clang-format crashes on clang/test/Sema/attr-external-source-symbol.c

[owenca]

The minimum test case to reproduce the crash using the latest trunk version:

$ ls .clang-format
ls: .clang-format: No such file or directory
$ clang-format
int (^)() = ^ ()
  external_source_symbol() { //
  return 1;
};
Assertion failed: ((!TypeIsFinalized || T == Type) && "Please use overwriteFixedType to change a fixed type."), function setType, file FormatToken.h, line 351.
...

May be a duplicate of #54367.

[llvmbot]

@llvm/issue-subscribers-clang-format

[HazardyKnusperkeks]

Review https://reviews.llvm.org/D121596