Rework redundant_closure

* Better track when a early-bound region appears when a late-bound region is required
* Don't lint when the closure gives explicit types.

Author: Jarcho

clippy_lints/src/eta_reduction.rs

@@ -189,7 +189,6 @@ impl LateLintPass<'_> for IncorrectImpls {
                 .diagnostic_items(trait_impl.def_id.krate)
                 .name_to_id
                 .get(&sym::Ord)
-            && trait_impl.self_ty() == trait_impl.args.type_at(1)
             && implements_trait(cx, hir_ty_to_ty(cx.tcx, imp.self_ty), *ord_def_id, &[])
         {
             // If the `cmp` call likely needs to be fully qualified in the suggestion

clippy_lints/src/incorrect_impls.rs

@@ -419,6 +419,11 @@ pub fn is_type_lang_item(cx: &LateContext<'_>, ty: Ty<'_>, lang_item: hir::LangI
     }
 }
 
+/// Gets the diagnostic name of the type, if it has one
+pub fn type_diagnostic_name(cx: &LateContext<'_>, ty: Ty<'_>) -> Option<Symbol> {
+    ty.ty_adt_def().and_then(|adt| cx.tcx.get_diagnostic_name(adt.did()))
+}
+
 /// Return `true` if the passed `typ` is `isize` or `usize`.
 pub fn is_isize_or_usize(typ: Ty<'_>) -> bool {
     matches!(typ.kind(), ty::Int(IntTy::Isize) | ty::Uint(UintTy::Usize))

clippy_utils/src/ty.rs

@@ -1,15 +1,15 @@
-use crate::visitors::{for_each_expr, for_each_expr_with_closures, Descend};
+use crate::visitors::{for_each_expr, for_each_expr_with_closures, Descend, Visitable};
+use crate::{self as utils, get_enclosing_loop_or_multi_call_closure};
 use core::ops::ControlFlow;
 use hir::def::Res;
 use rustc_hir::intravisit::{self, Visitor};
-use rustc_hir::{Expr, ExprKind, HirId, HirIdSet, Node};
+use rustc_hir::{self as hir, Expr, ExprKind, HirId, HirIdSet};
 use rustc_hir_typeck::expr_use_visitor::{Delegate, ExprUseVisitor, PlaceBase, PlaceWithHirId};
 use rustc_infer::infer::TyCtxtInferExt;
 use rustc_lint::LateContext;
 use rustc_middle::hir::nested_filter;
 use rustc_middle::mir::FakeReadCause;
 use rustc_middle::ty;
-use {crate as utils, rustc_hir as hir};
 
 /// Returns a set of mutated local variable IDs, or `None` if mutations could not be determined.
 pub fn mutated_variables<'tcx>(expr: &'tcx Expr<'_>, cx: &LateContext<'tcx>) -> Option<HirIdSet> {
@@ -154,6 +154,17 @@ pub fn contains_return_break_continue_macro(expression: &Expr<'_>) -> bool {
     .is_some()
 }
 
+pub fn local_used_in<'tcx>(cx: &LateContext<'tcx>, local_id: HirId, v: impl Visitable<'tcx>) -> bool {
+    for_each_expr_with_closures(cx, v, |e| {
+        if utils::path_to_local_id(e, local_id) {
+            ControlFlow::Break(())
+        } else {
+            ControlFlow::Continue(())
+        }
+    })
+    .is_some()
+}
+
 pub fn local_used_after_expr(cx: &LateContext<'_>, local_id: HirId, after: &Expr<'_>) -> bool {
     let Some(block) = utils::get_enclosing_block(cx, local_id) else {
         return false;
@@ -166,32 +177,21 @@ pub fn local_used_after_expr(cx: &LateContext<'_>, local_id: HirId, after: &Expr
     // let closure = || local;
     // closure();
     // closure();
-    let in_loop_or_closure = cx
-        .tcx
-        .hir()
-        .parent_iter(after.hir_id)
-        .take_while(|&(id, _)| id != block.hir_id)
-        .any(|(_, node)| {
-            matches!(
-                node,
-                Node::Expr(Expr {
-                    kind: ExprKind::Loop(..) | ExprKind::Closure { .. },
-                    ..
-                })
-            )
-        });
-    if in_loop_or_closure {
-        return true;
-    }
+    let loop_start = get_enclosing_loop_or_multi_call_closure(cx, after).map(|e| e.hir_id);
 
     let mut past_expr = false;
     for_each_expr_with_closures(cx, block, |e| {
-        if e.hir_id == after.hir_id {
+        if past_expr {
+            if utils::path_to_local_id(e, local_id) {
+                ControlFlow::Break(())
+            } else {
+                ControlFlow::Continue(Descend::Yes)
+            }
+        } else if e.hir_id == after.hir_id {
             past_expr = true;
             ControlFlow::Continue(Descend::No)
-        } else if past_expr && utils::path_to_local_id(e, local_id) {
-            ControlFlow::Break(())
         } else {
+            past_expr = Some(e.hir_id) == loop_start;
             ControlFlow::Continue(Descend::Yes)
         }
     })

clippy_utils/src/usage.rs

@@ -52,6 +52,16 @@ pub trait Visitable<'tcx> {
     /// Calls the corresponding `visit_*` function on the visitor.
     fn visit<V: Visitor<'tcx>>(self, visitor: &mut V);
 }
+impl<'tcx, T> Visitable<'tcx> for &'tcx [T]
+where
+    &'tcx T: Visitable<'tcx>,
+{
+    fn visit<V: Visitor<'tcx>>(self, visitor: &mut V) {
+        for x in self {
+            x.visit(visitor);
+        }
+    }
+}
 macro_rules! visitable_ref {
     ($t:ident, $f:ident) => {
         impl<'tcx> Visitable<'tcx> for &'tcx $t<'tcx> {

clippy_utils/src/visitors.rs

@@ -345,3 +345,58 @@ fn angle_brackets_and_args() {
     let dyn_opt: Option<&dyn TestTrait> = Some(&test_struct);
     dyn_opt.map(<dyn TestTrait>::method_on_dyn);
 }
+
+fn _late_bound_to_early_bound_regions() {
+    struct Foo<'a>(&'a u32);
+    impl<'a> Foo<'a> {
+        fn f(x: &'a u32) -> Self {
+            Foo(x)
+        }
+    }
+    fn f(f: impl for<'a> Fn(&'a u32) -> Foo<'a>) -> Foo<'static> {
+        f(&0)
+    }
+
+    let _ = f(|x| Foo::f(x));
+
+    struct Bar;
+    impl<'a> From<&'a u32> for Bar {
+        fn from(x: &'a u32) -> Bar {
+            Bar
+        }
+    }
+    fn f2(f: impl for<'a> Fn(&'a u32) -> Bar) -> Bar {
+        f(&0)
+    }
+
+    let _ = f2(|x| <Bar>::from(x));
+
+    struct Baz<'a>(&'a u32);
+    fn f3(f: impl Fn(&u32) -> Baz<'_>) -> Baz<'static> {
+        f(&0)
+    }
+
+    let _ = f3(|x| Baz(x));
+}
+
+fn _mixed_late_bound_and_early_bound_regions() {
+    fn f<T>(t: T, f: impl Fn(T, &u32) -> u32) -> u32 {
+        f(t, &0)
+    }
+    fn f2<'a, T: 'a>(_: &'a T, y: &u32) -> u32 {
+        *y
+    }
+    let _ = f(&0, f2);
+}
+
+fn _closure_with_types() {
+    fn f<T>(x: T) -> T {
+        x
+    }
+    fn f2<T: Default>(f: impl Fn(T) -> T) -> T {
+        f(T::default())
+    }
+
+    let _ = f2(|x: u32| f(x));
+    let _ = f2(|x| -> u32 { f(x) });
+}

tests/ui/eta.fixed

@@ -345,3 +345,58 @@ fn angle_brackets_and_args() {
     let dyn_opt: Option<&dyn TestTrait> = Some(&test_struct);
     dyn_opt.map(|d| d.method_on_dyn());
 }
+
+fn _late_bound_to_early_bound_regions() {
+    struct Foo<'a>(&'a u32);
+    impl<'a> Foo<'a> {
+        fn f(x: &'a u32) -> Self {
+            Foo(x)
+        }
+    }
+    fn f(f: impl for<'a> Fn(&'a u32) -> Foo<'a>) -> Foo<'static> {
+        f(&0)
+    }
+
+    let _ = f(|x| Foo::f(x));
+
+    struct Bar;
+    impl<'a> From<&'a u32> for Bar {
+        fn from(x: &'a u32) -> Bar {
+            Bar
+        }
+    }
+    fn f2(f: impl for<'a> Fn(&'a u32) -> Bar) -> Bar {
+        f(&0)
+    }
+
+    let _ = f2(|x| <Bar>::from(x));
+
+    struct Baz<'a>(&'a u32);
+    fn f3(f: impl Fn(&u32) -> Baz<'_>) -> Baz<'static> {
+        f(&0)
+    }
+
+    let _ = f3(|x| Baz(x));
+}
+
+fn _mixed_late_bound_and_early_bound_regions() {
+    fn f<T>(t: T, f: impl Fn(T, &u32) -> u32) -> u32 {
+        f(t, &0)
+    }
+    fn f2<'a, T: 'a>(_: &'a T, y: &u32) -> u32 {
+        *y
+    }
+    let _ = f(&0, |x, y| f2(x, y));
+}
+
+fn _closure_with_types() {
+    fn f<T>(x: T) -> T {
+        x
+    }
+    fn f2<T: Default>(f: impl Fn(T) -> T) -> T {
+        f(T::default())
+    }
+
+    let _ = f2(|x: u32| f(x));
+    let _ = f2(|x| -> u32 { f(x) });
+}

tests/ui/eta.rs

@@ -158,5 +158,11 @@ error: redundant closure
 LL |     dyn_opt.map(|d| d.method_on_dyn());
    |                 ^^^^^^^^^^^^^^^^^^^^^ help: replace the closure with the method itself: `<dyn TestTrait>::method_on_dyn`
 
-error: aborting due to 26 previous errors
+error: redundant closure
+  --> $DIR/eta.rs:389:19
+   |
+LL |     let _ = f(&0, |x, y| f2(x, y));
+   |                   ^^^^^^^^^^^^^^^ help: replace the closure with the function itself: `f2`
+
+error: aborting due to 27 previous errors