fix corner case in functions (#5037)

fixes #5036

lib/compress.js

@@ -6574,12 +6574,10 @@ merge(Compressor.prototype, {
                         return all(def.references, function(ref) {
                             var scope = ref.scope;
                             if (scope.find_variable(name) !== sym) return false;
-                            if (forbidden) {
+                            if (forbidden) do {
                                 scope = scope.resolve();
-                                do {
                                 if (forbidden(scope)) return false;
-                                } while ((scope = scope.parent_scope.resolve()) && scope !== fn);
-                            }
+                            } while (scope !== fn && (scope = scope.parent_scope));
                             return true;
                         }) && def;
                     }

test/compress/functions.js

@@ -6258,3 +6258,28 @@ issue_5025: {
     }
     expect_stdout: "object"
 }
+
+issue_5036: {
+    options = {
+        functions: true,
+        reduce_vars: true,
+        unused: true,
+    }
+    input: {
+        console.log(typeof function() {
+            var await = function f() {
+                return f;
+            };
+            return await() === await;
+        }() ? "PASS" : "FAIL");
+    }
+    expect: {
+        console.log(typeof function() {
+            function await() {
+                return await;
+            }
+            return await() === await;
+        }() ? "PASS" : "FAIL");
+    }
+    expect_stdout: "PASS"
+}