[clang] [Sema] Add check for bitfield assignments to integral types (PR #69049)

[Aaron Ballman via cfe-commits]

AaronBallman wrote:

It looks like these changes surfaced an existing bug with `GetExprRange()`: https://github.com/llvm/llvm-project/blob/4554eac5d4fd7c7a02f947767fc25bd27f004106/clang/lib/Sema/SemaChecking.cpp#L13734

`getSourceExpr()` can return nullptr:

https://github.com/llvm/llvm-project/blob/4554eac5d4fd7c7a02f947767fc25bd27f004106/clang/include/clang/AST/ASTNodeTraverser.h#L735
https://github.com/llvm/llvm-project/blob/4554eac5d4fd7c7a02f947767fc25bd27f004106/clang/lib/AST/ComputeDependence.cpp#L30
https://github.com/llvm/llvm-project/blob/4554eac5d4fd7c7a02f947767fc25bd27f004106/clang/lib/AST/Expr.cpp#L3919

Note: I did not investigate whether the source expression *should* be null in this case, just verified that it can be and is in this code example.

https://github.com/llvm/llvm-project/pull/69049