Issue 1738. Check type of DartMethodDeclaration.getName().

compiler/java/com/google/dart/compiler/ast/DartUnit.java

Index: compiler/java/com/google/dart/compiler/ast/DartUnit.java
diff --git a/compiler/java/com/google/dart/compiler/ast/DartUnit.java b/compiler/java/com/google/dart/compiler/ast/DartUnit.java
index 40faf843fc5a987fdfbbc8ab94d8e73c5c10e599..638bd7f206683103c765fc47967e1f38f8e5e433 100644
--- a/compiler/java/com/google/dart/compiler/ast/DartUnit.java
+++ b/compiler/java/com/google/dart/compiler/ast/DartUnit.java
@@ -160,7 +160,9 @@ public class DartUnit extends DartNode {
       }
       if (node instanceof DartMethodDefinition) {
         DartExpression name = ((DartMethodDefinition) node).getName();
-        topLevelSymbols.add(((DartIdentifier) name).getTargetName());
+        if (name instanceof DartIdentifier) {
+          topLevelSymbols.add(((DartIdentifier) name).getTargetName());
+        }
       }
       if (node instanceof DartFieldDefinition) {
         DartFieldDefinition fieldDefinition = (DartFieldDefinition) node;