[flang] Fix for flang-compiler/f18#694 - Unexpected error when compiling submodule

Incorporated all review comments and updated the test case.

Change-Id: I03939bfc705cc5319a0b7da3305026b8403b8edc

Original-commit: flang-compiler/f18@010da4228e
Reviewed-on: https://github.com/flang-compiler/f18/pull/817
Tree-same-pre-rewrite: false

flang/lib/semantics/resolve-names.cc

@@ -2802,23 +2802,11 @@ bool SubprogramVisitor::BeginMpSubprogram(const parser::Name &name) {
 }
 
 // A subprogram declared with SUBROUTINE or function
-// If the subprogram is not in interface block, check if its declared as separate 
-// module procedures
 bool SubprogramVisitor::BeginSubprogram(
     const parser::Name &name, Symbol::Flag subpFlag, bool hasModulePrefix) {
-  bool isSeparateModuleProc = false;
-  // Check if Subprogram has Module Prefix and Subprogram is not inside Interface Block 
   if (hasModulePrefix && !inInterfaceBlock()) {
-    // Check if the Subprogram is declared as separate module procedures
-    auto *symbol{FindSymbol(name)};
-    if (symbol && symbol->has<SubprogramNameDetails>()) {
-      symbol = FindSymbol(currScope().parent(), name);
-    }
-    if (symbol)
-      isSeparateModuleProc = symbol->IsSeparateModuleProc();
-
-    // Issue error: Subprogram is not declared as separate module procedure
-    if (!isSeparateModuleProc) {
+    auto *symbol{FindSymbol(currScope().parent(), name)};
+    if (!symbol || !symbol->IsSeparateModuleProc()) {
       Say(name, "'%s' was not declared a separate module procedure"_err_en_US);
       return false;
     }

flang/test/semantics/CMakeLists.txt

@@ -186,7 +186,7 @@ set(ERROR_TESTS
   call13.f90
   call14.f90
   misc-declarations.f90
-  separate_module_procs_2.f90
+  separate-module-procs.f90
 )
 
 # These test files have expected symbols in the source

flang/test/semantics/separate-module-procs.f90

@@ -0,0 +1,115 @@
+!===-- separate-module-procs-2.f90 - Test separate module procedure ---------===
+!
+! Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+! See https://llvm.org/LICENSE.txt for license information.
+! SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+!
+!===-------------------------------------------------------------------------===
+
+! case 1: ma_create_new_fun' was not declared a separate module procedure
+module m1
+  integer :: i
+  interface ma
+    module function ma_create_fun( ) result(this)
+      integer this
+    end function
+  end interface
+end module
+
+submodule (m1) ma_submodule
+  integer :: j
+  contains
+  module function ma_create_fun() result(this)
+    integer this
+    i = 1
+    j = 2
+  end function
+
+  !ERROR: 'ma_create_new_fun' was not declared a separate module procedure
+  module function ma_create_new_fun() result(this)
+    integer :: this
+    i = 2
+    j = 1
+    print *, "Hello"
+  end function
+end submodule
+
+! case 2: 'mb_create_new_sub' was not declared a separate module procedure
+module m2
+  integer :: i
+  interface mb
+    module subroutine  mb_create_sub
+    end subroutine mb_create_sub
+  end interface
+end module
+
+submodule (m2) mb_submodule
+  integer :: j
+  contains
+  module subroutine  mb_create_sub
+    integer this
+    i = 1
+    j = 2
+  end subroutine mb_create_sub
+
+  !ERROR: 'mb_create_new_sub' was not declared a separate module procedure
+  module SUBROUTINE  mb_create_new_sub() 
+    integer :: this
+    i = 2
+    j = 1
+  end SUBROUTINE mb_create_new_sub
+end submodule
+
+! case 3: separate module procedure without module prefix
+module m3
+  interface mc
+    function mc_create( ) result(this)
+      integer :: this
+    end function
+  end interface
+end module
+
+submodule (m3) mc_submodule
+  contains
+  !ERROR: 'mc_create' was not declared a separate module procedure
+  module function mc_create() result(this)
+    integer :: this
+  end function
+end submodule
+
+! case 4: Submodule having separate module procedure rather than a module
+module m4
+  interface
+    real module function func1()   ! module procedure interface body for func1
+    end function
+  end interface
+end module
+
+submodule (m4) m4sub
+  interface
+    module function func2(b)       ! module procedure interface body for func2
+      integer :: b
+      integer :: func2
+    end function
+
+    real module function func3()   ! module procedure interface body for func3
+    end function
+  end interface
+  contains
+    real module function func1()   ! implementation of func1 declared in m4
+      func1 = 20
+    end function
+end submodule
+
+submodule (m4:m4sub) m4sub2
+  contains
+    module function func2(b)       ! implementation of func2 declared in m4sub
+      integer :: b
+      integer :: func2
+      func2 = b
+    end function
+
+    real module function func3()   ! implementation of func3 declared in m4sub
+      func3 = 20
+    end function
+end submodule