Rollup merge of #112876 - compiler-errors:check-subst-compat-in-OpaqueTypeCollector, r=oli-obk

Don't substitute a GAT that has mismatched generics in `OpaqueTypeCollector`

Fixes #111828

I didn't put up minimized UI tests for #112510 or #112873 because they'd minimize to literally the same code, but with different substs on the trait/impl. I don't think that warrants duplicate tests given the nature of the fix.

r? `@oli-obk`

----

Side-note: I checked, and this isn't fixed by #112652 -- I think we discussed whether or not that PR fixed it either intentionally or by accident. The code here isn't really touched by that PR either as far as I can tell?

Also, sorry, did some other drive-bys. Hope it doesn't make rebasing #112652 too difficult :sweat_smile:

4 files changed, 103 insertions, 0 deletions

diff --git a/tests/ui/type-alias-impl-trait/impl-trait-in-type-alias-with-bad-substs.rs b/tests/ui/type-alias-impl-trait/impl-trait-in-type-alias-with-bad-substs.rs
new file mode 100644
index 00000000000..a3f65146f75
--- /dev/null
+++ b/tests/ui/type-alias-impl-trait/impl-trait-in-type-alias-with-bad-substs.rs
@@ -0,0 +1,28 @@
+#![feature(impl_trait_in_assoc_type)]
+
+// We weren't checking that the trait and impl generics line up in the
+// normalization-shortcut code in `OpaqueTypeCollector`.
+
+use std::ops::Deref;
+
+trait Foo {
+    type Bar<'a>;
+
+    type Baz<'a>;
+
+    fn test<'a>() -> Self::Bar<'a>;
+}
+
+impl Foo for () {
+    type Bar<'a> = impl Deref<Target = Self::Baz<'a>>;
+
+    type Baz<T> = impl Sized;
+    //~^ ERROR type `Baz` has 1 type parameter but its trait declaration has 0 type parameters
+    //~| ERROR unconstrained opaque type
+
+    fn test<'a>() -> Self::Bar<'a> {
+        &()
+    }
+}
+
+fn main() {}
diff --git a/tests/ui/type-alias-impl-trait/impl-trait-in-type-alias-with-bad-substs.stderr b/tests/ui/type-alias-impl-trait/impl-trait-in-type-alias-with-bad-substs.stderr
new file mode 100644
index 00000000000..13f5d8b8ea6
--- /dev/null
+++ b/tests/ui/type-alias-impl-trait/impl-trait-in-type-alias-with-bad-substs.stderr
@@ -0,0 +1,20 @@
+error[E0049]: type `Baz` has 1 type parameter but its trait declaration has 0 type parameters
+  --> $DIR/impl-trait-in-type-alias-with-bad-substs.rs:19:14
+   |
+LL |     type Baz<'a>;
+   |              -- expected 0 type parameters
+...
+LL |     type Baz<T> = impl Sized;
+   |              ^ found 1 type parameter
+
+error: unconstrained opaque type
+  --> $DIR/impl-trait-in-type-alias-with-bad-substs.rs:19:19
+   |
+LL |     type Baz<T> = impl Sized;
+   |                   ^^^^^^^^^^
+   |
+   = note: `Baz` must be used in combination with a concrete type within the same impl
+
+error: aborting due to 2 previous errors
+
+For more information about this error, try `rustc --explain E0049`.
diff --git a/tests/ui/type-alias-impl-trait/not-matching-trait-refs-isnt-defining.rs b/tests/ui/type-alias-impl-trait/not-matching-trait-refs-isnt-defining.rs
new file mode 100644
index 00000000000..131f8d999d8
--- /dev/null
+++ b/tests/ui/type-alias-impl-trait/not-matching-trait-refs-isnt-defining.rs
@@ -0,0 +1,33 @@
+#![feature(impl_trait_in_assoc_type)]
+
+trait Foo<T> {
+    type Assoc;
+
+    fn test() -> u32;
+}
+
+struct DefinesOpaque;
+impl Foo<DefinesOpaque> for () {
+    type Assoc = impl Sized;
+
+    // This test's return type is `u32`, *not* the opaque that is defined above.
+    // Previously we were only checking that the self type of the assoc matched,
+    // but this doesn't account for other impls with different trait substs.
+    fn test() -> <() as Foo<NoOpaques>>::Assoc {
+        let _: <Self as Foo<DefinesOpaque>>::Assoc = "";
+        //~^ ERROR mismatched types
+
+        1
+    }
+}
+
+struct NoOpaques;
+impl Foo<NoOpaques> for () {
+    type Assoc = u32;
+
+    fn test() -> u32 {
+        1
+    }
+}
+
+fn main() {}
diff --git a/tests/ui/type-alias-impl-trait/not-matching-trait-refs-isnt-defining.stderr b/tests/ui/type-alias-impl-trait/not-matching-trait-refs-isnt-defining.stderr
new file mode 100644
index 00000000000..d2d00749091
--- /dev/null
+++ b/tests/ui/type-alias-impl-trait/not-matching-trait-refs-isnt-defining.stderr
@@ -0,0 +1,22 @@
+error[E0308]: mismatched types
+  --> $DIR/not-matching-trait-refs-isnt-defining.rs:17:54
+   |
+LL |     type Assoc = impl Sized;
+   |                  ---------- the expected opaque type
+...
+LL |         let _: <Self as Foo<DefinesOpaque>>::Assoc = "";
+   |                -----------------------------------   ^^ expected opaque type, found `&str`
+   |                |
+   |                expected due to this
+   |
+   = note: expected opaque type `<() as Foo<DefinesOpaque>>::Assoc`
+                found reference `&'static str`
+note: this item must have the opaque type in its signature in order to be able to register hidden types
+  --> $DIR/not-matching-trait-refs-isnt-defining.rs:16:5
+   |
+LL |     fn test() -> <() as Foo<NoOpaques>>::Assoc {
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0308`.