Rollup merge of #142079 - lcnr:opaque-types-universes, r=BoxyUwU

nll-relate: improve hr opaque types support

This should currently not be user-facing outside of diagnostics as even if we successfully relate the opaque types, we don't support opaque types with non-param arguments and also require all member regions to be equal to the arguments or `'static`. This means there's no way to end up with a placeholder in the hidden type.

r? types

4 files changed, 10 insertions, 17 deletions

diff --git a/tests/ui/type-alias-impl-trait/higher_kinded_params3.rs b/tests/ui/type-alias-impl-trait/higher_kinded_params3.rs
index 4fb2e60b5c5..04208faddde 100644
--- a/tests/ui/type-alias-impl-trait/higher_kinded_params3.rs
+++ b/tests/ui/type-alias-impl-trait/higher_kinded_params3.rs
@@ -24,8 +24,7 @@ type Successors<'a> = impl std::fmt::Debug + 'a;
 impl Terminator {
     #[define_opaque(Successors, Tait)]
     fn successors(&self, mut f: for<'x> fn(&'x ()) -> <&'x A as B>::C) -> Successors<'_> {
-        f = g;
-        //~^ ERROR mismatched types
+        f = g; //~ ERROR expected generic lifetime parameter, found `'x`
     }
 }
 
diff --git a/tests/ui/type-alias-impl-trait/higher_kinded_params3.stderr b/tests/ui/type-alias-impl-trait/higher_kinded_params3.stderr
index 558792987f3..8e6778bdd0b 100644
--- a/tests/ui/type-alias-impl-trait/higher_kinded_params3.stderr
+++ b/tests/ui/type-alias-impl-trait/higher_kinded_params3.stderr
@@ -1,15 +1,12 @@
-error[E0308]: mismatched types
+error[E0792]: expected generic lifetime parameter, found `'x`
   --> $DIR/higher_kinded_params3.rs:27:9
    |
 LL | type Tait<'a> = impl std::fmt::Debug + 'a;
-   |                 ------------------------- the expected opaque type
+   |           -- this generic parameter must be used with a generic lifetime parameter
 ...
 LL |         f = g;
-   |         ^^^^^ one type is more general than the other
-   |
-   = note: expected fn pointer `for<'x> fn(&'x ()) -> Tait<'x>`
-              found fn pointer `for<'a> fn(&'a ()) -> &'a ()`
+   |         ^^^^^
 
 error: aborting due to 1 previous error
 
-For more information about this error, try `rustc --explain E0308`.
+For more information about this error, try `rustc --explain E0792`.
diff --git a/tests/ui/type-alias-impl-trait/hkl_forbidden3.rs b/tests/ui/type-alias-impl-trait/hkl_forbidden3.rs
index c7f04dc07bb..ba75b114a11 100644
--- a/tests/ui/type-alias-impl-trait/hkl_forbidden3.rs
+++ b/tests/ui/type-alias-impl-trait/hkl_forbidden3.rs
@@ -8,7 +8,7 @@ fn foo<'a>(x: &'a ()) -> &'a () {
 
 #[define_opaque(Opaque)]
 fn test() -> for<'a> fn(&'a ()) -> Opaque<'a> {
-    foo //~ ERROR: mismatched types
+    foo //~ ERROR: expected generic lifetime parameter, found `'a`
 }
 
 fn main() {}
diff --git a/tests/ui/type-alias-impl-trait/hkl_forbidden3.stderr b/tests/ui/type-alias-impl-trait/hkl_forbidden3.stderr
index b8c04185a7d..d699059e397 100644
--- a/tests/ui/type-alias-impl-trait/hkl_forbidden3.stderr
+++ b/tests/ui/type-alias-impl-trait/hkl_forbidden3.stderr
@@ -1,15 +1,12 @@
-error[E0308]: mismatched types
+error[E0792]: expected generic lifetime parameter, found `'a`
   --> $DIR/hkl_forbidden3.rs:11:5
    |
 LL | type Opaque<'a> = impl Sized + 'a;
-   |                   --------------- the expected opaque type
+   |             -- this generic parameter must be used with a generic lifetime parameter
 ...
 LL |     foo
-   |     ^^^ one type is more general than the other
-   |
-   = note: expected fn pointer `for<'a> fn(&'a ()) -> Opaque<'a>`
-              found fn pointer `for<'a> fn(&'a ()) -> &'a ()`
+   |     ^^^
 
 error: aborting due to 1 previous error
 
-For more information about this error, try `rustc --explain E0308`.
+For more information about this error, try `rustc --explain E0792`.