[Bug c++/94886] New: coroutines: ICE building folly, in transform_local_var_uses, at cp/coroutines.cc:1908

[iains at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94886

            Bug ID: 94886
           Summary: coroutines: ICE building folly, in
                    transform_local_var_uses, at cp/coroutines.cc:1908
           Product: gcc
           Version: 10.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: iains at gcc dot gnu.org
  Target Milestone: ---

Created attachment 48424
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=48424&action=edit
fix under test

the code below should build but produces an ICE

this is because the range-based for generates three artificial variables that
need to be allocated to the coroutine frame but, when walking the BIND_EXR that
contains these, the DECL_INITIAL for one of them refers to an entry appearing
later, which means that the frame entry hasn't been allocated when that INITIAL
is walked.

The solution is to defer walking the DECL_INITIAL/SIZE etc. until all the
BIND_EXPR vars have been processed.

coro1
my_coro ()
{
  const std::array<int, 5> expectedValues = {{0, 3, 1, 4, 2}};

  for (int expectedValue : expectedValues) {
    co_yield expectedValue;
  }
}