Use inlined double temporary object for unary operation, add tests. Fix disassembler crash.

runtime/vm/compiler.cc

 // 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.
 
 #include "vm/compiler.h"
 
 #include "vm/assembler.h"
 #include "vm/ast_printer.h"
 #include "vm/code_generator.h"
 #include "vm/code_index_table.h"
@@ skipping 164 matching lines @@
     OS::Print("}\n");
     OS::Print("PC Descriptors for function '%s' {\n", function_fullname);
     OS::Print("(pc, kind, id, try-index, token-index)\n");
     const PcDescriptors& descriptors =
         PcDescriptors::Handle(code.pc_descriptors());
     OS::Print("%s", descriptors.ToCString());
     OS::Print("}\n");
     OS::Print("Variable Descriptors for function '%s' {\n", function_fullname);
     const LocalVarDescriptors& var_descriptors =
         LocalVarDescriptors::Handle(code.var_descriptors());
-    intptr_t var_desc_length = var_descriptors.Length();
+    intptr_t var_desc_length =
+        var_descriptors.IsNull() ? 0 : var_descriptors.Length();
     String& var_name = String::Handle();
     for (intptr_t i = 0; i < var_desc_length; i++) {
       var_name = var_descriptors.GetName(i);
       intptr_t scope_id, begin_pos, end_pos;
       var_descriptors.GetScopeInfo(i, &scope_id, &begin_pos, &end_pos);
       intptr_t slot = var_descriptors.GetSlotIndex(i);
       OS::Print("  var %s scope %ld (valid %d-%d) offset %ld\n",
                 var_name.ToCString(), scope_id, begin_pos, end_pos, slot);
     }
     OS::Print("}\n");
@@ skipping 83 matching lines @@
                               kNoArgumentNames));
   if (result.IsUnhandledException()) {
     // TODO(srdjan): implement proper exit from compiler.
     UNIMPLEMENTED();
   }
   return result.raw();
 }
 
 
 }  // namespace dart