Rollup merge of #109238 - spastorino:new-rpitit-12, r=compiler-errors

Fix generics mismatch errors for RPITITs on -Zlower-impl-trait-in-trait-to-assoc-ty

This PR stops reporting errors due to different count of generics on the new synthesized associated types for RPITITs. Those were already reported when we compare the function on the triat with the function on the impl.

r? ``@compiler-errors``

4 files changed, 27 insertions, 1 deletions

diff --git a/compiler/rustc_hir_analysis/src/check/compare_impl_item.rs b/compiler/rustc_hir_analysis/src/check/compare_impl_item.rs
index 6e6f8c1533b..32b6aeed5f8 100644
--- a/compiler/rustc_hir_analysis/src/check/compare_impl_item.rs
+++ b/compiler/rustc_hir_analysis/src/check/compare_impl_item.rs
@@ -1205,6 +1205,17 @@ fn compare_number_of_generics<'tcx>(
         return Ok(());
     }
 
+    // We never need to emit a separate error for RPITITs, since if an RPITIT
+    // has mismatched type or const generic arguments, then the method that it's
+    // inheriting the generics from will also have mismatched arguments, and
+    // we'll report an error for that instead. Delay a bug for safety, though.
+    if tcx.opt_rpitit_info(trait_.def_id).is_some() {
+        return Err(tcx.sess.delay_span_bug(
+            rustc_span::DUMMY_SP,
+            "errors comparing numbers of generics of trait/impl functions were not emitted",
+        ));
+    }
+
     let matchings = [
         ("type", trait_own_counts.types, impl_own_counts.types),
         ("const", trait_own_counts.consts, impl_own_counts.consts),
diff --git a/tests/ui/impl-trait/in-trait/generics-mismatch.stderr b/tests/ui/impl-trait/in-trait/generics-mismatch.current.stderr
index cd42683e022..310edbcb6cd 100644
--- a/tests/ui/impl-trait/in-trait/generics-mismatch.stderr
+++ b/tests/ui/impl-trait/in-trait/generics-mismatch.current.stderr
@@ -1,5 +1,5 @@
 error[E0049]: method `bar` has 1 type parameter but its trait declaration has 0 type parameters
-  --> $DIR/generics-mismatch.rs:11:12
+  --> $DIR/generics-mismatch.rs:14:12
    |
 LL |     fn bar(&self) -> impl Sized;
    |           - expected 0 type parameters
diff --git a/tests/ui/impl-trait/in-trait/generics-mismatch.next.stderr b/tests/ui/impl-trait/in-trait/generics-mismatch.next.stderr
new file mode 100644
index 00000000000..310edbcb6cd
--- /dev/null
+++ b/tests/ui/impl-trait/in-trait/generics-mismatch.next.stderr
@@ -0,0 +1,12 @@
+error[E0049]: method `bar` has 1 type parameter but its trait declaration has 0 type parameters
+  --> $DIR/generics-mismatch.rs:14:12
+   |
+LL |     fn bar(&self) -> impl Sized;
+   |           - expected 0 type parameters
+...
+LL |     fn bar<T>(&self) {}
+   |            ^ found 1 type parameter
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0049`.
diff --git a/tests/ui/impl-trait/in-trait/generics-mismatch.rs b/tests/ui/impl-trait/in-trait/generics-mismatch.rs
index cc0fc720ebb..9259ca193d1 100644
--- a/tests/ui/impl-trait/in-trait/generics-mismatch.rs
+++ b/tests/ui/impl-trait/in-trait/generics-mismatch.rs
@@ -1,3 +1,6 @@
+// [next] compile-flags: -Zlower-impl-trait-in-trait-to-assoc-ty
+// revisions: current next
+
 #![feature(return_position_impl_trait_in_trait)]
 #![allow(incomplete_features)]