Convert top-level inference errors to hints

pkg/analyzer/lib/src/task/strong/checker.dart

 // Copyright (c) 2015, 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.
 
 // TODO(jmesserly): this was ported from package:dev_compiler, and needs to be
 // refactored to fit into analyzer.
 library analyzer.src.task.strong.checker;
 
 import 'package:analyzer/analyzer.dart';
 import 'package:analyzer/dart/ast/ast.dart';
@@ skipping 1029 matching lines @@
 
   void _recordMessage(AstNode node, ErrorCode errorCode, List arguments) {
     // Compute the right severity taking the analysis options into account.
     // We construct a dummy error to make the common case where we end up
     // ignoring the strong mode message cheaper.
     var processor = ErrorProcessor.getProcessor(_options,
         new AnalysisError.forValues(null, -1, 0, errorCode, null, null));
     var severity =
         (processor != null) ? processor.severity : errorCode.errorSeverity;
 
-    if (severity == ErrorSeverity.ERROR) _failure = true;
+    if (errorCode.type == ErrorType.HINT &&
+        errorCode.name.startsWith('STRONG_MODE_TOP_LEVEL_')) {
+      severity = ErrorSeverity.ERROR;
+    }
+    if (severity == ErrorSeverity.ERROR) {
+      _failure = true;

[Leaf, 2017/03/30 19:39:59]

I don't think we want to set _failure for these errors while we're treating
these as hints: otherwise I think DDC may refuse to compile them.  Perhaps put
the previous conditional after this one?

[Brian Wilkerson, 2017/03/30 19:45:18]

Done

+    }
     if (severity != ErrorSeverity.INFO || _options.strongModeHints) {
       int begin = node is AnnotatedNode
           ? node.firstTokenAfterCommentAndMetadata.offset
           : node.offset;
       int length = node.end - begin;
       var source = resolutionMap
           .elementDeclaredByCompilationUnit(node.root as CompilationUnit)
           .source;
       var error =
           new AnalysisError(source, begin, length, errorCode, arguments);
@@ skipping 496 matching lines @@
     var visited = new Set<InterfaceType>();
     do {
       visited.add(current);
       current.mixins.reversed.forEach(
           (m) => _checkIndividualOverridesFromClass(node, m, seen, true));
       _checkIndividualOverridesFromClass(node, current.superclass, seen, true);
       current = current.superclass;
     } while (!current.isObject && !visited.contains(current));
   }
 }