Auto merge of #140737 - amandasystems:revised-constraint-search, r=lcnr

Region inference: Use outlives-static constraints in constraint search

Revise the extra `r: 'static` constraints added upon universe issues to add an explanation, and use that explanation during constraint blame search. This greatly simplifies the region inference logic, which now does not need to reverse-engineer the event that caused a region to outlive `'static`.

This cosmetically changes the output of two UI tests. I blessed them i separate commits with separate motivations, but that can of course be squashed as desired. We probably want that.

The PR was extracted out of rust-lang/rust#130227 and consists of one-third of its functional payload.

r? lcnr

6 files changed, 25 insertions, 28 deletions

diff --git a/tests/ui/associated-inherent-types/issue-111404-1.stderr b/tests/ui/associated-inherent-types/issue-111404-1.stderr
index ce49126c316..9a5b69497c0 100644
--- a/tests/ui/associated-inherent-types/issue-111404-1.stderr
+++ b/tests/ui/associated-inherent-types/issue-111404-1.stderr
@@ -32,12 +32,10 @@ LL | fn bar(_: fn(Foo<for<'b> fn(Foo<fn(&'b ())>::Assoc)>::Assoc)) {}
    = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
 
 error: higher-ranked subtype error
-  --> $DIR/issue-111404-1.rs:10:1
+  --> $DIR/issue-111404-1.rs:10:8
    |
 LL | fn bar(_: fn(Foo<for<'b> fn(Foo<fn(&'b ())>::Assoc)>::Assoc)) {}
-   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-   |
-   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
+   |        ^
 
 error: aborting due to 5 previous errors
 
diff --git a/tests/ui/higher-ranked/higher-ranked-lifetime-error.stderr b/tests/ui/higher-ranked/higher-ranked-lifetime-error.stderr
index d7add865aa0..2e3fd612334 100644
--- a/tests/ui/higher-ranked/higher-ranked-lifetime-error.stderr
+++ b/tests/ui/higher-ranked/higher-ranked-lifetime-error.stderr
@@ -2,7 +2,7 @@ error: implementation of `FnMut` is not general enough
   --> $DIR/higher-ranked-lifetime-error.rs:12:5
    |
 LL |     assert_all::<_, &String>(id);
-   |     ^^^^^^^^^^^^^^^^^^^^^^^^ implementation of `FnMut` is not general enough
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ implementation of `FnMut` is not general enough
    |
    = note: `for<'a> fn(&'a String) -> &'a String {id}` must implement `FnMut<(&String,)>`
    = note: ...but it actually implements `FnMut<(&'0 String,)>`, for some specific lifetime `'0`
diff --git a/tests/ui/higher-ranked/trait-bounds/due-to-where-clause.stderr b/tests/ui/higher-ranked/trait-bounds/due-to-where-clause.stderr
index 916854e07af..6c17b1f4874 100644
--- a/tests/ui/higher-ranked/trait-bounds/due-to-where-clause.stderr
+++ b/tests/ui/higher-ranked/trait-bounds/due-to-where-clause.stderr
@@ -2,7 +2,7 @@ error: implementation of `Foo` is not general enough
   --> $DIR/due-to-where-clause.rs:2:5
    |
 LL |     test::<FooS>(&mut 42);
-   |     ^^^^^^^^^^^^ implementation of `Foo` is not general enough
+   |     ^^^^^^^^^^^^^^^^^^^^^ implementation of `Foo` is not general enough
    |
    = note: `FooS<'_>` must implement `Foo<'0>`, for any lifetime `'0`...
    = note: ...but `FooS<'_>` actually implements `Foo<'1>`, for some specific lifetime `'1`
diff --git a/tests/ui/mismatched_types/hr-projection-mismatch.current.stderr b/tests/ui/mismatched_types/hr-projection-mismatch.current.stderr
index a2cec972e4a..6bda7840f7b 100644
--- a/tests/ui/mismatched_types/hr-projection-mismatch.current.stderr
+++ b/tests/ui/mismatched_types/hr-projection-mismatch.current.stderr
@@ -2,7 +2,7 @@ error[E0308]: mismatched types
   --> $DIR/hr-projection-mismatch.rs:20:5
    |
 LL |     wrap::<_, Thing>();
-   |     ^^^^^^^^^^^^^^^^ one type is more general than the other
+   |     ^^^^^^^^^^^^^^^^^^ one type is more general than the other
    |
    = note: expected reference `&'a _`
               found reference `&_`
diff --git a/tests/ui/nll/ice-106874.stderr b/tests/ui/nll/ice-106874.stderr
index ead4d490a62..0edbd7b44ef 100644
--- a/tests/ui/nll/ice-106874.stderr
+++ b/tests/ui/nll/ice-106874.stderr
@@ -17,6 +17,15 @@ LL |     A(B(C::new(D::new(move |st| f(st)))))
    = note: ...but it actually implements `FnOnce<(&'1 mut V,)>`, for some specific lifetime `'1`
    = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
 
+error: implementation of `FnOnce` is not general enough
+  --> $DIR/ice-106874.rs:8:7
+   |
+LL |     A(B(C::new(D::new(move |st| f(st)))))
+   |       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ implementation of `FnOnce` is not general enough
+   |
+   = note: closure with signature `fn(&'2 mut V)` must implement `FnOnce<(&'1 mut V,)>`, for any lifetime `'1`...
+   = note: ...but it actually implements `FnOnce<(&'2 mut V,)>`, for some specific lifetime `'2`
+
 error: implementation of `Fn` is not general enough
   --> $DIR/ice-106874.rs:8:7
    |
@@ -34,6 +43,7 @@ LL |     A(B(C::new(D::new(move |st| f(st)))))
    |
    = note: closure with signature `fn(&'2 mut V)` must implement `FnOnce<(&'1 mut V,)>`, for any lifetime `'1`...
    = note: ...but it actually implements `FnOnce<(&'2 mut V,)>`, for some specific lifetime `'2`
+   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
 
 error: implementation of `Fn` is not general enough
   --> $DIR/ice-106874.rs:8:7
@@ -46,45 +56,36 @@ LL |     A(B(C::new(D::new(move |st| f(st)))))
    = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
 
 error: implementation of `FnOnce` is not general enough
-  --> $DIR/ice-106874.rs:8:9
+  --> $DIR/ice-106874.rs:8:7
    |
 LL |     A(B(C::new(D::new(move |st| f(st)))))
-   |         ^^^^^^ implementation of `FnOnce` is not general enough
+   |       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ implementation of `FnOnce` is not general enough
    |
    = note: closure with signature `fn(&'2 mut V)` must implement `FnOnce<(&'1 mut V,)>`, for any lifetime `'1`...
    = note: ...but it actually implements `FnOnce<(&'2 mut V,)>`, for some specific lifetime `'2`
+   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
 
 error: implementation of `Fn` is not general enough
-  --> $DIR/ice-106874.rs:8:9
+  --> $DIR/ice-106874.rs:8:7
    |
 LL |     A(B(C::new(D::new(move |st| f(st)))))
-   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ implementation of `Fn` is not general enough
+   |       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ implementation of `Fn` is not general enough
    |
    = note: closure with signature `fn(&'2 mut V)` must implement `Fn<(&'1 mut V,)>`, for any lifetime `'1`...
    = note: ...but it actually implements `Fn<(&'2 mut V,)>`, for some specific lifetime `'2`
-
-error: implementation of `FnOnce` is not general enough
-  --> $DIR/ice-106874.rs:8:9
-   |
-LL |     A(B(C::new(D::new(move |st| f(st)))))
-   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ implementation of `FnOnce` is not general enough
-   |
-   = note: closure with signature `fn(&'2 mut V)` must implement `FnOnce<(&'1 mut V,)>`, for any lifetime `'1`...
-   = note: ...but it actually implements `FnOnce<(&'2 mut V,)>`, for some specific lifetime `'2`
+   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
 
 error: higher-ranked subtype error
-  --> $DIR/ice-106874.rs:8:41
+  --> $DIR/ice-106874.rs:8:7
    |
 LL |     A(B(C::new(D::new(move |st| f(st)))))
-   |                                         ^
+   |       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: higher-ranked subtype error
   --> $DIR/ice-106874.rs:8:41
    |
 LL |     A(B(C::new(D::new(move |st| f(st)))))
    |                                         ^
-   |
-   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
 
 error: aborting due to 10 previous errors
 
diff --git a/tests/ui/nll/missing-universe-cause-issue-114907.stderr b/tests/ui/nll/missing-universe-cause-issue-114907.stderr
index 26ad1efec05..c2e91edd138 100644
--- a/tests/ui/nll/missing-universe-cause-issue-114907.stderr
+++ b/tests/ui/nll/missing-universe-cause-issue-114907.stderr
@@ -38,18 +38,16 @@ LL |     accept(callback);
    = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
 
 error: higher-ranked subtype error
-  --> $DIR/missing-universe-cause-issue-114907.rs:33:21
+  --> $DIR/missing-universe-cause-issue-114907.rs:33:5
    |
 LL |     accept(callback);
-   |                     ^
+   |     ^^^^^^^^^^^^^^^^
 
 error: higher-ranked subtype error
   --> $DIR/missing-universe-cause-issue-114907.rs:33:21
    |
 LL |     accept(callback);
    |                     ^
-   |
-   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
 
 error: aborting due to 6 previous errors