Rollup merge of rust-lang#108295 - compiler-errors:wtf-is-this, r=cjgillot

Use DefKind to give more item kind information during BindingObligation note

The current label says "required by a bound in this". When I see that label, my immediate impression is "this... **what**?". It feels like it was cut short.

Alternative to this would be saying "in this item", but adding the item kind is strictly more informational and adds very little overhead to the existing error presentation.

Author: matthiaskrgr

compiler/rustc_trait_selection/src/traits/error_reporting/suggestions.rs

@@ -2784,7 +2784,13 @@ impl<'tcx> TypeErrCtxtExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
                             _ => true,
                         };
                     if ident.span.is_visible(sm) && !ident.span.overlaps(span) && !same_line {
-                        multispan.push_span_label(ident.span, "required by a bound in this");
+                        multispan.push_span_label(
+                            ident.span,
+                            format!(
+                                "required by a bound in this {}",
+                                tcx.def_kind(item_def_id).descr(item_def_id)
+                            ),
+                        );
                     }
                 }
                 let descr = format!("required by a bound in `{item_name}`");

tests/ui/associated-types/associated-types-eq-hr.stderr

@@ -15,7 +15,7 @@ note: required by a bound in `foo`
   --> $DIR/associated-types-eq-hr.rs:45:36
    |
 LL | fn foo<T>()
-   |    --- required by a bound in this
+   |    --- required by a bound in this function
 LL | where
 LL |     T: for<'x> TheTrait<&'x isize, A = &'x isize>,
    |                                    ^^^^^^^^^^^^^ required by this bound in `foo`
@@ -37,7 +37,7 @@ note: required by a bound in `bar`
   --> $DIR/associated-types-eq-hr.rs:52:36
    |
 LL | fn bar<T>()
-   |    --- required by a bound in this
+   |    --- required by a bound in this function
 LL | where
 LL |     T: for<'x> TheTrait<&'x isize, A = &'x usize>,
    |                                    ^^^^^^^^^^^^^ required by this bound in `bar`

tests/ui/associated-types/defaults-suitability.stderr

@@ -27,7 +27,7 @@ LL |     Self::Ty: Clone,
    |               ^^^^^ required by this bound in `Tr2::Ty`
 LL | {
 LL |     type Ty = NotClone;
-   |          -- required by a bound in this
+   |          -- required by a bound in this associated type
 help: consider annotating `NotClone` with `#[derive(Clone)]`
    |
 LL | #[derive(Clone)]
@@ -75,7 +75,7 @@ LL |     Self::Assoc: IsU8<Self::Assoc>,
    |                  ^^^^^^^^^^^^^^^^^ required by this bound in `D::Assoc`
 ...
 LL |     type Assoc = NotClone;
-   |          ----- required by a bound in this
+   |          ----- required by a bound in this associated type
 
 error[E0277]: the trait bound `<Self as Foo2<T>>::Baz: Clone` is not satisfied
   --> $DIR/defaults-suitability.rs:65:23
@@ -124,7 +124,7 @@ LL |     Self::Baz: Clone,
    |                ^^^^^ required by this bound in `Foo3::Baz`
 ...
 LL |     type Baz = T;
-   |          --- required by a bound in this
+   |          --- required by a bound in this associated type
 help: consider further restricting type parameter `T`
    |
 LL |     Self::Baz: Clone, T: std::clone::Clone

tests/ui/associated-types/hr-associated-type-bound-1.stderr

@@ -9,7 +9,7 @@ note: required by a bound in `X`
   --> $DIR/hr-associated-type-bound-1.rs:3:33
    |
 LL | trait X<'a>
-   |       - required by a bound in this
+   |       - required by a bound in this trait
 LL | where
 LL |     for<'b> <Self as X<'b>>::U: Clone,
    |                                 ^^^^^ required by this bound in `X`

tests/ui/associated-types/hr-associated-type-bound-object.stderr

@@ -8,7 +8,7 @@ note: required by a bound in `X`
   --> $DIR/hr-associated-type-bound-object.rs:3:33
    |
 LL | trait X<'a>
-   |       - required by a bound in this
+   |       - required by a bound in this trait
 LL | where
 LL |     for<'b> <Self as X<'b>>::U: Clone,
    |                                 ^^^^^ required by this bound in `X`

tests/ui/associated-types/hr-associated-type-bound-param-1.stderr

@@ -9,7 +9,7 @@ note: required by a bound in `Y`
   --> $DIR/hr-associated-type-bound-param-1.rs:4:36
    |
 LL | trait Y<'a, T: ?Sized>
-   |       - required by a bound in this
+   |       - required by a bound in this trait
 ...
 LL |     for<'b> <Self as Y<'b, T>>::V: Clone,
    |                                    ^^^^^ required by this bound in `Y`

tests/ui/associated-types/hr-associated-type-bound-param-2.stderr

@@ -9,7 +9,7 @@ note: required by a bound in `Z`
   --> $DIR/hr-associated-type-bound-param-2.rs:6:35
    |
 LL | trait Z<'a, T: ?Sized>
-   |       - required by a bound in this
+   |       - required by a bound in this trait
 ...
 LL |     for<'b> <T as Z<'b, u16>>::W: Clone,
    |                                   ^^^^^ required by this bound in `Z`
@@ -25,7 +25,7 @@ note: required by a bound in `Z`
   --> $DIR/hr-associated-type-bound-param-2.rs:6:35
    |
 LL | trait Z<'a, T: ?Sized>
-   |       - required by a bound in this
+   |       - required by a bound in this trait
 ...
 LL |     for<'b> <T as Z<'b, u16>>::W: Clone,
    |                                   ^^^^^ required by this bound in `Z`
@@ -41,7 +41,7 @@ note: required by a bound in `Z`
   --> $DIR/hr-associated-type-bound-param-2.rs:6:35
    |
 LL | trait Z<'a, T: ?Sized>
-   |       - required by a bound in this
+   |       - required by a bound in this trait
 ...
 LL |     for<'b> <T as Z<'b, u16>>::W: Clone,
    |                                   ^^^^^ required by this bound in `Z`

tests/ui/associated-types/hr-associated-type-bound-param-3.stderr

@@ -9,7 +9,7 @@ note: required by a bound in `X`
   --> $DIR/hr-associated-type-bound-param-3.rs:4:33
    |
 LL | trait X<'a, T>
-   |       - required by a bound in this
+   |       - required by a bound in this trait
 ...
 LL |     for<'b> <T as X<'b, T>>::U: Clone,
    |                                 ^^^^^ required by this bound in `X`

tests/ui/associated-types/hr-associated-type-bound-param-4.stderr

@@ -9,7 +9,7 @@ note: required by a bound in `X`
   --> $DIR/hr-associated-type-bound-param-4.rs:4:36
    |
 LL | trait X<'a, T>
-   |       - required by a bound in this
+   |       - required by a bound in this trait
 ...
 LL |     for<'b> <(T,) as X<'b, T>>::U: Clone,
    |                                    ^^^^^ required by this bound in `X`

tests/ui/associated-types/hr-associated-type-bound-param-5.stderr

@@ -9,7 +9,7 @@ note: required by a bound in `X`
   --> $DIR/hr-associated-type-bound-param-5.rs:17:45
    |
 LL | trait X<'a, T: Cycle + for<'b> X<'b, T>>
-   |       - required by a bound in this
+   |       - required by a bound in this trait
 ...
 LL |     for<'b> <T::Next as X<'b, T::Next>>::U: Clone,
    |                                             ^^^^^ required by this bound in `X`
@@ -25,7 +25,7 @@ note: required by a bound in `X`
   --> $DIR/hr-associated-type-bound-param-5.rs:17:45
    |
 LL | trait X<'a, T: Cycle + for<'b> X<'b, T>>
-   |       - required by a bound in this
+   |       - required by a bound in this trait
 ...
 LL |     for<'b> <T::Next as X<'b, T::Next>>::U: Clone,
    |                                             ^^^^^ required by this bound in `X`