Issue a strong mode warning for type inference that is unsafe with AST-based summaries.

pkg/analyzer/lib/src/generated/error.dart

Index: pkg/analyzer/lib/src/generated/error.dart
diff --git a/pkg/analyzer/lib/src/generated/error.dart b/pkg/analyzer/lib/src/generated/error.dart
index 10d5a24933b1ca8a2c678e2c6e6efe9f8fa2ebc5..c13d6208740a103a6a5337487d2f924f4dc721ee 100644
--- a/pkg/analyzer/lib/src/generated/error.dart
+++ b/pkg/analyzer/lib/src/generated/error.dart
@@ -2881,6 +2881,7 @@ abstract class ErrorCode {
     StrongModeCode.INVALID_SUPER_INVOCATION,
     StrongModeCode.NON_GROUND_TYPE_CHECK_INFO,
     StrongModeCode.STATIC_TYPE_ERROR,
+    StrongModeCode.UNSAFE_BLOCK_CLOSURE_INFERENCE,
 
     TodoCode.TODO,
 
@@ -5897,6 +5898,11 @@ class StrongModeCode extends ErrorCode {
   static const String _implicitCastMessage =
       'Unsound implicit cast from {0} to {1}';
 
+  static const String _unsafeBlockClosureInferenceMessage =
+      'Unsafe use of block closure in a type-inferred variable outside a '
+      'function body.  Workaround: add a type annotation for `{0}`.  See '
+      'dartbug.com/26947';
+
   static const String _typeCheckMessage =
       'Type check failed: {0} is not of type {1}';
 
@@ -6044,6 +6050,12 @@ class StrongModeCode extends ErrorCode {
       "Missing type arguments for calling generic function type '{0}'"
       "$_implicitDynamicTip");
 
+  static const StrongModeCode UNSAFE_BLOCK_CLOSURE_INFERENCE =
+      const StrongModeCode(
+          ErrorType.STATIC_WARNING,
+          'UNSAFE_BLOCK_CLOSURE_INFERENCE',
+          _unsafeBlockClosureInferenceMessage);
+
   @override
   final ErrorType type;