[flang] Missing diagnostic on incorrect KIND value of intrinsic `ACHAR`

[DanielCChen]

Consider the following case:

           integer :: k1

           k1 = kind(achar(88, 2))

END

2 is not a correct KIND value.
All ifort, gfortran and XLF issue an error message

[llvmbot]

@llvm/issue-subscribers-flang-frontend

Author: Daniel Chen (DanielCChen)

Details

Consider the following case: ``` integer :: k1

       k1 = kind(achar(88, 2))

END

2 is not a correct KIND value.
All ifort, gfortran and XLF issue an error message
</details>

[klausler]

CHARACTER(KIND=2) is supported by f18 and denotes UCS-16 (two-byte Unicode).

[DanielCChen]

@klausler Does it support CHARACTER(KIND=4) as well? We have a test case with that and also passes.

[klausler]

@klausler Does it support CHARACTER(KIND=4) as well? We have a test case with that and also passes.

Yes, 1, 2, and 4 are the supported CHARACTER kinds.