[Patch,Fortran] PR93309 – permit repeated 'implicit none(external)' in sub-scoping unit

[Tobias Burnus]

Using "implicit none" multiple times in a scoping unit is not permitted 
– and checked for.

However, using one in the parent name space and re-confirming it in the 
current name space is permitted – but was before rejected.

OK for the trunk?

Tobias

	PR fortran/93309
	* interface.c (gfc_procedure_use): Also check parent namespace for
	'implict none (external)'.
	* symbol.c (gfc_get_namespace): Don't set has_implicit_none_export
	to parent namespace's setting. 

	PR fortran/93309
	* gfortran.dg/external_implicit_none_2.f90: New.

diff --git a/gcc/fortran/interface.c b/gcc/fortran/interface.c
index c4a6882533b..5193ac4a314 100644
--- a/gcc/fortran/interface.c
+++ b/gcc/fortran/interface.c
@@ -3798,8 +3798,13 @@ gfc_procedure_use (gfc_symbol *sym, gfc_actual_arglist **ap, locus *where)
      explicitly declared at all if requested.  */
   if (sym->attr.if_source == IFSRC_UNKNOWN && !sym->attr.is_iso_c)
     {
+      bool has_implicit_none_export = false;
       implicit = true;
-      if (sym->ns->has_implicit_none_export && sym->attr.proc == PROC_UNKNOWN)
+      if (sym->attr.proc == PROC_UNKNOWN)
+	for (gfc_namespace *ns = sym->ns; ns; ns = ns->parent)
+	   if (ns->has_implicit_none_export)
+	     has_implicit_none_export = true;
+      if (has_implicit_none_export)
 	{
 	  const char *guessed
 	    = gfc_lookup_function_fuzzy (sym->name, sym->ns->sym_root);
diff --git a/gcc/fortran/symbol.c b/gcc/fortran/symbol.c
index 526f6c466b3..47b716454f2 100644
--- a/gcc/fortran/symbol.c
+++ b/gcc/fortran/symbol.c
@@ -2898,9 +2898,6 @@ gfc_get_namespace (gfc_namespace *parent, int parent_types)
 	}
     }
 
-  if (parent_types && ns->parent != NULL)
-    ns->has_implicit_none_export = ns->parent->has_implicit_none_export;
-
   ns->refs = 1;
 
   return ns;
diff --git a/gcc/testsuite/gfortran.dg/external_implicit_none_2.f90 b/gcc/testsuite/gfortran.dg/external_implicit_none_2.f90
new file mode 100644
index 00000000000..b2b1dd1e6d7
--- /dev/null
+++ b/gcc/testsuite/gfortran.dg/external_implicit_none_2.f90
@@ -0,0 +1,28 @@
+! { dg-do compile }
+!
+! PR fortran/93309
+!
+module m
+  implicit none(external)
+contains
+  subroutine s
+    implicit none(external) ! OK
+  end subroutine
+end module
+
+module m2
+  implicit none(external)
+contains
+  subroutine s
+    call foo(1)  ! { dg-error "not explicitly declared" }
+  end subroutine
+end module
+
+module m3
+  implicit none(external)
+contains
+  subroutine s
+    implicit none(external) ! OK
+    implicit none(external) ! { dg-error "Duplicate IMPLICIT NONE statement" }
+  end subroutine
+end module