Index: gcc/fortran/primary.c
===================================================================
*** gcc/fortran/primary.c	(révision 116697)
--- gcc/fortran/primary.c	(copie de travail)
*************** match_variable (gfc_expr ** result, int 
*** 2282,2287 ****
--- 2285,2301 ----
    gfc_expr *expr;
    locus where;
    match m;
+ 
+   /* Since nothing has any business being an lvalue in a module
+      specification block, an interface block or a contains section,
+      we force the changed_symbols mechanism to work by setting
+      host_flag to 0. This prevents valid symbols that have the name
+      of keywords, such as 'end', being turned into variables by
+      failed matching to assignments for, eg., END INTERFACE.  */
+   if (gfc_current_state () == COMP_MODULE
+       || gfc_current_state () == COMP_INTERFACE
+       || gfc_current_state () == COMP_CONTAINS)
+     host_flag = 0;
  
    m = gfc_match_sym_tree (&st, host_flag);
    if (m != MATCH_YES)
Index: gcc/testsuite/gfortran.dg/keyword_symbol_1.f90
===================================================================
*** gcc/testsuite/gfortran.dg/keyword_symbol_1.f90	(révision 0)
--- gcc/testsuite/gfortran.dg/keyword_symbol_1.f90	(révision 0)
***************
*** 0 ****
--- 1,57 ----
+ ! ' dg-do compile }
+ ! This tests the fix for PR28526, in which a public interface named
+ ! 'end' would be treated as a variable because the matcher tried
+ ! 'END INTERFACE' as an assignment and left the symbol modified in
+ ! failing. The various pitfalls that were encountered in developing
+ ! the fix are checked here.
+ !
+ ! Contributed by Paul Thomas  <pault@gcc.gnu.org>
+ !
+ module blahblah
+   public function, end
+ 
+ ! The original PR from Yusuke IGUCHI <iguchi@coral.t.u-tokyo.ac.jp>
+   interface end
+     module procedure foo1
+   end interface
+ 
+ ! A contribution to the PR from Tobias Schlueter  <tobi@gcc.gnu.org>
+   interface function
+      module procedure foo2 ! { dg-error "is neither function nor" }
+   end interface
+ 
+   interface function
+      module procedure foo3
+   end interface
+ 
+   interface
+     function foo4 ()
+       real foo4
+       x = 1.0          ! { dg-error "in MODULE" }
+     end function foo4
+   end interface
+ 
+   interface
+     x = 2.0            ! { dg-error "in INTERFACE block" }
+     function foo5 ()
+       real foo5
+     end function foo5
+   end interface
+ 
+   x = 3.0              ! { dg-error "in MODULE" }
+ 
+ contains
+ 
+   subroutine foo1
+   end subroutine foo1
+ 
+   function foo2        ! { dg-error "Expected formal argument list" }
+     foo2 = 0           ! { dg-error "already been host associated" }
+   end function foo2    ! { dg-error "Expecting END MODULE" }
+ 
+   function foo3 ()
+     real foo3
+   end function foo3
+ 
+   x = 4.0              ! { dg-error "in CONTAINS section" }
+ end module blahblah