[flang] [llvm] [flang][folding] fix i(a)char folding regression (PR #155909)

[Eugene Epshteyn via llvm-commits]

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@@ -123,3 +123,12 @@ subroutine s4(ix)
   call s4(index3)
   call s4(index4) ! ok
 end
+
+subroutine ichar_tests()
+  integer, parameter :: a1 = ichar('B')
+  !Without -Wportability, the warning isn't emitted and the parameter is constant.
+  integer, parameter :: a2 = ichar('B ')
+  !ERROR: Character in intrinsic function ichar must have length one
+  !ERROR: Must be a constant value
+  integer, parameter :: a3 = ichar('')
+end subroutine
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eugeneepshteyn wrote:

I think github wants you to have extra end of line here

https://github.com/llvm/llvm-project/pull/155909