Canonicalize expressions that may be used as constants

runtime/vm/parser.cc

 // 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.
 
 #include "vm/parser.h"
 #include "vm/flags.h"
 
 #ifndef DART_PRECOMPILED
 
 #include "lib/invocation_mirror.h"
@@ skipping 11184 matching lines @@
                                   NULL);  // No existing function.
   } else if (cls.IsTopLevel() &&
       (cls.library() == Library::CoreLibrary()) &&
       (func.name() == Symbols::Identical().raw())) {
     // This is the predefined toplevel function identical(a,b).
     // Create a comparison node instead of a static call to the function, unless
     // javascript warnings are desired and identical is not invoked from a patch
     // source.
     if (!FLAG_warn_on_javascript_compatibility || is_patch_source()) {
       ASSERT(num_arguments == 2);
+
+      // If both arguments are constant expressions of type string,
+      // evaluate and canonicalize them.
+      // This guarantees that identical("ab", "a"+"b") is true.
+      // An alternative way to guarantee this would be to introduce
+      // an AST node that canonicalizes a value.
+      AstNode* arg0 = arguments->NodeAt(0);
+      const Instance* val0 = arg0->EvalConstExpr();
+      if ((val0 != NULL) && (val0->IsString())) {
+        AstNode* arg1 = arguments->NodeAt(1);
+        const Instance* val1 = arg1->EvalConstExpr();
+        if ((val1 != NULL) && (val1->IsString())) {
+          arguments->SetNodeAt(0,
+              new(Z) LiteralNode(arg0->token_pos(),
+                                 EvaluateConstExpr(arg0->token_pos(), arg0)));
+          arguments->SetNodeAt(1,
+              new(Z) LiteralNode(arg1->token_pos(),
+                                 EvaluateConstExpr(arg1->token_pos(), arg1)));
+        }
+      }
       return new(Z) ComparisonNode(ident_pos,
                                    Token::kEQ_STRICT,
                                    arguments->NodeAt(0),
                                    arguments->NodeAt(1));
     }
   }
   return new(Z) StaticCallNode(ident_pos, func, arguments);
 }
 
 
@@ skipping 3273 matching lines @@
     const ArgumentListNode& function_args,
     const LocalVariable* temp_for_last_arg,
     bool is_super_invocation) {
   UNREACHABLE();
   return NULL;
 }
 
 }  // namespace dart
 
 #endif  // DART_PRECOMPILED