Rollup merge of #93362 - compiler-errors:ice-gat-in-rpit, r=oli-obk

Do not register infer var for GAT projection in RPIT

Fixes #93340
Fixes #91603

r? ```@oli-obk```

Author: matthiaskrgr

compiler/rustc_infer/src/infer/opaque_types.rs

@@ -569,13 +569,15 @@ impl<'a, 'tcx> Instantiator<'a, 'tcx> {
             let predicate = predicate.fold_with(&mut BottomUpFolder {
                 tcx,
                 ty_op: |ty| match ty.kind() {
-                    ty::Projection(projection_ty) => infcx.infer_projection(
-                        self.param_env,
-                        *projection_ty,
-                        traits::ObligationCause::misc(self.value_span, self.body_id),
-                        0,
-                        &mut self.obligations,
-                    ),
+                    ty::Projection(projection_ty) if !projection_ty.has_escaping_bound_vars() => {
+                        infcx.infer_projection(
+                            self.param_env,
+                            *projection_ty,
+                            traits::ObligationCause::misc(self.value_span, self.body_id),
+                            0,
+                            &mut self.obligations,
+                        )
+                    }
                     _ => ty,
                 },
                 lt_op: |lt| lt,

src/test/ui/generic-associated-types/issue-93340.rs

@@ -0,0 +1,20 @@
+// check-pass
+
+#![feature(generic_associated_types)]
+
+pub trait Scalar: 'static {
+    type RefType<'a>: ScalarRef<'a>;
+}
+
+pub trait ScalarRef<'a>: 'a {}
+
+fn cmp_eq<'a, 'b, A: Scalar, B: Scalar, O: Scalar>(a: A::RefType<'a>, b: B::RefType<'b>) -> O {
+    todo!()
+}
+
+fn build_expression<A: Scalar, B: Scalar, O: Scalar>(
+) -> impl Fn(A::RefType<'_>, B::RefType<'_>) -> O {
+    cmp_eq
+}
+
+fn main() {}