[cfe-dev] Keeping invalid AST nodes

[Vassil Vassilev]

On 11/5/12 6:18 AM, Erik Verbruggen wrote:
> When using libclang for syntax highlighting, I noticed that no AST nodes get built for e.g. invalid expressions. For example, in the following C++ code:
>
> int func(int i) {
>      int j = undefinedFunction(i) + i;
>      return j;
> }
>
> the whole initialisation for int j gets dropped, including the (somewhat) valid references to i. I understand that this is done to keep the AST valid after parsing, but an IDE or refactoring tools cannot help out with fixing the problem in that snippet. My question: is there some way to keep the invalid AST nodes, or is somebody already working on this?
Have you considered flagging the broken (invalid) nodes as dependent? 
There is a hook in clang::ExternalSemaSource:: LookupUnqualified 
<http://clang.llvm.org/doxygen/classclang_1_1ExternalSemaSource.html#a971a425e22c9ebbfb3a2c8deb032fc7f>, 
which gets called by clang just before complaining about an error and 
dropping the node. At that point I believe you can declare the name as 
dependent (which will lead to creating a broken AST) and continue 
compilation.

Does that make sense to you?

Vassil
>
> Regards,
> Erik.
>
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