option_if_let_else - distinguish pure from impure else expressions

14 files changed, 420 insertions, 214 deletions

diff --git a/clippy_lints/src/methods/bind_instead_of_map.rs b/clippy_lints/src/methods/bind_instead_of_map.rs
index 498f12518f8..ae37942e55a 100644
--- a/clippy_lints/src/methods/bind_instead_of_map.rs
+++ b/clippy_lints/src/methods/bind_instead_of_map.rs
@@ -12,6 +12,7 @@ use rustc_middle::hir::map::Map;
 use rustc_span::Span;
 
 pub(crate) struct OptionAndThenSome;
+
 impl BindInsteadOfMap for OptionAndThenSome {
     const TYPE_NAME: &'static str = "Option";
     const TYPE_QPATH: &'static [&'static str] = &paths::OPTION;
@@ -24,6 +25,7 @@ impl BindInsteadOfMap for OptionAndThenSome {
 }
 
 pub(crate) struct ResultAndThenOk;
+
 impl BindInsteadOfMap for ResultAndThenOk {
     const TYPE_NAME: &'static str = "Result";
     const TYPE_QPATH: &'static [&'static str] = &paths::RESULT;
@@ -36,6 +38,7 @@ impl BindInsteadOfMap for ResultAndThenOk {
 }
 
 pub(crate) struct ResultOrElseErrInfo;
+
 impl BindInsteadOfMap for ResultOrElseErrInfo {
     const TYPE_NAME: &'static str = "Result";
     const TYPE_QPATH: &'static [&'static str] = &paths::RESULT;
@@ -120,9 +123,9 @@ pub(crate) trait BindInsteadOfMap {
         }
     }
 
-    fn lint_closure(cx: &LateContext<'_>, expr: &hir::Expr<'_>, closure_expr: &hir::Expr<'_>) {
+    fn lint_closure(cx: &LateContext<'_>, expr: &hir::Expr<'_>, closure_expr: &hir::Expr<'_>) -> bool {
         let mut suggs = Vec::new();
-        let can_sugg = find_all_ret_expressions(cx, closure_expr, |ret_expr| {
+        let can_sugg: bool = find_all_ret_expressions(cx, closure_expr, |ret_expr| {
             if_chain! {
                 if !in_macro(ret_expr.span);
                 if let hir::ExprKind::Call(ref func_path, ref args) = ret_expr.kind;
@@ -153,12 +156,13 @@ pub(crate) trait BindInsteadOfMap {
                 )
             });
         }
+        can_sugg
     }
 
     /// Lint use of `_.and_then(|x| Some(y))` for `Option`s
-    fn lint(cx: &LateContext<'_>, expr: &hir::Expr<'_>, args: &[hir::Expr<'_>]) {
+    fn lint(cx: &LateContext<'_>, expr: &hir::Expr<'_>, args: &[hir::Expr<'_>]) -> bool {
         if !match_type(cx, cx.typeck_results().expr_ty(&args[0]), Self::TYPE_QPATH) {
-            return;
+            return false;
         }
 
         match args[1].kind {
@@ -166,8 +170,10 @@ pub(crate) trait BindInsteadOfMap {
                 let closure_body = cx.tcx.hir().body(body_id);
                 let closure_expr = remove_blocks(&closure_body.value);
 
-                if !Self::lint_closure_autofixable(cx, expr, args, closure_expr, closure_args_span) {
-                    Self::lint_closure(cx, expr, closure_expr);
+                if Self::lint_closure_autofixable(cx, expr, args, closure_expr, closure_args_span) {
+                    true
+                } else {
+                    Self::lint_closure(cx, expr, closure_expr)
                 }
             },
             // `_.and_then(Some)` case, which is no-op.
@@ -181,8 +187,9 @@ pub(crate) trait BindInsteadOfMap {
                     snippet(cx, args[0].span, "..").into(),
                     Applicability::MachineApplicable,
                 );
+                true
             },
-            _ => {},
+            _ => false,
         }
     }
 }
diff --git a/clippy_lints/src/methods/mod.rs b/clippy_lints/src/methods/mod.rs
index 98e027b6d22..914f9f94e77 100644
--- a/clippy_lints/src/methods/mod.rs
+++ b/clippy_lints/src/methods/mod.rs
@@ -25,14 +25,15 @@ use rustc_span::source_map::Span;
 use rustc_span::symbol::{sym, SymbolStr};
 
 use crate::consts::{constant, Constant};
+use crate::utils::eager_or_lazy::is_lazyness_candidate;
 use crate::utils::usage::mutated_variables;
 use crate::utils::{
     contains_ty, get_arg_name, get_parent_expr, get_trait_def_id, has_iter_method, higher, implements_trait, in_macro,
-    is_copy, is_ctor_or_promotable_const_function, is_expn_of, is_type_diagnostic_item, iter_input_pats,
-    last_path_segment, match_def_path, match_qpath, match_trait_method, match_type, match_var, method_calls,
-    method_chain_args, paths, remove_blocks, return_ty, single_segment_path, snippet, snippet_with_applicability,
-    snippet_with_macro_callsite, span_lint, span_lint_and_help, span_lint_and_note, span_lint_and_sugg,
-    span_lint_and_then, sugg, walk_ptrs_ty, walk_ptrs_ty_depth, SpanlessEq,
+    is_copy, is_expn_of, is_type_diagnostic_item, iter_input_pats, last_path_segment, match_def_path, match_qpath,
+    match_trait_method, match_type, match_var, method_calls, method_chain_args, paths, remove_blocks, return_ty,
+    single_segment_path, snippet, snippet_with_applicability, snippet_with_macro_callsite, span_lint,
+    span_lint_and_help, span_lint_and_note, span_lint_and_sugg, span_lint_and_then, sugg, walk_ptrs_ty,
+    walk_ptrs_ty_depth, SpanlessEq,
 };
 
 declare_clippy_lint! {
@@ -1454,18 +1455,21 @@ impl<'tcx> LateLintPass<'tcx> for Methods {
             ["unwrap_or", "map"] => option_map_unwrap_or::lint(cx, expr, arg_lists[1], arg_lists[0], method_spans[1]),
             ["unwrap_or_else", "map"] => {
                 if !lint_map_unwrap_or_else(cx, expr, arg_lists[1], arg_lists[0]) {
-                    unnecessary_lazy_eval::lint(cx, expr, arg_lists[0], true, "unwrap_or");
+                    unnecessary_lazy_eval::lint(cx, expr, arg_lists[0], "unwrap_or");
                 }
             },
             ["map_or", ..] => lint_map_or_none(cx, expr, arg_lists[0]),
             ["and_then", ..] => {
-                unnecessary_lazy_eval::lint(cx, expr, arg_lists[0], false, "and");
-                bind_instead_of_map::OptionAndThenSome::lint(cx, expr, arg_lists[0]);
-                bind_instead_of_map::ResultAndThenOk::lint(cx, expr, arg_lists[0]);
+                let biom_option_linted = bind_instead_of_map::OptionAndThenSome::lint(cx, expr, arg_lists[0]);
+                let biom_result_linted = bind_instead_of_map::ResultAndThenOk::lint(cx, expr, arg_lists[0]);
+                if !biom_option_linted && !biom_result_linted {
+                    unnecessary_lazy_eval::lint(cx, expr, arg_lists[0], "and");
+                }
             },
             ["or_else", ..] => {
-                unnecessary_lazy_eval::lint(cx, expr, arg_lists[0], false, "or");
-                bind_instead_of_map::ResultOrElseErrInfo::lint(cx, expr, arg_lists[0]);
+                if !bind_instead_of_map::ResultOrElseErrInfo::lint(cx, expr, arg_lists[0]) {
+                    unnecessary_lazy_eval::lint(cx, expr, arg_lists[0], "or");
+                }
             },
             ["next", "filter"] => lint_filter_next(cx, expr, arg_lists[1]),
             ["next", "skip_while"] => lint_skip_while_next(cx, expr, arg_lists[1]),
@@ -1508,9 +1512,9 @@ impl<'tcx> LateLintPass<'tcx> for Methods {
             ["is_file", ..] => lint_filetype_is_file(cx, expr, arg_lists[0]),
             ["map", "as_ref"] => lint_option_as_ref_deref(cx, expr, arg_lists[1], arg_lists[0], false),
             ["map", "as_mut"] => lint_option_as_ref_deref(cx, expr, arg_lists[1], arg_lists[0], true),
-            ["unwrap_or_else", ..] => unnecessary_lazy_eval::lint(cx, expr, arg_lists[0], true, "unwrap_or"),
-            ["get_or_insert_with", ..] => unnecessary_lazy_eval::lint(cx, expr, arg_lists[0], true, "get_or_insert"),
-            ["ok_or_else", ..] => unnecessary_lazy_eval::lint(cx, expr, arg_lists[0], true, "ok_or"),
+            ["unwrap_or_else", ..] => unnecessary_lazy_eval::lint(cx, expr, arg_lists[0], "unwrap_or"),
+            ["get_or_insert_with", ..] => unnecessary_lazy_eval::lint(cx, expr, arg_lists[0], "get_or_insert"),
+            ["ok_or_else", ..] => unnecessary_lazy_eval::lint(cx, expr, arg_lists[0], "ok_or"),
             _ => {},
         }
 
@@ -1714,37 +1718,6 @@ fn lint_or_fun_call<'tcx>(
     name: &str,
     args: &'tcx [hir::Expr<'_>],
 ) {
-    // Searches an expression for method calls or function calls that aren't ctors
-    struct FunCallFinder<'a, 'tcx> {
-        cx: &'a LateContext<'tcx>,
-        found: bool,
-    }
-
-    impl<'a, 'tcx> intravisit::Visitor<'tcx> for FunCallFinder<'a, 'tcx> {
-        type Map = Map<'tcx>;
-
-        fn visit_expr(&mut self, expr: &'tcx hir::Expr<'_>) {
-            let call_found = match &expr.kind {
-                // ignore enum and struct constructors
-                hir::ExprKind::Call(..) => !is_ctor_or_promotable_const_function(self.cx, expr),
-                hir::ExprKind::MethodCall(..) => true,
-                _ => false,
-            };
-
-            if call_found {
-                self.found |= true;
-            }
-
-            if !self.found {
-                intravisit::walk_expr(self, expr);
-            }
-        }
-
-        fn nested_visit_map(&mut self) -> intravisit::NestedVisitorMap<Self::Map> {
-            intravisit::NestedVisitorMap::None
-        }
-    }
-
     /// Checks for `unwrap_or(T::new())` or `unwrap_or(T::default())`.
     fn check_unwrap_or_default(
         cx: &LateContext<'_>,
@@ -1825,8 +1798,7 @@ fn lint_or_fun_call<'tcx>(
         if_chain! {
             if know_types.iter().any(|k| k.2.contains(&name));
 
-            let mut finder = FunCallFinder { cx: &cx, found: false };
-            if { finder.visit_expr(&arg); finder.found };
+            if is_lazyness_candidate(cx, arg);
             if !contains_return(&arg);
 
             let self_ty = cx.typeck_results().expr_ty(self_expr);
diff --git a/clippy_lints/src/methods/unnecessary_lazy_eval.rs b/clippy_lints/src/methods/unnecessary_lazy_eval.rs
index 31517659c34..08b3eab9b7c 100644
--- a/clippy_lints/src/methods/unnecessary_lazy_eval.rs
+++ b/clippy_lints/src/methods/unnecessary_lazy_eval.rs
@@ -1,78 +1,17 @@
-use crate::utils::{is_type_diagnostic_item, match_qpath, snippet, span_lint_and_sugg};
-use if_chain::if_chain;
+use crate::utils::{eager_or_lazy, usage};
+use crate::utils::{is_type_diagnostic_item, snippet, span_lint_and_sugg};
 use rustc_errors::Applicability;
 use rustc_hir as hir;
 use rustc_lint::LateContext;
 
 use super::UNNECESSARY_LAZY_EVALUATIONS;
 
-// Return true if the expression is an accessor of any of the arguments
-fn expr_uses_argument(expr: &hir::Expr<'_>, params: &[hir::Param<'_>]) -> bool {
-    params.iter().any(|arg| {
-        if_chain! {
-            if let hir::PatKind::Binding(_, _, ident, _) = arg.pat.kind;
-            if let hir::ExprKind::Path(hir::QPath::Resolved(_, ref path)) = expr.kind;
-            if let [p, ..] = path.segments;
-            then {
-                ident.name == p.ident.name
-            } else {
-                false
-            }
-        }
-    })
-}
-
-fn match_any_qpath(path: &hir::QPath<'_>, paths: &[&[&str]]) -> bool {
-    paths.iter().any(|candidate| match_qpath(path, candidate))
-}
-
-fn can_simplify(expr: &hir::Expr<'_>, params: &[hir::Param<'_>], variant_calls: bool) -> bool {
-    match expr.kind {
-        // Closures returning literals can be unconditionally simplified
-        hir::ExprKind::Lit(_) => true,
-
-        hir::ExprKind::Index(ref object, ref index) => {
-            // arguments are not being indexed into
-            if expr_uses_argument(object, params) {
-                false
-            } else {
-                // arguments are not used as index
-                !expr_uses_argument(index, params)
-            }
-        },
-
-        // Reading fields can be simplified if the object is not an argument of the closure
-        hir::ExprKind::Field(ref object, _) => !expr_uses_argument(object, params),
-
-        // Paths can be simplified if the root is not the argument, this also covers None
-        hir::ExprKind::Path(_) => !expr_uses_argument(expr, params),
-
-        // Calls to Some, Ok, Err can be considered literals if they don't derive an argument
-        hir::ExprKind::Call(ref func, ref args) => if_chain! {
-            if variant_calls; // Disable lint when rules conflict with bind_instead_of_map
-            if let hir::ExprKind::Path(ref path) = func.kind;
-            if match_any_qpath(path, &[&["Some"], &["Ok"], &["Err"]]);
-            then {
-                // Recursively check all arguments
-                args.iter().all(|arg| can_simplify(arg, params, variant_calls))
-            } else {
-                false
-            }
-        },
-
-        // For anything more complex than the above, a closure is probably the right solution,
-        // or the case is handled by an other lint
-        _ => false,
-    }
-}
-
 /// lint use of `<fn>_else(simple closure)` for `Option`s and `Result`s that can be
 /// replaced with `<fn>(return value of simple closure)`
 pub(super) fn lint<'tcx>(
     cx: &LateContext<'tcx>,
     expr: &'tcx hir::Expr<'_>,
     args: &'tcx [hir::Expr<'_>],
-    allow_variant_calls: bool,
     simplify_using: &str,
 ) {
     let is_option = is_type_diagnostic_item(cx, cx.typeck_results().expr_ty(&args[0]), sym!(option_type));
@@ -81,10 +20,13 @@ pub(super) fn lint<'tcx>(
     if is_option || is_result {
         if let hir::ExprKind::Closure(_, _, eid, _, _) = args[1].kind {
             let body = cx.tcx.hir().body(eid);
-            let ex = &body.value;
-            let params = &body.params;
+            let body_expr = &body.value;
+
+            if usage::BindingUsageFinder::are_params_used(cx, body) {
+                return;
+            }
 
-            if can_simplify(ex, params, allow_variant_calls) {
+            if eager_or_lazy::is_eagerness_candidate(cx, body_expr) {
                 let msg = if is_option {
                     "unnecessary closure used to substitute value for `Option::None`"
                 } else {
@@ -101,7 +43,7 @@ pub(super) fn lint<'tcx>(
                         "{0}.{1}({2})",
                         snippet(cx, args[0].span, ".."),
                         simplify_using,
-                        snippet(cx, ex.span, ".."),
+                        snippet(cx, body_expr.span, ".."),
                     ),
                     Applicability::MachineApplicable,
                 );
diff --git a/clippy_lints/src/option_if_let_else.rs b/clippy_lints/src/option_if_let_else.rs
index 9494efe736c..5e2652b48cb 100644
--- a/clippy_lints/src/option_if_let_else.rs
+++ b/clippy_lints/src/option_if_let_else.rs
@@ -1,4 +1,5 @@
 use crate::utils;
+use crate::utils::eager_or_lazy;
 use crate::utils::sugg::Sugg;
 use crate::utils::{match_type, paths, span_lint_and_sugg};
 use if_chain::if_chain;
@@ -13,22 +14,16 @@ use rustc_session::{declare_lint_pass, declare_tool_lint};
 declare_clippy_lint! {
     /// **What it does:**
     /// Lints usage of  `if let Some(v) = ... { y } else { x }` which is more
-    /// idiomatically done with `Option::map_or` (if the else bit is a simple
-    /// expression) or `Option::map_or_else` (if the else bit is a longer
-    /// block).
+    /// idiomatically done with `Option::map_or` (if the else bit is a pure
+    /// expression) or `Option::map_or_else` (if the else bit is an impure
+    /// expresion).
     ///
     /// **Why is this bad?**
     /// Using the dedicated functions of the Option type is clearer and
     /// more concise than an if let expression.
     ///
     /// **Known problems:**
-    /// This lint uses whether the block is just an expression or if it has
-    /// more statements to decide whether to use `Option::map_or` or
-    /// `Option::map_or_else`. If you have a single expression which calls
-    /// an expensive function, then it would be more efficient to use
-    /// `Option::map_or_else`, but this lint would suggest `Option::map_or`.
-    ///
-    /// Also, this lint uses a deliberately conservative metric for checking
+    /// This lint uses a deliberately conservative metric for checking
     /// if the inside of either body contains breaks or continues which will
     /// cause it to not suggest a fix if either block contains a loop with
     /// continues or breaks contained within the loop.
@@ -92,6 +87,7 @@ struct OptionIfLetElseOccurence {
 struct ReturnBreakContinueMacroVisitor {
     seen_return_break_continue: bool,
 }
+
 impl ReturnBreakContinueMacroVisitor {
     fn new() -> ReturnBreakContinueMacroVisitor {
         ReturnBreakContinueMacroVisitor {
@@ -99,6 +95,7 @@ impl ReturnBreakContinueMacroVisitor {
         }
     }
 }
+
 impl<'tcx> Visitor<'tcx> for ReturnBreakContinueMacroVisitor {
     type Map = Map<'tcx>;
     fn nested_visit_map(&mut self) -> NestedVisitorMap<Self::Map> {
@@ -157,7 +154,7 @@ fn extract_body_from_arm<'a>(arm: &'a Arm<'a>) -> Option<&'a Expr<'a>> {
 }
 
 /// If this is the else body of an if/else expression, then we need to wrap
-/// it in curcly braces. Otherwise, we don't.
+/// it in curly braces. Otherwise, we don't.
 fn should_wrap_in_braces(cx: &LateContext<'_>, expr: &Expr<'_>) -> bool {
     utils::get_enclosing_block(cx, expr.hir_id).map_or(false, |parent| {
         if let Some(Expr {
@@ -199,7 +196,10 @@ fn format_option_in_sugg(cx: &LateContext<'_>, cond_expr: &Expr<'_>, as_ref: boo
 /// If this expression is the option if let/else construct we're detecting, then
 /// this function returns an `OptionIfLetElseOccurence` struct with details if
 /// this construct is found, or None if this construct is not found.
-fn detect_option_if_let_else(cx: &LateContext<'_>, expr: &Expr<'_>) -> Option<OptionIfLetElseOccurence> {
+fn detect_option_if_let_else<'tcx>(
+    cx: &'_ LateContext<'tcx>,
+    expr: &'_ Expr<'tcx>,
+) -> Option<OptionIfLetElseOccurence> {
     if_chain! {
         if !utils::in_macro(expr.span); // Don't lint macros, because it behaves weirdly
         if let ExprKind::Match(cond_expr, arms, MatchSource::IfLetDesugar{contains_else_clause: true}) = &expr.kind;
@@ -214,10 +214,7 @@ fn detect_option_if_let_else(cx: &LateContext<'_>, expr: &Expr<'_>) -> Option<Op
             let capture_mut = if bind_annotation == &BindingAnnotation::Mutable { "mut " } else { "" };
             let some_body = extract_body_from_arm(&arms[0])?;
             let none_body = extract_body_from_arm(&arms[1])?;
-            let method_sugg = match &none_body.kind {
-                ExprKind::Block(..) => "map_or_else",
-                _ => "map_or",
-            };
+            let method_sugg = if eager_or_lazy::is_eagerness_candidate(cx, none_body) { "map_or" } else { "map_or_else" };
             let capture_name = id.name.to_ident_string();
             let wrap_braces = should_wrap_in_braces(cx, expr);
             let (as_ref, as_mut) = match &cond_expr.kind {
@@ -243,8 +240,8 @@ fn detect_option_if_let_else(cx: &LateContext<'_>, expr: &Expr<'_>) -> Option<Op
     }
 }
 
-impl<'a> LateLintPass<'a> for OptionIfLetElse {
-    fn check_expr(&mut self, cx: &LateContext<'a>, expr: &Expr<'_>) {
+impl<'tcx> LateLintPass<'tcx> for OptionIfLetElse {
+    fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &Expr<'tcx>) {
         if let Some(detection) = detect_option_if_let_else(cx, expr) {
             span_lint_and_sugg(
                 cx,
diff --git a/clippy_lints/src/utils/eager_or_lazy.rs b/clippy_lints/src/utils/eager_or_lazy.rs
new file mode 100644
index 00000000000..6938d9971d9
--- /dev/null
+++ b/clippy_lints/src/utils/eager_or_lazy.rs
@@ -0,0 +1,128 @@
+//! Utilities for evaluating whether eagerly evaluated expressions can be made lazy and vice versa.
+//!
+//! Things to consider:
+//!  - has the expression side-effects?
+//!  - is the expression computationally expensive?
+//!
+//! See lints:
+//!  - unnecessary-lazy-evaluations
+//!  - or-fun-call
+//!  - option-if-let-else
+
+use crate::utils::is_ctor_or_promotable_const_function;
+use rustc_hir::def::{DefKind, Res};
+
+use rustc_hir::intravisit;
+use rustc_hir::intravisit::{NestedVisitorMap, Visitor};
+
+use rustc_hir::{Block, Expr, ExprKind, Path, QPath};
+use rustc_lint::LateContext;
+use rustc_middle::hir::map::Map;
+
+/// Is the expr pure (is it free from side-effects)?
+/// This function is named so to stress that it isn't exhaustive and returns FNs.
+fn identify_some_pure_patterns(expr: &Expr<'_>) -> bool {
+    match expr.kind {
+        ExprKind::Lit(..) | ExprKind::Path(..) | ExprKind::Field(..) => true,
+        ExprKind::AddrOf(_, _, addr_of_expr) => identify_some_pure_patterns(addr_of_expr),
+        ExprKind::Tup(tup_exprs) => tup_exprs.iter().all(|expr| identify_some_pure_patterns(expr)),
+        ExprKind::Struct(_, fields, expr) => {
+            fields.iter().all(|f| identify_some_pure_patterns(f.expr))
+                && expr.map_or(true, |e| identify_some_pure_patterns(e))
+        },
+        ExprKind::Call(
+            &Expr {
+                kind:
+                    ExprKind::Path(QPath::Resolved(
+                        _,
+                        Path {
+                            res: Res::Def(DefKind::Ctor(..) | DefKind::Variant, ..),
+                            ..
+                        },
+                    )),
+                ..
+            },
+            args,
+        ) => args.iter().all(|expr| identify_some_pure_patterns(expr)),
+        ExprKind::Block(
+            &Block {
+                stmts,
+                expr: Some(expr),
+                ..
+            },
+            _,
+        ) => stmts.is_empty() && identify_some_pure_patterns(expr),
+        ExprKind::Box(..)
+        | ExprKind::Array(..)
+        | ExprKind::Call(..)
+        | ExprKind::MethodCall(..)
+        | ExprKind::Binary(..)
+        | ExprKind::Unary(..)
+        | ExprKind::Cast(..)
+        | ExprKind::Type(..)
+        | ExprKind::DropTemps(..)
+        | ExprKind::Loop(..)
+        | ExprKind::Match(..)
+        | ExprKind::Closure(..)
+        | ExprKind::Block(..)
+        | ExprKind::Assign(..)
+        | ExprKind::AssignOp(..)
+        | ExprKind::Index(..)
+        | ExprKind::Break(..)
+        | ExprKind::Continue(..)
+        | ExprKind::Ret(..)
+        | ExprKind::InlineAsm(..)
+        | ExprKind::LlvmInlineAsm(..)
+        | ExprKind::Repeat(..)
+        | ExprKind::Yield(..)
+        | ExprKind::Err => false,
+    }
+}
+
+/// Identify some potentially computationally expensive patterns.
+/// This function is named so to stress that its implementation is non-exhaustive.
+/// It returns FNs and FPs.
+fn identify_some_potentially_expensive_patterns<'a, 'tcx>(cx: &'a LateContext<'tcx>, expr: &'tcx Expr<'tcx>) -> bool {
+    // Searches an expression for method calls or function calls that aren't ctors
+    struct FunCallFinder<'a, 'tcx> {
+        cx: &'a LateContext<'tcx>,
+        found: bool,
+    }
+
+    impl<'a, 'tcx> intravisit::Visitor<'tcx> for FunCallFinder<'a, 'tcx> {
+        type Map = Map<'tcx>;
+
+        fn visit_expr(&mut self, expr: &'tcx Expr<'tcx>) {
+            let call_found = match &expr.kind {
+                // ignore enum and struct constructors
+                ExprKind::Call(..) => !is_ctor_or_promotable_const_function(self.cx, expr),
+                ExprKind::MethodCall(..) => true,
+                _ => false,
+            };
+
+            if call_found {
+                self.found |= true;
+            }
+
+            if !self.found {
+                intravisit::walk_expr(self, expr);
+            }
+        }
+
+        fn nested_visit_map(&mut self) -> NestedVisitorMap<Self::Map> {
+            NestedVisitorMap::None
+        }
+    }
+
+    let mut finder = FunCallFinder { cx, found: false };
+    finder.visit_expr(expr);
+    finder.found
+}
+
+pub fn is_eagerness_candidate<'a, 'tcx>(cx: &'a LateContext<'tcx>, expr: &'tcx Expr<'tcx>) -> bool {
+    !identify_some_potentially_expensive_patterns(cx, expr) && identify_some_pure_patterns(expr)
+}
+
+pub fn is_lazyness_candidate<'a, 'tcx>(cx: &'a LateContext<'tcx>, expr: &'tcx Expr<'tcx>) -> bool {
+    identify_some_potentially_expensive_patterns(cx, expr)
+}
diff --git a/clippy_lints/src/utils/mod.rs b/clippy_lints/src/utils/mod.rs
index 3ebbfed6456..7efeef62690 100644
--- a/clippy_lints/src/utils/mod.rs
+++ b/clippy_lints/src/utils/mod.rs
@@ -10,6 +10,7 @@ pub mod comparisons;
 pub mod conf;
 pub mod constants;
 mod diagnostics;
+pub mod eager_or_lazy;
 pub mod higher;
 mod hir_utils;
 pub mod inspector;
diff --git a/clippy_lints/src/utils/sugg.rs b/clippy_lints/src/utils/sugg.rs
index 811fde388d1..ec8b7e59b59 100644
--- a/clippy_lints/src/utils/sugg.rs
+++ b/clippy_lints/src/utils/sugg.rs
@@ -49,7 +49,7 @@ impl<'a> Sugg<'a> {
     /// Convenience function around `hir_opt` for suggestions with a default
     /// text.
     pub fn hir(cx: &LateContext<'_>, expr: &hir::Expr<'_>, default: &'a str) -> Self {
-        Self::hir_opt(cx, expr).unwrap_or_else(|| Sugg::NonParen(Cow::Borrowed(default)))
+        Self::hir_opt(cx, expr).unwrap_or(Sugg::NonParen(Cow::Borrowed(default)))
     }
 
     /// Same as `hir`, but it adapts the applicability level by following rules:
diff --git a/clippy_lints/src/utils/usage.rs b/clippy_lints/src/utils/usage.rs
index 4a64b935ac9..ea1dc3be29b 100644
--- a/clippy_lints/src/utils/usage.rs
+++ b/clippy_lints/src/utils/usage.rs
@@ -1,6 +1,8 @@
 use crate::utils::match_var;
 use rustc_data_structures::fx::FxHashSet;
+use rustc_hir as hir;
 use rustc_hir::def::Res;
+use rustc_hir::intravisit;
 use rustc_hir::intravisit::{walk_expr, NestedVisitorMap, Visitor};
 use rustc_hir::{Expr, HirId, Path};
 use rustc_infer::infer::TyCtxtInferExt;
@@ -108,3 +110,67 @@ pub fn is_unused<'tcx>(ident: &'tcx Ident, body: &'tcx Expr<'_>) -> bool {
     walk_expr(&mut visitor, body);
     !visitor.used
 }
+
+pub struct ParamBindingIdCollector {
+    binding_hir_ids: Vec<hir::HirId>,
+}
+impl<'tcx> ParamBindingIdCollector {
+    fn collect_binding_hir_ids(body: &'tcx hir::Body<'tcx>) -> Vec<hir::HirId> {
+        let mut finder = ParamBindingIdCollector {
+            binding_hir_ids: Vec::new(),
+        };
+        finder.visit_body(body);
+        finder.binding_hir_ids
+    }
+}
+impl<'tcx> intravisit::Visitor<'tcx> for ParamBindingIdCollector {
+    type Map = Map<'tcx>;
+
+    fn visit_param(&mut self, param: &'tcx hir::Param<'tcx>) {
+        if let hir::PatKind::Binding(_, hir_id, ..) = param.pat.kind {
+            self.binding_hir_ids.push(hir_id);
+        }
+    }
+
+    fn nested_visit_map(&mut self) -> intravisit::NestedVisitorMap<Self::Map> {
+        intravisit::NestedVisitorMap::None
+    }
+}
+
+pub struct BindingUsageFinder<'a, 'tcx> {
+    cx: &'a LateContext<'tcx>,
+    binding_ids: Vec<hir::HirId>,
+    usage_found: bool,
+}
+impl<'a, 'tcx> BindingUsageFinder<'a, 'tcx> {
+    pub fn are_params_used(cx: &'a LateContext<'tcx>, body: &'tcx hir::Body<'tcx>) -> bool {
+        let mut finder = BindingUsageFinder {
+            cx,
+            binding_ids: ParamBindingIdCollector::collect_binding_hir_ids(body),
+            usage_found: false,
+        };
+        finder.visit_body(body);
+        finder.usage_found
+    }
+}
+impl<'a, 'tcx> intravisit::Visitor<'tcx> for BindingUsageFinder<'a, 'tcx> {
+    type Map = Map<'tcx>;
+
+    fn visit_expr(&mut self, expr: &'tcx hir::Expr<'tcx>) {
+        if !self.usage_found {
+            intravisit::walk_expr(self, expr);
+        }
+    }
+
+    fn visit_path(&mut self, path: &'tcx hir::Path<'tcx>, _: hir::HirId) {
+        if let hir::def::Res::Local(id) = path.res {
+            if self.binding_ids.contains(&id) {
+                self.usage_found = true;
+            }
+        }
+    }
+
+    fn nested_visit_map(&mut self) -> intravisit::NestedVisitorMap<Self::Map> {
+        intravisit::NestedVisitorMap::OnlyBodies(self.cx.tcx.hir())
+    }
+}
diff --git a/tests/ui/option_if_let_else.fixed b/tests/ui/option_if_let_else.fixed
index 695a460cc4e..a7fb00a2705 100644
--- a/tests/ui/option_if_let_else.fixed
+++ b/tests/ui/option_if_let_else.fixed
@@ -1,5 +1,6 @@
 // run-rustfix
 #![warn(clippy::option_if_let_else)]
+#![allow(clippy::redundant_closure)]
 
 fn bad1(string: Option<&str>) -> (bool, &str) {
     string.map_or((false, "hello"), |x| (true, x))
@@ -36,6 +37,14 @@ fn longer_body(arg: Option<u32>) -> u32 {
     })
 }
 
+fn impure_else(arg: Option<i32>) {
+    let side_effect = || {
+        println!("return 1");
+        1
+    };
+    let _ = arg.map_or_else(|| side_effect(), |x| x);
+}
+
 fn test_map_or_else(arg: Option<u32>) {
     let _ = arg.map_or_else(|| {
         let mut y = 1;
@@ -71,4 +80,5 @@ fn main() {
     let _ = longer_body(None);
     test_map_or_else(None);
     let _ = negative_tests(None);
+    let _ = impure_else(None);
 }
diff --git a/tests/ui/option_if_let_else.rs b/tests/ui/option_if_let_else.rs
index dee80d26bd9..895fd86321f 100644
--- a/tests/ui/option_if_let_else.rs
+++ b/tests/ui/option_if_let_else.rs
@@ -1,5 +1,6 @@
 // run-rustfix
 #![warn(clippy::option_if_let_else)]
+#![allow(clippy::redundant_closure)]
 
 fn bad1(string: Option<&str>) -> (bool, &str) {
     if let Some(x) = string {
@@ -52,6 +53,19 @@ fn longer_body(arg: Option<u32>) -> u32 {
     }
 }
 
+fn impure_else(arg: Option<i32>) {
+    let side_effect = || {
+        println!("return 1");
+        1
+    };
+    let _ = if let Some(x) = arg {
+        x
+    } else {
+        // map_or_else must be suggested
+        side_effect()
+    };
+}
+
 fn test_map_or_else(arg: Option<u32>) {
     let _ = if let Some(x) = arg {
         x * x * x * x
@@ -89,4 +103,5 @@ fn main() {
     let _ = longer_body(None);
     test_map_or_else(None);
     let _ = negative_tests(None);
+    let _ = impure_else(None);
 }
diff --git a/tests/ui/option_if_let_else.stderr b/tests/ui/option_if_let_else.stderr
index 7005850efaf..b69fe767682 100644
--- a/tests/ui/option_if_let_else.stderr
+++ b/tests/ui/option_if_let_else.stderr
@@ -1,5 +1,5 @@
 error: use Option::map_or instead of an if let/else
-  --> $DIR/option_if_let_else.rs:5:5
+  --> $DIR/option_if_let_else.rs:6:5
    |
 LL | /     if let Some(x) = string {
 LL | |         (true, x)
@@ -11,7 +11,7 @@ LL | |     }
    = note: `-D clippy::option-if-let-else` implied by `-D warnings`
 
 error: use Option::map_or instead of an if let/else
-  --> $DIR/option_if_let_else.rs:15:12
+  --> $DIR/option_if_let_else.rs:16:12
    |
 LL |       } else if let Some(x) = string {
    |  ____________^
@@ -22,19 +22,19 @@ LL | |     }
    | |_____^ help: try: `{ string.map_or(Some((false, "")), |x| Some((true, x))) }`
 
 error: use Option::map_or instead of an if let/else
-  --> $DIR/option_if_let_else.rs:23:13
+  --> $DIR/option_if_let_else.rs:24:13
    |
 LL |     let _ = if let Some(s) = *string { s.len() } else { 0 };
    |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `string.map_or(0, |s| s.len())`
 
 error: use Option::map_or instead of an if let/else
-  --> $DIR/option_if_let_else.rs:24:13
+  --> $DIR/option_if_let_else.rs:25:13
    |
 LL |     let _ = if let Some(s) = &num { s } else { &0 };
    |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `num.as_ref().map_or(&0, |s| s)`
 
 error: use Option::map_or instead of an if let/else
-  --> $DIR/option_if_let_else.rs:25:13
+  --> $DIR/option_if_let_else.rs:26:13
    |
 LL |       let _ = if let Some(s) = &mut num {
    |  _____________^
@@ -54,13 +54,13 @@ LL |     });
    |
 
 error: use Option::map_or instead of an if let/else
-  --> $DIR/option_if_let_else.rs:31:13
+  --> $DIR/option_if_let_else.rs:32:13
    |
 LL |     let _ = if let Some(ref s) = num { s } else { &0 };
    |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `num.as_ref().map_or(&0, |s| s)`
 
 error: use Option::map_or instead of an if let/else
-  --> $DIR/option_if_let_else.rs:32:13
+  --> $DIR/option_if_let_else.rs:33:13
    |
 LL |       let _ = if let Some(mut s) = num {
    |  _____________^
@@ -80,7 +80,7 @@ LL |     });
    |
 
 error: use Option::map_or instead of an if let/else
-  --> $DIR/option_if_let_else.rs:38:13
+  --> $DIR/option_if_let_else.rs:39:13
    |
 LL |       let _ = if let Some(ref mut s) = num {
    |  _____________^
@@ -100,7 +100,7 @@ LL |     });
    |
 
 error: use Option::map_or instead of an if let/else
-  --> $DIR/option_if_let_else.rs:47:5
+  --> $DIR/option_if_let_else.rs:48:5
    |
 LL | /     if let Some(x) = arg {
 LL | |         let y = x * x;
@@ -119,7 +119,19 @@ LL |     })
    |
 
 error: use Option::map_or_else instead of an if let/else
-  --> $DIR/option_if_let_else.rs:56:13
+  --> $DIR/option_if_let_else.rs:61:13
+   |
+LL |       let _ = if let Some(x) = arg {
+   |  _____________^
+LL | |         x
+LL | |     } else {
+LL | |         // map_or_else must be suggested
+LL | |         side_effect()
+LL | |     };
+   | |_____^ help: try: `arg.map_or_else(|| side_effect(), |x| x)`
+
+error: use Option::map_or_else instead of an if let/else
+  --> $DIR/option_if_let_else.rs:70:13
    |
 LL |       let _ = if let Some(x) = arg {
    |  _____________^
@@ -142,10 +154,10 @@ LL |     }, |x| x * x * x * x);
    |
 
 error: use Option::map_or instead of an if let/else
-  --> $DIR/option_if_let_else.rs:85:13
+  --> $DIR/option_if_let_else.rs:99:13
    |
 LL |     let _ = if let Some(x) = optional { x + 2 } else { 5 };
    |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `optional.map_or(5, |x| x + 2)`
 
-error: aborting due to 11 previous errors
+error: aborting due to 12 previous errors
 
diff --git a/tests/ui/unnecessary_lazy_eval.fixed b/tests/ui/unnecessary_lazy_eval.fixed
index fa66e68794e..4980c111499 100644
--- a/tests/ui/unnecessary_lazy_eval.fixed
+++ b/tests/ui/unnecessary_lazy_eval.fixed
@@ -2,6 +2,7 @@
 #![warn(clippy::unnecessary_lazy_evaluations)]
 #![allow(clippy::redundant_closure)]
 #![allow(clippy::bind_instead_of_map)]
+#![allow(clippy::map_identity)]
 
 struct Deep(Option<usize>);
 
@@ -34,13 +35,13 @@ fn main() {
     let _ = opt.unwrap_or(2);
     let _ = opt.unwrap_or(astronomers_pi);
     let _ = opt.unwrap_or(ext_str.some_field);
-    let _ = opt.unwrap_or(ext_arr[0]);
+    let _ = opt.unwrap_or_else(|| ext_arr[0]);
     let _ = opt.and(ext_opt);
     let _ = opt.or(ext_opt);
     let _ = opt.or(None);
     let _ = opt.get_or_insert(2);
     let _ = opt.ok_or(2);
-    let _ = opt.ok_or(ext_arr[0]);
+    let _ = nested_tuple_opt.unwrap_or(Some((1, 2)));
 
     // Cases when unwrap is not called on a simple variable
     let _ = Some(10).unwrap_or(2);
@@ -60,7 +61,6 @@ fn main() {
     // Should not lint - Option
     let _ = opt.unwrap_or_else(|| ext_str.return_some_field());
     let _ = nested_opt.unwrap_or_else(|| Some(some_call()));
-    let _ = nested_tuple_opt.unwrap_or_else(|| Some((1, 2)));
     let _ = nested_tuple_opt.unwrap_or_else(|| Some((some_call(), some_call())));
     let _ = opt.or_else(some_call);
     let _ = opt.or_else(|| some_call());
@@ -69,13 +69,16 @@ fn main() {
     let _ = deep.0.get_or_insert_with(|| some_call());
     let _ = deep.0.or_else(some_call);
     let _ = deep.0.or_else(|| some_call());
+    let _ = opt.ok_or_else(|| ext_arr[0]);
 
-    // These are handled by bind_instead_of_map
+    // should not lint, bind_instead_of_map takes priority
     let _ = Some(10).and_then(|idx| Some(ext_arr[idx]));
     let _ = Some(10).and_then(|idx| Some(idx));
-    let _: Option<usize> = None.or_else(|| Some(3));
-    let _ = deep.0.or_else(|| Some(3));
-    let _ = opt.or_else(|| Some(3));
+
+    // should lint, bind_instead_of_map doesn't apply
+    let _: Option<usize> = None.or(Some(3));
+    let _ = deep.0.or(Some(3));
+    let _ = opt.or(Some(3));
 
     // Should lint - Result
     let res: Result<usize, usize> = Err(5);
@@ -92,26 +95,27 @@ fn main() {
     let _ = res2.unwrap_or_else(|err| err.return_some_field());
     let _ = res2.unwrap_or_else(|_| ext_str.return_some_field());
 
+    // should not lint, bind_instead_of_map takes priority
     let _: Result<usize, usize> = res.and_then(|x| Ok(x));
-    let _: Result<usize, usize> = res.and_then(|x| Err(x));
-
-    let _: Result<usize, usize> = res.or_else(|err| Ok(err));
     let _: Result<usize, usize> = res.or_else(|err| Err(err));
 
-    // These are handled by bind_instead_of_map
     let _: Result<usize, usize> = res.and_then(|_| Ok(2));
     let _: Result<usize, usize> = res.and_then(|_| Ok(astronomers_pi));
     let _: Result<usize, usize> = res.and_then(|_| Ok(ext_str.some_field));
 
-    let _: Result<usize, usize> = res.and_then(|_| Err(2));
-    let _: Result<usize, usize> = res.and_then(|_| Err(astronomers_pi));
-    let _: Result<usize, usize> = res.and_then(|_| Err(ext_str.some_field));
-
-    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.or_else(|_| Err(2));
     let _: Result<usize, usize> = res.or_else(|_| Err(astronomers_pi));
     let _: Result<usize, usize> = res.or_else(|_| Err(ext_str.some_field));
+
+    // should lint, bind_instead_of_map doesn't apply
+    let _: Result<usize, usize> = res.and_then(|x| Err(x));
+    let _: Result<usize, usize> = res.or_else(|err| Ok(err));
+
+    let _: Result<usize, usize> = res.and(Err(2));
+    let _: Result<usize, usize> = res.and(Err(astronomers_pi));
+    let _: Result<usize, usize> = res.and(Err(ext_str.some_field));
+
+    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));
 }
diff --git a/tests/ui/unnecessary_lazy_eval.rs b/tests/ui/unnecessary_lazy_eval.rs
index 04f47d1aa29..0b270939ec2 100644
--- a/tests/ui/unnecessary_lazy_eval.rs
+++ b/tests/ui/unnecessary_lazy_eval.rs
@@ -2,6 +2,7 @@
 #![warn(clippy::unnecessary_lazy_evaluations)]
 #![allow(clippy::redundant_closure)]
 #![allow(clippy::bind_instead_of_map)]
+#![allow(clippy::map_identity)]
 
 struct Deep(Option<usize>);
 
@@ -40,7 +41,7 @@ fn main() {
     let _ = opt.or_else(|| None);
     let _ = opt.get_or_insert_with(|| 2);
     let _ = opt.ok_or_else(|| 2);
-    let _ = opt.ok_or_else(|| ext_arr[0]);
+    let _ = nested_tuple_opt.unwrap_or_else(|| Some((1, 2)));
 
     // Cases when unwrap is not called on a simple variable
     let _ = Some(10).unwrap_or_else(|| 2);
@@ -60,7 +61,6 @@ fn main() {
     // Should not lint - Option
     let _ = opt.unwrap_or_else(|| ext_str.return_some_field());
     let _ = nested_opt.unwrap_or_else(|| Some(some_call()));
-    let _ = nested_tuple_opt.unwrap_or_else(|| Some((1, 2)));
     let _ = nested_tuple_opt.unwrap_or_else(|| Some((some_call(), some_call())));
     let _ = opt.or_else(some_call);
     let _ = opt.or_else(|| some_call());
@@ -69,10 +69,13 @@ fn main() {
     let _ = deep.0.get_or_insert_with(|| some_call());
     let _ = deep.0.or_else(some_call);
     let _ = deep.0.or_else(|| some_call());
+    let _ = opt.ok_or_else(|| ext_arr[0]);
 
-    // These are handled by bind_instead_of_map
+    // should not lint, bind_instead_of_map takes priority
     let _ = Some(10).and_then(|idx| Some(ext_arr[idx]));
     let _ = Some(10).and_then(|idx| Some(idx));
+
+    // should lint, bind_instead_of_map doesn't apply
     let _: Option<usize> = None.or_else(|| Some(3));
     let _ = deep.0.or_else(|| Some(3));
     let _ = opt.or_else(|| Some(3));
@@ -92,17 +95,22 @@ fn main() {
     let _ = res2.unwrap_or_else(|err| err.return_some_field());
     let _ = res2.unwrap_or_else(|_| ext_str.return_some_field());
 
+    // should not lint, bind_instead_of_map takes priority
     let _: Result<usize, usize> = res.and_then(|x| Ok(x));
-    let _: Result<usize, usize> = res.and_then(|x| Err(x));
-
-    let _: Result<usize, usize> = res.or_else(|err| Ok(err));
     let _: Result<usize, usize> = res.or_else(|err| Err(err));
 
-    // These are handled by bind_instead_of_map
     let _: Result<usize, usize> = res.and_then(|_| Ok(2));
     let _: Result<usize, usize> = res.and_then(|_| Ok(astronomers_pi));
     let _: Result<usize, usize> = res.and_then(|_| Ok(ext_str.some_field));
 
+    let _: Result<usize, usize> = res.or_else(|_| Err(2));
+    let _: Result<usize, usize> = res.or_else(|_| Err(astronomers_pi));
+    let _: Result<usize, usize> = res.or_else(|_| Err(ext_str.some_field));
+
+    // should lint, bind_instead_of_map doesn't apply
+    let _: Result<usize, usize> = res.and_then(|x| Err(x));
+    let _: Result<usize, usize> = res.or_else(|err| Ok(err));
+
     let _: Result<usize, usize> = res.and_then(|_| Err(2));
     let _: Result<usize, usize> = res.and_then(|_| Err(astronomers_pi));
     let _: Result<usize, usize> = res.and_then(|_| Err(ext_str.some_field));
@@ -110,8 +118,4 @@ 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.or_else(|_| Err(2));
-    let _: Result<usize, usize> = res.or_else(|_| Err(astronomers_pi));
-    let _: Result<usize, usize> = res.or_else(|_| Err(ext_str.some_field));
 }
diff --git a/tests/ui/unnecessary_lazy_eval.stderr b/tests/ui/unnecessary_lazy_eval.stderr
index 5c1b2eb1f14..1cf7ac46346 100644
--- a/tests/ui/unnecessary_lazy_eval.stderr
+++ b/tests/ui/unnecessary_lazy_eval.stderr
@@ -1,5 +1,5 @@
 error: unnecessary closure used to substitute value for `Option::None`
-  --> $DIR/unnecessary_lazy_eval.rs:34:13
+  --> $DIR/unnecessary_lazy_eval.rs:35:13
    |
 LL |     let _ = opt.unwrap_or_else(|| 2);
    |             ^^^^^^^^^^^^^^^^^^^^^^^^ help: Use `unwrap_or` instead: `opt.unwrap_or(2)`
@@ -7,142 +7,190 @@ LL |     let _ = opt.unwrap_or_else(|| 2);
    = note: `-D clippy::unnecessary-lazy-evaluations` implied by `-D warnings`
 
 error: unnecessary closure used to substitute value for `Option::None`
-  --> $DIR/unnecessary_lazy_eval.rs:35:13
+  --> $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)`
 
 error: unnecessary closure used to substitute value for `Option::None`
-  --> $DIR/unnecessary_lazy_eval.rs:36:13
+  --> $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)`
 
 error: unnecessary closure used to substitute value for `Option::None`
-  --> $DIR/unnecessary_lazy_eval.rs:37:13
-   |
-LL |     let _ = opt.unwrap_or_else(|| ext_arr[0]);
-   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: Use `unwrap_or` instead: `opt.unwrap_or(ext_arr[0])`
-
-error: unnecessary closure used to substitute value for `Option::None`
-  --> $DIR/unnecessary_lazy_eval.rs:38:13
+  --> $DIR/unnecessary_lazy_eval.rs:39:13
    |
 LL |     let _ = opt.and_then(|_| ext_opt);
    |             ^^^^^^^^^^^^^^^^^^^^^^^^^ help: Use `and` instead: `opt.and(ext_opt)`
 
 error: unnecessary closure used to substitute value for `Option::None`
-  --> $DIR/unnecessary_lazy_eval.rs:39:13
+  --> $DIR/unnecessary_lazy_eval.rs:40:13
    |
 LL |     let _ = opt.or_else(|| ext_opt);
    |             ^^^^^^^^^^^^^^^^^^^^^^^ help: Use `or` instead: `opt.or(ext_opt)`
 
 error: unnecessary closure used to substitute value for `Option::None`
-  --> $DIR/unnecessary_lazy_eval.rs:40:13
+  --> $DIR/unnecessary_lazy_eval.rs:41:13
    |
 LL |     let _ = opt.or_else(|| None);
    |             ^^^^^^^^^^^^^^^^^^^^ help: Use `or` instead: `opt.or(None)`
 
 error: unnecessary closure used to substitute value for `Option::None`
-  --> $DIR/unnecessary_lazy_eval.rs:41:13
+  --> $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)`
 
 error: unnecessary closure used to substitute value for `Option::None`
-  --> $DIR/unnecessary_lazy_eval.rs:42:13
+  --> $DIR/unnecessary_lazy_eval.rs:43:13
    |
 LL |     let _ = opt.ok_or_else(|| 2);
    |             ^^^^^^^^^^^^^^^^^^^^ help: Use `ok_or` instead: `opt.ok_or(2)`
 
 error: unnecessary closure used to substitute value for `Option::None`
-  --> $DIR/unnecessary_lazy_eval.rs:43:13
+  --> $DIR/unnecessary_lazy_eval.rs:44:13
    |
-LL |     let _ = opt.ok_or_else(|| ext_arr[0]);
-   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: Use `ok_or` instead: `opt.ok_or(ext_arr[0])`
+LL |     let _ = nested_tuple_opt.unwrap_or_else(|| Some((1, 2)));
+   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: Use `unwrap_or` instead: `nested_tuple_opt.unwrap_or(Some((1, 2)))`
 
 error: unnecessary closure used to substitute value for `Option::None`
-  --> $DIR/unnecessary_lazy_eval.rs:46:13
+  --> $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)`
 
 error: unnecessary closure used to substitute value for `Option::None`
-  --> $DIR/unnecessary_lazy_eval.rs:47:13
+  --> $DIR/unnecessary_lazy_eval.rs:48:13
    |
 LL |     let _ = Some(10).and_then(|_| ext_opt);
    |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: Use `and` instead: `Some(10).and(ext_opt)`
 
 error: unnecessary closure used to substitute value for `Option::None`
-  --> $DIR/unnecessary_lazy_eval.rs:48:28
+  --> $DIR/unnecessary_lazy_eval.rs:49:28
    |
 LL |     let _: Option<usize> = None.or_else(|| ext_opt);
    |                            ^^^^^^^^^^^^^^^^^^^^^^^^ help: Use `or` instead: `None.or(ext_opt)`
 
 error: unnecessary closure used to substitute value for `Option::None`
-  --> $DIR/unnecessary_lazy_eval.rs:49:13
+  --> $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)`
 
 error: unnecessary closure used to substitute value for `Option::None`
-  --> $DIR/unnecessary_lazy_eval.rs:50:35
+  --> $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)`
 
 error: unnecessary closure used to substitute value for `Option::None`
-  --> $DIR/unnecessary_lazy_eval.rs:51:28
+  --> $DIR/unnecessary_lazy_eval.rs:52:28
    |
 LL |     let _: Option<usize> = None.or_else(|| None);
    |                            ^^^^^^^^^^^^^^^^^^^^^ help: Use `or` instead: `None.or(None)`
 
 error: unnecessary closure used to substitute value for `Option::None`
-  --> $DIR/unnecessary_lazy_eval.rs:54:13
+  --> $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)`
 
 error: unnecessary closure used to substitute value for `Option::None`
-  --> $DIR/unnecessary_lazy_eval.rs:55:13
+  --> $DIR/unnecessary_lazy_eval.rs:56:13
    |
 LL |     let _ = deep.0.and_then(|_| ext_opt);
    |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: Use `and` instead: `deep.0.and(ext_opt)`
 
 error: unnecessary closure used to substitute value for `Option::None`
-  --> $DIR/unnecessary_lazy_eval.rs:56:13
+  --> $DIR/unnecessary_lazy_eval.rs:57:13
    |
 LL |     let _ = deep.0.or_else(|| None);
    |             ^^^^^^^^^^^^^^^^^^^^^^^ help: Use `or` instead: `deep.0.or(None)`
 
 error: unnecessary closure used to substitute value for `Option::None`
-  --> $DIR/unnecessary_lazy_eval.rs:57:13
+  --> $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)`
 
 error: unnecessary closure used to substitute value for `Option::None`
-  --> $DIR/unnecessary_lazy_eval.rs:58:13
+  --> $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)`
 
+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))`
+
+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))`
+
+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))`
+
 error: unnecessary closure used to substitute value for `Result::Err`
-  --> $DIR/unnecessary_lazy_eval.rs:84:13
+  --> $DIR/unnecessary_lazy_eval.rs:87:13
    |
 LL |     let _ = res2.unwrap_or_else(|_| 2);
    |             ^^^^^^^^^^^^^^^^^^^^^^^^^^ help: Use `unwrap_or` instead: `res2.unwrap_or(2)`
 
 error: unnecessary closure used to substitute value for `Result::Err`
-  --> $DIR/unnecessary_lazy_eval.rs:85:13
+  --> $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)`
 
 error: unnecessary closure used to substitute value for `Result::Err`
-  --> $DIR/unnecessary_lazy_eval.rs:86:13
+  --> $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)`
 
-error: aborting due to 24 previous errors
+error: unnecessary closure used to substitute value for `Result::Err`
+  --> $DIR/unnecessary_lazy_eval.rs:114:35
+   |
+LL |     let _: Result<usize, usize> = res.and_then(|_| Err(2));
+   |                                   ^^^^^^^^^^^^^^^^^^^^^^^^ help: Use `and` instead: `res.and(Err(2))`
+
+error: unnecessary closure used to substitute value for `Result::Err`
+  --> $DIR/unnecessary_lazy_eval.rs:115:35
+   |
+LL |     let _: Result<usize, usize> = res.and_then(|_| Err(astronomers_pi));
+   |                                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: Use `and` instead: `res.and(Err(astronomers_pi))`
+
+error: unnecessary closure used to substitute value for `Result::Err`
+  --> $DIR/unnecessary_lazy_eval.rs:116:35
+   |
+LL |     let _: Result<usize, usize> = res.and_then(|_| Err(ext_str.some_field));
+   |                                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: Use `and` instead: `res.and(Err(ext_str.some_field))`
+
+error: unnecessary closure used to substitute value for `Result::Err`
+  --> $DIR/unnecessary_lazy_eval.rs:118:35
+   |
+LL |     let _: Result<usize, usize> = res.or_else(|_| Ok(2));
+   |                                   ^^^^^^^^^^^^^^^^^^^^^^ help: Use `or` instead: `res.or(Ok(2))`
+
+error: unnecessary closure used to substitute value for `Result::Err`
+  --> $DIR/unnecessary_lazy_eval.rs:119:35
+   |
+LL |     let _: Result<usize, usize> = res.or_else(|_| Ok(astronomers_pi));
+   |                                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: Use `or` instead: `res.or(Ok(astronomers_pi))`
+
+error: unnecessary closure used to substitute value for `Result::Err`
+  --> $DIR/unnecessary_lazy_eval.rs:120:35
+   |
+LL |     let _: Result<usize, usize> = res.or_else(|_| Ok(ext_str.some_field));
+   |                                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: Use `or` instead: `res.or(Ok(ext_str.some_field))`
+
+error: aborting due to 32 previous errors