Improve detection of compile-time errors.

pkg/front_end/lib/src/fasta/vm.dart

 // Copyright (c) 2017, 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.
 
 /// API for compiling Dart source code to .dill (Kernel IR) files.
 library front_end.vm;
 // TODO(ahe): Move this to lib/ once the API has matured.
 
 import 'dart:async' show Future;
 
 import 'dart:io' show File, Platform;
 
 import 'dart:typed_data' show Uint8List;
 
-import 'outline.dart' as fasta;
+import 'fasta.dart' as fasta;
 
 /// Compilation status codes.
 ///
 /// Note: The [index] property of these constants must match
 /// `Dart_KernelCompilationStatus` in
 /// [dart_api.h](../../../../runtime/include/dart_api.h).
 enum Status {
   /// Compilation was successful.
   ok,
 
   /// Compilation failed with a compile time error.
   error,
 
   /// Compiler crashed.
   crash,
 }
 
 abstract class CompilationResult {
   CompilationResult._();
 
   factory CompilationResult.ok(Uint8List bytes) = _CompilationOk;
 
-  factory CompilationResult.error(List<String> errors) = _CompilationError;
+  factory CompilationResult.errors(List<String> errors) = _CompilationError;
+
+  factory CompilationResult.error(String error) {
+    return new _CompilationError(<String>[error]);
+  }
 
   factory CompilationResult.crash(Object exception, StackTrace stack) =
       _CompilationCrash;
 
   Status get status;
 
   get payload;
 
   List toResponse() => [status.index, payload];
 }
@@ skipping 86 matching lines @@
     if (await new File.fromUri(packagesFile).exists()) {
       return packagesFile;
     }
     if (dir.parent.path == dir.path) {
       break;
     }
     dir = dir.parent;
   }
   return null;
 }