2012-01-16  Tobias Burnus  <burnus@net-b.de>

	PR fortran/51809
	* class.c (gfc_find_derived_vtab): Mark __vtab and
	__def_init as FL_VARIABLE not as FL_PARAMETER.
	* expr.c (gfc_simplify_expr): Remove special
	handling of __vtab.
	* resolve.c (resolve_values): Ditto.
	* trans-decl.c (gfc_get_symbol_decl): Mark __vtab
	and __def_init as TREE_READONLY.

2012-01-16  Tobias Burnus  <burnus@net-b.de>

	PR fortran/51809
	* gfortran.dg/use_20.f90: New

diff --git a/gcc/fortran/class.c b/gcc/fortran/class.c
index a17fc0a..5e5de14 100644
--- a/gcc/fortran/class.c
+++ b/gcc/fortran/class.c
@@ -588,7 +588,7 @@ gfc_find_derived_vtab (gfc_symbol *derived)
 	{
 	  gfc_get_symbol (name, ns, &vtab);
 	  vtab->ts.type = BT_DERIVED;
-	  if (gfc_add_flavor (&vtab->attr, FL_PARAMETER, NULL,
+	  if (gfc_add_flavor (&vtab->attr, FL_VARIABLE, NULL,
 	                      &gfc_current_locus) == FAILURE)
 	    goto cleanup;
 	  vtab->attr.target = 1;
@@ -682,7 +682,7 @@ gfc_find_derived_vtab (gfc_symbol *derived)
 		  def_init->attr.target = 1;
 		  def_init->attr.save = SAVE_IMPLICIT;
 		  def_init->attr.access = ACCESS_PUBLIC;
-		  def_init->attr.flavor = FL_PARAMETER;
+		  def_init->attr.flavor = FL_VARIABLE;
 		  gfc_set_sym_referenced (def_init);
 		  def_init->ts.type = BT_DERIVED;
 		  def_init->ts.u.derived = derived;
diff --git a/gcc/fortran/expr.c b/gcc/fortran/expr.c
index a6baa68..8f04c73 100644
--- a/gcc/fortran/expr.c
+++ b/gcc/fortran/expr.c
@@ -1883,8 +1883,7 @@ gfc_simplify_expr (gfc_expr *p, int type)
 	 initialization expression, or we want a subsection.  */
       if (p->symtree->n.sym->attr.flavor == FL_PARAMETER
 	  && (gfc_init_expr_flag || p->ref
-	      || p->symtree->n.sym->value->expr_type != EXPR_ARRAY)
-	  && !p->symtree->n.sym->attr.vtab)
+	      || p->symtree->n.sym->value->expr_type != EXPR_ARRAY))
 	{
 	  if (simplify_parameter_variable (p, type) == FAILURE)
 	    return FAILURE;
diff --git a/gcc/fortran/resolve.c b/gcc/fortran/resolve.c
index 352d22d..c169b9e 100644
--- a/gcc/fortran/resolve.c
+++ b/gcc/fortran/resolve.c
@@ -9637,7 +9637,7 @@ resolve_values (gfc_symbol *sym)
 {
   gfc_try t;
 
-  if (sym->value == NULL || sym->attr.use_assoc)
+  if (sym->value == NULL)
     return;
 
   if (sym->value->expr_type == EXPR_STRUCTURE)
@@ -12195,7 +12195,7 @@ resolve_fl_parameter (gfc_symbol *sym)
   /* Make sure the types of derived parameters are consistent.  This
      type checking is deferred until resolution because the type may
      refer to a derived type from the host.  */
-  if (sym->ts.type == BT_DERIVED && sym->value
+  if (sym->ts.type == BT_DERIVED
       && !gfc_compare_types (&sym->ts, &sym->value->ts))
     {
       gfc_error ("Incompatible derived type in PARAMETER at %L",
diff --git a/gcc/fortran/trans-decl.c b/gcc/fortran/trans-decl.c
index 0761ebb..e8e54c7 100644
--- a/gcc/fortran/trans-decl.c
+++ b/gcc/fortran/trans-decl.c
@@ -1485,7 +1485,10 @@ gfc_get_symbol_decl (gfc_symbol * sym)
 
   if (sym->attr.vtab
       || (sym->name[0] == '_' && strncmp ("__def_init", sym->name, 10) == 0))
-    GFC_DECL_PUSH_TOPLEVEL (decl) = 1;
+    {
+      TREE_READONLY (decl) = 1;
+      GFC_DECL_PUSH_TOPLEVEL (decl) = 1;
+    }
 
   return decl;
 }
--- /dev/null	2012-01-16 08:28:57.351763035 +0100
+++ gcc/gcc/testsuite/gfortran.dg/use_20.f90	2012-01-16 18:41:44.000000000 +0100
@@ -0,0 +1,49 @@
+! { dg-do compile }
+!
+! PR fortran/51809
+!
+! Contributed by Kacper Kowalik
+!
+module foo
+   implicit none
+
+   type foo_t
+   contains
+      procedure :: func_foo
+   end type foo_t
+
+contains
+
+   subroutine func_foo(this)
+      implicit none
+      class(foo_t), intent(in) :: this
+   end subroutine func_foo
+
+end module foo
+
+module bar
+   use foo,   only: foo_t
+
+   implicit none
+
+   type, extends(foo_t) :: bar_t
+   contains
+      procedure :: func_bar
+   end type bar_t
+
+contains
+
+   subroutine func_bar(this)
+      use foo,    only: foo_t     ! <--- removing this line also fixes ICE
+      implicit none
+      class(bar_t), intent(in) :: this
+   end subroutine func_bar
+
+end module bar
+
+module merry_ICE
+   use foo,  only: foo_t   ! <------ change order to prevent ICE
+   use bar,  only: bar_t   ! <------ change order to prevent ICE
+end module merry_ICE
+
+! { dg-final { cleanup-modules "foo bar merry_ice" } }
