Tests: Add Fortran submodule tests

Co-Author: Damian Rouson <damian@sourceryinstitute.org>
Issue: #16234

Tests/CMakeLists.txt

@@ -3109,6 +3109,7 @@ ${CMake_BINARY_DIR}/bin/cmake -DDIR=dev -P ${CMake_SOURCE_DIR}/Utilities/Release
         --build-project FortranModules
         --build-options ${build_options}
           -DCMake_TEST_NESTED_MAKE_PROGRAM:FILEPATH=${CMake_TEST_EXPLICIT_MAKE_PROGRAM}
+          -DCMake_TEST_Fortran_SUBMODULES:BOOL=${CMake_TEST_Fortran_SUBMODULES}
         )
       list(APPEND TEST_BUILD_DIRS "${CMake_BINARY_DIR}/Tests/FortranModules")
     endif()

Tests/FortranModules/CMakeLists.txt

@@ -5,6 +5,33 @@ if(NOT DEFINED CMake_TEST_NESTED_MAKE_PROGRAM AND NOT CMAKE_GENERATOR MATCHES "V
   set(CMake_TEST_NESTED_MAKE_PROGRAM "${CMAKE_MAKE_PROGRAM}")
 endif()
 
+if("x${CMake_TEST_Fortran_SUBMODULES}" STREQUAL "x"
+    AND NOT CMAKE_VERSION VERSION_LESS 3.6.20160923 # for CheckFortranSourceCompiles SRC_EXT
+    )
+  include(CheckFortranSourceCompiles)
+  CHECK_Fortran_SOURCE_COMPILES([[
+module parent
+  interface
+    module function id(x)
+       real, intent(in) :: x
+       real :: id
+    end function id
+  end interface
+end module parent
+submodule ( parent ) child
+contains
+  module procedure id
+    f = x
+  end procedure id
+end submodule child
+program main
+end program
+]] HAVE_SUBMODULES SRC_EXT F90)
+  set(CMake_TEST_Fortran_SUBMODULES ${HAVE_SUBMODULES})
+elseif(CMake_TEST_Fortran_SUBMODULES)
+  message(STATUS "Enabling Fortran submodule tests by explicit request.")
+endif()
+
 add_executable(test_module
   test_module_main.f90
   test_module_implementation.f90
@@ -76,3 +103,7 @@ endif()
 add_subdirectory(Library)
 add_subdirectory(Subdir)
 add_subdirectory(Executable)
+
+if(CMake_TEST_Fortran_SUBMODULES)
+  add_subdirectory(Submodules)
+endif()

Tests/FortranModules/Submodules/CMakeLists.txt

+add_executable(submod main.f90 provide.f90)

Tests/FortranModules/Submodules/main.f90

+program main
+  use parent, only : child_function,grandchild_subroutine
+  implicit none
+  if (child_function()) call grandchild_subroutine
+end program

Tests/FortranModules/Submodules/provide.f90

+! The program units in this file consist of a
+! module/submodule tree represented by the following
+! graph:
+!
+!        parent
+!          |
+!         / \
+!        /   \
+!    child   sibling
+!      |
+!  grandchild
+!
+! where the parent node is a module and all other
+! nodes are submodules.
+
+module parent
+  implicit none
+
+  interface
+
+    ! Test Fortran 2008 "module function" syntax
+    module function child_function() result(child_stuff)
+      logical :: child_stuff
+    end function
+
+    ! Test Fortran 2008 "module subroutine" syntax
+    module subroutine grandchild_subroutine()
+    end subroutine
+
+  end interface
+
+end module parent
+
+! Test the notation for a 1st-generation direct
+! descendant of a parent module
+submodule ( parent ) child
+  implicit none
+contains
+  module function child_function() result(child_stuff)
+    logical :: child_stuff
+    child_stuff=.true.
+  end function
+end submodule child
+
+! Empty submodule for checking disambiguation of
+! nodes at the same vertical level in the tree
+submodule ( parent ) sibling
+end submodule sibling
+
+! Test the notation for an Nth-generation descendant
+! for N>1, which necessitates the colon.
+submodule ( parent : child ) grandchild
+contains
+  module subroutine grandchild_subroutine()
+    print *,"Test passed."
+  end subroutine
+end submodule grandchild