Erroneous syntax highlighting with subroutine names and preprocessor conditionals

[gnikit]

Describe the bug
end subroutine surrounded by preprocessor conditionals is erroneous

Screenshots

Code sample

  function blasmul_mm(A, B) result(C)
    !!< Use DGEMM to multiply A * B and get C.

    real, dimension(:, :), intent(in) :: A, B
    real, dimension(size(A, 1), size(B, 2)) :: C

    interface
#ifdef DOUBLEP
      SUBROUTINE DGEMM ( TRANSA, TRANSB, M, N, K, ALPHA, A, LDA, B, LDB, &
                         BETA, C, LDC )
#else
      SUBROUTINE SGEMM ( TRANSA, TRANSB, M, N, K, ALPHA, A, LDA, B, LDB, &
                         BETA, C, LDC )
#endif
      CHARACTER*1        TRANSA, TRANSB
      INTEGER            M, N, K, LDA, LDB, LDC
      REAL               ALPHA, BETA
      REAL               A( LDA, * ), B( LDB, * ), C( LDC, * )
#ifdef DOUBLEP
      END SUBROUTINE DGEMM
#else
      END SUBROUTINE SGEMM
#endif
    end interface

    assert(size(A, 2) == size(B, 1))

#ifdef DOUBLEP
    call DGEMM('N', 'N', size(A, 1), size(B, 2), size(A, 2), 1.0, A, size(A, 1), B, size(B, 1), &
               0.0, C, size(A, 1))
#else
    call SGEMM('N', 'N', size(A, 1), size(B, 2), size(A, 2), 1.0, A, size(A, 1), B, size(B, 1), &
               0.0, C, size(A, 1))
#endif 
  end function blasmul_mm

Fortran Form
Free form (F90+)

Build info (please complete the following information):

• OS: Linux x64
• Extension Version :2.5.0 internal dev version
• Visual Studio Code Version: 1.63.0-insider

[gnikit]

This is a much more interesting "bug" than what it seems. Its root is that the regex responsible for opening the scopes matches the end of the match with the name of the subroutine (function, submodule, etc.) so it expects that inner scopes are closed first, followed by outer scopes, e.g.

subroutine scope_1()
  subroutine scope_2()
    subroutine scope_3()
    end subroutine scope_3
  end subroutine scope_2
end subroutine scope_1

However, when preprocessor directives are used the order is upsetted and it no longer makes sense to close the scopes in the same order

subroutine scope_1()
#ifdef DEF
  subroutine scope_2()
#else
  subroutine scope_3()
#endif

#ifdef DEF
  end subroutine scope_2()
#else
  end subroutine scope_3()
#endif
end subroutine scope_1

Now scope 2 and scope 3 are on the same level since they are guarded by a preproc conditional.

Solution

I think it is reasonable to expect our grammar not being responsible for catching coding errors such as using the wrong subroutine,function, etc. when closing a scope. I will edit the scopes to exit upon a C++ variable name (names can be preprocessor macros)