fix SelfVisitor::is_self_ty ICE

Author: TaKO8Ki

compiler/rustc_resolve/src/late.rs

@@ -1928,11 +1928,11 @@ impl<'a: 'ast, 'b, 'ast> LateResolutionVisitor<'a, 'b, 'ast> {
                 match ty.kind {
                     TyKind::ImplicitSelf => true,
                     TyKind::Path(None, _) => {
-                        let path_res = self.r.partial_res_map[&ty.id].expect_full_res();
-                        if let Res::SelfTyParam { .. } | Res::SelfTyAlias { .. } = path_res {
+                        let path_res = self.r.partial_res_map[&ty.id].full_res();
+                        if let Some(Res::SelfTyParam { .. } | Res::SelfTyAlias { .. }) = path_res {
                             return true;
                         }
-                        Some(path_res) == self.impl_self
+                        path_res == self.impl_self
                     }
                     _ => false,
                 }

src/test/ui/resolve/issue-103202.rs

@@ -0,0 +1,7 @@
+struct S {}
+
+impl S {
+    fn f(self: &S::x) {} //~ ERROR ambiguous associated type
+}
+
+fn main() {}

src/test/ui/resolve/issue-103202.stderr

@@ -0,0 +1,9 @@
+error[E0223]: ambiguous associated type
+  --> $DIR/issue-103202.rs:4:17
+   |
+LL |     fn f(self: &S::x) {}
+   |                 ^^^^ help: use fully-qualified syntax: `<S as Trait>::x`
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0223`.