Issue 4553. Any constant is valid for 'case'.

compiler/java/com/google/dart/compiler/resolver/CompileTimeConstantAnalyzer.java

Index: compiler/java/com/google/dart/compiler/resolver/CompileTimeConstantAnalyzer.java
diff --git a/compiler/java/com/google/dart/compiler/resolver/CompileTimeConstantAnalyzer.java b/compiler/java/com/google/dart/compiler/resolver/CompileTimeConstantAnalyzer.java
index 6418eb1c473ca59db7c5992ac21ff4e7478134f1..6df713b74c9f6612158af2557447966e539365f9 100644
--- a/compiler/java/com/google/dart/compiler/resolver/CompileTimeConstantAnalyzer.java
+++ b/compiler/java/com/google/dart/compiler/resolver/CompileTimeConstantAnalyzer.java
@@ -14,6 +14,7 @@ import com.google.dart.compiler.ast.ASTVisitor;
 import com.google.dart.compiler.ast.DartArrayLiteral;
 import com.google.dart.compiler.ast.DartBinaryExpression;
 import com.google.dart.compiler.ast.DartBooleanLiteral;
+import com.google.dart.compiler.ast.DartCase;
 import com.google.dart.compiler.ast.DartClass;
 import com.google.dart.compiler.ast.DartDeclaration;
 import com.google.dart.compiler.ast.DartDoubleLiteral;
@@ -681,6 +682,12 @@ public class CompileTimeConstantAnalyzer {
       }
       return super.visitInitializer(node);
     }
+    
+    @Override
+    public Void visitCase(DartCase node) {
+      checkConstantExpression(node.getExpr());
+      return super.visitCase(node);
+    }
 
     @Override
     public Void visitMapLiteral(DartMapLiteral node) {