[clang] [Clang][Sema] Reject array prvalue operands (PR #140702)

[Aaron Ballman via cfe-commits]

AaronBallman wrote:

> > Is this going to break behavior in C?
> 
> Array **prvalues** is C++11+ exclusive thing. Compound literals are lvalues in C 

Ah, good point, I wasn't remembering that C and C++ are different in how they handle compound literals. And you can return a pointer to an array in C, but that's still an lvalue.

> Anyway, here is a check:
> 
> ```shell
> $ build/bin/clang -fsyntax-only test.c
> test.c:2:3: warning: expression result unused [-Wunused-value]
>     2 |   *((int []){ 1, 2, 3});
>       |   ^~~~~~~~~~~~~~~~~~~~~
> test.c:3:24: warning: expression result unused [-Wunused-value]
>     3 |   ((int []){ 1, 2, 3}) + 0;
>       |   ~~~~~~~~~~~~~~~~~~~~ ^ ~
> 2 warnings generated.
> ```

Thank you!

https://github.com/llvm/llvm-project/pull/140702