Keep existing names of regions in placeholder_error

compiler/rustc_infer/src/infer/error_reporting/nice_region_error/placeholder_error.rs

@@ -118,9 +118,9 @@ impl NiceRegionError<'me, 'tcx> {
                 sub_region @ ty::RePlaceholder(_),
                 sup_region,
             )) => self.try_report_trait_placeholder_mismatch(
-                Some(sup_region),
+                (!sup_region.has_name()).then_some(sup_region),
                 cause,
-                Some(*sub_region),
+                Some(sub_region),
                 None,
                 values,
             ),
@@ -130,10 +130,10 @@ impl NiceRegionError<'me, 'tcx> {
                 sub_region,
                 sup_region @ ty::RePlaceholder(_),
             )) => self.try_report_trait_placeholder_mismatch(
-                Some(sub_region),
+                (!sub_region.has_name()).then_some(sub_region),
                 cause,
                 None,
-                Some(*sup_region),
+                Some(sup_region),
                 values,
             ),
 

src/test/ui/generator/auto-trait-regions.stderr

@@ -4,17 +4,17 @@ error: implementation of `Foo` is not general enough
 LL |     assert_foo(gen);
    |     ^^^^^^^^^^ implementation of `Foo` is not general enough
    |
-   = note: `Foo` would have to be implemented for the type `&'0 OnlyFooIfStaticRef`, for any lifetime `'0`...
-   = note: ...but `Foo` is actually implemented for the type `&'1 OnlyFooIfStaticRef`, for some specific lifetime `'1`
+   = note: `&'0 OnlyFooIfStaticRef` must implement `Foo`, for any lifetime `'0`...
+   = note: ...but `Foo` is actually implemented for the type `&'static OnlyFooIfStaticRef`
 
 error: implementation of `Foo` is not general enough
   --> $DIR/auto-trait-regions.rs:31:5
    |
 LL |     assert_foo(gen);
    |     ^^^^^^^^^^ implementation of `Foo` is not general enough
    |
-   = note: `Foo` would have to be implemented for the type `&'0 OnlyFooIfStaticRef`, for any lifetime `'0`...
-   = note: ...but `Foo` is actually implemented for the type `&'1 OnlyFooIfStaticRef`, for some specific lifetime `'1`
+   = note: `&'0 OnlyFooIfStaticRef` must implement `Foo`, for any lifetime `'0`...
+   = note: ...but `Foo` is actually implemented for the type `&'static OnlyFooIfStaticRef`
 
 error: implementation of `Foo` is not general enough
   --> $DIR/auto-trait-regions.rs:50:5

src/test/ui/hrtb/hrtb-just-for-static.stderr

@@ -5,7 +5,7 @@ LL |     want_hrtb::<StaticInt>()
    |     ^^^^^^^^^^^^^^^^^^^^^^ implementation of `Foo` is not general enough
    |
    = note: `StaticInt` must implement `Foo<&'0 isize>`, for any lifetime `'0`...
-   = note: ...but it actually implements `Foo<&'1 isize>`, for some specific lifetime `'1`
+   = note: ...but it actually implements `Foo<&'static isize>`
 
 error: implementation of `Foo` is not general enough
   --> $DIR/hrtb-just-for-static.rs:30:5

src/test/ui/hrtb/hrtb-perfect-forwarding.stderr

@@ -5,7 +5,7 @@ LL |     foo_hrtb_bar_not(&mut t);
    |     ^^^^^^^^^^^^^^^^ implementation of `Bar` is not general enough
    |
    = note: `T` must implement `Bar<&'0 isize>`, for any lifetime `'0`...
-   = note: ...but it actually implements `Bar<&'1 isize>`, for some specific lifetime `'1`
+   = note: ...but it actually implements `Bar<&'b isize>`
 
 error: implementation of `Bar` is not general enough
   --> $DIR/hrtb-perfect-forwarding.rs:43:5
@@ -14,7 +14,7 @@ LL |     foo_hrtb_bar_not(&mut t);
    |     ^^^^^^^^^^^^^^^^ implementation of `Bar` is not general enough
    |
    = note: `T` must implement `Bar<&'0 isize>`, for any lifetime `'0`...
-   = note: ...but it actually implements `Bar<&'1 isize>`, for some specific lifetime `'1`
+   = note: ...but it actually implements `Bar<&'b isize>`
 
 error: aborting due to 2 previous errors
 

src/test/ui/mismatched_types/closure-arg-type-mismatch.stderr

@@ -47,8 +47,8 @@ error: implementation of `FnOnce` is not general enough
 LL |     baz(f);
    |     ^^^ implementation of `FnOnce` is not general enough
    |
-   = note: `fn(*mut &'2 u32)` must implement `FnOnce<(*mut &'1 u32,)>`, for any lifetime `'1`...
-   = note: ...but it actually implements `FnOnce<(*mut &'2 u32,)>`, for some specific lifetime `'2`
+   = note: `fn(*mut &'a u32)` must implement `FnOnce<(*mut &'0 u32,)>`, for any lifetime `'0`...
+   = note: ...but it actually implements `FnOnce<(*mut &'a u32,)>`
 
 error[E0308]: mismatched types
   --> $DIR/closure-arg-type-mismatch.rs:10:5
@@ -75,8 +75,8 @@ error: implementation of `FnOnce` is not general enough
 LL |     baz(f);
    |     ^^^ implementation of `FnOnce` is not general enough
    |
-   = note: `fn(*mut &'2 u32)` must implement `FnOnce<(*mut &'1 u32,)>`, for any lifetime `'1`...
-   = note: ...but it actually implements `FnOnce<(*mut &'2 u32,)>`, for some specific lifetime `'2`
+   = note: `fn(*mut &'a u32)` must implement `FnOnce<(*mut &'0 u32,)>`, for any lifetime `'0`...
+   = note: ...but it actually implements `FnOnce<(*mut &'a u32,)>`
 
 error: aborting due to 7 previous errors
 

src/test/ui/type-alias-impl-trait/issue-57611-trait-alias.nll.stderr

@@ -30,8 +30,8 @@ error: implementation of `FnOnce` is not general enough
 LL |     type Bar = impl Baz<Self, Self>;
    |                ^^^^^^^^^^^^^^^^^^^^ implementation of `FnOnce` is not general enough
    |
-   = note: closure with signature `fn(&'2 X) -> &'2 X` must implement `FnOnce<(&'1 X,)>`, for any lifetime `'1`...
-   = note: ...but it actually implements `FnOnce<(&'2 X,)>`, for some specific lifetime `'2`
+   = note: closure with signature `fn(&'static X) -> &'static X` must implement `FnOnce<(&'0 X,)>`, for any lifetime `'0`...
+   = note: ...but it actually implements `FnOnce<(&'static X,)>`
 
 error: aborting due to 4 previous errors
 

src/test/ui/where-clauses/where-for-self-2.stderr

@@ -4,8 +4,8 @@ error: implementation of `Bar` is not general enough
 LL |     foo(&X);
    |     ^^^ implementation of `Bar` is not general enough
    |
-   = note: `Bar` would have to be implemented for the type `&'0 u32`, for any lifetime `'0`...
-   = note: ...but `Bar` is actually implemented for the type `&'1 u32`, for some specific lifetime `'1`
+   = note: `&'0 u32` must implement `Bar`, for any lifetime `'0`...
+   = note: ...but `Bar` is actually implemented for the type `&'static u32`
 
 error: aborting due to previous error