[Flang] GENERIC INTERFACE: Incorrect diagnose when the proc-interface of a procedure pointer is a function that returns polymorphic pointer

[DanielCChen]

Consider the following code:

  MODULE M

    TYPE :: DT
      INTEGER :: ID
    END TYPE

    CONTAINS

    FUNCTION ModDt(Arg)
    TYPE(DT) :: Arg
    CLASS(DT), POINTER :: ModDt
    END FUNCTION

  END MODULE

  PROGRAM PtrAssignGen
  USE M
  IMPLICIT NONE

  INTERFACE ModDt
    MODULE PROCEDURE  ModDt
  END INTERFACE

  PROCEDURE(ModDt), POINTER :: ProcPtr

  END

Flang currently issues an error as

./t.f:21:5: error: A PROCEDURE statement is only allowed in a generic interface block
    MODULE PROCEDURE  ModDt
    ^^^^^^^^^^^^^^^^^^^^^^^

The code seems conforming to me. If I remove the generic name from the interface block, it compiles successfully.

[llvmbot]

@llvm/issue-subscribers-bug

Author: Daniel Chen (DanielCChen)

Consider the following code: ``` MODULE M

TYPE :: DT
  INTEGER :: ID
END TYPE

CONTAINS

FUNCTION ModDt(Arg)
TYPE(DT) :: Arg
CLASS(DT), POINTER :: ModDt
END FUNCTION

END MODULE

PROGRAM PtrAssignGen
USE M
IMPLICIT NONE

INTERFACE ModDt
MODULE PROCEDURE ModDt
END INTERFACE

PROCEDURE(ModDt), POINTER :: ProcPtr

END

Flang currently issues an error as

./t.f:21:5: error: A PROCEDURE statement is only allowed in a generic interface block
MODULE PROCEDURE ModDt
^^^^^^^^^^^^^^^^^^^^^^^

The code seems conforming to me. If I remove the generic name from the interface block, it compiles successfully. 
  
</details>

[llvmbot]

@llvm/issue-subscribers-flang-frontend

Author: Daniel Chen (DanielCChen)

Consider the following code: ``` MODULE M

TYPE :: DT
  INTEGER :: ID
END TYPE

CONTAINS

FUNCTION ModDt(Arg)
TYPE(DT) :: Arg
CLASS(DT), POINTER :: ModDt
END FUNCTION

END MODULE

PROGRAM PtrAssignGen
USE M
IMPLICIT NONE

INTERFACE ModDt
MODULE PROCEDURE ModDt
END INTERFACE

PROCEDURE(ModDt), POINTER :: ProcPtr

END

Flang currently issues an error as

./t.f:21:5: error: A PROCEDURE statement is only allowed in a generic interface block
MODULE PROCEDURE ModDt
^^^^^^^^^^^^^^^^^^^^^^^

The code seems conforming to me. If I remove the generic name from the interface block, it compiles successfully. 
  
</details>

[DanielCChen]

The test case in the issue compiles successfully now.
Just to confirm that PR #82837 fixed this issue.