Split note, fix const/static impl trait error

compiler/rustc_ast_lowering/messages.ftl

@@ -106,7 +106,8 @@ ast_lowering_misplaced_double_dot =
     .note = only allowed in tuple, tuple struct, and slice patterns
 
 ast_lowering_misplaced_impl_trait =
-    `impl Trait` only allowed in function and inherent method argument and return types, not in {$position}
+    `impl Trait` is not allowed in {$position}
+    .note = `impl Trait` is only allowed in arguments and return types of functions and methods
 
 ast_lowering_misplaced_relax_trait_bound =
     `?Trait` bounds are only permitted at the point where a type parameter is declared

compiler/rustc_ast_lowering/src/errors.rs

@@ -90,6 +90,7 @@ pub enum AssocTyParenthesesSub {
 
 #[derive(Diagnostic)]
 #[diag(ast_lowering_misplaced_impl_trait, code = "E0562")]
+#[note]
 pub struct MisplacedImplTrait<'a> {
     #[primary_span]
     pub span: Span,

compiler/rustc_ast_lowering/src/item.rs

@@ -182,7 +182,8 @@ impl<'hir> LoweringContext<'_, 'hir> {
                 self.lower_use_tree(use_tree, &prefix, id, vis_span, ident, attrs)
             }
             ItemKind::Static(box ast::StaticItem { ty: t, mutability: m, expr: e }) => {
-                let (ty, body_id) = self.lower_const_item(t, span, e.as_deref());
+                let (ty, body_id) =
+                    self.lower_const_item(t, span, e.as_deref(), ImplTraitPosition::StaticTy);
                 hir::ItemKind::Static(ty, *m, body_id)
             }
             ItemKind::Const(box ast::ConstItem { generics, ty, expr, .. }) => {
@@ -191,7 +192,9 @@ impl<'hir> LoweringContext<'_, 'hir> {
                     Const::No,
                     id,
                     &ImplTraitContext::Disallowed(ImplTraitPosition::Generic),
-                    |this| this.lower_const_item(ty, span, expr.as_deref()),
+                    |this| {
+                        this.lower_const_item(ty, span, expr.as_deref(), ImplTraitPosition::ConstTy)
+                    },
                 );
                 hir::ItemKind::Const(ty, generics, body_id)
             }
@@ -448,8 +451,9 @@ impl<'hir> LoweringContext<'_, 'hir> {
         ty: &Ty,
         span: Span,
         body: Option<&Expr>,
+        impl_trait_position: ImplTraitPosition,
     ) -> (&'hir hir::Ty<'hir>, hir::BodyId) {
-        let ty = self.lower_ty(ty, &ImplTraitContext::Disallowed(ImplTraitPosition::ConstTy));
+        let ty = self.lower_ty(ty, &ImplTraitContext::Disallowed(impl_trait_position));
         (ty, self.lower_const_body(span, body))
     }
 

compiler/rustc_ast_lowering/src/lib.rs

@@ -322,7 +322,7 @@ impl std::fmt::Display for ImplTraitPosition {
     fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
         let name = match self {
             ImplTraitPosition::Path => "paths",
-            ImplTraitPosition::Variable => "variable bindings",
+            ImplTraitPosition::Variable => "the type of variable bindings",
             ImplTraitPosition::Trait => "traits",
             ImplTraitPosition::AsyncBlock => "async blocks",
             ImplTraitPosition::Bound => "bounds",
@@ -334,7 +334,7 @@ impl std::fmt::Display for ImplTraitPosition {
             ImplTraitPosition::ExternFnReturn => "`extern fn` return types",
             ImplTraitPosition::ClosureReturn => "closure return types",
             ImplTraitPosition::PointerReturn => "`fn` pointer return types",
-            ImplTraitPosition::FnTraitReturn => "the return types of `Fn` trait bounds",
+            ImplTraitPosition::FnTraitReturn => "the return type of `Fn` trait bounds",
             ImplTraitPosition::GenericDefault => "generic parameter defaults",
             ImplTraitPosition::ConstTy => "const types",
             ImplTraitPosition::StaticTy => "static types",

tests/ui/associated-consts/issue-105330.stderr

@@ -33,11 +33,13 @@ LL | fn main<A: TraitWAssocConst<A=32>>() {
    = note: see issue #92827 <https://github.com/rust-lang/rust/issues/92827> for more information
    = help: add `#![feature(associated_const_equality)]` to the crate attributes to enable
 
-error[E0562]: `impl Trait` only allowed in function and inherent method argument and return types, not in impl headers
+error[E0562]: `impl Trait` is not allowed in impl headers
   --> $DIR/issue-105330.rs:6:27
    |
 LL | impl TraitWAssocConst for impl Demo {
    |                           ^^^^^^^^^
+   |
+   = note: `impl Trait` is only allowed in arguments and return types of functions and methods
 
 error[E0131]: `main` function is not allowed to have generic parameters
   --> $DIR/issue-105330.rs:15:8

tests/ui/feature-gates/feature-gate-associated_type_bounds.rs

@@ -54,20 +54,20 @@ fn _rpit_dyn() -> Box<dyn Tr1<As1: Copy>> { Box::new(S1) }
 
 const _cdef: impl Tr1<As1: Copy> = S1;
 //~^ ERROR associated type bounds are unstable
-//~| ERROR `impl Trait` only allowed in function and inherent method argument and return types
+//~| ERROR `impl Trait` is not allowed in const types
 // FIXME: uncomment when `impl_trait_in_bindings` feature is fixed.
 // const _cdef_dyn: &dyn Tr1<As1: Copy> = &S1;
 
 static _sdef: impl Tr1<As1: Copy> = S1;
 //~^ ERROR associated type bounds are unstable
-//~| ERROR `impl Trait` only allowed in function and inherent method argument and return types
+//~| ERROR `impl Trait` is not allowed in static types
 // FIXME: uncomment when `impl_trait_in_bindings` feature is fixed.
 // static _sdef_dyn: &dyn Tr1<As1: Copy> = &S1;
 
 fn main() {
     let _: impl Tr1<As1: Copy> = S1;
     //~^ ERROR associated type bounds are unstable
-    //~| ERROR `impl Trait` only allowed in function and inherent method argument and return types
+    //~| ERROR `impl Trait` is not allowed in the type of variable bindings
     // FIXME: uncomment when `impl_trait_in_bindings` feature is fixed.
     // let _: &dyn Tr1<As1: Copy> = &S1;
 }

tests/ui/feature-gates/feature-gate-associated_type_bounds.stderr

@@ -115,23 +115,29 @@ LL |     let _: impl Tr1<As1: Copy> = S1;
    = note: see issue #52662 <https://github.com/rust-lang/rust/issues/52662> for more information
    = help: add `#![feature(associated_type_bounds)]` to the crate attributes to enable
 
-error[E0562]: `impl Trait` only allowed in function and inherent method argument and return types, not in const types
+error[E0562]: `impl Trait` is not allowed in const types
   --> $DIR/feature-gate-associated_type_bounds.rs:55:14
    |
 LL | const _cdef: impl Tr1<As1: Copy> = S1;
    |              ^^^^^^^^^^^^^^^^^^^
+   |
+   = note: `impl Trait` is only allowed in arguments and return types of functions and methods
 
-error[E0562]: `impl Trait` only allowed in function and inherent method argument and return types, not in const types
+error[E0562]: `impl Trait` is not allowed in static types
   --> $DIR/feature-gate-associated_type_bounds.rs:61:15
    |
 LL | static _sdef: impl Tr1<As1: Copy> = S1;
    |               ^^^^^^^^^^^^^^^^^^^
+   |
+   = note: `impl Trait` is only allowed in arguments and return types of functions and methods
 
-error[E0562]: `impl Trait` only allowed in function and inherent method argument and return types, not in variable bindings
+error[E0562]: `impl Trait` is not allowed in the type of variable bindings
   --> $DIR/feature-gate-associated_type_bounds.rs:68:12
    |
 LL |     let _: impl Tr1<As1: Copy> = S1;
    |            ^^^^^^^^^^^^^^^^^^^
+   |
+   = note: `impl Trait` is only allowed in arguments and return types of functions and methods
 
 error[E0277]: the trait bound `<<Self as _Tr3>::A as Iterator>::Item: Copy` is not satisfied
   --> $DIR/feature-gate-associated_type_bounds.rs:12:28

tests/ui/feature-gates/feature-gate-impl_trait_in_fn_trait_return.rs

@@ -1,6 +1,6 @@
 fn f() -> impl Fn() -> impl Sized { || () }
-//~^ ERROR `impl Trait` only allowed in function and inherent method argument and return types, not in the return types of `Fn` trait bounds
+//~^ ERROR `impl Trait` is not allowed in the return type of `Fn` trait bounds
 fn g() -> &'static dyn Fn() -> impl Sized { &|| () }
-//~^ ERROR `impl Trait` only allowed in function and inherent method argument and return types, not in the return types of `Fn` trait bounds
+//~^ ERROR `impl Trait` is not allowed in the return type of `Fn` trait bounds
 
 fn main() {}

tests/ui/feature-gates/feature-gate-impl_trait_in_fn_trait_return.stderr

@@ -1,18 +1,20 @@
-error[E0562]: `impl Trait` only allowed in function and inherent method argument and return types, not in the return types of `Fn` trait bounds
+error[E0562]: `impl Trait` is not allowed in the return type of `Fn` trait bounds
   --> $DIR/feature-gate-impl_trait_in_fn_trait_return.rs:1:24
    |
 LL | fn f() -> impl Fn() -> impl Sized { || () }
    |                        ^^^^^^^^^^
    |
+   = note: `impl Trait` is only allowed in arguments and return types of functions and methods
    = note: see issue #99697 <https://github.com/rust-lang/rust/issues/99697> for more information
    = help: add `#![feature(impl_trait_in_fn_trait_return)]` to the crate attributes to enable
 
-error[E0562]: `impl Trait` only allowed in function and inherent method argument and return types, not in the return types of `Fn` trait bounds
+error[E0562]: `impl Trait` is not allowed in the return type of `Fn` trait bounds
   --> $DIR/feature-gate-impl_trait_in_fn_trait_return.rs:3:32
    |
 LL | fn g() -> &'static dyn Fn() -> impl Sized { &|| () }
    |                                ^^^^^^^^^^
    |
+   = note: `impl Trait` is only allowed in arguments and return types of functions and methods
    = note: see issue #99697 <https://github.com/rust-lang/rust/issues/99697> for more information
    = help: add `#![feature(impl_trait_in_fn_trait_return)]` to the crate attributes to enable
 

tests/ui/impl-trait/issues/issue-54600.rs

@@ -2,6 +2,6 @@ use std::fmt::Debug;
 
 fn main() {
     let x: Option<impl Debug> = Some(44_u32);
-    //~^ `impl Trait` only allowed in function and inherent method argument and return types
+    //~^ `impl Trait` is not allowed in the type of variable bindings
     println!("{:?}", x);
 }

tests/ui/impl-trait/issues/issue-54600.stderr

@@ -1,8 +1,10 @@
-error[E0562]: `impl Trait` only allowed in function and inherent method argument and return types, not in variable bindings
+error[E0562]: `impl Trait` is not allowed in the type of variable bindings
   --> $DIR/issue-54600.rs:4:19
    |
 LL |     let x: Option<impl Debug> = Some(44_u32);
    |                   ^^^^^^^^^^
+   |
+   = note: `impl Trait` is only allowed in arguments and return types of functions and methods
 
 error: aborting due to 1 previous error
 

tests/ui/impl-trait/issues/issue-54840.rs

@@ -3,5 +3,5 @@ use std::ops::Add;
 fn main() {
     let i: i32 = 0;
     let j: &impl Add = &i;
-    //~^ `impl Trait` only allowed in function and inherent method argument and return types
+    //~^ `impl Trait` is not allowed in the type of variable bindings
 }

tests/ui/impl-trait/issues/issue-54840.stderr

@@ -1,8 +1,10 @@
-error[E0562]: `impl Trait` only allowed in function and inherent method argument and return types, not in variable bindings
+error[E0562]: `impl Trait` is not allowed in the type of variable bindings
   --> $DIR/issue-54840.rs:5:13
    |
 LL |     let j: &impl Add = &i;
    |             ^^^^^^^^
+   |
+   = note: `impl Trait` is only allowed in arguments and return types of functions and methods
 
 error: aborting due to 1 previous error
 

tests/ui/impl-trait/issues/issue-58504.rs

@@ -8,5 +8,5 @@ fn mk_gen() -> impl Coroutine<Return=!, Yield=()> {
 
 fn main() {
     let gens: [impl Coroutine<Return=!, Yield=()>;2] = [ mk_gen(), mk_gen() ];
-    //~^ `impl Trait` only allowed in function and inherent method argument and return types
+    //~^ `impl Trait` is not allowed in the type of variable bindings
 }

tests/ui/impl-trait/issues/issue-58504.stderr

@@ -1,8 +1,10 @@
-error[E0562]: `impl Trait` only allowed in function and inherent method argument and return types, not in variable bindings
+error[E0562]: `impl Trait` is not allowed in the type of variable bindings
   --> $DIR/issue-58504.rs:10:16
    |
 LL |     let gens: [impl Coroutine<Return=!, Yield=()>;2] = [ mk_gen(), mk_gen() ];
    |                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: `impl Trait` is only allowed in arguments and return types of functions and methods
 
 error: aborting due to 1 previous error
 

tests/ui/impl-trait/issues/issue-58956.rs

@@ -5,9 +5,9 @@ impl Lam for B {}
 pub struct Wrap<T>(T);
 
 const _A: impl Lam = {
-    //~^ `impl Trait` only allowed in function and inherent method argument and return types
+    //~^ `impl Trait` is not allowed in const types
     let x: Wrap<impl Lam> = Wrap(B);
-    //~^ `impl Trait` only allowed in function and inherent method argument and return types
+    //~^ `impl Trait` is not allowed in the type of variable bindings
     x.0
 };
 

tests/ui/impl-trait/issues/issue-58956.stderr

@@ -1,14 +1,18 @@
-error[E0562]: `impl Trait` only allowed in function and inherent method argument and return types, not in const types
+error[E0562]: `impl Trait` is not allowed in const types
   --> $DIR/issue-58956.rs:7:11
    |
 LL | const _A: impl Lam = {
    |           ^^^^^^^^
+   |
+   = note: `impl Trait` is only allowed in arguments and return types of functions and methods
 
-error[E0562]: `impl Trait` only allowed in function and inherent method argument and return types, not in variable bindings
+error[E0562]: `impl Trait` is not allowed in the type of variable bindings
   --> $DIR/issue-58956.rs:9:17
    |
 LL |     let x: Wrap<impl Lam> = Wrap(B);
    |                 ^^^^^^^^
+   |
+   = note: `impl Trait` is only allowed in arguments and return types of functions and methods
 
 error: aborting due to 2 previous errors
 

tests/ui/impl-trait/issues/issue-70971.rs

@@ -1,4 +1,4 @@
 fn main() {
     let x : (impl Copy,) = (true,);
-    //~^ `impl Trait` only allowed in function and inherent method argument and return types
+    //~^ `impl Trait` is not allowed in the type of variable bindings
 }

tests/ui/impl-trait/issues/issue-70971.stderr

@@ -1,8 +1,10 @@
-error[E0562]: `impl Trait` only allowed in function and inherent method argument and return types, not in variable bindings
+error[E0562]: `impl Trait` is not allowed in the type of variable bindings
   --> $DIR/issue-70971.rs:2:14
    |
 LL |     let x : (impl Copy,) = (true,);
    |              ^^^^^^^^^
+   |
+   = note: `impl Trait` is only allowed in arguments and return types of functions and methods
 
 error: aborting due to 1 previous error
 

tests/ui/impl-trait/issues/issue-79099.rs

@@ -1,7 +1,7 @@
 struct Bug {
     V1: [(); {
         let f: impl core::future::Future<Output = u8> = async { 1 };
-        //~^ `impl Trait` only allowed in function and inherent method argument and return types
+        //~^ `impl Trait` is not allowed in the type of variable bindings
         //~| expected identifier
         1
     }],

tests/ui/impl-trait/issues/issue-79099.stderr

@@ -9,11 +9,13 @@ LL |         let f: impl core::future::Future<Output = u8> = async { 1 };
    = help: pass `--edition 2021` to `rustc`
    = note: for more on editions, read https://doc.rust-lang.org/edition-guide
 
-error[E0562]: `impl Trait` only allowed in function and inherent method argument and return types, not in variable bindings
+error[E0562]: `impl Trait` is not allowed in the type of variable bindings
   --> $DIR/issue-79099.rs:3:16
    |
 LL |         let f: impl core::future::Future<Output = u8> = async { 1 };
    |                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: `impl Trait` is only allowed in arguments and return types of functions and methods
 
 error: aborting due to 2 previous errors
 

tests/ui/impl-trait/issues/issue-83929-impl-trait-in-generic-default.rs

@@ -1,8 +1,8 @@
 struct Foo<T = impl Copy>(T);
-//~^ ERROR `impl Trait` only allowed in function and inherent method argument and return types
+//~^ ERROR `impl Trait` is not allowed in generic parameter defaults
 
 type Result<T, E = impl std::error::Error> = std::result::Result<T, E>;
-//~^ ERROR `impl Trait` only allowed in function and inherent method argument and return types
+//~^ ERROR `impl Trait` is not allowed in generic parameter defaults
 
 // should not cause ICE
 fn x() -> Foo {

tests/ui/impl-trait/issues/issue-83929-impl-trait-in-generic-default.stderr

@@ -1,14 +1,18 @@
-error[E0562]: `impl Trait` only allowed in function and inherent method argument and return types, not in generic parameter defaults
+error[E0562]: `impl Trait` is not allowed in generic parameter defaults
   --> $DIR/issue-83929-impl-trait-in-generic-default.rs:1:16
    |
 LL | struct Foo<T = impl Copy>(T);
    |                ^^^^^^^^^
+   |
+   = note: `impl Trait` is only allowed in arguments and return types of functions and methods
 
-error[E0562]: `impl Trait` only allowed in function and inherent method argument and return types, not in generic parameter defaults
+error[E0562]: `impl Trait` is not allowed in generic parameter defaults
   --> $DIR/issue-83929-impl-trait-in-generic-default.rs:4:20
    |
 LL | type Result<T, E = impl std::error::Error> = std::result::Result<T, E>;
    |                    ^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: `impl Trait` is only allowed in arguments and return types of functions and methods
 
 error: aborting due to 2 previous errors
 

tests/ui/impl-trait/issues/issue-84919.rs

@@ -3,7 +3,7 @@ impl Trait for () {}
 
 fn foo<'a: 'a>() {
     let _x: impl Trait = ();
-    //~^ `impl Trait` only allowed in function and inherent method argument and return types
+    //~^ `impl Trait` is not allowed in the type of variable bindings
 }
 
 fn main() {}

tests/ui/impl-trait/issues/issue-84919.stderr

@@ -1,8 +1,10 @@
-error[E0562]: `impl Trait` only allowed in function and inherent method argument and return types, not in variable bindings
+error[E0562]: `impl Trait` is not allowed in the type of variable bindings
   --> $DIR/issue-84919.rs:5:13
    |
 LL |     let _x: impl Trait = ();
    |             ^^^^^^^^^^
+   |
+   = note: `impl Trait` is only allowed in arguments and return types of functions and methods
 
 error: aborting due to 1 previous error
 

tests/ui/impl-trait/issues/issue-86642.rs

@@ -1,5 +1,5 @@
 static x: impl Fn(&str) -> Result<&str, ()> = move |source| {
-    //~^ `impl Trait` only allowed in function and inherent method argument and return types
+    //~^ `impl Trait` is not allowed in static types
     let res = (move |source| Ok(source))(source);
     let res = res.or((move |source| Ok(source))(source));
     res

tests/ui/impl-trait/issues/issue-86642.stderr

@@ -1,8 +1,10 @@
-error[E0562]: `impl Trait` only allowed in function and inherent method argument and return types, not in const types
+error[E0562]: `impl Trait` is not allowed in static types
   --> $DIR/issue-86642.rs:1:11
    |
 LL | static x: impl Fn(&str) -> Result<&str, ()> = move |source| {
    |           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: `impl Trait` is only allowed in arguments and return types of functions and methods
 
 error: aborting due to 1 previous error
 

tests/ui/impl-trait/issues/issue-87295.rs

@@ -14,5 +14,5 @@ impl<F> Struct<F> {
 
 fn main() {
     let _do_not_waste: Struct<impl Trait<Output = i32>> = Struct::new(());
-    //~^ `impl Trait` only allowed in function and inherent method argument and return types
+    //~^ `impl Trait` is not allowed in the type of variable bindings
 }

tests/ui/impl-trait/issues/issue-87295.stderr

@@ -1,8 +1,10 @@
-error[E0562]: `impl Trait` only allowed in function and inherent method argument and return types, not in variable bindings
+error[E0562]: `impl Trait` is not allowed in the type of variable bindings
   --> $DIR/issue-87295.rs:16:31
    |
 LL |     let _do_not_waste: Struct<impl Trait<Output = i32>> = Struct::new(());
    |                               ^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: `impl Trait` is only allowed in arguments and return types of functions and methods
 
 error: aborting due to 1 previous error
 

tests/ui/impl-trait/nested_impl_trait.rs

@@ -9,7 +9,7 @@ fn bad_in_ret_position(x: impl Into<u32>) -> impl Into<impl Debug> { x }
 
 fn bad_in_fn_syntax(x: fn() -> impl Into<impl Debug>) {}
 //~^ ERROR nested `impl Trait` is not allowed
-//~| `impl Trait` only allowed in function and inherent method argument and return types
+//~| `impl Trait` is not allowed in `fn` pointer
 
 fn bad_in_arg_position(_: impl Into<impl Debug>) { }
 //~^ ERROR nested `impl Trait` is not allowed

tests/ui/impl-trait/nested_impl_trait.stderr

@@ -34,11 +34,13 @@ LL |     fn bad(x: impl Into<u32>) -> impl Into<impl Debug> { x }
    |                                  |         nested `impl Trait` here
    |                                  outer `impl Trait`
 
-error[E0562]: `impl Trait` only allowed in function and inherent method argument and return types, not in `fn` pointer return types
+error[E0562]: `impl Trait` is not allowed in `fn` pointer return types
   --> $DIR/nested_impl_trait.rs:10:32
    |
 LL | fn bad_in_fn_syntax(x: fn() -> impl Into<impl Debug>) {}
    |                                ^^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: `impl Trait` is only allowed in arguments and return types of functions and methods
 
 error[E0277]: the trait bound `impl Debug: From<impl Into<u32>>` is not satisfied
   --> $DIR/nested_impl_trait.rs:6:46

tests/ui/impl-trait/where-allowed.rs

@@ -16,47 +16,47 @@ fn in_adt_in_parameters(_: Vec<impl Debug>) { panic!() }
 
 // Disallowed
 fn in_fn_parameter_in_parameters(_: fn(impl Debug)) { panic!() }
-//~^ ERROR `impl Trait` only allowed in function and inherent method argument and return types
+//~^ ERROR `impl Trait` is not allowed in `fn` pointer
 
 // Disallowed
 fn in_fn_return_in_parameters(_: fn() -> impl Debug) { panic!() }
-//~^ ERROR `impl Trait` only allowed in function and inherent method argument and return types
+//~^ ERROR `impl Trait` is not allowed in `fn` pointer
 
 // Disallowed
 fn in_fn_parameter_in_return() -> fn(impl Debug) { panic!() }
-//~^ ERROR `impl Trait` only allowed in function and inherent method argument and return types
+//~^ ERROR `impl Trait` is not allowed in `fn` pointer
 
 // Disallowed
 fn in_fn_return_in_return() -> fn() -> impl Debug { panic!() }
-//~^ ERROR `impl Trait` only allowed in function and inherent method argument and return types
+//~^ ERROR `impl Trait` is not allowed in `fn` pointer
 
 // Disallowed
 fn in_dyn_Fn_parameter_in_parameters(_: &dyn Fn(impl Debug)) { panic!() }
-//~^ ERROR `impl Trait` only allowed in function and inherent method argument and return types
+//~^ ERROR `impl Trait` is not allowed in the parameters of `Fn` trait bounds
 
 // Disallowed
 fn in_dyn_Fn_return_in_parameters(_: &dyn Fn() -> impl Debug) { panic!() }
-//~^ ERROR `impl Trait` only allowed in function and inherent method argument and return types
+//~^ ERROR `impl Trait` is not allowed in the return type of `Fn` trait bounds
 
 // Disallowed
 fn in_dyn_Fn_parameter_in_return() -> &'static dyn Fn(impl Debug) { panic!() }
-//~^ ERROR `impl Trait` only allowed in function and inherent method argument and return types
+//~^ ERROR `impl Trait` is not allowed in the parameters of `Fn` trait bounds
 
 // Allowed
 fn in_dyn_Fn_return_in_return() -> &'static dyn Fn() -> impl Debug { panic!() }
 
 // Disallowed
 fn in_impl_Fn_parameter_in_parameters(_: &impl Fn(impl Debug)) { panic!() }
-//~^ ERROR `impl Trait` only allowed in function and inherent method argument and return types
+//~^ ERROR `impl Trait` is not allowed in the parameters of `Fn` trait bounds
 //~^^ ERROR nested `impl Trait` is not allowed
 
 // Disallowed
 fn in_impl_Fn_return_in_parameters(_: &impl Fn() -> impl Debug) { panic!() }
-//~^ ERROR `impl Trait` only allowed in function and inherent method argument and return types
+//~^ ERROR `impl Trait` is not allowed in the return type of `Fn` trait bounds
 
 // Disallowed
 fn in_impl_Fn_parameter_in_return() -> &'static impl Fn(impl Debug) { panic!() }
-//~^ ERROR `impl Trait` only allowed in function and inherent method argument and return types
+//~^ ERROR `impl Trait` is not allowed in the parameters of `Fn` trait bounds
 //~| ERROR nested `impl Trait` is not allowed
 
 // Allowed
@@ -64,11 +64,11 @@ fn in_impl_Fn_return_in_return() -> &'static impl Fn() -> impl Debug { panic!()
 
 // Disallowed
 fn in_Fn_parameter_in_generics<F: Fn(impl Debug)> (_: F) { panic!() }
-//~^ ERROR `impl Trait` only allowed in function and inherent method argument and return types
+//~^ ERROR `impl Trait` is not allowed in the parameters of `Fn` trait bounds
 
 // Disallowed
 fn in_Fn_return_in_generics<F: Fn() -> impl Debug> (_: F) { panic!() }
-//~^ ERROR `impl Trait` only allowed in function and inherent method argument and return types
+//~^ ERROR `impl Trait` is not allowed in the return type of `Fn` trait bounds
 
 
 // Allowed
@@ -81,22 +81,22 @@ fn in_impl_Trait_in_return() -> impl IntoIterator<Item = impl IntoIterator> {
 
 // Disallowed
 struct InBraceStructField { x: impl Debug }
-//~^ ERROR `impl Trait` only allowed in function and inherent method argument and return types
+//~^ ERROR `impl Trait` is not allowed in field types
 
 // Disallowed
 struct InAdtInBraceStructField { x: Vec<impl Debug> }
-//~^ ERROR `impl Trait` only allowed in function and inherent method argument and return types
+//~^ ERROR `impl Trait` is not allowed in field types
 
 // Disallowed
 struct InTupleStructField(impl Debug);
-//~^ ERROR `impl Trait` only allowed in function and inherent method argument and return types
+//~^ ERROR `impl Trait` is not allowed in field types
 
 // Disallowed
 enum InEnum {
     InBraceVariant { x: impl Debug },
-    //~^ ERROR `impl Trait` only allowed in function and inherent method argument and return types
+    //~^ ERROR `impl Trait` is not allowed in field types
     InTupleVariant(impl Debug),
-    //~^ ERROR `impl Trait` only allowed in function and inherent method argument and return types
+    //~^ ERROR `impl Trait` is not allowed in field types
 }
 
 // Allowed
@@ -136,10 +136,10 @@ impl DummyType {
 // Disallowed
 extern "C" {
     fn in_foreign_parameters(_: impl Debug);
-    //~^ ERROR `impl Trait` only allowed in function and inherent method argument and return types
+    //~^ ERROR `impl Trait` is not allowed in `extern fn`
 
     fn in_foreign_return() -> impl Debug;
-    //~^ ERROR `impl Trait` only allowed in function and inherent method argument and return types
+    //~^ ERROR `impl Trait` is not allowed in `extern fn`
 }
 
 // Allowed
@@ -155,97 +155,97 @@ type InTypeAlias<R> = impl Debug;
 //~^ ERROR `impl Trait` in type aliases is unstable
 
 type InReturnInTypeAlias<R> = fn() -> impl Debug;
-//~^ ERROR `impl Trait` only allowed in function and inherent method argument and return types
+//~^ ERROR `impl Trait` is not allowed in `fn` pointer
 //~| ERROR `impl Trait` in type aliases is unstable
 
 // Disallowed in impl headers
 impl PartialEq<impl Debug> for () {
-    //~^ ERROR `impl Trait` only allowed in function and inherent method argument and return types
+    //~^ ERROR `impl Trait` is not allowed in traits
 }
 
 // Disallowed in impl headers
 impl PartialEq<()> for impl Debug {
-    //~^ ERROR `impl Trait` only allowed in function and inherent method argument and return types
+    //~^ ERROR `impl Trait` is not allowed in impl headers
 }
 
 // Disallowed in inherent impls
 impl impl Debug {
-    //~^ ERROR `impl Trait` only allowed in function and inherent method argument and return types
+    //~^ ERROR `impl Trait` is not allowed in impl headers
 }
 
 // Disallowed in inherent impls
 struct InInherentImplAdt<T> { t: T }
 impl InInherentImplAdt<impl Debug> {
-    //~^ ERROR `impl Trait` only allowed in function and inherent method argument and return types
+    //~^ ERROR `impl Trait` is not allowed in impl headers
 }
 
 // Disallowed in where clauses
 fn in_fn_where_clause()
     where impl Debug: Debug
-//~^ ERROR `impl Trait` only allowed in function and inherent method argument and return types
+//~^ ERROR `impl Trait` is not allowed in bounds
 {
 }
 
 // Disallowed in where clauses
 fn in_adt_in_fn_where_clause()
     where Vec<impl Debug>: Debug
-//~^ ERROR `impl Trait` only allowed in function and inherent method argument and return types
+//~^ ERROR `impl Trait` is not allowed in bounds
 {
 }
 
 // Disallowed
 fn in_trait_parameter_in_fn_where_clause<T>()
     where T: PartialEq<impl Debug>
-//~^ ERROR `impl Trait` only allowed in function and inherent method argument and return types
+//~^ ERROR `impl Trait` is not allowed in bounds
 {
 }
 
 // Disallowed
 fn in_Fn_parameter_in_fn_where_clause<T>()
     where T: Fn(impl Debug)
-//~^ ERROR `impl Trait` only allowed in function and inherent method argument and return types
+//~^ ERROR `impl Trait` is not allowed in the parameters of `Fn` trait bounds
 {
 }
 
 // Disallowed
 fn in_Fn_return_in_fn_where_clause<T>()
     where T: Fn() -> impl Debug
-//~^ ERROR `impl Trait` only allowed in function and inherent method argument and return types
+//~^ ERROR `impl Trait` is not allowed in the return type of `Fn` trait bounds
 {
 }
 
 // Disallowed
 struct InStructGenericParamDefault<T = impl Debug>(T);
-//~^ ERROR `impl Trait` only allowed in function and inherent method argument and return types
+//~^ ERROR `impl Trait` is not allowed in generic parameter defaults
 
 // Disallowed
 enum InEnumGenericParamDefault<T = impl Debug> { Variant(T) }
-//~^ ERROR `impl Trait` only allowed in function and inherent method argument and return types
+//~^ ERROR `impl Trait` is not allowed in generic parameter defaults
 
 // Disallowed
 trait InTraitGenericParamDefault<T = impl Debug> {}
-//~^ ERROR `impl Trait` only allowed in function and inherent method argument and return types
+//~^ ERROR `impl Trait` is not allowed in generic parameter defaults
 
 // Disallowed
 type InTypeAliasGenericParamDefault<T = impl Debug> = T;
-//~^ ERROR `impl Trait` only allowed in function and inherent method argument and return types
+//~^ ERROR `impl Trait` is not allowed in generic parameter defaults
 
 // Disallowed
 impl <T = impl Debug> T {}
 //~^ ERROR defaults for type parameters are only allowed in `struct`, `enum`, `type`, or `trait` definitions
 //~| WARNING this was previously accepted by the compiler but is being phased out
-//~| ERROR `impl Trait` only allowed in function and inherent method argument and return types
+//~| ERROR `impl Trait` is not allowed in generic parameter defaults
 //~| ERROR no nominal type found
 
 // Disallowed
 fn in_method_generic_param_default<T = impl Debug>(_: T) {}
 //~^ ERROR defaults for type parameters are only allowed in `struct`, `enum`, `type`, or `trait` definitions
 //~| WARNING this was previously accepted by the compiler but is being phased out
-//~| ERROR `impl Trait` only allowed in function and inherent method argument and return types
+//~| ERROR `impl Trait` is not allowed in generic parameter defaults
 
 fn main() {
     let _in_local_variable: impl Fn() = || {};
-    //~^ ERROR `impl Trait` only allowed in function and inherent method argument and return types
+    //~^ ERROR `impl Trait` is not allowed in the type of variable bindings
     let _in_return_in_local_variable = || -> impl Fn() { || {} };
-    //~^ ERROR `impl Trait` only allowed in function and inherent method argument and return types
+    //~^ ERROR `impl Trait` is not allowed in closure return types
 }

tests/ui/impl-trait/where-allowed.stderr

@@ -43,227 +43,301 @@ LL | type InReturnInTypeAlias<R> = fn() -> impl Debug;
    = note: see issue #63063 <https://github.com/rust-lang/rust/issues/63063> for more information
    = help: add `#![feature(type_alias_impl_trait)]` to the crate attributes to enable
 
-error[E0562]: `impl Trait` only allowed in function and inherent method argument and return types, not in `fn` pointer parameters
+error[E0562]: `impl Trait` is not allowed in `fn` pointer parameters
   --> $DIR/where-allowed.rs:18:40
    |
 LL | fn in_fn_parameter_in_parameters(_: fn(impl Debug)) { panic!() }
    |                                        ^^^^^^^^^^
+   |
+   = note: `impl Trait` is only allowed in arguments and return types of functions and methods
 
-error[E0562]: `impl Trait` only allowed in function and inherent method argument and return types, not in `fn` pointer return types
+error[E0562]: `impl Trait` is not allowed in `fn` pointer return types
   --> $DIR/where-allowed.rs:22:42
    |
 LL | fn in_fn_return_in_parameters(_: fn() -> impl Debug) { panic!() }
    |                                          ^^^^^^^^^^
+   |
+   = note: `impl Trait` is only allowed in arguments and return types of functions and methods
 
-error[E0562]: `impl Trait` only allowed in function and inherent method argument and return types, not in `fn` pointer parameters
+error[E0562]: `impl Trait` is not allowed in `fn` pointer parameters
   --> $DIR/where-allowed.rs:26:38
    |
 LL | fn in_fn_parameter_in_return() -> fn(impl Debug) { panic!() }
    |                                      ^^^^^^^^^^
+   |
+   = note: `impl Trait` is only allowed in arguments and return types of functions and methods
 
-error[E0562]: `impl Trait` only allowed in function and inherent method argument and return types, not in `fn` pointer return types
+error[E0562]: `impl Trait` is not allowed in `fn` pointer return types
   --> $DIR/where-allowed.rs:30:40
    |
 LL | fn in_fn_return_in_return() -> fn() -> impl Debug { panic!() }
    |                                        ^^^^^^^^^^
+   |
+   = note: `impl Trait` is only allowed in arguments and return types of functions and methods
 
-error[E0562]: `impl Trait` only allowed in function and inherent method argument and return types, not in the parameters of `Fn` trait bounds
+error[E0562]: `impl Trait` is not allowed in the parameters of `Fn` trait bounds
   --> $DIR/where-allowed.rs:34:49
    |
 LL | fn in_dyn_Fn_parameter_in_parameters(_: &dyn Fn(impl Debug)) { panic!() }
    |                                                 ^^^^^^^^^^
+   |
+   = note: `impl Trait` is only allowed in arguments and return types of functions and methods
 
-error[E0562]: `impl Trait` only allowed in function and inherent method argument and return types, not in the return types of `Fn` trait bounds
+error[E0562]: `impl Trait` is not allowed in the return type of `Fn` trait bounds
   --> $DIR/where-allowed.rs:38:51
    |
 LL | fn in_dyn_Fn_return_in_parameters(_: &dyn Fn() -> impl Debug) { panic!() }
    |                                                   ^^^^^^^^^^
+   |
+   = note: `impl Trait` is only allowed in arguments and return types of functions and methods
 
-error[E0562]: `impl Trait` only allowed in function and inherent method argument and return types, not in the parameters of `Fn` trait bounds
+error[E0562]: `impl Trait` is not allowed in the parameters of `Fn` trait bounds
   --> $DIR/where-allowed.rs:42:55
    |
 LL | fn in_dyn_Fn_parameter_in_return() -> &'static dyn Fn(impl Debug) { panic!() }
    |                                                       ^^^^^^^^^^
+   |
+   = note: `impl Trait` is only allowed in arguments and return types of functions and methods
 
-error[E0562]: `impl Trait` only allowed in function and inherent method argument and return types, not in the parameters of `Fn` trait bounds
+error[E0562]: `impl Trait` is not allowed in the parameters of `Fn` trait bounds
   --> $DIR/where-allowed.rs:49:51
    |
 LL | fn in_impl_Fn_parameter_in_parameters(_: &impl Fn(impl Debug)) { panic!() }
    |                                                   ^^^^^^^^^^
+   |
+   = note: `impl Trait` is only allowed in arguments and return types of functions and methods
 
-error[E0562]: `impl Trait` only allowed in function and inherent method argument and return types, not in the return types of `Fn` trait bounds
+error[E0562]: `impl Trait` is not allowed in the return type of `Fn` trait bounds
   --> $DIR/where-allowed.rs:54:53
    |
 LL | fn in_impl_Fn_return_in_parameters(_: &impl Fn() -> impl Debug) { panic!() }
    |                                                     ^^^^^^^^^^
+   |
+   = note: `impl Trait` is only allowed in arguments and return types of functions and methods
 
-error[E0562]: `impl Trait` only allowed in function and inherent method argument and return types, not in the parameters of `Fn` trait bounds
+error[E0562]: `impl Trait` is not allowed in the parameters of `Fn` trait bounds
   --> $DIR/where-allowed.rs:58:57
    |
 LL | fn in_impl_Fn_parameter_in_return() -> &'static impl Fn(impl Debug) { panic!() }
    |                                                         ^^^^^^^^^^
+   |
+   = note: `impl Trait` is only allowed in arguments and return types of functions and methods
 
-error[E0562]: `impl Trait` only allowed in function and inherent method argument and return types, not in the parameters of `Fn` trait bounds
+error[E0562]: `impl Trait` is not allowed in the parameters of `Fn` trait bounds
   --> $DIR/where-allowed.rs:66:38
    |
 LL | fn in_Fn_parameter_in_generics<F: Fn(impl Debug)> (_: F) { panic!() }
    |                                      ^^^^^^^^^^
+   |
+   = note: `impl Trait` is only allowed in arguments and return types of functions and methods
 
-error[E0562]: `impl Trait` only allowed in function and inherent method argument and return types, not in the return types of `Fn` trait bounds
+error[E0562]: `impl Trait` is not allowed in the return type of `Fn` trait bounds
   --> $DIR/where-allowed.rs:70:40
    |
 LL | fn in_Fn_return_in_generics<F: Fn() -> impl Debug> (_: F) { panic!() }
    |                                        ^^^^^^^^^^
+   |
+   = note: `impl Trait` is only allowed in arguments and return types of functions and methods
 
-error[E0562]: `impl Trait` only allowed in function and inherent method argument and return types, not in field types
+error[E0562]: `impl Trait` is not allowed in field types
   --> $DIR/where-allowed.rs:83:32
    |
 LL | struct InBraceStructField { x: impl Debug }
    |                                ^^^^^^^^^^
+   |
+   = note: `impl Trait` is only allowed in arguments and return types of functions and methods
 
-error[E0562]: `impl Trait` only allowed in function and inherent method argument and return types, not in field types
+error[E0562]: `impl Trait` is not allowed in field types
   --> $DIR/where-allowed.rs:87:41
    |
 LL | struct InAdtInBraceStructField { x: Vec<impl Debug> }
    |                                         ^^^^^^^^^^
+   |
+   = note: `impl Trait` is only allowed in arguments and return types of functions and methods
 
-error[E0562]: `impl Trait` only allowed in function and inherent method argument and return types, not in field types
+error[E0562]: `impl Trait` is not allowed in field types
   --> $DIR/where-allowed.rs:91:27
    |
 LL | struct InTupleStructField(impl Debug);
    |                           ^^^^^^^^^^
+   |
+   = note: `impl Trait` is only allowed in arguments and return types of functions and methods
 
-error[E0562]: `impl Trait` only allowed in function and inherent method argument and return types, not in field types
+error[E0562]: `impl Trait` is not allowed in field types
   --> $DIR/where-allowed.rs:96:25
    |
 LL |     InBraceVariant { x: impl Debug },
    |                         ^^^^^^^^^^
+   |
+   = note: `impl Trait` is only allowed in arguments and return types of functions and methods
 
-error[E0562]: `impl Trait` only allowed in function and inherent method argument and return types, not in field types
+error[E0562]: `impl Trait` is not allowed in field types
   --> $DIR/where-allowed.rs:98:20
    |
 LL |     InTupleVariant(impl Debug),
    |                    ^^^^^^^^^^
+   |
+   = note: `impl Trait` is only allowed in arguments and return types of functions and methods
 
-error[E0562]: `impl Trait` only allowed in function and inherent method argument and return types, not in `extern fn` parameters
+error[E0562]: `impl Trait` is not allowed in `extern fn` parameters
   --> $DIR/where-allowed.rs:138:33
    |
 LL |     fn in_foreign_parameters(_: impl Debug);
    |                                 ^^^^^^^^^^
+   |
+   = note: `impl Trait` is only allowed in arguments and return types of functions and methods
 
-error[E0562]: `impl Trait` only allowed in function and inherent method argument and return types, not in `extern fn` return types
+error[E0562]: `impl Trait` is not allowed in `extern fn` return types
   --> $DIR/where-allowed.rs:141:31
    |
 LL |     fn in_foreign_return() -> impl Debug;
    |                               ^^^^^^^^^^
+   |
+   = note: `impl Trait` is only allowed in arguments and return types of functions and methods
 
-error[E0562]: `impl Trait` only allowed in function and inherent method argument and return types, not in `fn` pointer return types
+error[E0562]: `impl Trait` is not allowed in `fn` pointer return types
   --> $DIR/where-allowed.rs:157:39
    |
 LL | type InReturnInTypeAlias<R> = fn() -> impl Debug;
    |                                       ^^^^^^^^^^
+   |
+   = note: `impl Trait` is only allowed in arguments and return types of functions and methods
 
-error[E0562]: `impl Trait` only allowed in function and inherent method argument and return types, not in traits
+error[E0562]: `impl Trait` is not allowed in traits
   --> $DIR/where-allowed.rs:162:16
    |
 LL | impl PartialEq<impl Debug> for () {
    |                ^^^^^^^^^^
+   |
+   = note: `impl Trait` is only allowed in arguments and return types of functions and methods
 
-error[E0562]: `impl Trait` only allowed in function and inherent method argument and return types, not in impl headers
+error[E0562]: `impl Trait` is not allowed in impl headers
   --> $DIR/where-allowed.rs:167:24
    |
 LL | impl PartialEq<()> for impl Debug {
    |                        ^^^^^^^^^^
+   |
+   = note: `impl Trait` is only allowed in arguments and return types of functions and methods
 
-error[E0562]: `impl Trait` only allowed in function and inherent method argument and return types, not in impl headers
+error[E0562]: `impl Trait` is not allowed in impl headers
   --> $DIR/where-allowed.rs:172:6
    |
 LL | impl impl Debug {
    |      ^^^^^^^^^^
+   |
+   = note: `impl Trait` is only allowed in arguments and return types of functions and methods
 
-error[E0562]: `impl Trait` only allowed in function and inherent method argument and return types, not in impl headers
+error[E0562]: `impl Trait` is not allowed in impl headers
   --> $DIR/where-allowed.rs:178:24
    |
 LL | impl InInherentImplAdt<impl Debug> {
    |                        ^^^^^^^^^^
+   |
+   = note: `impl Trait` is only allowed in arguments and return types of functions and methods
 
-error[E0562]: `impl Trait` only allowed in function and inherent method argument and return types, not in bounds
+error[E0562]: `impl Trait` is not allowed in bounds
   --> $DIR/where-allowed.rs:184:11
    |
 LL |     where impl Debug: Debug
    |           ^^^^^^^^^^
+   |
+   = note: `impl Trait` is only allowed in arguments and return types of functions and methods
 
-error[E0562]: `impl Trait` only allowed in function and inherent method argument and return types, not in bounds
+error[E0562]: `impl Trait` is not allowed in bounds
   --> $DIR/where-allowed.rs:191:15
    |
 LL |     where Vec<impl Debug>: Debug
    |               ^^^^^^^^^^
+   |
+   = note: `impl Trait` is only allowed in arguments and return types of functions and methods
 
-error[E0562]: `impl Trait` only allowed in function and inherent method argument and return types, not in bounds
+error[E0562]: `impl Trait` is not allowed in bounds
   --> $DIR/where-allowed.rs:198:24
    |
 LL |     where T: PartialEq<impl Debug>
    |                        ^^^^^^^^^^
+   |
+   = note: `impl Trait` is only allowed in arguments and return types of functions and methods
 
-error[E0562]: `impl Trait` only allowed in function and inherent method argument and return types, not in the parameters of `Fn` trait bounds
+error[E0562]: `impl Trait` is not allowed in the parameters of `Fn` trait bounds
   --> $DIR/where-allowed.rs:205:17
    |
 LL |     where T: Fn(impl Debug)
    |                 ^^^^^^^^^^
+   |
+   = note: `impl Trait` is only allowed in arguments and return types of functions and methods
 
-error[E0562]: `impl Trait` only allowed in function and inherent method argument and return types, not in the return types of `Fn` trait bounds
+error[E0562]: `impl Trait` is not allowed in the return type of `Fn` trait bounds
   --> $DIR/where-allowed.rs:212:22
    |
 LL |     where T: Fn() -> impl Debug
    |                      ^^^^^^^^^^
+   |
+   = note: `impl Trait` is only allowed in arguments and return types of functions and methods
 
-error[E0562]: `impl Trait` only allowed in function and inherent method argument and return types, not in generic parameter defaults
+error[E0562]: `impl Trait` is not allowed in generic parameter defaults
   --> $DIR/where-allowed.rs:218:40
    |
 LL | struct InStructGenericParamDefault<T = impl Debug>(T);
    |                                        ^^^^^^^^^^
+   |
+   = note: `impl Trait` is only allowed in arguments and return types of functions and methods
 
-error[E0562]: `impl Trait` only allowed in function and inherent method argument and return types, not in generic parameter defaults
+error[E0562]: `impl Trait` is not allowed in generic parameter defaults
   --> $DIR/where-allowed.rs:222:36
    |
 LL | enum InEnumGenericParamDefault<T = impl Debug> { Variant(T) }
    |                                    ^^^^^^^^^^
+   |
+   = note: `impl Trait` is only allowed in arguments and return types of functions and methods
 
-error[E0562]: `impl Trait` only allowed in function and inherent method argument and return types, not in generic parameter defaults
+error[E0562]: `impl Trait` is not allowed in generic parameter defaults
   --> $DIR/where-allowed.rs:226:38
    |
 LL | trait InTraitGenericParamDefault<T = impl Debug> {}
    |                                      ^^^^^^^^^^
+   |
+   = note: `impl Trait` is only allowed in arguments and return types of functions and methods
 
-error[E0562]: `impl Trait` only allowed in function and inherent method argument and return types, not in generic parameter defaults
+error[E0562]: `impl Trait` is not allowed in generic parameter defaults
   --> $DIR/where-allowed.rs:230:41
    |
 LL | type InTypeAliasGenericParamDefault<T = impl Debug> = T;
    |                                         ^^^^^^^^^^
+   |
+   = note: `impl Trait` is only allowed in arguments and return types of functions and methods
 
-error[E0562]: `impl Trait` only allowed in function and inherent method argument and return types, not in generic parameter defaults
+error[E0562]: `impl Trait` is not allowed in generic parameter defaults
   --> $DIR/where-allowed.rs:234:11
    |
 LL | impl <T = impl Debug> T {}
    |           ^^^^^^^^^^
+   |
+   = note: `impl Trait` is only allowed in arguments and return types of functions and methods
 
-error[E0562]: `impl Trait` only allowed in function and inherent method argument and return types, not in generic parameter defaults
+error[E0562]: `impl Trait` is not allowed in generic parameter defaults
   --> $DIR/where-allowed.rs:241:40
    |
 LL | fn in_method_generic_param_default<T = impl Debug>(_: T) {}
    |                                        ^^^^^^^^^^
+   |
+   = note: `impl Trait` is only allowed in arguments and return types of functions and methods
 
-error[E0562]: `impl Trait` only allowed in function and inherent method argument and return types, not in variable bindings
+error[E0562]: `impl Trait` is not allowed in the type of variable bindings
   --> $DIR/where-allowed.rs:247:29
    |
 LL |     let _in_local_variable: impl Fn() = || {};
    |                             ^^^^^^^^^
+   |
+   = note: `impl Trait` is only allowed in arguments and return types of functions and methods
 
-error[E0562]: `impl Trait` only allowed in function and inherent method argument and return types, not in closure return types
+error[E0562]: `impl Trait` is not allowed in closure return types
   --> $DIR/where-allowed.rs:249:46
    |
 LL |     let _in_return_in_local_variable = || -> impl Fn() { || {} };
    |                                              ^^^^^^^^^
+   |
+   = note: `impl Trait` is only allowed in arguments and return types of functions and methods
 
 error: defaults for type parameters are only allowed in `struct`, `enum`, `type`, or `trait` definitions
   --> $DIR/where-allowed.rs:234:7

tests/ui/issues/issue-47715.rs

@@ -7,22 +7,22 @@ trait Iterable {
 }
 
 struct Container<T: Iterable<Item = impl Foo>> {
-    //~^ ERROR `impl Trait` only allowed in function and inherent method argument and return types
+    //~^ ERROR `impl Trait` is not allowed in generics
     field: T
 }
 
 enum Enum<T: Iterable<Item = impl Foo>> {
-    //~^ ERROR `impl Trait` only allowed in function and inherent method argument and return types
+    //~^ ERROR `impl Trait` is not allowed in generics
     A(T),
 }
 
 union Union<T: Iterable<Item = impl Foo> + Copy> {
-    //~^ ERROR `impl Trait` only allowed in function and inherent method argument and return types
+    //~^ ERROR `impl Trait` is not allowed in generics
     x: T,
 }
 
 type Type<T: Iterable<Item = impl Foo>> = T;
-//~^ ERROR `impl Trait` only allowed in function and inherent method argument and return types
+//~^ ERROR `impl Trait` is not allowed in generics
 
 fn main() {
 }

tests/ui/issues/issue-47715.stderr

@@ -1,26 +1,34 @@
-error[E0562]: `impl Trait` only allowed in function and inherent method argument and return types, not in generics
+error[E0562]: `impl Trait` is not allowed in generics
   --> $DIR/issue-47715.rs:9:37
    |
 LL | struct Container<T: Iterable<Item = impl Foo>> {
    |                                     ^^^^^^^^
+   |
+   = note: `impl Trait` is only allowed in arguments and return types of functions and methods
 
-error[E0562]: `impl Trait` only allowed in function and inherent method argument and return types, not in generics
+error[E0562]: `impl Trait` is not allowed in generics
   --> $DIR/issue-47715.rs:14:30
    |
 LL | enum Enum<T: Iterable<Item = impl Foo>> {
    |                              ^^^^^^^^
+   |
+   = note: `impl Trait` is only allowed in arguments and return types of functions and methods
 
-error[E0562]: `impl Trait` only allowed in function and inherent method argument and return types, not in generics
+error[E0562]: `impl Trait` is not allowed in generics
   --> $DIR/issue-47715.rs:19:32
    |
 LL | union Union<T: Iterable<Item = impl Foo> + Copy> {
    |                                ^^^^^^^^
+   |
+   = note: `impl Trait` is only allowed in arguments and return types of functions and methods
 
-error[E0562]: `impl Trait` only allowed in function and inherent method argument and return types, not in generics
+error[E0562]: `impl Trait` is not allowed in generics
   --> $DIR/issue-47715.rs:24:30
    |
 LL | type Type<T: Iterable<Item = impl Foo>> = T;
    |                              ^^^^^^^^
+   |
+   = note: `impl Trait` is only allowed in arguments and return types of functions and methods
 
 error: aborting due to 4 previous errors
 

tests/ui/type-alias-impl-trait/type-alias-impl-trait-fn-type.rs

@@ -4,7 +4,7 @@
 // FIXME: this is ruled out for now but should work
 
 type Foo = fn() -> impl Send;
-//~^ ERROR: `impl Trait` only allowed in function and inherent method argument and return types
+//~^ ERROR: `impl Trait` is not allowed in `fn` pointer return types
 
 fn make_foo() -> Foo {
     || 15

tests/ui/type-alias-impl-trait/type-alias-impl-trait-fn-type.stderr

@@ -1,8 +1,10 @@
-error[E0562]: `impl Trait` only allowed in function and inherent method argument and return types, not in `fn` pointer return types
+error[E0562]: `impl Trait` is not allowed in `fn` pointer return types
   --> $DIR/type-alias-impl-trait-fn-type.rs:6:20
    |
 LL | type Foo = fn() -> impl Send;
    |                    ^^^^^^^^^
+   |
+   = note: `impl Trait` is only allowed in arguments and return types of functions and methods
 
 error: aborting due to 1 previous error
 

tests/ui/typeck/issue-104513-ice.rs

@@ -1,6 +1,6 @@
 struct S;
 fn f() {
     let _: S<impl Oops> = S; //~ ERROR cannot find trait `Oops` in this scope
-    //~^ ERROR `impl Trait` only allowed in function and inherent method argument and return types
+    //~^ ERROR `impl Trait` is not allowed in the type of variable bindings
 }
 fn main() {}

tests/ui/typeck/issue-104513-ice.stderr

@@ -4,11 +4,13 @@ error[E0405]: cannot find trait `Oops` in this scope
 LL |     let _: S<impl Oops> = S;
    |                   ^^^^ not found in this scope
 
-error[E0562]: `impl Trait` only allowed in function and inherent method argument and return types, not in variable bindings
+error[E0562]: `impl Trait` is not allowed in the type of variable bindings
   --> $DIR/issue-104513-ice.rs:3:14
    |
 LL |     let _: S<impl Oops> = S;
    |              ^^^^^^^^^
+   |
+   = note: `impl Trait` is only allowed in arguments and return types of functions and methods
 
 error: aborting due to 2 previous errors