Re-apply "support for typedef in checked mode" and fix the checked mode failures on drt by not shar…

sdk/lib/_internal/compiler/implementation/ssa/codegen.dart

 // Copyright (c) 2012, 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.
 
 part of ssa;
 
 class SsaCodeGeneratorTask extends CompilerTask {
 
   final JavaScriptBackend backend;
 
@@ skipping 2273 matching lines @@
 
   void checkFixedArray(HInstruction input) {
     checkFieldExists(input, 'fixed\$length');
   }
 
   void checkNull(HInstruction input) {
     use(input);
     push(new js.Binary('==', pop(), new js.LiteralNull()));
   }
 
+  void checkNonNull(HInstruction input) {
+    use(input);
+    push(new js.Binary('!=', pop(), new js.LiteralNull()));
+  }
+
   void checkFunction(HInstruction input, DartType type) {
     checkTypeOf(input, '===', 'function');
     js.Expression functionTest = pop();
     checkObject(input, '===');
     js.Expression objectTest = pop();
     checkType(input, type);
     push(new js.Binary('||',
                        functionTest,
                        new js.Binary('&&', objectTest, pop())));
   }
@@ skipping 104 matching lines @@
     } else if (Elements.isNumberOrStringSupertype(element, compiler)) {
       handleNumberOrStringSupertypeCheck(input, type);
       attachLocationToLast(node);
     } else if (Elements.isStringOnlySupertype(element, compiler)) {
       handleStringSupertypeCheck(input, type);
       attachLocationToLast(node);
     } else if (identical(element, compiler.listClass)
                || Elements.isListSupertype(element, compiler)) {
       handleListOrSupertypeCheck(input, type);
       attachLocationToLast(node);
+    } else if (element.isTypedef()) {
+      checkNonNull(input);
+      js.Expression nullTest = pop();
+      checkType(input, type);
+      push(new js.Binary('&&', nullTest, pop()));
+      attachLocationToLast(node);
     } else if (types[input].canBePrimitive() || types[input].canBeNull()) {
       checkObject(input, '===');
       js.Expression objectTest = pop();
       checkType(input, type);
       push(new js.Binary('&&', objectTest, pop()), node);
     } else {
       checkType(input, type);
       attachLocationToLast(node);
     }
     if (node.hasArgumentChecks()) {
@@ skipping 639 matching lines @@
   if (leftType.canBeNull() && rightType.canBeNull()) {
     if (left.isConstantNull() || right.isConstantNull() ||
         (leftType.isPrimitive() && leftType == rightType)) {
       return '==';
     }
     return null;
   } else {
     return '===';
   }
 }