Inlining, nested functions, and VLAs

[Richard Kenner]

This comes in with an ICE for the ACATS test c61008a.  This was complex and
took quite a while to understand, but here's the gist of the situation:

Suppose we have a function F with a nested function Q.  Q has one argument,
which we'll call P, of type T.  But T depends on some variables in F and F
contains a call to Q, with, say, value V.

Now F gets inlined and let's look at handling of the Q (V) call.  V has type
T, but T depends on variables in F and so *does* get remapped.  However, we
haven't remapped the PARM_DECL in Q, so we are making a call to Q with
mismatched types.  This causes a subsequent ICE in fold_convert when we try
to inline Q.

It seems to me that the right way to inline this is to make a copy of Q
remapping it's argument types with respect to F, but I don't think that makes
sense.

So I think the alternative is not to inline a function if it has nested
functions whose argument types depend on variables in that function.  Does
that seem right?  (Note that I think we have to do this recursively because Q
might have normal args but have a nested function Z with an arg that depended
on variables in F.)  If we do this, what's the best way to look for the
nested functions, using cgraph?