Infer generic args for trait ref and its assoc type

This was already there before the switch to the new solver, but it was reverted during the switch for some reason.

Author: ChayimFriedman2

crates/hir-ty/src/lower/path.rs

@@ -183,7 +183,7 @@ impl<'a, 'b, 'db> PathLoweringContext<'a, 'b, 'db> {
                         let trait_ref = self.lower_trait_ref_from_resolved_path(
                             trait_,
                             Ty::new_error(self.ctx.interner, ErrorGuaranteed),
-                            false,
+                            infer_args,
                         );
                         tracing::debug!(?trait_ref);
                         self.skip_resolved_segment();
@@ -201,7 +201,7 @@ impl<'a, 'b, 'db> PathLoweringContext<'a, 'b, 'db> {
                                 // this point (`trait_ref.substitution`).
                                 let substitution = self.substs_from_path_segment(
                                     associated_ty.into(),
-                                    false,
+                                    infer_args,
                                     None,
                                     true,
                                 );

crates/ide-diagnostics/src/handlers/incorrect_generics_len.rs

@@ -220,6 +220,23 @@ type Result<T, E = Error> = core::result::Result<T, E>;
 
 fn main() {
     let _ = Result::<()>::Ok(());
+}
+        "#,
+        );
+    }
+
+    #[test]
+    fn type_as_trait_does_not_count() {
+        check_diagnostics(
+            r#"
+pub trait Lock<T> {
+    fn new(b: T) -> Self;
+}
+pub trait LockChoice {
+    type Lock<T>: Lock<T>;
+}
+fn f<L: LockChoice>() {
+    <L as LockChoice>::Lock::new(());
 }
         "#,
         );