Mark top-level error field as static.

pkg/front_end/lib/src/fasta/kernel/verifier.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.verifier;
 
 import 'package:kernel/ast.dart'
     show
         InvalidExpression,
         InvalidStatement,
@@ skipping 28 matching lines @@
 class FastaVerifyingVisitor extends VerifyingVisitor
     implements TypeSchemaVisitor {
   final List<LocatedMessage> errors = <LocatedMessage>[];
 
   String fileUri;
 
   FastaVerifyingVisitor(bool isOutline) {
     this.isOutline = isOutline;
   }
 
+  String checkLocation(TreeNode node, String name) {

[sjindel, 2017/08/16 10:27:01]

How are these changes related?

[ahe, 2017/08/16 11:59:15]

Without the change on line 79, Uri.parse would throw a NSM error as #errors
doesn't have a fileUri.

But that got me thinking that it would be a good idea to verify that all nodes
have location information, unless they're synthetic.

[ahe, 2017/08/16 12:01:47]

It would throw a NSM error *before* I modified kernel_target.dart.

If you're asking why I'm making changes to the verifier, then the answer is that
this should prevent me or others from repeating the same mistake.

+    if (name == null || name.contains("#")) {
+      // TODO(ahe): Investigate if these checks can be enabled:
+      // if (node.fileUri != null && node is! Library) {
+      //   problem(node, "A synthetic node shouldn't have a fileUri",
+      //       context: node);
+      // }
+      // if (node.fileOffset != -1) {
+      //   problem(node, "A synthetic node shouldn't have a fileOffset",
+      //       context: node);
+      // }
+      return fileUri;
+    } else {
+      if (node.fileUri == null) {
+        problem(node, "'$name' has no fileUri", context: node);
+        return fileUri;
+      }
+      if (node.fileOffset == -1 && node is! Library) {
+        problem(node, "'$name' has no fileOffset", context: node);
+      }
+      return node.fileUri;
+    }
+  }
+
   @override
   problem(TreeNode node, String details, {TreeNode context}) {
     node ??= (context ?? this.context);
     int offset = node?.fileOffset ?? -1;
     LocatedMessage message = templateInternalVerificationError
         .withArguments(details)
-        .withLocation(Uri.parse(fileUri), offset);
+        .withLocation(fileUri == null ? null : Uri.parse(fileUri), offset);
     CompilerContext.current.report(message, Severity.error);
     errors.add(message);
   }
 
   @override
   visitExpressionStatement(ExpressionStatement node) {
     // Bypass verification of the [StaticGet] in [RedirectingFactoryBody] as
     // this is a static get without a getter.
     if (node is! RedirectingFactoryBody) {
       super.visitExpressionStatement(node);
     }
   }
 
   @override
   visitLibrary(Library node) {
-    fileUri = node.fileUri;
+    fileUri = checkLocation(node, node.name);
     super.visitLibrary(node);
   }
 
   @override
   visitClass(Class node) {
-    fileUri = node.fileUri;
+    fileUri = checkLocation(node, node.name);
     super.visitClass(node);
   }
 
   @override
   visitField(Field node) {
-    fileUri = node.fileUri;
+    fileUri = checkLocation(node, node.name.name);
     super.visitField(node);
   }
 
   @override
   visitProcedure(Procedure node) {
-    fileUri = node.fileUri;
+    fileUri = checkLocation(node, node.name.name);
     super.visitProcedure(node);
   }
 
   @override
   visitInvalidExpression(InvalidExpression node) {
     problem(node, "Invalid expression.");
   }
 
   @override
   visitInvalidStatement(InvalidStatement node) {
     problem(node, "Invalid statement.");
   }
 
   @override
   visitInvalidInitializer(InvalidInitializer node) {
     problem(node, "Invalid initializer.");
   }
 
   @override
   visitUnknownType(UnknownType node) {
     // Note: we can't pass [node] to [problem] because it's not a [TreeNode].
     problem(null, "Unexpected appearance of the unknown type.");
   }
 }