Added String Concat -> Interpolation Intention (KT-4750)

core/descriptors/src/org/jetbrains/jet/lang/types/lang/KotlinBuiltIns.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2010-2012 JetBrains s.r.o.
+ * Copyright 2010-2014 JetBrains s.r.o.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -826,6 +826,10 @@ public class KotlinBuiltIns {
         return !(type instanceof PackageType) && type.equals(getUnitType());
     }
 
+    public boolean isString(@Nullable JetType type) {
+        return !(type instanceof PackageType) && getStringType().equals(type);
+    }
+
     public boolean isData(@NotNull ClassDescriptor classDescriptor) {
         return containsAnnotation(classDescriptor, getDataClassAnnotation());
     }