Promote analyzer warnings to ddc errors

lib/src/checker/resolver.dart

Index: lib/src/checker/resolver.dart
diff --git a/lib/src/checker/resolver.dart b/lib/src/checker/resolver.dart
index 6af5659330ab0f5c3a426b0e02c02fb852c5da20..5c29d47cd1c1f432585a41ec9129e5a7bdb2e151 100644
--- a/lib/src/checker/resolver.dart
+++ b/lib/src/checker/resolver.dart
@@ -111,7 +111,7 @@ class TypeResolver {
 class AnalyzerError extends Message {
   factory AnalyzerError.from(analyzer.AnalysisError error) {
     var severity = error.errorCode.type.severity;
-    var isError = severity == analyzer.ErrorSeverity.ERROR;
+    var isError = severity == analyzer.ErrorSeverity.WARNING;
     var level = isError ? logger.Level.SEVERE : logger.Level.WARNING;
     int begin = error.offset;
     int end = begin + error.length;
@@ -119,7 +119,7 @@ class AnalyzerError extends Message {
   }
 
   const AnalyzerError(String message, logger.Level level, int begin, int end)
-      : super('[from analyzer]: $message', level, begin, end);
+      : super(message, level, begin, end);
 }
 
 /// Creates an analysis context that contains our restricted typing rules.