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-rw-r--r--clippy_lints/src/await_holding_invalid.rs8
-rw-r--r--clippy_lints/src/infinite_iter.rs15
-rw-r--r--clippy_lints/src/inherent_to_string.rs7
-rw-r--r--clippy_lints/src/lib.register_internal.rs2
-rw-r--r--clippy_lints/src/lib.register_lints.rs4
-rw-r--r--clippy_lints/src/lib.rs2
-rw-r--r--clippy_lints/src/manual_retain.rs2
-rw-r--r--clippy_lints/src/methods/filetype_is_file.rs7
-rw-r--r--clippy_lints/src/methods/inefficient_to_string.rs2
-rw-r--r--clippy_lints/src/methods/manual_str_repeat.rs8
-rw-r--r--clippy_lints/src/methods/useless_asref.rs5
-rw-r--r--clippy_lints/src/minmax.rs4
-rw-r--r--clippy_lints/src/non_octal_unix_permissions.rs5
-rw-r--r--clippy_lints/src/slow_vector_initialization.rs4
-rw-r--r--clippy_lints/src/unnecessary_owned_empty_strings.rs4
-rw-r--r--clippy_lints/src/unused_io_amount.rs7
-rw-r--r--clippy_lints/src/useless_conversion.rs4
-rw-r--r--clippy_lints/src/utils/internal_lints.rs277
18 files changed, 260 insertions, 107 deletions
diff --git a/clippy_lints/src/await_holding_invalid.rs b/clippy_lints/src/await_holding_invalid.rs
index 1761360fb28..24a3588ecf1 100644
--- a/clippy_lints/src/await_holding_invalid.rs
+++ b/clippy_lints/src/await_holding_invalid.rs
@@ -6,7 +6,7 @@ use rustc_hir::{def::Res, AsyncGeneratorKind, Body, BodyId, GeneratorKind};
 use rustc_lint::{LateContext, LateLintPass};
 use rustc_middle::ty::GeneratorInteriorTypeCause;
 use rustc_session::{declare_tool_lint, impl_lint_pass};
-use rustc_span::Span;
+use rustc_span::{sym, Span};
 
 use crate::utils::conf::DisallowedType;
 
@@ -276,9 +276,9 @@ fn emit_invalid_type(cx: &LateContext<'_>, span: Span, disallowed: &DisallowedTy
 }
 
 fn is_mutex_guard(cx: &LateContext<'_>, def_id: DefId) -> bool {
-    match_def_path(cx, def_id, &paths::MUTEX_GUARD)
-        || match_def_path(cx, def_id, &paths::RWLOCK_READ_GUARD)
-        || match_def_path(cx, def_id, &paths::RWLOCK_WRITE_GUARD)
+    cx.tcx.is_diagnostic_item(sym::MutexGuard, def_id)
+        || cx.tcx.is_diagnostic_item(sym::RwLockReadGuard, def_id)
+        || cx.tcx.is_diagnostic_item(sym::RwLockWriteGuard, def_id)
         || match_def_path(cx, def_id, &paths::PARKING_LOT_MUTEX_GUARD)
         || match_def_path(cx, def_id, &paths::PARKING_LOT_RWLOCK_READ_GUARD)
         || match_def_path(cx, def_id, &paths::PARKING_LOT_RWLOCK_WRITE_GUARD)
diff --git a/clippy_lints/src/infinite_iter.rs b/clippy_lints/src/infinite_iter.rs
index 8c2c96fa105..d1d2db27c6f 100644
--- a/clippy_lints/src/infinite_iter.rs
+++ b/clippy_lints/src/infinite_iter.rs
@@ -1,6 +1,6 @@
 use clippy_utils::diagnostics::span_lint;
+use clippy_utils::higher;
 use clippy_utils::ty::{implements_trait, is_type_diagnostic_item};
-use clippy_utils::{higher, match_def_path, path_def_id, paths};
 use rustc_hir::{BorrowKind, Closure, Expr, ExprKind};
 use rustc_lint::{LateContext, LateLintPass};
 use rustc_session::{declare_lint_pass, declare_tool_lint};
@@ -168,9 +168,16 @@ fn is_infinite(cx: &LateContext<'_>, expr: &Expr<'_>) -> Finiteness {
         },
         ExprKind::Block(block, _) => block.expr.as_ref().map_or(Finite, |e| is_infinite(cx, e)),
         ExprKind::Box(e) | ExprKind::AddrOf(BorrowKind::Ref, _, e) => is_infinite(cx, e),
-        ExprKind::Call(path, _) => path_def_id(cx, path)
-            .map_or(false, |id| match_def_path(cx, id, &paths::ITER_REPEAT))
-            .into(),
+        ExprKind::Call(path, _) => {
+            if let ExprKind::Path(ref qpath) = path.kind {
+                cx.qpath_res(qpath, path.hir_id)
+                    .opt_def_id()
+                    .map_or(false, |id| cx.tcx.is_diagnostic_item(sym::iter_repeat, id))
+                    .into()
+            } else {
+                Finite
+            }
+        },
         ExprKind::Struct(..) => higher::Range::hir(expr).map_or(false, |r| r.end.is_none()).into(),
         _ => Finite,
     }
diff --git a/clippy_lints/src/inherent_to_string.rs b/clippy_lints/src/inherent_to_string.rs
index d0e603dcf4e..676136df572 100644
--- a/clippy_lints/src/inherent_to_string.rs
+++ b/clippy_lints/src/inherent_to_string.rs
@@ -1,6 +1,6 @@
 use clippy_utils::diagnostics::span_lint_and_help;
 use clippy_utils::ty::{implements_trait, is_type_diagnostic_item};
-use clippy_utils::{get_trait_def_id, paths, return_ty, trait_ref_of_method};
+use clippy_utils::{return_ty, trait_ref_of_method};
 use if_chain::if_chain;
 use rustc_hir::{GenericParamKind, ImplItem, ImplItemKind};
 use rustc_lint::{LateContext, LateLintPass};
@@ -118,7 +118,10 @@ impl<'tcx> LateLintPass<'tcx> for InherentToString {
 }
 
 fn show_lint(cx: &LateContext<'_>, item: &ImplItem<'_>) {
-    let display_trait_id = get_trait_def_id(cx, &paths::DISPLAY_TRAIT).expect("Failed to get trait ID of `Display`!");
+    let display_trait_id = cx
+        .tcx
+        .get_diagnostic_item(sym::Display)
+        .expect("Failed to get trait ID of `Display`!");
 
     // Get the real type of 'self'
     let self_type = cx.tcx.fn_sig(item.def_id).input(0);
diff --git a/clippy_lints/src/lib.register_internal.rs b/clippy_lints/src/lib.register_internal.rs
index be63646a12f..71dfdab369b 100644
--- a/clippy_lints/src/lib.register_internal.rs
+++ b/clippy_lints/src/lib.register_internal.rs
@@ -13,10 +13,10 @@ store.register_group(true, "clippy::internal", Some("clippy_internal"), vec![
     LintId::of(utils::internal_lints::INVALID_CLIPPY_VERSION_ATTRIBUTE),
     LintId::of(utils::internal_lints::INVALID_PATHS),
     LintId::of(utils::internal_lints::LINT_WITHOUT_LINT_PASS),
-    LintId::of(utils::internal_lints::MATCH_TYPE_ON_DIAGNOSTIC_ITEM),
     LintId::of(utils::internal_lints::MISSING_CLIPPY_VERSION_ATTRIBUTE),
     LintId::of(utils::internal_lints::MISSING_MSRV_ATTR_IMPL),
     LintId::of(utils::internal_lints::OUTER_EXPN_EXPN_DATA),
     LintId::of(utils::internal_lints::PRODUCE_ICE),
+    LintId::of(utils::internal_lints::UNNECESSARY_DEF_PATH),
     LintId::of(utils::internal_lints::UNNECESSARY_SYMBOL_STR),
 ])
diff --git a/clippy_lints/src/lib.register_lints.rs b/clippy_lints/src/lib.register_lints.rs
index b8a20de9768..307ec40f40b 100644
--- a/clippy_lints/src/lib.register_lints.rs
+++ b/clippy_lints/src/lib.register_lints.rs
@@ -24,8 +24,6 @@ store.register_lints(&[
     #[cfg(feature = "internal")]
     utils::internal_lints::LINT_WITHOUT_LINT_PASS,
     #[cfg(feature = "internal")]
-    utils::internal_lints::MATCH_TYPE_ON_DIAGNOSTIC_ITEM,
-    #[cfg(feature = "internal")]
     utils::internal_lints::MISSING_CLIPPY_VERSION_ATTRIBUTE,
     #[cfg(feature = "internal")]
     utils::internal_lints::MISSING_MSRV_ATTR_IMPL,
@@ -34,6 +32,8 @@ store.register_lints(&[
     #[cfg(feature = "internal")]
     utils::internal_lints::PRODUCE_ICE,
     #[cfg(feature = "internal")]
+    utils::internal_lints::UNNECESSARY_DEF_PATH,
+    #[cfg(feature = "internal")]
     utils::internal_lints::UNNECESSARY_SYMBOL_STR,
     almost_complete_letter_range::ALMOST_COMPLETE_LETTER_RANGE,
     approx_const::APPROX_CONSTANT,
diff --git a/clippy_lints/src/lib.rs b/clippy_lints/src/lib.rs
index 05a9e13c9fb..3b78e492baa 100644
--- a/clippy_lints/src/lib.rs
+++ b/clippy_lints/src/lib.rs
@@ -535,7 +535,7 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf:
         store.register_late_pass(|_| Box::new(utils::internal_lints::InvalidPaths));
         store.register_late_pass(|_| Box::<utils::internal_lints::InterningDefinedSymbol>::default());
         store.register_late_pass(|_| Box::<utils::internal_lints::LintWithoutLintPass>::default());
-        store.register_late_pass(|_| Box::new(utils::internal_lints::MatchTypeOnDiagItem));
+        store.register_late_pass(|_| Box::new(utils::internal_lints::UnnecessaryDefPath));
         store.register_late_pass(|_| Box::new(utils::internal_lints::OuterExpnDataPass));
         store.register_late_pass(|_| Box::new(utils::internal_lints::MsrvAttrImpl));
     }
diff --git a/clippy_lints/src/manual_retain.rs b/clippy_lints/src/manual_retain.rs
index 570fe736818..3181bc86d17 100644
--- a/clippy_lints/src/manual_retain.rs
+++ b/clippy_lints/src/manual_retain.rs
@@ -92,7 +92,7 @@ fn check_into_iter(
         && match_def_path(cx, filter_def_id, &paths::CORE_ITER_FILTER)
         && let hir::ExprKind::MethodCall(_, struct_expr, [], _) = &into_iter_expr.kind
         && let Some(into_iter_def_id) = cx.typeck_results().type_dependent_def_id(into_iter_expr.hir_id)
-        && match_def_path(cx, into_iter_def_id, &paths::CORE_ITER_INTO_ITER)
+        && cx.tcx.lang_items().require(hir::LangItem::IntoIterIntoIter).ok() == Some(into_iter_def_id)
         && match_acceptable_type(cx, left_expr, msrv)
         && SpanlessEq::new(cx).eq_expr(left_expr, struct_expr) {
         suggest(cx, parent_expr, left_expr, target_expr);
diff --git a/clippy_lints/src/methods/filetype_is_file.rs b/clippy_lints/src/methods/filetype_is_file.rs
index 60f8283c3e0..3fef53739fb 100644
--- a/clippy_lints/src/methods/filetype_is_file.rs
+++ b/clippy_lints/src/methods/filetype_is_file.rs
@@ -1,17 +1,18 @@
 use clippy_utils::diagnostics::span_lint_and_help;
-use clippy_utils::ty::match_type;
-use clippy_utils::{get_parent_expr, paths};
+use clippy_utils::get_parent_expr;
+use clippy_utils::ty::is_type_diagnostic_item;
 use if_chain::if_chain;
 use rustc_hir as hir;
 use rustc_lint::LateContext;
 use rustc_span::source_map::Span;
+use rustc_span::sym;
 
 use super::FILETYPE_IS_FILE;
 
 pub(super) fn check(cx: &LateContext<'_>, expr: &hir::Expr<'_>, recv: &hir::Expr<'_>) {
     let ty = cx.typeck_results().expr_ty(recv);
 
-    if !match_type(cx, ty, &paths::FILE_TYPE) {
+    if !is_type_diagnostic_item(cx, ty, sym::FileType) {
         return;
     }
 
diff --git a/clippy_lints/src/methods/inefficient_to_string.rs b/clippy_lints/src/methods/inefficient_to_string.rs
index e5dc3711b0b..ede3b8bb74e 100644
--- a/clippy_lints/src/methods/inefficient_to_string.rs
+++ b/clippy_lints/src/methods/inefficient_to_string.rs
@@ -65,7 +65,7 @@ fn specializes_tostring(cx: &LateContext<'_>, ty: Ty<'_>) -> bool {
     }
 
     if let ty::Adt(adt, substs) = ty.kind() {
-        match_def_path(cx, adt.did(), &paths::COW) && substs.type_at(1).is_str()
+        cx.tcx.is_diagnostic_item(sym::Cow, adt.did()) && substs.type_at(1).is_str()
     } else {
         false
     }
diff --git a/clippy_lints/src/methods/manual_str_repeat.rs b/clippy_lints/src/methods/manual_str_repeat.rs
index 67e504af161..8b6b8f1bf16 100644
--- a/clippy_lints/src/methods/manual_str_repeat.rs
+++ b/clippy_lints/src/methods/manual_str_repeat.rs
@@ -1,8 +1,8 @@
 use clippy_utils::diagnostics::span_lint_and_sugg;
+use clippy_utils::is_path_diagnostic_item;
 use clippy_utils::source::{snippet_with_applicability, snippet_with_context};
 use clippy_utils::sugg::Sugg;
-use clippy_utils::ty::{is_type_diagnostic_item, is_type_lang_item, match_type};
-use clippy_utils::{is_expr_path_def_path, paths};
+use clippy_utils::ty::{is_type_diagnostic_item, is_type_lang_item};
 use if_chain::if_chain;
 use rustc_ast::LitKind;
 use rustc_errors::Applicability;
@@ -38,7 +38,7 @@ fn parse_repeat_arg(cx: &LateContext<'_>, e: &Expr<'_>) -> Option<RepeatKind> {
         let ty = cx.typeck_results().expr_ty(e);
         if is_type_diagnostic_item(cx, ty, sym::String)
             || (is_type_lang_item(cx, ty, LangItem::OwnedBox) && get_ty_param(ty).map_or(false, Ty::is_str))
-            || (match_type(cx, ty, &paths::COW) && get_ty_param(ty).map_or(false, Ty::is_str))
+            || (is_type_diagnostic_item(cx, ty, sym::Cow) && get_ty_param(ty).map_or(false, Ty::is_str))
         {
             Some(RepeatKind::String)
         } else {
@@ -57,7 +57,7 @@ pub(super) fn check(
 ) {
     if_chain! {
         if let ExprKind::Call(repeat_fn, [repeat_arg]) = take_self_arg.kind;
-        if is_expr_path_def_path(cx, repeat_fn, &paths::ITER_REPEAT);
+        if is_path_diagnostic_item(cx, repeat_fn, sym::iter_repeat);
         if is_type_diagnostic_item(cx, cx.typeck_results().expr_ty(collect_expr), sym::String);
         if let Some(collect_id) = cx.typeck_results().type_dependent_def_id(collect_expr.hir_id);
         if let Some(take_id) = cx.typeck_results().type_dependent_def_id(take_expr.hir_id);
diff --git a/clippy_lints/src/methods/useless_asref.rs b/clippy_lints/src/methods/useless_asref.rs
index 0380a82411a..c1139d84e2f 100644
--- a/clippy_lints/src/methods/useless_asref.rs
+++ b/clippy_lints/src/methods/useless_asref.rs
@@ -1,11 +1,12 @@
 use clippy_utils::diagnostics::span_lint_and_sugg;
 use clippy_utils::source::snippet_with_applicability;
 use clippy_utils::ty::walk_ptrs_ty_depth;
-use clippy_utils::{get_parent_expr, match_trait_method, paths};
+use clippy_utils::{get_parent_expr, is_trait_method};
 use if_chain::if_chain;
 use rustc_errors::Applicability;
 use rustc_hir as hir;
 use rustc_lint::LateContext;
+use rustc_span::sym;
 
 use super::USELESS_ASREF;
 
@@ -13,7 +14,7 @@ use super::USELESS_ASREF;
 pub(super) fn check(cx: &LateContext<'_>, expr: &hir::Expr<'_>, call_name: &str, recvr: &hir::Expr<'_>) {
     // when we get here, we've already checked that the call name is "as_ref" or "as_mut"
     // check if the call is to the actual `AsRef` or `AsMut` trait
-    if match_trait_method(cx, expr, &paths::ASREF_TRAIT) || match_trait_method(cx, expr, &paths::ASMUT_TRAIT) {
+    if is_trait_method(cx, expr, sym::AsRef) || is_trait_method(cx, expr, sym::AsMut) {
         // check if the type after `as_ref` or `as_mut` is the same as before
         let rcv_ty = cx.typeck_results().expr_ty(recvr);
         let res_ty = cx.typeck_results().expr_ty(expr);
diff --git a/clippy_lints/src/minmax.rs b/clippy_lints/src/minmax.rs
index 4d8579135fc..4f967755bfa 100644
--- a/clippy_lints/src/minmax.rs
+++ b/clippy_lints/src/minmax.rs
@@ -1,6 +1,6 @@
 use clippy_utils::consts::{constant_simple, Constant};
 use clippy_utils::diagnostics::span_lint;
-use clippy_utils::{match_trait_method, paths};
+use clippy_utils::is_trait_method;
 use rustc_hir::{Expr, ExprKind};
 use rustc_lint::{LateContext, LateLintPass};
 use rustc_session::{declare_lint_pass, declare_tool_lint};
@@ -83,7 +83,7 @@ fn min_max<'a>(cx: &LateContext<'_>, expr: &'a Expr<'a>) -> Option<(MinMax, Cons
             }
         },
         ExprKind::MethodCall(path, receiver, args @ [_], _) => {
-            if cx.typeck_results().expr_ty(receiver).is_floating_point() || match_trait_method(cx, expr, &paths::ORD) {
+            if cx.typeck_results().expr_ty(receiver).is_floating_point() || is_trait_method(cx, expr, sym::Ord) {
                 if path.ident.name == sym!(max) {
                     fetch_const(cx, Some(receiver), args, MinMax::Max)
                 } else if path.ident.name == sym!(min) {
diff --git a/clippy_lints/src/non_octal_unix_permissions.rs b/clippy_lints/src/non_octal_unix_permissions.rs
index 25fb4f0f4cf..1a765b14892 100644
--- a/clippy_lints/src/non_octal_unix_permissions.rs
+++ b/clippy_lints/src/non_octal_unix_permissions.rs
@@ -1,12 +1,13 @@
 use clippy_utils::diagnostics::span_lint_and_sugg;
 use clippy_utils::source::{snippet_opt, snippet_with_applicability};
-use clippy_utils::ty::match_type;
+use clippy_utils::ty::{is_type_diagnostic_item, match_type};
 use clippy_utils::{match_def_path, paths};
 use if_chain::if_chain;
 use rustc_errors::Applicability;
 use rustc_hir::{Expr, ExprKind};
 use rustc_lint::{LateContext, LateLintPass};
 use rustc_session::{declare_lint_pass, declare_tool_lint};
+use rustc_span::sym;
 
 declare_clippy_lint! {
     /// ### What it does
@@ -49,7 +50,7 @@ impl<'tcx> LateLintPass<'tcx> for NonOctalUnixPermissions {
                 if_chain! {
                     if (path.ident.name == sym!(mode)
                         && (match_type(cx, obj_ty, &paths::OPEN_OPTIONS)
-                            || match_type(cx, obj_ty, &paths::DIR_BUILDER)))
+                            || is_type_diagnostic_item(cx, obj_ty, sym::DirBuilder)))
                         || (path.ident.name == sym!(set_mode) && match_type(cx, obj_ty, &paths::PERMISSIONS));
                     if let ExprKind::Lit(_) = param.kind;
 
diff --git a/clippy_lints/src/slow_vector_initialization.rs b/clippy_lints/src/slow_vector_initialization.rs
index 6e5d88e1b59..76039923151 100644
--- a/clippy_lints/src/slow_vector_initialization.rs
+++ b/clippy_lints/src/slow_vector_initialization.rs
@@ -2,7 +2,7 @@ use clippy_utils::diagnostics::span_lint_and_then;
 use clippy_utils::sugg::Sugg;
 use clippy_utils::ty::is_type_diagnostic_item;
 use clippy_utils::{
-    get_enclosing_block, is_expr_path_def_path, is_integer_literal, path_to_local, path_to_local_id, paths, SpanlessEq,
+    get_enclosing_block, is_integer_literal, is_path_diagnostic_item, path_to_local, path_to_local_id, SpanlessEq,
 };
 use if_chain::if_chain;
 use rustc_errors::Applicability;
@@ -254,7 +254,7 @@ impl<'a, 'tcx> VectorInitializationVisitor<'a, 'tcx> {
     fn is_repeat_zero(&self, expr: &Expr<'_>) -> bool {
         if_chain! {
             if let ExprKind::Call(fn_expr, [repeat_arg]) = expr.kind;
-            if is_expr_path_def_path(self.cx, fn_expr, &paths::ITER_REPEAT);
+            if is_path_diagnostic_item(self.cx, fn_expr, sym::iter_repeat);
             if is_integer_literal(repeat_arg, 0);
             then {
                 true
diff --git a/clippy_lints/src/unnecessary_owned_empty_strings.rs b/clippy_lints/src/unnecessary_owned_empty_strings.rs
index 8a4f4c0ad97..016aacbf9da 100644
--- a/clippy_lints/src/unnecessary_owned_empty_strings.rs
+++ b/clippy_lints/src/unnecessary_owned_empty_strings.rs
@@ -3,7 +3,7 @@ use clippy_utils::{match_def_path, paths};
 use if_chain::if_chain;
 use rustc_ast::ast::LitKind;
 use rustc_errors::Applicability;
-use rustc_hir::{BorrowKind, Expr, ExprKind, Mutability};
+use rustc_hir::{BorrowKind, Expr, ExprKind, LangItem, Mutability};
 use rustc_lint::{LateContext, LateLintPass};
 use rustc_middle::ty;
 use rustc_session::{declare_lint_pass, declare_tool_lint};
@@ -55,7 +55,7 @@ impl<'tcx> LateLintPass<'tcx> for UnnecessaryOwnedEmptyStrings {
                         );
                 } else {
                     if_chain! {
-                        if match_def_path(cx, fun_def_id, &paths::FROM_FROM);
+                        if cx.tcx.lang_items().require(LangItem::FromFrom).ok() == Some(fun_def_id);
                         if let [.., last_arg] = args;
                         if let ExprKind::Lit(spanned) = &last_arg.kind;
                         if let LitKind::Str(symbol, _) = spanned.node;
diff --git a/clippy_lints/src/unused_io_amount.rs b/clippy_lints/src/unused_io_amount.rs
index b38d71784fc..8bcdff66331 100644
--- a/clippy_lints/src/unused_io_amount.rs
+++ b/clippy_lints/src/unused_io_amount.rs
@@ -1,8 +1,9 @@
 use clippy_utils::diagnostics::{span_lint, span_lint_and_help};
-use clippy_utils::{is_try, match_trait_method, paths};
+use clippy_utils::{is_trait_method, is_try, match_trait_method, paths};
 use rustc_hir as hir;
 use rustc_lint::{LateContext, LateLintPass};
 use rustc_session::{declare_lint_pass, declare_tool_lint};
+use rustc_span::sym;
 
 declare_clippy_lint! {
     /// ### What it does
@@ -116,13 +117,13 @@ fn check_method_call(cx: &LateContext<'_>, call: &hir::Expr<'_>, expr: &hir::Exp
             match_trait_method(cx, call, &paths::FUTURES_IO_ASYNCREADEXT)
                 || match_trait_method(cx, call, &paths::TOKIO_IO_ASYNCREADEXT)
         } else {
-            match_trait_method(cx, call, &paths::IO_READ)
+            is_trait_method(cx, call, sym::IoRead)
         };
         let write_trait = if is_await {
             match_trait_method(cx, call, &paths::FUTURES_IO_ASYNCWRITEEXT)
                 || match_trait_method(cx, call, &paths::TOKIO_IO_ASYNCWRITEEXT)
         } else {
-            match_trait_method(cx, call, &paths::IO_WRITE)
+            is_trait_method(cx, call, sym::IoWrite)
         };
 
         match (read_trait, write_trait, symbol, is_await) {
diff --git a/clippy_lints/src/useless_conversion.rs b/clippy_lints/src/useless_conversion.rs
index 50c5a832430..a82643a59f9 100644
--- a/clippy_lints/src/useless_conversion.rs
+++ b/clippy_lints/src/useless_conversion.rs
@@ -5,7 +5,7 @@ use clippy_utils::ty::{is_type_diagnostic_item, same_type_and_consts};
 use clippy_utils::{get_parent_expr, is_trait_method, match_def_path, paths};
 use if_chain::if_chain;
 use rustc_errors::Applicability;
-use rustc_hir::{Expr, ExprKind, HirId, MatchSource};
+use rustc_hir::{Expr, ExprKind, HirId, LangItem, MatchSource};
 use rustc_lint::{LateContext, LateLintPass};
 use rustc_middle::ty;
 use rustc_session::{declare_tool_lint, impl_lint_pass};
@@ -154,7 +154,7 @@ impl<'tcx> LateLintPass<'tcx> for UselessConversion {
                         }
 
                         if_chain! {
-                            if match_def_path(cx, def_id, &paths::FROM_FROM);
+                            if cx.tcx.lang_items().require(LangItem::FromFrom).ok() == Some(def_id);
                             if same_type_and_consts(a, b);
 
                             then {
diff --git a/clippy_lints/src/utils/internal_lints.rs b/clippy_lints/src/utils/internal_lints.rs
index bc3f920a087..6309a04c73d 100644
--- a/clippy_lints/src/utils/internal_lints.rs
+++ b/clippy_lints/src/utils/internal_lints.rs
@@ -2,11 +2,11 @@ use crate::utils::internal_lints::metadata_collector::is_deprecated_lint;
 use clippy_utils::consts::{constant_simple, Constant};
 use clippy_utils::diagnostics::{span_lint, span_lint_and_help, span_lint_and_sugg, span_lint_and_then};
 use clippy_utils::macros::root_macro_call_first_node;
-use clippy_utils::source::snippet;
+use clippy_utils::source::{snippet, snippet_with_applicability};
 use clippy_utils::ty::match_type;
 use clippy_utils::{
-    def_path_res, higher, is_else_clause, is_expn_of, is_expr_path_def_path, is_lint_allowed, match_def_path,
-    method_calls, paths, peel_blocks_with_stmt, SpanlessEq,
+    def_path_res, higher, is_else_clause, is_expn_of, is_expr_path_def_path, is_lint_allowed, match_any_def_paths,
+    match_def_path, method_calls, paths, peel_blocks_with_stmt, peel_hir_expr_refs, SpanlessEq,
 };
 use if_chain::if_chain;
 use rustc_ast as ast;
@@ -20,21 +20,24 @@ use rustc_hir::def_id::DefId;
 use rustc_hir::hir_id::CRATE_HIR_ID;
 use rustc_hir::intravisit::Visitor;
 use rustc_hir::{
-    BinOpKind, Block, Closure, Expr, ExprKind, HirId, Item, Local, MutTy, Mutability, Node, Path, Stmt, StmtKind, Ty,
+    BinOpKind, Block, Closure, Expr, ExprKind, HirId, Item, Local, MutTy, Mutability, Node, Path, Stmt, StmtKind,
     TyKind, UnOp,
 };
 use rustc_hir_analysis::hir_ty_to_ty;
 use rustc_lint::{EarlyContext, EarlyLintPass, LateContext, LateLintPass, LintContext};
 use rustc_middle::hir::nested_filter;
-use rustc_middle::mir::interpret::ConstValue;
-use rustc_middle::ty::{self, fast_reject::SimplifiedTypeGen, subst::GenericArgKind, FloatTy};
+use rustc_middle::mir::interpret::{Allocation, ConstValue, GlobalAlloc};
+use rustc_middle::ty::{
+    self, fast_reject::SimplifiedTypeGen, subst::GenericArgKind, AssocKind, DefIdTree, FloatTy, Ty,
+};
 use rustc_semver::RustcVersion;
 use rustc_session::{declare_lint_pass, declare_tool_lint, impl_lint_pass};
 use rustc_span::source_map::Spanned;
-use rustc_span::symbol::Symbol;
+use rustc_span::symbol::{Ident, Symbol};
 use rustc_span::{sym, BytePos, Span};
 
 use std::borrow::{Borrow, Cow};
+use std::str;
 
 #[cfg(feature = "internal")]
 pub mod metadata_collector;
@@ -226,11 +229,11 @@ declare_clippy_lint! {
 
 declare_clippy_lint! {
     /// ### What it does
-    /// Checks for calls to `utils::match_type()` on a type diagnostic item
-    /// and suggests to use `utils::is_type_diagnostic_item()` instead.
+    /// Checks for usages of def paths when a diagnostic item or a `LangItem` could be used.
     ///
     /// ### Why is this bad?
-    /// `utils::is_type_diagnostic_item()` does not require hardcoded paths.
+    /// The path for an item is subject to change and is less efficient to look up than a
+    /// diagnostic item or a `LangItem`.
     ///
     /// ### Example
     /// ```rust,ignore
@@ -241,9 +244,9 @@ declare_clippy_lint! {
     /// ```rust,ignore
     /// utils::is_type_diagnostic_item(cx, ty, sym::Vec)
     /// ```
-    pub MATCH_TYPE_ON_DIAGNOSTIC_ITEM,
+    pub UNNECESSARY_DEF_PATH,
     internal,
-    "using `utils::match_type()` instead of `utils::is_type_diagnostic_item()`"
+    "using a def path when a diagnostic item or a `LangItem` is available"
 }
 
 declare_clippy_lint! {
@@ -537,7 +540,7 @@ impl<'tcx> LateLintPass<'tcx> for LintWithoutLintPass {
     }
 }
 
-fn is_lint_ref_type<'tcx>(cx: &LateContext<'tcx>, ty: &Ty<'_>) -> bool {
+fn is_lint_ref_type<'tcx>(cx: &LateContext<'tcx>, ty: &hir::Ty<'_>) -> bool {
     if let TyKind::Rptr(
         _,
         MutTy {
@@ -888,89 +891,225 @@ fn suggest_note(
     );
 }
 
-declare_lint_pass!(MatchTypeOnDiagItem => [MATCH_TYPE_ON_DIAGNOSTIC_ITEM]);
+declare_lint_pass!(UnnecessaryDefPath => [UNNECESSARY_DEF_PATH]);
 
-impl<'tcx> LateLintPass<'tcx> for MatchTypeOnDiagItem {
+#[allow(clippy::too_many_lines)]
+impl<'tcx> LateLintPass<'tcx> for UnnecessaryDefPath {
     fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx hir::Expr<'_>) {
-        if is_lint_allowed(cx, MATCH_TYPE_ON_DIAGNOSTIC_ITEM, expr.hir_id) {
+        enum Item {
+            LangItem(Symbol),
+            DiagnosticItem(Symbol),
+        }
+        static PATHS: &[&[&str]] = &[
+            &["clippy_utils", "match_def_path"],
+            &["clippy_utils", "match_trait_method"],
+            &["clippy_utils", "ty", "match_type"],
+            &["clippy_utils", "is_expr_path_def_path"],
+        ];
+
+        if is_lint_allowed(cx, UNNECESSARY_DEF_PATH, expr.hir_id) {
             return;
         }
 
         if_chain! {
-            // Check if this is a call to utils::match_type()
-            if let ExprKind::Call(fn_path, [context, ty, ty_path]) = expr.kind;
-            if is_expr_path_def_path(cx, fn_path, &["clippy_utils", "ty", "match_type"]);
+            if let ExprKind::Call(func, [cx_arg, def_arg, args@..]) = expr.kind;
+            if let ExprKind::Path(path) = &func.kind;
+            if let Some(id) = cx.qpath_res(path, func.hir_id).opt_def_id();
+            if let Some(which_path) = match_any_def_paths(cx, id, PATHS);
+            let item_arg = if which_path == 4 { &args[1] } else { &args[0] };
             // Extract the path to the matched type
-            if let Some(segments) = path_to_matched_type(cx, ty_path);
-            let segments: Vec<&str> = segments.iter().map(Symbol::as_str).collect();
-            if let Some(ty_did) = def_path_res(cx, &segments[..]).opt_def_id();
-            // Check if the matched type is a diagnostic item
-            if let Some(item_name) = cx.tcx.get_diagnostic_name(ty_did);
+            if let Some(segments) = path_to_matched_type(cx, item_arg);
+            let segments: Vec<&str> = segments.iter().map(|sym| &**sym).collect();
+            if let Some(def_id) = def_path_res(cx, &segments[..]).opt_def_id();
             then {
-                // TODO: check paths constants from external crates.
-                let cx_snippet = snippet(cx, context.span, "_");
-                let ty_snippet = snippet(cx, ty.span, "_");
+                // def_path_res will match field names before anything else, but for this we want to match
+                // inherent functions first.
+                let def_id = if cx.tcx.def_kind(def_id) == DefKind::Field {
+                    let method_name = *segments.last().unwrap();
+                    cx.tcx.def_key(def_id).parent
+                        .and_then(|parent_idx|
+                            cx.tcx.inherent_impls(DefId { index: parent_idx, krate: def_id.krate }).iter()
+                                .find_map(|impl_id| cx.tcx.associated_items(*impl_id)
+                                    .find_by_name_and_kind(
+                                        cx.tcx,
+                                        Ident::from_str(method_name),
+                                        AssocKind::Fn,
+                                        *impl_id,
+                                    )
+                                )
+                        )
+                        .map_or(def_id, |item| item.def_id)
+                } else {
+                    def_id
+                };
 
-                span_lint_and_sugg(
+                // Check if the target item is a diagnostic item or LangItem.
+                let (msg, item) = if let Some(item_name)
+                    = cx.tcx.diagnostic_items(def_id.krate).id_to_name.get(&def_id)
+                {
+                    (
+                        "use of a def path to a diagnostic item",
+                        Item::DiagnosticItem(*item_name),
+                    )
+                } else if let Some(lang_item) = cx.tcx.lang_items().items().iter().position(|id| *id == Some(def_id)) {
+                    let lang_items = def_path_res(cx, &["rustc_hir", "lang_items", "LangItem"]).def_id();
+                    let item_name = cx.tcx.adt_def(lang_items).variants().iter().nth(lang_item).unwrap().name;
+                    (
+                        "use of a def path to a `LangItem`",
+                        Item::LangItem(item_name),
+                    )
+                } else {
+                    return;
+                };
+
+                let has_ctor = match cx.tcx.def_kind(def_id) {
+                    DefKind::Struct => {
+                        let variant = cx.tcx.adt_def(def_id).non_enum_variant();
+                        variant.ctor_def_id.is_some() && variant.fields.iter().all(|f| f.vis.is_public())
+                    }
+                    DefKind::Variant => {
+                        let variant = cx.tcx.adt_def(cx.tcx.parent(def_id)).variant_with_id(def_id);
+                        variant.ctor_def_id.is_some() && variant.fields.iter().all(|f| f.vis.is_public())
+                    }
+                    _ => false,
+                };
+
+                let mut app = Applicability::MachineApplicable;
+                let cx_snip = snippet_with_applicability(cx, cx_arg.span, "..", &mut app);
+                let def_snip = snippet_with_applicability(cx, def_arg.span, "..", &mut app);
+                let (sugg, with_note) = match (which_path, item) {
+                    // match_def_path
+                    (0, Item::DiagnosticItem(item)) =>
+                        (format!("{cx_snip}.tcx.is_diagnostic_item(sym::{item}, {def_snip})"), has_ctor),
+                    (0, Item::LangItem(item)) => (
+                        format!("{cx_snip}.tcx.lang_items().require(LangItem::{item}).ok() == Some({def_snip})"),
+                        has_ctor
+                    ),
+                    // match_trait_method
+                    (1, Item::DiagnosticItem(item)) =>
+                        (format!("is_trait_method({cx_snip}, {def_snip}, sym::{item})"), false),
+                    // match_type
+                    (2, Item::DiagnosticItem(item)) =>
+                        (format!("is_type_diagnostic_item({cx_snip}, {def_snip}, sym::{item})"), false),
+                    (2, Item::LangItem(item)) =>
+                        (format!("is_type_lang_item({cx_snip}, {def_snip}, LangItem::{item})"), false),
+                    // is_expr_path_def_path
+                    (3, Item::DiagnosticItem(item)) if has_ctor => (
+                        format!(
+                            "is_res_diag_ctor({cx_snip}, path_res({cx_snip}, {def_snip}), sym::{item})",
+                        ),
+                        false,
+                    ),
+                    (3, Item::LangItem(item)) if has_ctor => (
+                        format!(
+                            "is_res_lang_ctor({cx_snip}, path_res({cx_snip}, {def_snip}), LangItem::{item})",
+                        ),
+                        false,
+                    ),
+                    (3, Item::DiagnosticItem(item)) =>
+                        (format!("is_path_diagnostic_item({cx_snip}, {def_snip}, sym::{item})"), false),
+                    (3, Item::LangItem(item)) => (
+                        format!(
+                            "path_res({cx_snip}, {def_snip}).opt_def_id()\
+                                .map_or(false, |id| {cx_snip}.tcx.lang_items().require(LangItem::{item}).ok() == Some(id))",
+                        ),
+                        false,
+                    ),
+                    _ => return,
+                };
+
+                span_lint_and_then(
                     cx,
-                    MATCH_TYPE_ON_DIAGNOSTIC_ITEM,
+                    UNNECESSARY_DEF_PATH,
                     expr.span,
-                    "usage of `clippy_utils::ty::match_type()` on a type diagnostic item",
-                    "try",
-                    format!("clippy_utils::ty::is_type_diagnostic_item({cx_snippet}, {ty_snippet}, sym::{item_name})"),
-                    Applicability::MaybeIncorrect,
+                    msg,
+                    |diag| {
+                        diag.span_suggestion(expr.span, "try", sugg, app);
+                        if with_note {
+                            diag.help(
+                                "if this `DefId` came from a constructor expression or pattern then the \
+                                    parent `DefId` should be used instead"
+                            );
+                        }
+                    },
                 );
             }
         }
     }
 }
 
-fn path_to_matched_type(cx: &LateContext<'_>, expr: &hir::Expr<'_>) -> Option<Vec<Symbol>> {
-    use rustc_hir::ItemKind;
-
-    match &expr.kind {
-        ExprKind::AddrOf(.., expr) => return path_to_matched_type(cx, expr),
-        ExprKind::Path(qpath) => match cx.qpath_res(qpath, expr.hir_id) {
+fn path_to_matched_type(cx: &LateContext<'_>, expr: &hir::Expr<'_>) -> Option<Vec<String>> {
+    match peel_hir_expr_refs(expr).0.kind {
+        ExprKind::Path(ref qpath) => match cx.qpath_res(qpath, expr.hir_id) {
             Res::Local(hir_id) => {
                 let parent_id = cx.tcx.hir().get_parent_node(hir_id);
-                if let Some(Node::Local(local)) = cx.tcx.hir().find(parent_id) {
-                    if let Some(init) = local.init {
-                        return path_to_matched_type(cx, init);
-                    }
+                if let Some(Node::Local(Local { init: Some(init), .. })) = cx.tcx.hir().find(parent_id) {
+                    path_to_matched_type(cx, init)
+                } else {
+                    None
                 }
             },
-            Res::Def(DefKind::Const | DefKind::Static(..), def_id) => {
-                if let Some(Node::Item(item)) = cx.tcx.hir().get_if_local(def_id) {
-                    if let ItemKind::Const(.., body_id) | ItemKind::Static(.., body_id) = item.kind {
-                        let body = cx.tcx.hir().body(body_id);
-                        return path_to_matched_type(cx, body.value);
-                    }
-                }
+            Res::Def(DefKind::Static(_), def_id) => read_mir_alloc_def_path(
+                cx,
+                cx.tcx.eval_static_initializer(def_id).ok()?.inner(),
+                cx.tcx.type_of(def_id),
+            ),
+            Res::Def(DefKind::Const, def_id) => match cx.tcx.const_eval_poly(def_id).ok()? {
+                ConstValue::ByRef { alloc, offset } if offset.bytes() == 0 => {
+                    read_mir_alloc_def_path(cx, alloc.inner(), cx.tcx.type_of(def_id))
+                },
+                _ => None,
             },
-            _ => {},
+            _ => None,
         },
-        ExprKind::Array(exprs) => {
-            let segments: Vec<Symbol> = exprs
-                .iter()
-                .filter_map(|expr| {
-                    if let ExprKind::Lit(lit) = &expr.kind {
-                        if let LitKind::Str(sym, _) = lit.node {
-                            return Some(sym);
-                        }
+        ExprKind::Array(exprs) => exprs
+            .iter()
+            .map(|expr| {
+                if let ExprKind::Lit(lit) = &expr.kind {
+                    if let LitKind::Str(sym, _) = lit.node {
+                        return Some((*sym.as_str()).to_owned());
                     }
+                }
 
-                    None
-                })
-                .collect();
-
-            if segments.len() == exprs.len() {
-                return Some(segments);
-            }
-        },
-        _ => {},
+                None
+            })
+            .collect(),
+        _ => None,
     }
+}
 
-    None
+fn read_mir_alloc_def_path<'tcx>(cx: &LateContext<'tcx>, alloc: &'tcx Allocation, ty: Ty<'_>) -> Option<Vec<String>> {
+    let (alloc, ty) = if let ty::Ref(_, ty, Mutability::Not) = *ty.kind() {
+        let &alloc = alloc.provenance().values().next()?;
+        if let GlobalAlloc::Memory(alloc) = cx.tcx.global_alloc(alloc) {
+            (alloc.inner(), ty)
+        } else {
+            return None;
+        }
+    } else {
+        (alloc, ty)
+    };
+
+    if let ty::Array(ty, _) | ty::Slice(ty) = *ty.kind()
+        && let ty::Ref(_, ty, Mutability::Not) = *ty.kind()
+        && ty.is_str()
+    {
+        alloc
+            .provenance()
+            .values()
+            .map(|&alloc| {
+                if let GlobalAlloc::Memory(alloc) = cx.tcx.global_alloc(alloc) {
+                    let alloc = alloc.inner();
+                    str::from_utf8(alloc.inspect_with_uninit_and_ptr_outside_interpreter(0..alloc.len()))
+                        .ok().map(ToOwned::to_owned)
+                } else {
+                    None
+                }
+            })
+            .collect()
+    } else {
+        None
+    }
 }
 
 // This is not a complete resolver for paths. It works on all the paths currently used in the paths