Do not mark type variables as needing a box inside try; they are immutable.

pkg/compiler/lib/src/ssa/builder.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 SsaFunctionCompiler implements FunctionCompiler {
   SsaCodeGeneratorTask generator;
   SsaBuilderTask builder;
   SsaOptimizerTask optimizer;
@@ skipping 2428 matching lines @@
           original, representations);
     } else if (type.isTypeVariable) {
       TypeMask subtype = original.instructionType;
       HInstruction typeVariable = addTypeVariableReference(type);
       return new HTypeConversion.withTypeRepresentation(type, kind, subtype,
           original, typeVariable);
     } else if (type.isFunctionType) {
       String name = kind == HTypeConversion.CAST_TYPE_CHECK
           ? '_asCheck' : '_assertCheck';
 
-      List arguments = [buildFunctionType(type), original];
+      List<HInstruction> arguments =
+          <HInstruction>[buildFunctionType(type), original];
       pushInvokeDynamic(
           null,
           new Selector.call(name, backend.jsHelperLibrary, 1),
           arguments);
 
       return new HTypeConversion(type, kind, original.instructionType, pop());
     } else {
       return original.convertType(compiler, type, kind);
     }
   }
@@ skipping 5412 matching lines @@
     if (unaliased is TypedefType) throw 'unable to unalias $type';
     unaliased.accept(this, builder);
   }
 
   void visitDynamicType(DynamicType type, SsaBuilder builder) {
     JavaScriptBackend backend = builder.compiler.backend;
     ClassElement cls = backend.findHelper('DynamicRuntimeType');
     builder.push(new HDynamicType(type, new TypeMask.exact(cls, classWorld)));
   }
 }