Throw isn't a constant expression.

pkg/front_end/lib/src/fasta/kernel/body_builder.dart

Index: pkg/front_end/lib/src/fasta/kernel/body_builder.dart
diff --git a/pkg/front_end/lib/src/fasta/kernel/body_builder.dart b/pkg/front_end/lib/src/fasta/kernel/body_builder.dart
index 489a6bc10bddd4c2a254bd0045ac6a38a1a31b50..45faf3f7e6f0911d8b6796699b2593a33a16fbf9 100644
--- a/pkg/front_end/lib/src/fasta/kernel/body_builder.dart
+++ b/pkg/front_end/lib/src/fasta/kernel/body_builder.dart
@@ -1380,7 +1380,12 @@ class BodyBuilder extends ScopeListener<JumpTarget> implements BuilderHelper {
   void endThrowExpression(Token throwToken, Token endToken) {
     debugEvent("ThrowExpression");
     Expression expression = popForValue();
-    push(new Throw(expression)..fileOffset = throwToken.charOffset);
+    if (constantExpressionRequired) {
+      push(buildCompileTimeError(
+          "Not a constant expression.", throwToken.charOffset));
+    } else {
+      push(new Throw(expression)..fileOffset = throwToken.charOffset);
+    }
   }
 
   @override