   |         ^^^^^^^^^^^^^^^^^^^^^^^
 
-error: this `match` has identical arm bodies
-  --> $DIR/match_same_arms2.rs:144:14
+error: this match arm has an identical body to another arm
+  --> $DIR/match_same_arms2.rs:144:9
    |
 LL |           1 => {
-   |  ______________^
+   |           ^ help: try merging the arm patterns: `1 | 0`
+   |  _________|
+   | |
 LL | |             empty!(0);
 LL | |         },
    | |_________^
    |
-note: same as this
-  --> $DIR/match_same_arms2.rs:141:14
+   = help: or try changing either arm body
+note: other arm here
+  --> $DIR/match_same_arms2.rs:141:9
    |
-LL |           0 => {
-   |  ______________^
+LL | /         0 => {
 LL | |             empty!(0);
 LL | |         },
    | |_________^
-help: consider refactoring into `0 | 1`
-  --> $DIR/match_same_arms2.rs:141:9
-   |
-LL |         0 => {
-   |         ^
-   = help: ...or consider changing the match arm bodies
 
 error: match expression looks like `matches!` macro
   --> $DIR/match_same_arms2.rs:162:16
@@ -184,5 +147,50 @@ LL | |     };
    |
    = note: `-D clippy::match-like-matches-macro` implied by `-D warnings`
 
-error: aborting due to 9 previous errors
+error: this match arm has an identical body to another arm
+  --> $DIR/match_same_arms2.rs:194:9
+   |
+LL |         Foo::X(0) => 1,
+   |         ---------^^^^^
+   |         |
+   |         help: try merging the arm patterns: `Foo::X(0) | Foo::Z(_)`
+   |
+   = help: or try changing either arm body
+note: other arm here
+  --> $DIR/match_same_arms2.rs:196:9
+   |
+LL |         Foo::Z(_) => 1,
+   |         ^^^^^^^^^^^^^^
+
+error: this match arm has an identical body to another arm
+  --> $DIR/match_same_arms2.rs:204:9
+   |
+LL |         Foo::Z(_) => 1,
+   |         ---------^^^^^
+   |         |
+   |         help: try merging the arm patterns: `Foo::Z(_) | Foo::X(0)`
+   |
+   = help: or try changing either arm body
+note: other arm here
+  --> $DIR/match_same_arms2.rs:202:9
+   |
+LL |         Foo::X(0) => 1,
+   |         ^^^^^^^^^^^^^^
+
+error: this match arm has an identical body to another arm
+  --> $DIR/match_same_arms2.rs:227:9
+   |
+LL |         Some(Bar { y: 0, x: 5, .. }) => 1,
+   |         ----------------------------^^^^^
+   |         |
+   |         help: try merging the arm patterns: `Some(Bar { y: 0, x: 5, .. }) | Some(Bar { x: 0, y: 5, .. })`
+   |
+   = help: or try changing either arm body
+note: other arm here
+  --> $DIR/match_same_arms2.rs:224:9
+   |
+LL |         Some(Bar { x: 0, y: 5, .. }) => 1,
+   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: aborting due to 12 previous errors
 
diff --git a/tests/ui/or_then_unwrap.fixed b/tests/ui/or_then_unwrap.fixed
new file mode 100644
index 00000000000..27d4b795a5e
--- /dev/null
+++ b/tests/ui/or_then_unwrap.fixed
@@ -0,0 +1,52 @@
+// run-rustfix
+
+#![warn(clippy::or_then_unwrap)]
+#![allow(clippy::map_identity)]
+
+struct SomeStruct {}
+impl SomeStruct {
+    fn or(self, _: Option<Self>) -> Self {
+        self
+    }
+    fn unwrap(&self) {}
+}
+
+struct SomeOtherStruct {}
+impl SomeOtherStruct {
+    fn or(self) -> Self {
+        self
+    }
+    fn unwrap(&self) {}
+}
+
+fn main() {
+    let option: Option<&str> = None;
+    let _ = option.unwrap_or("fallback"); // should trigger lint
+
+    let result: Result<&str, &str> = Err("Error");
+    let _ = result.unwrap_or("fallback"); // should trigger lint
+
+    // as part of a method chain
+    let option: Option<&str> = None;
+    let _ = option.map(|v| v).unwrap_or("fallback").to_string().chars(); // should trigger lint
+
+    // Not Option/Result
+    let instance = SomeStruct {};
+    let _ = instance.or(Some(SomeStruct {})).unwrap(); // should not trigger lint
+
+    // or takes no argument
+    let instance = SomeOtherStruct {};
+    let _ = instance.or().unwrap(); // should not trigger lint and should not panic
+
+    // None in or
+    let option: Option<&str> = None;
+    let _ = option.or(None).unwrap(); // should not trigger lint
+
+    // Not Err in or
+    let result: Result<&str, &str> = Err("Error");
+    let _ = result.or::<&str>(Err("Other Error")).unwrap(); // should not trigger lint
+
+    // other function between
+    let option: Option<&str> = None;
+    let _ = option.or(Some("fallback")).map(|v| v).unwrap(); // should not trigger lint
+}
diff --git a/tests/ui/or_then_unwrap.rs b/tests/ui/or_then_unwrap.rs
new file mode 100644
index 00000000000..0dab5ae2f1c
--- /dev/null
+++ b/tests/ui/or_then_unwrap.rs
@@ -0,0 +1,52 @@
+// run-rustfix
+
+#![warn(clippy::or_then_unwrap)]
+#![allow(clippy::map_identity)]
+
+struct SomeStruct {}
+impl SomeStruct {
+    fn or(self, _: Option<Self>) -> Self {
+        self
+    }
+    fn unwrap(&self) {}
+}
+
+struct SomeOtherStruct {}
+impl SomeOtherStruct {
+    fn or(self) -> Self {
+        self
+    }
+    fn unwrap(&self) {}
+}
+
+fn main() {
+    let option: Option<&str> = None;
+    let _ = option.or(Some("fallback")).unwrap(); // should trigger lint
+
+    let result: Result<&str, &str> = Err("Error");
+    let _ = result.or::<&str>(Ok("fallback")).unwrap(); // should trigger lint
+
+    // as part of a method chain
+    let option: Option<&str> = None;
+    let _ = option.map(|v| v).or(Some("fallback")).unwrap().to_string().chars(); // should trigger lint
+
+    // Not Option/Result
+    let instance = SomeStruct {};
+    let _ = instance.or(Some(SomeStruct {})).unwrap(); // should not trigger lint
+
+    // or takes no argument
+    let instance = SomeOtherStruct {};
+    let _ = instance.or().unwrap(); // should not trigger lint and should not panic
+
+    // None in or
+    let option: Option<&str> = None;
+    let _ = option.or(None).unwrap(); // should not trigger lint
+
+    // Not Err in or
+    let result: Result<&str, &str> = Err("Error");
+    let _ = result.or::<&str>(Err("Other Error")).unwrap(); // should not trigger lint
+
+    // other function between
+    let option: Option<&str> = None;
+    let _ = option.or(Some("fallback")).map(|v| v).unwrap(); // should not trigger lint
+}
diff --git a/tests/ui/or_then_unwrap.stderr b/tests/ui/or_then_unwrap.stderr
new file mode 100644
index 00000000000..da88154c59f
--- /dev/null
+++ b/tests/ui/or_then_unwrap.stderr
@@ -0,0 +1,22 @@
+error: found `.or(Some(…)).unwrap()`
+  --> $DIR/or_then_unwrap.rs:24:20
+   |
+LL |     let _ = option.or(Some("fallback")).unwrap(); // should trigger lint
+   |                    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try this: `unwrap_or("fallback")`
+   |
+   = note: `-D clippy::or-then-unwrap` implied by `-D warnings`
+
+error: found `.or(Ok(…)).unwrap()`
+  --> $DIR/or_then_unwrap.rs:27:20
+   |
+LL |     let _ = result.or::<&str>(Ok("fallback")).unwrap(); // should trigger lint
+   |                    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try this: `unwrap_or("fallback")`
+
+error: found `.or(Some(…)).unwrap()`
+  --> $DIR/or_then_unwrap.rs:31:31
+   |
+LL |     let _ = option.map(|v| v).or(Some("fallback")).unwrap().to_string().chars(); // should trigger lint
+   |                               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try this: `unwrap_or("fallback")`
+
+error: aborting due to 3 previous errors
+
diff --git a/tests/ui/ptr_arg.rs b/tests/ui/ptr_arg.rs
index 97990fedd51..03dd938a233 100644
--- a/tests/ui/ptr_arg.rs
+++ b/tests/ui/ptr_arg.rs
@@ -194,3 +194,10 @@ fn two_vecs(a: &mut Vec<u32>, b: &mut Vec<u32>) {
     a.push(0);
     b.push(1);
 }
+
+// Issue #8495
+fn cow_conditional_to_mut(a: &mut Cow<str>) {
+    if a.is_empty() {
+        a.to_mut().push_str("foo");
+    }
+}
diff --git a/tests/ui/single_component_path_imports_macro.fixed b/tests/ui/single_component_path_imports_macro.fixed
deleted file mode 100644
index e43f5d381aa..00000000000
--- a/tests/ui/single_component_path_imports_macro.fixed
+++ /dev/null
@@ -1,20 +0,0 @@
-// run-rustfix
-#![warn(clippy::single_component_path_imports)]
-#![allow(unused_imports)]
-
-// #7106: use statements exporting a macro within a crate should not trigger lint
-
-macro_rules! m1 {
-    () => {};
-}
-pub(crate) use m1; // ok
-
-macro_rules! m2 {
-    () => {};
-}
- // fail
-
-fn main() {
-    m1!();
-    m2!();
-}
diff --git a/tests/ui/single_component_path_imports_macro.rs b/tests/ui/single_component_path_imports_macro.rs
index 3c65ca3054c..fda294a6154 100644
--- a/tests/ui/single_component_path_imports_macro.rs
+++ b/tests/ui/single_component_path_imports_macro.rs
@@ -1,8 +1,8 @@
-// run-rustfix
 #![warn(clippy::single_component_path_imports)]
 #![allow(unused_imports)]
 
 // #7106: use statements exporting a macro within a crate should not trigger lint
+// #7923: normal `use` statements of macros should also not trigger the lint
 
 macro_rules! m1 {
     () => {};
@@ -12,7 +12,7 @@ pub(crate) use m1; // ok
 macro_rules! m2 {
     () => {};
 }
-use m2; // fail
+use m2; // ok
 
 fn main() {
     m1!();
diff --git a/tests/ui/single_component_path_imports_macro.stderr b/tests/ui/single_component_path_imports_macro.stderr
deleted file mode 100644
index 37d5176129f..00000000000
--- a/tests/ui/single_component_path_imports_macro.stderr
+++ /dev/null
@@ -1,10 +0,0 @@
-error: this import is redundant
-  --> $DIR/single_component_path_imports_macro.rs:15:1
-   |
-LL | use m2; // fail
-   | ^^^^^^^ help: remove it entirely
-   |
-   = note: `-D clippy::single-component-path-imports` implied by `-D warnings`
-
-error: aborting due to previous error
-
diff --git a/tests/ui/temporary_assignment.rs b/tests/ui/temporary_assignment.rs
index b4a931043b0..ac4c1bc6597 100644
--- a/tests/ui/temporary_assignment.rs
+++ b/tests/ui/temporary_assignment.rs
@@ -1,5 +1,4 @@
 #![warn(clippy::temporary_assignment)]
-#![allow(const_item_mutation)]
 
 use std::ops::{Deref, DerefMut};
 
diff --git a/tests/ui/temporary_assignment.stderr b/tests/ui/temporary_assignment.stderr
index 4cc32c79f05..7d79901a28d 100644
--- a/tests/ui/temporary_assignment.stderr
+++ b/tests/ui/temporary_assignment.stderr
@@ -1,5 +1,5 @@
 error: assignment to temporary
-  --> $DIR/temporary_assignment.rs:48:5
+  --> $DIR/temporary_assignment.rs:47:5
    |
 LL |     Struct { field: 0 }.field = 1;
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -7,7 +7,7 @@ LL |     Struct { field: 0 }.field = 1;
    = note: `-D clippy::temporary-assignment` implied by `-D warnings`
 
 error: assignment to temporary
-  --> $DIR/temporary_assignment.rs:49:5
+  --> $DIR/temporary_assignment.rs:48:5
    |
 LL | /     MultiStruct {
 LL | |         structure: Struct { field: 0 },
@@ -17,13 +17,13 @@ LL | |     .field = 1;
    | |______________^
 
 error: assignment to temporary
-  --> $DIR/temporary_assignment.rs:54:5
+  --> $DIR/temporary_assignment.rs:53:5
    |
 LL |     ArrayStruct { array: [0] }.array[0] = 1;
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: assignment to temporary
-  --> $DIR/temporary_assignment.rs:55:5
+  --> $DIR/temporary_assignment.rs:54:5
    |
 LL |     (0, 0).0 = 1;
    |     ^^^^^^^^^^^^
diff --git a/tests/ui/transmute_undefined_repr.rs b/tests/ui/transmute_undefined_repr.rs
index b163d605634..b06ed4a9173 100644
--- a/tests/ui/transmute_undefined_repr.rs
+++ b/tests/ui/transmute_undefined_repr.rs
@@ -1,8 +1,9 @@
 #![warn(clippy::transmute_undefined_repr)]
 #![allow(clippy::unit_arg, clippy::transmute_ptr_to_ref)]
 
+use core::any::TypeId;
 use core::ffi::c_void;
-use core::mem::{size_of, transmute};
+use core::mem::{size_of, transmute, MaybeUninit};
 
 fn value<T>() -> T {
     unimplemented!()
@@ -87,5 +88,57 @@ fn main() {
 
         let _: *const [u8] = transmute(value::<Box<[u8]>>()); // Ok
         let _: Box<[u8]> = transmute(value::<*mut [u8]>()); // Ok
+
+        let _: Ty2<u32, u32> = transmute(value::<(Ty2<u32, u32>,)>()); // Ok
+        let _: (Ty2<u32, u32>,) = transmute(value::<Ty2<u32, u32>>()); // Ok
+
+        let _: Ty2<u32, u32> = transmute(value::<(Ty2<u32, u32>, ())>()); // Ok
+        let _: (Ty2<u32, u32>, ()) = transmute(value::<Ty2<u32, u32>>()); // Ok
+
+        let _: Ty2<u32, u32> = transmute(value::<((), Ty2<u32, u32>)>()); // Ok
+        let _: ((), Ty2<u32, u32>) = transmute(value::<Ty2<u32, u32>>()); // Ok
+
+        let _: (usize, usize) = transmute(value::<&[u8]>()); // Ok
+        let _: &[u8] = transmute(value::<(usize, usize)>()); // Ok
+
+        trait Trait {}
+        let _: (isize, isize) = transmute(value::<&dyn Trait>()); // Ok
+        let _: &dyn Trait = transmute(value::<(isize, isize)>()); // Ok
+
+        let _: MaybeUninit<Ty2<u32, u32>> = transmute(value::<Ty2<u32, u32>>()); // Ok
+        let _: Ty2<u32, u32> = transmute(value::<MaybeUninit<Ty2<u32, u32>>>()); // Ok
+
+        let _: Ty<&[u32]> = transmute::<&[u32], _>(value::<&Vec<u32>>()); // Ok
+    }
+}
+
+fn _with_generics<T: 'static, U: 'static>() {
+    if TypeId::of::<T>() != TypeId::of::<u32>() || TypeId::of::<T>() != TypeId::of::<U>() {
+        return;
+    }
+    unsafe {
+        let _: &u32 = transmute(value::<&T>()); // Ok
+        let _: &T = transmute(value::<&u32>()); // Ok
+
+        let _: Vec<U> = transmute(value::<Vec<T>>()); // Ok
+        let _: Vec<T> = transmute(value::<Vec<U>>()); // Ok
+
+        let _: Ty<&u32> = transmute(value::<&T>()); // Ok
+        let _: Ty<&T> = transmute(value::<&u32>()); // Ok
+
+        let _: Vec<u32> = transmute(value::<Vec<T>>()); // Ok
+        let _: Vec<T> = transmute(value::<Vec<u32>>()); // Ok
+
+        let _: &Ty2<u32, u32> = transmute(value::<&Ty2<T, U>>()); // Ok
+        let _: &Ty2<T, U> = transmute(value::<&Ty2<u32, u32>>()); // Ok
+
+        let _: Vec<Vec<u32>> = transmute(value::<Vec<Vec<T>>>()); // Ok
+        let _: Vec<Vec<T>> = transmute(value::<Vec<Vec<u32>>>()); // Ok
+
+        let _: Vec<Ty2<T, u32>> = transmute(value::<Vec<Ty2<U, i32>>>()); // Err
+        let _: Vec<Ty2<U, i32>> = transmute(value::<Vec<Ty2<T, u32>>>()); // Err
+
+        let _: *const u32 = transmute(value::<Box<T>>()); // Ok
+        let _: Box<T> = transmute(value::<*const u32>()); // Ok
     }
 }
diff --git a/tests/ui/transmute_undefined_repr.stderr b/tests/ui/transmute_undefined_repr.stderr
index 42d544fc954..28bfba6c757 100644
--- a/tests/ui/transmute_undefined_repr.stderr
+++ b/tests/ui/transmute_undefined_repr.stderr
@@ -1,5 +1,5 @@
 error: transmute from `Ty2<u32, i32>` which has an undefined layout
-  --> $DIR/transmute_undefined_repr.rs:26:33
+  --> $DIR/transmute_undefined_repr.rs:27:33
    |
 LL |         let _: Ty2C<u32, i32> = transmute(value::<Ty2<u32, i32>>()); // Lint, Ty2 is unordered
    |                                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -7,13 +7,13 @@ LL |         let _: Ty2C<u32, i32> = transmute(value::<Ty2<u32, i32>>()); // Lin
    = note: `-D clippy::transmute-undefined-repr` implied by `-D warnings`
 
 error: transmute into `Ty2<u32, i32>` which has an undefined layout
-  --> $DIR/transmute_undefined_repr.rs:27:32
+  --> $DIR/transmute_undefined_repr.rs:28:32
    |
 LL |         let _: Ty2<u32, i32> = transmute(value::<Ty2C<u32, i32>>()); // Lint, Ty2 is unordered
    |                                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: transmute from `Ty<Ty2<u32, i32>>` to `Ty2<u32, f32>`, both of which have an undefined layout
-  --> $DIR/transmute_undefined_repr.rs:32:32
+  --> $DIR/transmute_undefined_repr.rs:33:32
    |
 LL |         let _: Ty2<u32, f32> = transmute(value::<Ty<Ty2<u32, i32>>>()); // Lint, different Ty2 instances
    |                                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -21,7 +21,7 @@ LL |         let _: Ty2<u32, f32> = transmute(value::<Ty<Ty2<u32, i32>>>()); //
    = note: two instances of the same generic type (`Ty2`) may have different layouts
 
 error: transmute from `Ty2<u32, f32>` to `Ty<Ty2<u32, i32>>`, both of which have an undefined layout
-  --> $DIR/transmute_undefined_repr.rs:33:36
+  --> $DIR/transmute_undefined_repr.rs:34:36
    |
 LL |         let _: Ty<Ty2<u32, i32>> = transmute(value::<Ty2<u32, f32>>()); // Lint, different Ty2 instances
    |                                    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -29,7 +29,7 @@ LL |         let _: Ty<Ty2<u32, i32>> = transmute(value::<Ty2<u32, f32>>()); //
    = note: two instances of the same generic type (`Ty2`) may have different layouts
 
 error: transmute from `Ty<&Ty2<u32, i32>>` to `&Ty2<u32, f32>`, both of which have an undefined layout
-  --> $DIR/transmute_undefined_repr.rs:38:33
+  --> $DIR/transmute_undefined_repr.rs:39:33
    |
 LL |         let _: &Ty2<u32, f32> = transmute(value::<Ty<&Ty2<u32, i32>>>()); // Lint, different Ty2 instances
    |                                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -37,7 +37,7 @@ LL |         let _: &Ty2<u32, f32> = transmute(value::<Ty<&Ty2<u32, i32>>>()); /
    = note: two instances of the same generic type (`Ty2`) may have different layouts
 
 error: transmute from `&Ty2<u32, f32>` to `Ty<&Ty2<u32, i32>>`, both of which have an undefined layout
-  --> $DIR/transmute_undefined_repr.rs:39:37
+  --> $DIR/transmute_undefined_repr.rs:40:37
    |
 LL |         let _: Ty<&Ty2<u32, i32>> = transmute(value::<&Ty2<u32, f32>>()); // Lint, different Ty2 instances
    |                                     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -45,7 +45,7 @@ LL |         let _: Ty<&Ty2<u32, i32>> = transmute(value::<&Ty2<u32, f32>>()); /
    = note: two instances of the same generic type (`Ty2`) may have different layouts
 
 error: transmute from `std::boxed::Box<Ty2<u32, u32>>` to `&mut Ty2<u32, f32>`, both of which have an undefined layout
-  --> $DIR/transmute_undefined_repr.rs:56:45
+  --> $DIR/transmute_undefined_repr.rs:57:45
    |
 LL |         let _: &'static mut Ty2<u32, f32> = transmute(value::<Box<Ty2<u32, u32>>>()); // Lint, different Ty2 instances
    |                                             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -53,12 +53,28 @@ LL |         let _: &'static mut Ty2<u32, f32> = transmute(value::<Box<Ty2<u32,
    = note: two instances of the same generic type (`Ty2`) may have different layouts
 
 error: transmute from `&mut Ty2<u32, f32>` to `std::boxed::Box<Ty2<u32, u32>>`, both of which have an undefined layout
-  --> $DIR/transmute_undefined_repr.rs:57:37
+  --> $DIR/transmute_undefined_repr.rs:58:37
    |
 LL |         let _: Box<Ty2<u32, u32>> = transmute(value::<&'static mut Ty2<u32, f32>>()); // Lint, different Ty2 instances
    |                                     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
    = note: two instances of the same generic type (`Ty2`) may have different layouts
 
-error: aborting due to 8 previous errors
+error: transmute from `std::vec::Vec<Ty2<U, i32>>` to `std::vec::Vec<Ty2<T, u32>>`, both of which have an undefined layout
+  --> $DIR/transmute_undefined_repr.rs:138:35
+   |
+LL |         let _: Vec<Ty2<T, u32>> = transmute(value::<Vec<Ty2<U, i32>>>()); // Err
+   |                                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: two instances of the same generic type (`Vec`) may have different layouts
+
+error: transmute from `std::vec::Vec<Ty2<T, u32>>` to `std::vec::Vec<Ty2<U, i32>>`, both of which have an undefined layout
+  --> $DIR/transmute_undefined_repr.rs:139:35
+   |
+LL |         let _: Vec<Ty2<U, i32>> = transmute(value::<Vec<Ty2<T, u32>>>()); // Err
+   |                                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: two instances of the same generic type (`Vec`) may have different layouts
+
+error: aborting due to 10 previous errors
 
diff --git a/tests/ui/transmutes_expressible_as_ptr_casts.stderr b/tests/ui/transmutes_expressible_as_ptr_casts.stderr
index d9b64a0ed7b..de9418c8d1a 100644
--- a/tests/ui/transmutes_expressible_as_ptr_casts.stderr
+++ b/tests/ui/transmutes_expressible_as_ptr_casts.stderr
@@ -34,13 +34,13 @@ error: transmute from a reference to a pointer
 LL |     let _array_ptr_transmute = unsafe { transmute::<&[i32; 4], *const [i32; 4]>(array_ref) };
    |                                         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `array_ref as *const [i32; 4]`
 
-error: transmute from `fn(usize) -> u8 {main::foo}` to `*const usize` which could be expressed as a pointer cast instead
+error: transmute from `fn(usize) -> u8` to `*const usize` which could be expressed as a pointer cast instead
   --> $DIR/transmutes_expressible_as_ptr_casts.rs:48:41
    |
 LL |     let _usize_ptr_transmute = unsafe { transmute::<fn(usize) -> u8, *const usize>(foo) };
    |                                         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `foo as *const usize`
 
-error: transmute from `fn(usize) -> u8 {main::foo}` to `usize` which could be expressed as a pointer cast instead
+error: transmute from `fn(usize) -> u8` to `usize` which could be expressed as a pointer cast instead
   --> $DIR/transmutes_expressible_as_ptr_casts.rs:52:49
    |
 LL |     let _usize_from_fn_ptr_transmute = unsafe { transmute::<fn(usize) -> u8, usize>(foo) };
diff --git a/tests/ui/unnecessary_join.fixed b/tests/ui/unnecessary_join.fixed
new file mode 100644
index 00000000000..7e12c6ae4be
--- /dev/null
+++ b/tests/ui/unnecessary_join.fixed
@@ -0,0 +1,35 @@
+// run-rustfix
+
+#![warn(clippy::unnecessary_join)]
+
+fn main() {
+    // should be linted
+    let vector = vec!["hello", "world"];
+    let output = vector
+        .iter()
+        .map(|item| item.to_uppercase())
+        .collect::<String>();
+    println!("{}", output);
+
+    // should be linted
+    let vector = vec!["hello", "world"];
+    let output = vector
+        .iter()
+        .map(|item| item.to_uppercase())
+        .collect::<String>();
+    println!("{}", output);
+
+    // should not be linted
+    let vector = vec!["hello", "world"];
+    let output = vector
+        .iter()
+        .map(|item| item.to_uppercase())
+        .collect::<Vec<String>>()
+        .join("\n");
+    println!("{}", output);
+
+    // should not be linted
+    let vector = vec!["hello", "world"];
+    let output = vector.iter().map(|item| item.to_uppercase()).collect::<String>();
+    println!("{}", output);
+}
diff --git a/tests/ui/unnecessary_join.rs b/tests/ui/unnecessary_join.rs
new file mode 100644
index 00000000000..0a21656a755
--- /dev/null
+++ b/tests/ui/unnecessary_join.rs
@@ -0,0 +1,37 @@
+// run-rustfix
+
+#![warn(clippy::unnecessary_join)]
+
+fn main() {
+    // should be linted
+    let vector = vec!["hello", "world"];
+    let output = vector
+        .iter()
+        .map(|item| item.to_uppercase())
+        .collect::<Vec<String>>()
+        .join("");
+    println!("{}", output);
+
+    // should be linted
+    let vector = vec!["hello", "world"];
+    let output = vector
+        .iter()
+        .map(|item| item.to_uppercase())
+        .collect::<Vec<_>>()
+        .join("");
+    println!("{}", output);
+
+    // should not be linted
+    let vector = vec!["hello", "world"];
+    let output = vector
+        .iter()
+        .map(|item| item.to_uppercase())
+        .collect::<Vec<String>>()
+        .join("\n");
+    println!("{}", output);
+
+    // should not be linted
+    let vector = vec!["hello", "world"];
+    let output = vector.iter().map(|item| item.to_uppercase()).collect::<String>();
+    println!("{}", output);
+}
diff --git a/tests/ui/unnecessary_join.stderr b/tests/ui/unnecessary_join.stderr
new file mode 100644
index 00000000000..0b14b143aff
--- /dev/null
+++ b/tests/ui/unnecessary_join.stderr
@@ -0,0 +1,20 @@
+error: called `.collect<Vec<String>>().join("")` on an iterator
+  --> $DIR/unnecessary_join.rs:11:10
+   |
+LL |           .collect::<Vec<String>>()
+   |  __________^
+LL | |         .join("");
+   | |_________________^ help: try using: `collect::<String>()`
+   |
+   = note: `-D clippy::unnecessary-join` implied by `-D warnings`
+
+error: called `.collect<Vec<String>>().join("")` on an iterator
+  --> $DIR/unnecessary_join.rs:20:10
+   |
+LL |           .collect::<Vec<_>>()
+   |  __________^
+LL | |         .join("");
+   | |_________________^ help: try using: `collect::<String>()`
+
+error: aborting due to 2 previous errors
+
diff --git a/tests/ui/unnecessary_lazy_eval.fixed b/tests/ui/unnecessary_lazy_eval.fixed
index 4ba2a0a5dbc..65fcdc43061 100644
--- a/tests/ui/unnecessary_lazy_eval.fixed
+++ b/tests/ui/unnecessary_lazy_eval.fixed
@@ -115,6 +115,14 @@ fn main() {
     let _: Result<usize, usize> = res.or(Ok(2));
     let _: Result<usize, usize> = res.or(Ok(astronomers_pi));
     let _: Result<usize, usize> = res.or(Ok(ext_str.some_field));
+    let _: Result<usize, usize> = res.
+        // some lines
+        // some lines
+        // some lines
+        // some lines
+        // some lines
+        // some lines
+        or(Ok(ext_str.some_field));
 
     // neither bind_instead_of_map nor unnecessary_lazy_eval applies here
     let _: Result<usize, usize> = res.and_then(|x| Err(x));
diff --git a/tests/ui/unnecessary_lazy_eval.rs b/tests/ui/unnecessary_lazy_eval.rs
index 466915217e4..206080ed69a 100644
--- a/tests/ui/unnecessary_lazy_eval.rs
+++ b/tests/ui/unnecessary_lazy_eval.rs
@@ -115,6 +115,14 @@ fn main() {
     let _: Result<usize, usize> = res.or_else(|_| Ok(2));
     let _: Result<usize, usize> = res.or_else(|_| Ok(astronomers_pi));
     let _: Result<usize, usize> = res.or_else(|_| Ok(ext_str.some_field));
+    let _: Result<usize, usize> = res.
+        // some lines
+        // some lines
+        // some lines
+        // some lines
+        // some lines
+        // some lines
+        or_else(|_| Ok(ext_str.some_field));
 
     // neither bind_instead_of_map nor unnecessary_lazy_eval applies here
     let _: Result<usize, usize> = res.and_then(|x| Err(x));
diff --git a/tests/ui/unnecessary_lazy_eval.stderr b/tests/ui/unnecessary_lazy_eval.stderr
index cc94bd5cd9e..7e4dd7730e7 100644
--- a/tests/ui/unnecessary_lazy_eval.stderr
+++ b/tests/ui/unnecessary_lazy_eval.stderr
@@ -2,7 +2,9 @@ error: unnecessary closure used to substitute value for `Option::None`
   --> $DIR/unnecessary_lazy_eval.rs:35:13
    |
 LL |     let _ = opt.unwrap_or_else(|| 2);
-   |             ^^^^^^^^^^^^^^^^^^^^^^^^ help: use `unwrap_or` instead: `opt.unwrap_or(2)`
+   |             ^^^^--------------------
+   |                 |
+   |                 help: use `unwrap_or(..)` instead: `unwrap_or(2)`
    |
    = note: `-D clippy::unnecessary-lazy-evaluations` implied by `-D warnings`
 
@@ -10,187 +12,264 @@ error: unnecessary closure used to substitute value for `Option::None`
   --> $DIR/unnecessary_lazy_eval.rs:36:13
    |
 LL |     let _ = opt.unwrap_or_else(|| astronomers_pi);
-   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: use `unwrap_or` instead: `opt.unwrap_or(astronomers_pi)`
+   |             ^^^^---------------------------------
+   |                 |
+   |                 help: use `unwrap_or(..)` instead: `unwrap_or(astronomers_pi)`
 
 error: unnecessary closure used to substitute value for `Option::None`
   --> $DIR/unnecessary_lazy_eval.rs:37:13
    |
 LL |     let _ = opt.unwrap_or_else(|| ext_str.some_field);
-   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: use `unwrap_or` instead: `opt.unwrap_or(ext_str.some_field)`
+   |             ^^^^-------------------------------------
+   |                 |
+   |                 help: use `unwrap_or(..)` instead: `unwrap_or(ext_str.some_field)`
 
 error: unnecessary closure used to substitute value for `Option::None`
   --> $DIR/unnecessary_lazy_eval.rs:39:13
    |
 LL |     let _ = opt.and_then(|_| ext_opt);
-   |             ^^^^^^^^^^^^^^^^^^^^^^^^^ help: use `and` instead: `opt.and(ext_opt)`
+   |             ^^^^---------------------
+   |                 |
+   |                 help: use `and(..)` instead: `and(ext_opt)`
 
 error: unnecessary closure used to substitute value for `Option::None`
   --> $DIR/unnecessary_lazy_eval.rs:40:13
    |
 LL |     let _ = opt.or_else(|| ext_opt);
-   |             ^^^^^^^^^^^^^^^^^^^^^^^ help: use `or` instead: `opt.or(ext_opt)`
+   |             ^^^^-------------------
+   |                 |
+   |                 help: use `or(..)` instead: `or(ext_opt)`
 
 error: unnecessary closure used to substitute value for `Option::None`
   --> $DIR/unnecessary_lazy_eval.rs:41:13
    |
 LL |     let _ = opt.or_else(|| None);
-   |             ^^^^^^^^^^^^^^^^^^^^ help: use `or` instead: `opt.or(None)`
+   |             ^^^^----------------
+   |                 |
+   |                 help: use `or(..)` instead: `or(None)`
 
 error: unnecessary closure used to substitute value for `Option::None`
   --> $DIR/unnecessary_lazy_eval.rs:42:13
    |
 LL |     let _ = opt.get_or_insert_with(|| 2);
-   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: use `get_or_insert` instead: `opt.get_or_insert(2)`
+   |             ^^^^------------------------
+   |                 |
+   |                 help: use `get_or_insert(..)` instead: `get_or_insert(2)`
 
 error: unnecessary closure used to substitute value for `Option::None`
   --> $DIR/unnecessary_lazy_eval.rs:43:13
    |
 LL |     let _ = opt.ok_or_else(|| 2);
-   |             ^^^^^^^^^^^^^^^^^^^^ help: use `ok_or` instead: `opt.ok_or(2)`
+   |             ^^^^----------------
+   |                 |
+   |                 help: use `ok_or(..)` instead: `ok_or(2)`
 
 error: unnecessary closure used to substitute value for `Option::None`
   --> $DIR/unnecessary_lazy_eval.rs:44:13
    |
 LL |     let _ = nested_tuple_opt.unwrap_or_else(|| Some((1, 2)));
-   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: use `unwrap_or` instead: `nested_tuple_opt.unwrap_or(Some((1, 2)))`
+   |             ^^^^^^^^^^^^^^^^^-------------------------------
+   |                              |
+   |                              help: use `unwrap_or(..)` instead: `unwrap_or(Some((1, 2)))`
 
 error: unnecessary closure used to substitute value for `Option::None`
   --> $DIR/unnecessary_lazy_eval.rs:47:13
    |
 LL |     let _ = Some(10).unwrap_or_else(|| 2);
-   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: use `unwrap_or` instead: `Some(10).unwrap_or(2)`
+   |             ^^^^^^^^^--------------------
+   |                      |
+   |                      help: use `unwrap_or(..)` instead: `unwrap_or(2)`
 
 error: unnecessary closure used to substitute value for `Option::None`
   --> $DIR/unnecessary_lazy_eval.rs:48:13
    |
 LL |     let _ = Some(10).and_then(|_| ext_opt);
-   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: use `and` instead: `Some(10).and(ext_opt)`
+   |             ^^^^^^^^^---------------------
+   |                      |
+   |                      help: use `and(..)` instead: `and(ext_opt)`
 
 error: unnecessary closure used to substitute value for `Option::None`
   --> $DIR/unnecessary_lazy_eval.rs:49:28
    |
 LL |     let _: Option<usize> = None.or_else(|| ext_opt);
-   |                            ^^^^^^^^^^^^^^^^^^^^^^^^ help: use `or` instead: `None.or(ext_opt)`
+   |                            ^^^^^-------------------
+   |                                 |
+   |                                 help: use `or(..)` instead: `or(ext_opt)`
 
 error: unnecessary closure used to substitute value for `Option::None`
   --> $DIR/unnecessary_lazy_eval.rs:50:13
    |
 LL |     let _ = None.get_or_insert_with(|| 2);
-   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: use `get_or_insert` instead: `None.get_or_insert(2)`
+   |             ^^^^^------------------------
+   |                  |
+   |                  help: use `get_or_insert(..)` instead: `get_or_insert(2)`
 
 error: unnecessary closure used to substitute value for `Option::None`
   --> $DIR/unnecessary_lazy_eval.rs:51:35
    |
 LL |     let _: Result<usize, usize> = None.ok_or_else(|| 2);
-   |                                   ^^^^^^^^^^^^^^^^^^^^^ help: use `ok_or` instead: `None.ok_or(2)`
+   |                                   ^^^^^----------------
+   |                                        |
+   |                                        help: use `ok_or(..)` instead: `ok_or(2)`
 
 error: unnecessary closure used to substitute value for `Option::None`
   --> $DIR/unnecessary_lazy_eval.rs:52:28
    |
 LL |     let _: Option<usize> = None.or_else(|| None);
-   |                            ^^^^^^^^^^^^^^^^^^^^^ help: use `or` instead: `None.or(None)`
+   |                            ^^^^^----------------
+   |                                 |
+   |                                 help: use `or(..)` instead: `or(None)`
 
 error: unnecessary closure used to substitute value for `Option::None`
   --> $DIR/unnecessary_lazy_eval.rs:55:13
    |
 LL |     let _ = deep.0.unwrap_or_else(|| 2);
-   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: use `unwrap_or` instead: `deep.0.unwrap_or(2)`
+   |             ^^^^^^^--------------------
+   |                    |
+   |                    help: use `unwrap_or(..)` instead: `unwrap_or(2)`
 
 error: unnecessary closure used to substitute value for `Option::None`
   --> $DIR/unnecessary_lazy_eval.rs:56:13
    |
 LL |     let _ = deep.0.and_then(|_| ext_opt);
-   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: use `and` instead: `deep.0.and(ext_opt)`
+   |             ^^^^^^^---------------------
+   |                    |
+   |                    help: use `and(..)` instead: `and(ext_opt)`
 
 error: unnecessary closure used to substitute value for `Option::None`
   --> $DIR/unnecessary_lazy_eval.rs:57:13
    |
 LL |     let _ = deep.0.or_else(|| None);
-   |             ^^^^^^^^^^^^^^^^^^^^^^^ help: use `or` instead: `deep.0.or(None)`
+   |             ^^^^^^^----------------
+   |                    |
+   |                    help: use `or(..)` instead: `or(None)`
 
 error: unnecessary closure used to substitute value for `Option::None`
   --> $DIR/unnecessary_lazy_eval.rs:58:13
    |
 LL |     let _ = deep.0.get_or_insert_with(|| 2);
-   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: use `get_or_insert` instead: `deep.0.get_or_insert(2)`
+   |             ^^^^^^^------------------------
+   |                    |
+   |                    help: use `get_or_insert(..)` instead: `get_or_insert(2)`
 
 error: unnecessary closure used to substitute value for `Option::None`
   --> $DIR/unnecessary_lazy_eval.rs:59:13
    |
 LL |     let _ = deep.0.ok_or_else(|| 2);
-   |             ^^^^^^^^^^^^^^^^^^^^^^^ help: use `ok_or` instead: `deep.0.ok_or(2)`
+   |             ^^^^^^^----------------
+   |                    |
+   |                    help: use `ok_or(..)` instead: `ok_or(2)`
 
 error: unnecessary closure used to substitute value for `Option::None`
   --> $DIR/unnecessary_lazy_eval.rs:79:28
    |
 LL |     let _: Option<usize> = None.or_else(|| Some(3));
-   |                            ^^^^^^^^^^^^^^^^^^^^^^^^ help: use `or` instead: `None.or(Some(3))`
+   |                            ^^^^^-------------------
+   |                                 |
+   |                                 help: use `or(..)` instead: `or(Some(3))`
 
 error: unnecessary closure used to substitute value for `Option::None`
   --> $DIR/unnecessary_lazy_eval.rs:80:13
    |
 LL |     let _ = deep.0.or_else(|| Some(3));
-   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^ help: use `or` instead: `deep.0.or(Some(3))`
+   |             ^^^^^^^-------------------
+   |                    |
+   |                    help: use `or(..)` instead: `or(Some(3))`
 
 error: unnecessary closure used to substitute value for `Option::None`
   --> $DIR/unnecessary_lazy_eval.rs:81:13
    |
 LL |     let _ = opt.or_else(|| Some(3));
-   |             ^^^^^^^^^^^^^^^^^^^^^^^ help: use `or` instead: `opt.or(Some(3))`
+   |             ^^^^-------------------
+   |                 |
+   |                 help: use `or(..)` instead: `or(Some(3))`
 
 error: unnecessary closure used to substitute value for `Result::Err`
   --> $DIR/unnecessary_lazy_eval.rs:87:13
    |
 LL |     let _ = res2.unwrap_or_else(|_| 2);
-   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^ help: use `unwrap_or` instead: `res2.unwrap_or(2)`
+   |             ^^^^^---------------------
+   |                  |
+   |                  help: use `unwrap_or(..)` instead: `unwrap_or(2)`
 
 error: unnecessary closure used to substitute value for `Result::Err`
   --> $DIR/unnecessary_lazy_eval.rs:88:13
    |
 LL |     let _ = res2.unwrap_or_else(|_| astronomers_pi);
-   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: use `unwrap_or` instead: `res2.unwrap_or(astronomers_pi)`
+   |             ^^^^^----------------------------------
+   |                  |
+   |                  help: use `unwrap_or(..)` instead: `unwrap_or(astronomers_pi)`
 
 error: unnecessary closure used to substitute value for `Result::Err`
   --> $DIR/unnecessary_lazy_eval.rs:89:13
    |
 LL |     let _ = res2.unwrap_or_else(|_| ext_str.some_field);
-   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: use `unwrap_or` instead: `res2.unwrap_or(ext_str.some_field)`
+   |             ^^^^^--------------------------------------
+   |                  |
+   |                  help: use `unwrap_or(..)` instead: `unwrap_or(ext_str.some_field)`
 
 error: unnecessary closure used to substitute value for `Result::Err`
   --> $DIR/unnecessary_lazy_eval.rs:111:35
    |
 LL |     let _: Result<usize, usize> = res.and_then(|_| Err(2));
-   |                                   ^^^^^^^^^^^^^^^^^^^^^^^^ help: use `and` instead: `res.and(Err(2))`
+   |                                   ^^^^--------------------
+   |                                       |
+   |                                       help: use `and(..)` instead: `and(Err(2))`
 
 error: unnecessary closure used to substitute value for `Result::Err`
   --> $DIR/unnecessary_lazy_eval.rs:112:35
    |
 LL |     let _: Result<usize, usize> = res.and_then(|_| Err(astronomers_pi));
-   |                                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: use `and` instead: `res.and(Err(astronomers_pi))`
+   |                                   ^^^^---------------------------------
+   |                                       |
+   |                                       help: use `and(..)` instead: `and(Err(astronomers_pi))`
 
 error: unnecessary closure used to substitute value for `Result::Err`
   --> $DIR/unnecessary_lazy_eval.rs:113:35
    |
 LL |     let _: Result<usize, usize> = res.and_then(|_| Err(ext_str.some_field));
-   |                                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: use `and` instead: `res.and(Err(ext_str.some_field))`
+   |                                   ^^^^-------------------------------------
+   |                                       |
+   |                                       help: use `and(..)` instead: `and(Err(ext_str.some_field))`
 
 error: unnecessary closure used to substitute value for `Result::Err`
   --> $DIR/unnecessary_lazy_eval.rs:115:35
    |
 LL |     let _: Result<usize, usize> = res.or_else(|_| Ok(2));
-   |                                   ^^^^^^^^^^^^^^^^^^^^^^ help: use `or` instead: `res.or(Ok(2))`
+   |                                   ^^^^------------------
+   |                                       |
+   |                                       help: use `or(..)` instead: `or(Ok(2))`
 
 error: unnecessary closure used to substitute value for `Result::Err`
   --> $DIR/unnecessary_lazy_eval.rs:116:35
    |
 LL |     let _: Result<usize, usize> = res.or_else(|_| Ok(astronomers_pi));
-   |                                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: use `or` instead: `res.or(Ok(astronomers_pi))`
+   |                                   ^^^^-------------------------------
+   |                                       |
+   |                                       help: use `or(..)` instead: `or(Ok(astronomers_pi))`
 
 error: unnecessary closure used to substitute value for `Result::Err`
   --> $DIR/unnecessary_lazy_eval.rs:117:35
    |
 LL |     let _: Result<usize, usize> = res.or_else(|_| Ok(ext_str.some_field));
-   |                                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: use `or` instead: `res.or(Ok(ext_str.some_field))`
+   |                                   ^^^^-----------------------------------
+   |                                       |
+   |                                       help: use `or(..)` instead: `or(Ok(ext_str.some_field))`
 
-error: aborting due to 32 previous errors
+error: unnecessary closure used to substitute value for `Result::Err`
+  --> $DIR/unnecessary_lazy_eval.rs:118:35
+   |
+LL |       let _: Result<usize, usize> = res.
+   |  ___________________________________^
+LL | |         // some lines
+LL | |         // some lines
+LL | |         // some lines
+...  |
+LL | |         // some lines
+LL | |         or_else(|_| Ok(ext_str.some_field));
+   | |_________----------------------------------^
+   |           |
+   |           help: use `or(..)` instead: `or(Ok(ext_str.some_field))`
+
+error: aborting due to 33 previous errors
 
diff --git a/tests/ui/unnecessary_lazy_eval_unfixable.stderr b/tests/ui/unnecessary_lazy_eval_unfixable.stderr
index 75674b0a9d2..20acab6e844 100644
--- a/tests/ui/unnecessary_lazy_eval_unfixable.stderr
+++ b/tests/ui/unnecessary_lazy_eval_unfixable.stderr
@@ -2,7 +2,9 @@ error: unnecessary closure used to substitute value for `Result::Err`
   --> $DIR/unnecessary_lazy_eval_unfixable.rs:12:13
    |
 LL |     let _ = Ok(1).unwrap_or_else(|()| 2);
-   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: use `unwrap_or` instead: `Ok(1).unwrap_or(2)`
+   |             ^^^^^^----------------------
+   |                   |
+   |                   help: use `unwrap_or(..)` instead: `unwrap_or(2)`
    |
    = note: `-D clippy::unnecessary-lazy-evaluations` implied by `-D warnings`
 
@@ -10,13 +12,17 @@ error: unnecessary closure used to substitute value for `Result::Err`
   --> $DIR/unnecessary_lazy_eval_unfixable.rs:16:13
    |
 LL |     let _ = Ok(1).unwrap_or_else(|e::E| 2);
-   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: use `unwrap_or` instead: `Ok(1).unwrap_or(2)`
+   |             ^^^^^^------------------------
+   |                   |
+   |                   help: use `unwrap_or(..)` instead: `unwrap_or(2)`
 
 error: unnecessary closure used to substitute value for `Result::Err`
   --> $DIR/unnecessary_lazy_eval_unfixable.rs:17:13
    |
 LL |     let _ = Ok(1).unwrap_or_else(|SomeStruct { .. }| 2);
-   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: use `unwrap_or` instead: `Ok(1).unwrap_or(2)`
+   |             ^^^^^^-------------------------------------
+   |                   |
+   |                   help: use `unwrap_or(..)` instead: `unwrap_or(2)`
 
 error: aborting due to 3 previous errors
 
diff --git a/tests/ui/unnecessary_to_owned.fixed b/tests/ui/unnecessary_to_owned.fixed
index 720138db137..38ba41ac54e 100644
--- a/tests/ui/unnecessary_to_owned.fixed
+++ b/tests/ui/unnecessary_to_owned.fixed
@@ -212,3 +212,51 @@ fn get_file_path(_file_type: &FileType) -> Result<std::path::PathBuf, std::io::E
 }
 
 fn require_string(_: &String) {}
+
+// https://github.com/rust-lang/rust-clippy/issues/8507
+mod issue_8507 {
+    #![allow(dead_code)]
+
+    struct Opaque<P>(P);
+
+    pub trait Abstracted {}
+
+    impl<P> Abstracted for Opaque<P> {}
+
+    fn build<P>(p: P) -> Opaque<P>
+    where
+        P: AsRef<str>,
+    {
+        Opaque(p)
+    }
+
+    // Should not lint.
+    fn test_str(s: &str) -> Box<dyn Abstracted> {
+        Box::new(build(s.to_string()))
+    }
+
+    // Should not lint.
+    fn test_x(x: super::X) -> Box<dyn Abstracted> {
+        Box::new(build(x))
+    }
+
+    #[derive(Clone, Copy)]
+    struct Y(&'static str);
+
+    impl AsRef<str> for Y {
+        fn as_ref(&self) -> &str {
+            self.0
+        }
+    }
+
+    impl ToString for Y {
+        fn to_string(&self) -> String {
+            self.0.to_string()
+        }
+    }
+
+    // Should lint because Y is copy.
+    fn test_y(y: Y) -> Box<dyn Abstracted> {
+        Box::new(build(y))
+    }
+}
diff --git a/tests/ui/unnecessary_to_owned.rs b/tests/ui/unnecessary_to_owned.rs
index 60b2e718f5d..15fb7ee83e3 100644
--- a/tests/ui/unnecessary_to_owned.rs
+++ b/tests/ui/unnecessary_to_owned.rs
@@ -212,3 +212,51 @@ fn get_file_path(_file_type: &FileType) -> Result<std::path::PathBuf, std::io::E
 }
 
 fn require_string(_: &String) {}
+
+// https://github.com/rust-lang/rust-clippy/issues/8507
+mod issue_8507 {
+    #![allow(dead_code)]
+
+    struct Opaque<P>(P);
+
+    pub trait Abstracted {}
+
+    impl<P> Abstracted for Opaque<P> {}
+
+    fn build<P>(p: P) -> Opaque<P>
+    where
+        P: AsRef<str>,
+    {
+        Opaque(p)
+    }
+
+    // Should not lint.
+    fn test_str(s: &str) -> Box<dyn Abstracted> {
+        Box::new(build(s.to_string()))
+    }
+
+    // Should not lint.
+    fn test_x(x: super::X) -> Box<dyn Abstracted> {
+        Box::new(build(x))
+    }
+
+    #[derive(Clone, Copy)]
+    struct Y(&'static str);
+
+    impl AsRef<str> for Y {
+        fn as_ref(&self) -> &str {
+            self.0
+        }
+    }
+
+    impl ToString for Y {
+        fn to_string(&self) -> String {
+            self.0.to_string()
+        }
+    }
+
+    // Should lint because Y is copy.
+    fn test_y(y: Y) -> Box<dyn Abstracted> {
+        Box::new(build(y.to_string()))
+    }
+}
diff --git a/tests/ui/unnecessary_to_owned.stderr b/tests/ui/unnecessary_to_owned.stderr
index 1dfc65e22e2..c53ce32be77 100644
--- a/tests/ui/unnecessary_to_owned.stderr
+++ b/tests/ui/unnecessary_to_owned.stderr
@@ -491,5 +491,11 @@ LL -         let path = match get_file_path(&t) {
 LL +         let path = match get_file_path(t) {
    | 
 
-error: aborting due to 76 previous errors
+error: unnecessary use of `to_string`
+  --> $DIR/unnecessary_to_owned.rs:260:24
+   |
+LL |         Box::new(build(y.to_string()))
+   |                        ^^^^^^^^^^^^^ help: use: `y`
+
+error: aborting due to 77 previous errors