Add test checking that const contexts are not applied where they shouldn't.

Change-Id: I39782577b7555dc63311531ca17f61f8deec5b4a
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/98854
Reviewed-by: Lasse R.H. Nielsen <lrn@google.com>
Reviewed-by: Aske Simon Christensen <askesc@google.com>
Commit-Queue: Lasse R.H. Nielsen <lrn@google.com>

tests/language_2/implicit_creation/implicit_const_context_not_test.dart

@@ -0,0 +1,78 @@
+// Copyright (c) 2019, 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.
+
+import "package:expect/expect.dart";
+
+// Check places that are *not* supposed to be constant contexts,
+// but which do require constant values, do not introduce an implicit const.
+// Nested expressions still do.
+// (Also acts as regression test for http:/dartbug.com/36533)
+
+class C {
+  final v;
+
+  // Initializer of final field in class with const constructor.
+  // Can't use `const C()`, it's a cyclic constant dependency.
+  final i1 = []; //# 1: compile-time error
+  final i2 = const [];
+  final i3 = const [[]];
+
+  const C([this.v]);
+
+  // Initializer expression in generative const constructor.
+  const C.c1() : v = C(); //# 2: compile-time error
+  const C.c2() : v = const C();
+  const C.c3() : v = const C(C());
+
+  // Expression in redirecting generative const constuctor.
+  const C.r1() : this(C()); //# 3: compile-time error
+  const C.r2() : this(const C());
+  const C.r3() : this(const C(C()));
+
+  // Default value of positional optional parameter.
+  static List<C> foo([
+    p1 = C(), //# 4: compile-time error
+    p2 = const C(),
+    p3 = const C(C()),
+  ]) =>
+      [p2, p3];
+
+  // Default value of named optional parameter.
+  static List<C> bar({
+    p1 = C(), //# 5: compile-time error
+    p2 = const C(),
+    p3 = const C(C()),
+  }) =>
+      [p2, p3];
+}
+
+void main() {
+  var c = const C();
+  var cc = const C(C());
+
+  // Check that const constructors can be invoked without `const`,
+  // creating new instances every time.
+  var nc1 = C();
+  var nc2 = C.c2();
+  var nc3 = C.c3();
+  var nc4 = C.r2();
+  var nc5 = C.r3();
+  Expect.allDistinct([nc1, nc2, nc3, nc4, nc5, c, cc]);
+
+  // Check that const invocations create identical objects.
+  Expect.identical(c, C.c2().v);
+  Expect.identical(cc, C.c3().v);
+
+  Expect.identical(c, C.r2().v);
+  Expect.identical(cc, C.r3().v);
+
+  Expect.identical(const [], C().i2);
+  Expect.identical(const [[]], C().i3);
+
+  Expect.identical(c, C.foo()[0]);
+  Expect.identical(cc, C.foo()[1]);
+
+  Expect.identical(c, C.bar()[0]);
+  Expect.identical(cc, C.bar()[1]);
+}