Fix VM crash when parsing what looks like a closure call during metadata evaluation.

tests/lib/mirrors/metadata_nested_constructor_call_test.dart

+// Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+// Regression test for Issue 17141.
+
+library test.metadata_nested_constructor_call;
+
+import 'dart:mirrors';
+import 'package:expect/expect.dart';
+
+class Box {
+  final contents;
+  const Box([this.contents]);
+}
+
+class MutableBox {
+  var contents;
+  MutableBox([this.contents]);  // Not const.
+}
+
+@Box()
+class A {}
+
+@Box(const Box())
+class B {}
+
+@Box(const Box(const Box()))
+class C {}
+
+@Box(const Box(const MutableBox()))  /// 01: compile-time error
+class D {}
+
+@Box(const MutableBox(const Box()))  /// 02: compile-time error
+class E {}
+
+@Box(Box())  /// 03: compile-time error
+class F {}
+
+@Box(Box(const Box()))  /// 04: compile-time error
+class G {}
+
+@Box(Box(const MutableBox()))  /// 05: compile-time error
+class H {}
+
+@Box(MutableBox(const Box()))  /// 06: compile-time error
+class I {}
+
+final closure = () => 42;
+@Box(closure())  /// 07: compile-time error
+class J {}
+
+@Box(closure)  /// 08: compile-time error
+class K {}
+
+function() => 42;
+@Box(function())  /// 09: compile-time error
+class L {}
+
+// N.B. This is legal, but @function is not (tested by metadata_allowed_values).
+@Box(function)
+class M {}
+
+checkMetadata(DeclarationMirror mirror, List expectedMetadata) {
+  Expect.listEquals(expectedMetadata.map(reflect).toList(), mirror.metadata);
+}
+
+main() {
+  closure();
+  checkMetadata(reflectClass(A), [const Box()]);
+  checkMetadata(reflectClass(B), [const Box(const Box())]);
+  checkMetadata(reflectClass(C), [const Box(const Box(const Box()))]);
+  reflectClass(D).metadata;
+  reflectClass(E).metadata;
+  reflectClass(F).metadata;
+  reflectClass(G).metadata;
+  reflectClass(H).metadata;
+  reflectClass(I).metadata;
+  reflectClass(J).metadata;
+  reflectClass(K).metadata;
+  reflectClass(L).metadata;
+  reflectClass(M).metadata;
+}