Interpolated strings are never considered compile time const

runtime/vm/parser.h

 // 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.
 
 #ifndef VM_PARSER_H_
 #define VM_PARSER_H_
 
 #include "include/dart_api.h"
 
 #include "vm/ast.h"
@@ skipping 381 matching lines @@
 
   static SequenceNode* NodeAsSequenceNode(intptr_t sequence_pos,
                                           AstNode* node,
                                           LocalScope* scope);
 
   SequenceNode* MakeImplicitConstructor(const Function& func);
   AstNode* MakeStaticCall(const char* class_name,
                           const char* function_name,
                           ArgumentListNode* arguments);
   AstNode* MakeAssertCall(intptr_t begin, intptr_t end);
-  String& Interpolate(ArrayNode* strings);
 
   void CheckFunctionIsCallable(intptr_t token_index, const Function& function);
 
   const Script& script_;
   const TokenStream& tokens_;
   intptr_t token_index_;
   Token::Kind token_kind_;  // Cached token kind for the token_index_.
   Block* current_block_;
 
   // is_top_level_ is true if parsing the "top level" of a compilation unit,
@@ skipping 24 matching lines @@
   TryBlocks* try_blocks_list_;
 
   char error_msg_[kErrorBuflen];
 
   DISALLOW_COPY_AND_ASSIGN(Parser);
 };
 
 }  // namespace dart
 
 #endif  // VM_PARSER_H_