Rewrite parameter uses when rewriting function types.

[dtarditi]

In checked scopes , we rewrite function types with bounds-safe interfaces to be fully checked. We need to rewrite declarations of parameters and uses of parameters that have bounds-safe interfaces.

The following example illustrates the problem. We define 3 C typedefs:

1. one that defines a function pointer with a bounds-safe interface on a parameter.
2. one that defines the bounds-safe interface type the first one.
3. one that defined a fully checked version.

We define a function that returns 1, with a bounds-safe interface of 2. We try to assign the result to 3 and get a compiler error that makes no sense on the face of it:

#include <stdchecked.h>

#pragma CHECKED_SCOPE ON

typedef int (*callback_fn3)(int *a : count(n), int n);
typedef  ptr<int (int *a : bounds(a, a + n), int n)> bsi_callback_fn3;
typedef  ptr<int (array_ptr<int> a : bounds(a, a + n), int n)> checked_callback_fn3;

checked callback_fn3 return_function_pointer(void) : itype(bsi_callback_fn3);

checked void test_function_pointer_return(void) {
  checked_callback_fn3 fn = 0;
  fn = return_function_pointer();
}

Here is the compiler error:

tmp.c:13:6: error: assigning to 'checked_callback_fn3' (aka '_Ptr<int (_Array_ptr<int> : bounds(arg #0, arg #0 + arg
      #1), int)>') from incompatible type '_Ptr<int (_Array_ptr<int> : bounds(arg #0, arg #0 + arg #1), int)>'
  fn = return_function_pointer();
     ^ ~~~~~~~~~~~~~~~~~~~~~~~~~
1 error generated.

My guess is that the uses of a in bsi_callback_fn3 weren't rewritten, causing the types to differ for reasons that aren't apparent in the error message.

[dtarditi]

Fixed by PR #576.