Handle string interpolation/juxtaposition in kernel_impact.

pkg/compiler/lib/src/ssa/kernel_impact.dart

Index: pkg/compiler/lib/src/ssa/kernel_impact.dart
diff --git a/pkg/compiler/lib/src/ssa/kernel_impact.dart b/pkg/compiler/lib/src/ssa/kernel_impact.dart
index 15efe23e8b2da8e019c868e3dae9b1b49672008c..fef8f82a6282ad237893285a679b9207ed255810 100644
--- a/pkg/compiler/lib/src/ssa/kernel_impact.dart
+++ b/pkg/compiler/lib/src/ssa/kernel_impact.dart
@@ -5,6 +5,7 @@
 import 'package:kernel/ast.dart' as ir;
 
 import '../common.dart';
+import '../common/names.dart';
 import '../compiler.dart';
 import '../constants/expressions.dart';
 import '../dart_types.dart';
@@ -265,11 +266,6 @@ class KernelImpactBuilder extends ir.Visitor {
   }
 
   @override
-  void visitNot(ir.Not not) {

[Harry Terkelsen, 2016/09/20 18:00:18]

why get rid of this?

[Johnni Winther, 2016/09/21 08:33:40]

It was copied from the ssa builder, but after adding the defaultNode
implementation this doesn't do anything special.

-    not.operand.accept(this);
-  }
-
-  @override
   void visitAssertStatement(ir.AssertStatement node) {
     impactBuilder.registerFeature(
         node.message != null ? Feature.ASSERT_WITH_MESSAGE : Feature.ASSERT);
@@ -277,5 +273,12 @@ class KernelImpactBuilder extends ir.Visitor {
   }
 
   @override
+  void visitStringConcatenation(ir.StringConcatenation node) {
+    impactBuilder.registerFeature(Feature.STRING_INTERPOLATION);
+    impactBuilder.registerFeature(Feature.STRING_JUXTAPOSITION);
+    node.visitChildren(this);
+  }
+
+  @override
   void defaultNode(ir.Node node) => node.visitChildren(this);
 }