fix #28008, fix #28009 implement FutureOr<T>

pkg/dev_compiler/test/codegen_test.dart

 // Copyright (c) 2016, 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 code generation.
 ///
 /// Runs Dart Dev Compiler on all input in the `codegen` directory and checks
 /// that the output is what we expected.
 library dev_compiler.test.codegen_test;
 
@@ skipping 141 matching lines @@
       var files = new Set<String>();
       _collectTransitiveImports(contents, files, from: testFile);
       var unit = new BuildUnit(
           name, path.dirname(testFile), files.toList(), _moduleForLibrary);
 
       var compiler = sharedCompiler;
       if (analyzerOptions.declaredVariables.isNotEmpty) {
         compiler = new ModuleCompiler(analyzerOptions);
       }
       JSModuleFile module = null;
+      var error, trace;
       try {
         module = compiler.compile(unit, options);
-      } catch (e) {}
+      } catch (e, t) {
+        error = e;
+        trace = t;
+      }
 
       bool notStrong = notYetStrongTests.contains(name);
       bool crashing = _crashingTests.contains(name);
 
       if (module == null) {
         expect(crashing, isTrue,
-            reason: "test $name crashes during compilation.");
+            reason: "test $name crashes during compilation.\n\n"
+                "Exception: $error\n\nStack trace:\n\n$trace");
       } else if (module.isValid) {
         _writeModule(
             path.join(codegenOutputDir, name),
             isTopLevelTest ? path.join(codegenExpectDir, name) : null,
             moduleFormat,
             module);
 
         expect(crashing, isFalse, reason: "test $name no longer crashes.");
         expect(notStrong, isFalse,
             reason: "test $name expected strong mode errors, but compiled.");
@@ skipping 204 matching lines @@
   'language/mixin_illegal_syntax_test_06_multi',
   'language/mixin_illegal_syntax_test_07_multi',
   'language/mixin_illegal_syntax_test_08_multi',
   'language/mixin_illegal_syntax_test_09_multi',
   'language/mixin_illegal_syntax_test_10_multi',
   'language/mixin_illegal_syntax_test_11_multi',
   'language/mixin_illegal_syntax_test_12_multi',
   'language/mixin_illegal_syntax_test_13_multi',
   'language/mixin_illegal_syntax_test_14_multi'
 ]);