Avoid creating illegal symbols in symbol_conflict_test.

tests/language/symbol_conflict_test.dart

 // Copyright (c) 2015, 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.
 
 // Tests that const symbols are only equal to the symbol they represent.
 
 import 'package:expect/expect.dart';
 
 class A {
   noSuchMethod(invocation) {
     Expect.isFalse(oneAndTwoCharacterSymbols.contains(invocation.memberName));
   }
 }
 
 main() {
   var a = new A();
   a.foo = 23;
   a.foo;
   a.bar;
   a.longer;
   a.anotherOne;
   a.add(1);
   a.isEmpty;
 }
 
 /**
  The following constant was generated with the following program:
 
+   const RESERVED_WORDS = const [
+     'assert', 'break', 'case', 'catch', 'class', 'const', 'continue',
+     'default', 'do', 'else', 'enum', 'extends', 'false', 'final',
+     'finally', 'for', 'if', 'in', 'is', 'new', 'null', 'rethrow',
+     'return', 'super', 'switch', 'this', 'throw', 'true', 'try',
+     'var', 'void', 'while', 'with'];
+
    get chars sync* {
       for (int i = "a".codeUnitAt(0); i <= "z".codeUnitAt(0); i++) {
         yield new String.fromCharCodes([i]);
       }
       for (int i = "A".codeUnitAt(0); i <= "Z".codeUnitAt(0); i++) {
         yield new String.fromCharCodes([i]);
       }
     }
 
     main() {
       print("const oneAndTwoCharacterSymbols = const [");
       // One character symbols.
       for (String c in chars) {
         print("  const Symbol('$c'),");
       }
       // Two character symbols.
       for (String c1 in chars) {
         for (String c2 in chars) {
-          print("  const Symbol('$c1$c2'),");
+          if (!RESERVED_WORDS.contains('$c1$c2')) {

[karlklose, 2015/07/24 08:27:57]

You could actually make a multi-test that also tests that the compiler/analyzer
emits a compile-time error when encountering one of these by adding a counter id
and:
  } else {
    print("  const Symbol('$c1$c2'),  /// ${++id}: compile-time error");
  }

But that would generate to many long tests. Consider adding a
negative/multi-test in addition to this one.

[Paul Berry, 2015/07/24 13:26:25]

Actually there is already a test which verifies that "const Symbol('<keyword>')"
leads to a compile-time error: tests/corelib/symbol_reserved_word_test.dart/10. 
The VM and dart2js currently fail this test due to bugs 11669 and 19972.

I suppose that test really ought to be split up into one multitest case per
keyword (currently there's a single multitest case for all keywords, so if there
were a bug where the implementation allowed some keywords but not others, that
bug wouldn't be caught).  But considering that no one has found bug 11669
important enough to fix in two years (!) I'm having trouble getting excited
about changing anything :)

+            print("  const Symbol('$c1$c2'),");
+          }
         }
       }
       print("];");
     }
 */
 const oneAndTwoCharacterSymbols = const [
   const Symbol('a'),
   const Symbol('b'),
   const Symbol('c'),
   const Symbol('d'),
@@ skipping 208 matching lines @@
   const Symbol('de'),
   const Symbol('df'),
   const Symbol('dg'),
   const Symbol('dh'),
   const Symbol('di'),
   const Symbol('dj'),
   const Symbol('dk'),
   const Symbol('dl'),
   const Symbol('dm'),
   const Symbol('dn'),
-  const Symbol('do'),
   const Symbol('dp'),
   const Symbol('dq'),
   const Symbol('dr'),
   const Symbol('ds'),
   const Symbol('dt'),
   const Symbol('du'),
   const Symbol('dv'),
   const Symbol('dw'),
   const Symbol('dx'),
   const Symbol('dy'),
@@ skipping 230 matching lines @@
   const Symbol('hV'),
   const Symbol('hW'),
   const Symbol('hX'),
   const Symbol('hY'),
   const Symbol('hZ'),
   const Symbol('ia'),
   const Symbol('ib'),
   const Symbol('ic'),
   const Symbol('id'),
   const Symbol('ie'),
-  const Symbol('if'),
   const Symbol('ig'),
   const Symbol('ih'),
   const Symbol('ii'),
   const Symbol('ij'),
   const Symbol('ik'),
   const Symbol('il'),
   const Symbol('im'),
-  const Symbol('in'),
   const Symbol('io'),
   const Symbol('ip'),
   const Symbol('iq'),
   const Symbol('ir'),
-  const Symbol('is'),
   const Symbol('it'),
   const Symbol('iu'),
   const Symbol('iv'),
   const Symbol('iw'),
   const Symbol('ix'),
   const Symbol('iy'),
   const Symbol('iz'),
   const Symbol('iA'),
   const Symbol('iB'),
   const Symbol('iC'),
@@ skipping 2250 matching lines @@
   const Symbol('ZR'),
   const Symbol('ZS'),
   const Symbol('ZT'),
   const Symbol('ZU'),
   const Symbol('ZV'),
   const Symbol('ZW'),
   const Symbol('ZX'),
   const Symbol('ZY'),
   const Symbol('ZZ'),
 ];