Cancel the compilation if the SSA builder attempts to visit a type annotation.

dart/frog/leg/ssa/builder.dart

 // Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 class Interceptors {
   Compiler compiler;
   Interceptors(Compiler this.compiler);
 
   SourceString mapOperatorToMethodName(Operator op) {
     String name = op.source.stringValue;
@@ skipping 1171 matching lines @@
 
   visitThrow(Throw node) {
     if (node.expression === null) {
       compiler.unimplemented("SsaBuilder: throw without expression");
     }
     visit(node.expression);
     close(new HThrow(pop()));
   }
 
   visitTypeAnnotation(TypeAnnotation node) {
-    // We currently ignore type annotations for generating code.
+    compiler.internalError('visiting type annotation in SSA builder',
+                           node: node);
   }
 
   visitVariableDefinitions(VariableDefinitions node) {
     for (Link<Node> link = node.definitions.nodes;
          !link.isEmpty();
          link = link.tail) {
       Node definition = link.head;
       if (definition is Identifier) {
         HInstruction initialValue = new HLiteral(null, HType.UNKNOWN);
         add(initialValue);
@@ skipping 200 matching lines @@
   }
 
   visitCatchBlock(CatchBlock node) {
     compiler.unimplemented('SsaBuilder.visitCatchBlock', node: node);
   }
 
   visitTypedef(Typedef node) {
     compiler.unimplemented('SsaBuilder.visitTypedef', node: node);
   }
 }