Implement line and column numbers.

pkg/front_end/lib/src/fasta/messages.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.
+
+library fasta.messages;
+
+import 'package:kernel/ast.dart' show
+    Location,
+    Program;
+
+import 'util/relativize.dart' show
+    relativizeUri;
+
+import 'compiler_context.dart' show
+    CompilerContext;
+
+import 'errors.dart' show
+    InputError;
+
+import 'colors.dart' show
+    cyan,
+    magenta;
+
+const bool hideNits = false;
+
+const bool hideWarnings = false;
+
+void warning(Uri uri, int charOffset, String message) {
+  if (hideWarnings) return;
+  print(format(uri, charOffset, colorWarning("Warning: $message")));
+  if (CompilerContext.current.options.areWarningsFatal) {
+    if (CompilerContext.current.options.verbose) print(StackTrace.current);
+    throw new InputError(
+        uri, charOffset, "Compilation aborted due to fatal warnings.");
+  }
+}
+
+void nit(Uri uri, int charOffset, String message) {
+  if (hideNits) return;
+  print(format(uri, charOffset, colorNit("Nit: $message")));
+  if (CompilerContext.current.options.areNitsFatal) {
+    if (CompilerContext.current.options.verbose) print(StackTrace.current);
+    throw new InputError(
+        uri, charOffset, "Compilation aborted due to fatal nits.");
+  }
+}
+
+String colorWarning(String message) {
+  // TODO(ahe): Colors need to be optional. Doesn't work well in Emacs or on
+  // Windows.
+  return magenta(message);
+}
+
+String colorNit(String message) {
+  // TODO(ahe): Colors need to be optional. Doesn't work well in Emacs or on
+  // Windows.
+  return cyan(message);
+}
+
+String format(Uri uri, int charOffset, String message) {
+  if (uri != null) {
+    String path = relativizeUri(uri);
+    String position = charOffset == -1
+        ? path : "${getLocation(path, charOffset)}";
+    return "$position: $message";
+  } else {
+    return message;
+  }
+}
+
+Location getLocation(String path, int charOffset) {
+  return new Program(null, CompilerContext.current.uriToSource)
+      .getLocation(path, charOffset);
+}