[cfe-dev] How to change typedef in AST

[John McCall]

On Dec 22, 2012, at 8:15 PM, Jaymie Strecker <jstrecker at kosada.com> wrote:
> Is it possible to parse some code containing a typedef, then modify that typedef in the AST? For example, the input code contains `typedef int blah` and I want to change it to `typedef float blah`. 
> 
> I found some example code for traversing the AST, which I modified to visit each typedef declaration: 
> 
> 	bool VisitDecl(Decl *d) {
> 		d->dump();printf("\n");
> 		if (TypedefDecl::classof(d)) {
> 			TypedefDecl *td = static_cast<TypedefDecl *>(d);

The idiomatic way of writing this would be:
  if (TypedefDecl *td = dyn_cast<TypedefDecl>(d)) {
or (if you're not working on the compiler proper and you can use C++11 features):
  if (auto td = dyn_cast<TypedefDecl>(d)) {

That said, the AST is not designed to be mutable like this, which is why
TypedefDecl doesn't have a setter for the type.

John.
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