Type-checking error leads to compiler crash.

[dtarditi]

The following snippet of incorrect code causes the debug build of the compiler to assert:

struct S {
  int arr _Checked[10];
  int data;
};

void passing_test_2(int i) {
  struct S s = { { 9, 8, 7, 6, 5, 4, 3, 2, 1, 0 }, 10 };
  s->arr[i] = 1;
}

Here is the output and the line of the assert. The compiler is crashing during the checking of bounds declarations.

D:\test>%clang% -fcheckedc-extension tmp.c
tmp.c:8:4: error: member reference type 'struct S' is not a pointer; did you mean to use '.'?
  s->arr[i] = 1;
  ~^~
   .
Assertion failed: E->isLValue(), file D:\llvm\tools\clang\lib\Sema\SemaBounds.cpp, line 402

The assert is double-checking that an expression is an lvalue as expected.

[dtarditi]

There are two things to determine here:

1. This IR should be invalid, so I am surprised that there is a node in the AST for it that bounds checking sees.. It could be that IR can be "valid IR" but be type incorrect. Confirm that bounds checking really does receive invalid IR (by dumping the AST of a normal C program with the same error.
2. Decide what to do about invalid IR in this situation. Can we easily determine that the IR has a type error and avoid processing it? Or do we need to simply change the assert to a runtime check and return Bounds(None).