Clang checker: 'beginning of function' hook?

I’m working on my first Clang checker, and I would would like to setup initial state for the symbols referred to by a function’s parameters. This is an intraprodedural analysis, and I want a clean slate for the analysis of each function body, with some initial conditions determined by annotations in the comments.

I’m not sure which Checker callback is appropriate for this. checkASTDecl seems promising, but I don’t get a CheckerContext in that callback.

Any thoughts?