Add regression tests from Luke's bug reports. Part 1.

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;
+import 'package:kernel/ast.dart' show Library, Location, Program, TreeNode;
 
 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 hideWarnings = false;
@@ skipping 67 matching lines @@
   if (charOffset == -1) return null;
   String path = relativizeUri(uri);
   return getLocation(path, charOffset);
 }
 
 String getSourceLine(Location location) {
   if (location == null) return null;
   return CompilerContext.current.uriToSource[location.file]
       ?.getTextLine(location.line);
 }
+
+Location getLocationFromNode(TreeNode node) {
+  if (node.enclosingProgram == null) {
+    TreeNode parent = node;
+    while (parent != null && parent is! Library) {
+      parent = parent.parent;
+    }
+    if (parent is Library) {
+      // ignore: UNUSED_LOCAL_VARIABLE
+      Program program = new Program(

[Johnni Winther, 2017/06/23 10:51:44]

Maybe remove `Program program = ` and add a comment about the side effect of
creating a Program.

[ahe, 2017/06/23 12:21:51]

I've changed the code to make it more obvious. IMO.

+          libraries: <Library>[parent],
+          uriToSource: CompilerContext.current.uriToSource);
+      Location result = node.location;
+      parent.parent = null;
+      return result;
+    } else {
+      return null;
+    }
+  } else {
+    return node.location;
+  }
+}