Index: gcc/fortran/decl.c
===================================================================
--- gcc/fortran/decl.c	(revision 258727)
+++ gcc/fortran/decl.c	(working copy)
@@ -1245,16 +1245,27 @@ get_proc_name (const char *name, gfc_symbol **result, 
 		       "from a previous declaration",  name);
     }
 
-    if (sym && !sym->gfc_new
-	&& sym->attr.flavor != FL_UNKNOWN
-	&& sym->attr.referenced == 0 && sym->attr.subroutine == 1
-	&& gfc_state_stack->state == COMP_CONTAINS
-	&& gfc_state_stack->previous->state == COMP_SUBROUTINE)
-    {
-	gfc_error_now ("Procedure %qs at %C is already defined at %L",
-		       name, &sym->declared_at);
-    }
+  /* C1246 (R1225) MODULE shall appear only in the function-stmt or
+     subroutine-stmt of a module subprogram or of a nonabstract interface
+     body that is declared in the scoping unit of a module or submodule.  */
+  if (sym->attr.external
+      && (sym->attr.subroutine || sym->attr.function)
+      && sym->attr.if_source == IFSRC_IFBODY
+      && !current_attr.module_procedure
+      && sym->attr.proc == PROC_MODULE
+      && gfc_state_stack->state == COMP_CONTAINS)
+    gfc_error_now ("Procedure %qs defined in interface body at %L "
+		   "clashes with internal procedure defined at %C",
+		    name, &sym->declared_at);
 
+  if (sym && !sym->gfc_new
+      && sym->attr.flavor != FL_UNKNOWN
+      && sym->attr.referenced == 0 && sym->attr.subroutine == 1
+      && gfc_state_stack->state == COMP_CONTAINS
+      && gfc_state_stack->previous->state == COMP_SUBROUTINE)
+    gfc_error_now ("Procedure %qs at %C is already defined at %L",
+		    name, &sym->declared_at);
+
   if (gfc_current_ns->parent == NULL || *result == NULL)
     return rc;
 
Index: gcc/testsuite/gfortran.dg/interface_42.f90
===================================================================
--- gcc/testsuite/gfortran.dg/interface_42.f90	(nonexistent)
+++ gcc/testsuite/gfortran.dg/interface_42.f90	(working copy)
@@ -0,0 +1,24 @@
+! { dg-do compile }
+! { dg-options "-fmax-errors=1" }
+! PR fortran/84922
+! Code contributed by William Clodius, but simplified by me.
+module copy
+
+   interface
+      module subroutine foo_da(da, copy) ! { dg-error "(1)" }
+         integer, intent(in) :: da(:)
+         integer, allocatable, intent(out) :: copy(:)
+      end subroutine foo_da
+   end interface
+
+   contains
+
+      subroutine foo_da(da, copy) ! { dg-error "defined in interface body" }
+         integer, intent(in) :: da(:)
+         integer, allocatable, intent(out) :: copy(:)
+         allocate( copy( size(da) ) )
+         copy = da
+      end subroutine foo_da
+
+end module copy
+{ dg-prune-output "compilation terminated" }
Index: gcc/testsuite/gfortran.dg/interface_43.f90
===================================================================
--- gcc/testsuite/gfortran.dg/interface_43.f90	(nonexistent)
+++ gcc/testsuite/gfortran.dg/interface_43.f90	(working copy)
@@ -0,0 +1,25 @@
+! { dg-do compile }
+! PR fortran/84922
+! This should compile without error.
+module foom
+
+   implicit none
+
+   interface foo
+      module procedure foo_sngl
+      module procedure foo_dble
+   end interface foo
+
+   contains
+
+      subroutine foo_sngl(n, f, g, h)
+         integer n
+         real f, g, h
+      end subroutine foo_sngl
+
+      subroutine foo_dble(n, f, g, h)
+         integer n
+         double precision f, g, h
+      end subroutine foo_dble
+
+end module foom