Check for bound variables when reporting type error

`can_eq` ICEs if it's passed types with escaping bound variables, so we
need to check for them, even in error reporting.

Author: matthewjasper

compiler/rustc_trait_selection/src/error_reporting/traits/suggestions.rs

@@ -4076,7 +4076,8 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
                     })
                 } else if let Some(where_pred) = where_pred.as_projection_clause()
                     && let Some(failed_pred) = failed_pred.as_projection_clause()
-                    && let Some(found) = failed_pred.skip_binder().term.as_type()
+                    && let Some(failed_pred) = failed_pred.no_bound_vars()
+                    && let Some(found) = failed_pred.term.as_type()
                 {
                     type_diffs = vec![TypeError::Sorts(ty::error::ExpectedFound {
                         expected: where_pred

tests/ui/mismatched_types/mismatched-bound-projection-predicate.rs

@@ -0,0 +1,22 @@
+// Regression test for #145631
+
+pub struct Foo {}
+
+fn foo(foos: Vec<Foo>) {
+    let foos = foos.iter().collect::<Vec<_>>();
+    let bar = Bar {};
+    bar.bar(foos);
+    //~^ ERROR type mismatch resolving `<&Vec<&Foo> as IntoIterator>::Item == &Foo`
+}
+
+struct Bar {}
+
+impl Bar {
+    pub fn bar<I>(&self, iter: I)
+    where
+        for<'a> &'a I: IntoIterator<Item = &'a Foo>,
+    {
+    }
+}
+
+fn main() {}

tests/ui/mismatched_types/mismatched-bound-projection-predicate.stderr

@@ -0,0 +1,22 @@
+error[E0271]: type mismatch resolving `<&Vec<&Foo> as IntoIterator>::Item == &Foo`
+  --> $DIR/mismatched-bound-projection-predicate.rs:8:13
+   |
+LL |     bar.bar(foos);
+   |         --- ^^^^ expected `&Foo`, found `&&Foo`
+   |         |
+   |         required by a bound introduced by this call
+   |
+   = note: expected reference `&Foo`
+              found reference `&&Foo`
+note: required by a bound in `Bar::bar`
+  --> $DIR/mismatched-bound-projection-predicate.rs:17:37
+   |
+LL |     pub fn bar<I>(&self, iter: I)
+   |            --- required by a bound in this associated function
+LL |     where
+LL |         for<'a> &'a I: IntoIterator<Item = &'a Foo>,
+   |                                     ^^^^^^^^^^^^^^ required by this bound in `Bar::bar`
+
+error: aborting due to 1 previous error
+
+For more information about this error, try `rustc --explain E0271`.