Accept constant string concatenation and constant string length as constant

runtime/vm/ast.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/ast.h"
 #include "vm/compiler.h"
 #include "vm/dart_entry.h"
 #include "vm/isolate.h"
 #include "vm/object_store.h"
 #include "vm/resolver.h"
@@ skipping 306 matching lines @@
       return false;
   }
 }
 
 
 const Instance* BinaryOpNode::EvalConstExpr() const {
   const Instance* left_val = this->left()->EvalConstExpr();
   if (left_val == NULL) {
     return NULL;
   }
-  if (!left_val->IsNumber() && !left_val->IsBool()) {
+  if (!left_val->IsNumber() && !left_val->IsBool() && !left_val->IsString()) {
     return NULL;
   }
   const Instance* right_val = this->right()->EvalConstExpr();
   if (right_val == NULL) {
     return NULL;
   }
   switch (kind_) {
     case Token::kADD:
+      if (left_val->IsString()) {
+        return right_val->IsString() ? left_val : NULL;
+      }
+      // Fall-through intentional.
     case Token::kSUB:
     case Token::kMUL:
     case Token::kDIV:
     case Token::kMOD:
     case Token::kTRUNCDIV:
       if (left_val->IsInteger()) {
         if (right_val->IsInteger()) {
           return left_val;
         } else if (right_val->IsNumber()) {
           return right_val;
@@ skipping 178 matching lines @@
   }
   return new StoreStaticFieldNode(token_pos(), field(), rhs);
 }
 
 
 AstNode* InstanceGetterNode::MakeAssignmentNode(AstNode* rhs) {
   return new InstanceSetterNode(token_pos(), receiver(), field_name(), rhs);
 }
 
 
+bool InstanceGetterNode::IsPotentiallyConst() const {
+  return field_name().Equals(Symbols::Length()) &&
+    receiver()->IsPotentiallyConst();
+}
+
+
+const Instance* InstanceGetterNode::EvalConstExpr() const {
+  if (field_name().Equals(Symbols::Length())) {
+    const Instance* receiver_val = receiver()->EvalConstExpr();
+    if ((receiver_val != NULL) && receiver_val->IsString()) {
+      return &Instance::ZoneHandle(Smi::New(1));
+    }
+  }
+  return NULL;
+}
+
+
 AstNode* LoadIndexedNode::MakeAssignmentNode(AstNode* rhs) {
   return new StoreIndexedNode(token_pos(), array(), index_expr(),
                               rhs, super_class());
 }
 
 
 AstNode* StaticGetterNode::MakeAssignmentNode(AstNode* rhs) {
   const String& setter_name = String::Handle(Field::SetterName(field_name()));
 
   if (is_super_getter_) {
@@ skipping 96 matching lines @@
   if (result.IsError() || result.IsNull()) {
     // TODO(turnidge): We could get better error messages by returning
     // the Error object directly to the parser.  This will involve
     // replumbing all of the EvalConstExpr methods.
     return NULL;
   }
   return &Instance::ZoneHandle(Instance::Cast(result).raw());
 }
 
 }  // namespace dart