Don't upgrade the severity of *everything* to an error in strong mode.

pkg/analyzer/lib/source/error_processor.dart

Index: pkg/analyzer/lib/source/error_processor.dart
diff --git a/pkg/analyzer/lib/source/error_processor.dart b/pkg/analyzer/lib/source/error_processor.dart
index 6b69cb71fe24ab6d1049a89088f36faa637015b4..d9049cb70820f86952f555d5d9415853b59f7c9e 100644
--- a/pkg/analyzer/lib/source/error_processor.dart
+++ b/pkg/analyzer/lib/source/error_processor.dart
@@ -94,20 +94,18 @@ class ErrorProcessor {
       return null;
     }
 
-    // By default, the error is not processed.
-    ErrorProcessor processor;
+    // Let the user configure how specific errors are processed.
+    List<ErrorProcessor> processors =
+        context.getConfigurationData(CONFIGURED_ERROR_PROCESSORS);
 
     // Give strong mode a chance to upgrade it.
     if (context.analysisOptions.strongMode) {
-      processor = _StrongModeTypeErrorProcessor.instance;
+      processors = processors.toList();

[Brian Wilkerson, 2016/03/17 19:54:14]

It looks like it should already be a list. Is 'getConfigurationData' returning
something other than a list (in which case the 'toList' might want to be moved
up a couple of lines)?

[Bob Nystrom, 2016/03/17 19:58:25]

It is a list, but I want to copy it so I don't mutate the original one with the
.add() call.

+      processors.add(_StrongModeTypeErrorProcessor.instance);
     }
 
-    // Let the user configure how specific errors are processed.
-    List<ErrorProcessor> processors =
-        context.getConfigurationData(CONFIGURED_ERROR_PROCESSORS);
-
     return processors.firstWhere((ErrorProcessor p) => p.appliesTo(error),
-        orElse: () => processor);
+        orElse: () => null);
   }
 }