[PATCH] D80603: add isAtPosition narrowing matcher for parmVarDecl

[Vy Nguyen via Phabricator via cfe-commits]

oontvoo added a comment.

In D80603#2061131 <https://reviews.llvm.org/D80603#2061131>, @aaron.ballman wrote:

> In D80603#2059122 <https://reviews.llvm.org/D80603#2059122>, @gribozavr2 wrote:
>
> > In D80603#2058019 <https://reviews.llvm.org/D80603#2058019>, @aaron.ballman wrote:
> >
> > > I'm sorry if I'm being dense, but `hasParameter`  traverses to the `ParmVarDecl`, so I'm not certain I understand why this new matcher is needed as a public matcher. It seems like you can already accomplish this without adding a second API to do effectively the same thing: `functionDecl(hasParameter(0, parmVarDecl().bind("param")))`, can't you?
> >
> >
> > It is syntax sugar, true. Note that the proposed matcher is a narrowing matcher for `parmVarDecl()`, while your suggestion is a narrowing matcher for `functionDecl()`, so it is not an entirely apples-to-apples comparison. Think about use cases like: `declRefExpr(to(parmVarDecl(at(...))))`. To rewrite that with `hasParameter()`, we have to use `hasAncestor` to find the `functionDecl` first, and then compare the AST node pointers. So while it is possible to express this proposed operation today, it requires a complex matcher for such a conceptually simple operation.
>
>
> Thank you, that clarifies the need nicely for me!
>
> Is there a reason we want to support blocks but not lambdas?


Yes, the implementation does support lambdas

> Also, you need to update Registry.cpp to add this to the list of dynamic matchers.

Done


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