fix inference in nested closure

Author: HKalbasi

crates/hir-ty/src/infer/closure.rs

@@ -462,7 +462,7 @@ impl InferenceContext<'_> {
     }
 
     fn expr_ty(&mut self, expr: ExprId) -> Ty {
-        self.infer_expr_no_expect(expr)
+        self.result[expr].clone()
     }
 
     fn is_upvar(&self, place: &HirPlace) -> bool {

crates/hir-ty/src/tests/regression.rs

@@ -1067,6 +1067,23 @@ fn parse_arule() {
     )
 }
 
+#[test]
+fn nested_closure() {
+    check_types(
+        r#"
+//- minicore: fn, option
+
+fn map<T, U>(o: Option<T>, f: impl FnOnce(T) -> U) -> Option<U> { loop {} }
+
+fn test() {
+    let o = Some(Some(2));
+    map(o, |s| map(s, |x| x));
+                    // ^ i32
+}
+        "#,
+    );
+}
+
 #[test]
 fn call_expected_type_closure() {
     check_types(