C++ is the worst possible language in this case. Its complexity is immense and the C preprocessor layered on top makes a straight mapping between code and synta

C++ is the worst possible language in this case. Its complexity is immense and the C preprocessor layered on top makes a straight mapping between code and syntax tree impossible to achieve in general. Simpler languages like Java or C# (at least relative to C++) allow such syntax tree based tools to reach much, much further. I do believe that it should be possible to build an editor for "nice" languages of that kind that is entirely based on editing the syntax tree.