Fortran: avoid several NULL pointer dereferences during error recovery

gcc/fortran/ChangeLog:

	PR fortran/102332
	* expr.c (gfc_get_variable_expr): Avoid NULL pointer dereferences
	during handling of errors with invalid uses of CLASS variables.
	* match.c (select_type_set_tmp): Likewise.
	* primary.c (gfc_match_varspec): Likewise.
	* resolve.c (resolve_variable): Likewise.
	(resolve_select_type): Likewise.

gcc/testsuite/ChangeLog:

	PR fortran/102332
	* gfortran.dg/pr102332.f90: New test.

gcc/fortran/expr.c

@@ -5166,7 +5166,8 @@ gfc_get_variable_expr (gfc_symtree *var)
 
   if (var->n.sym->attr.flavor != FL_PROCEDURE
       && ((var->n.sym->as != NULL && var->n.sym->ts.type != BT_CLASS)
-	   || (var->n.sym->ts.type == BT_CLASS && CLASS_DATA (var->n.sym)
+	   || (var->n.sym->ts.type == BT_CLASS && var->n.sym->ts.u.derived
+	       && CLASS_DATA (var->n.sym)
 	       && CLASS_DATA (var->n.sym)->as)))
     {
       e->rank = var->n.sym->ts.type == BT_CLASS

gcc/fortran/match.c

@@ -6363,7 +6363,8 @@ select_type_set_tmp (gfc_typespec *ts)
       sym = tmp->n.sym;
       gfc_add_type (sym, ts, NULL);
 
-      if (selector->ts.type == BT_CLASS && selector->attr.class_ok)
+      if (selector->ts.type == BT_CLASS && selector->attr.class_ok
+	  && selector->ts.u.derived && CLASS_DATA (selector))
 	{
 	  sym->attr.pointer
 		= CLASS_DATA (selector)->attr.class_pointer;

gcc/fortran/primary.c

@@ -2151,6 +2151,7 @@ gfc_match_varspec (gfc_expr *primary, int equiv_flag, bool sub_flag,
 	  && !(gfc_matching_procptr_assignment
 	       && sym->attr.flavor == FL_PROCEDURE))
       || (sym->ts.type == BT_CLASS && sym->attr.class_ok
+	  && sym->ts.u.derived && CLASS_DATA (sym)
 	  && (CLASS_DATA (sym)->attr.dimension
 	      || CLASS_DATA (sym)->attr.codimension)))
     {

gcc/fortran/resolve.c

@@ -5736,6 +5736,8 @@ resolve_variable (gfc_expr *e)
      can't be translated that way.  */
   if (sym->assoc && e->rank == 0 && e->ref && sym->ts.type == BT_CLASS
       && sym->assoc->target && sym->assoc->target->ts.type == BT_CLASS
+      && sym->assoc->target->ts.u.derived
+      && CLASS_DATA (sym->assoc->target)
       && CLASS_DATA (sym->assoc->target)->as)
     {
       gfc_ref *ref = e->ref;
@@ -5799,7 +5801,8 @@ resolve_variable (gfc_expr *e)
   /* Like above, but for class types, where the checking whether an array
      ref is present is more complicated.  Furthermore make sure not to add
      the full array ref to _vptr or _len refs.  */
-  if (sym->assoc && sym->ts.type == BT_CLASS
+  if (sym->assoc && sym->ts.type == BT_CLASS && sym->ts.u.derived
+      && CLASS_DATA (sym)
       && CLASS_DATA (sym)->attr.dimension
       && (e->ts.type != BT_DERIVED || !e->ts.u.derived->attr.vtype))
     {
@@ -9432,6 +9435,7 @@ resolve_select_type (gfc_code *code, gfc_namespace *old_ns)
 
       /* Check F03:C815.  */
       if ((c->ts.type == BT_DERIVED || c->ts.type == BT_CLASS)
+	  && selector_type
 	  && !selector_type->attr.unlimited_polymorphic
 	  && !gfc_type_is_extensible (c->ts.u.derived))
 	{
@@ -9442,7 +9446,8 @@ resolve_select_type (gfc_code *code, gfc_namespace *old_ns)
 	}
 
       /* Check F03:C816.  */
-      if (c->ts.type != BT_UNKNOWN && !selector_type->attr.unlimited_polymorphic
+      if (c->ts.type != BT_UNKNOWN
+	  && selector_type && !selector_type->attr.unlimited_polymorphic
 	  && ((c->ts.type != BT_DERIVED && c->ts.type != BT_CLASS)
 	      || !gfc_type_is_extension_of (selector_type, c->ts.u.derived)))
 	{

gcc/testsuite/gfortran.dg/pr102332.f90

@@ -0,0 +1,69 @@
+! { dg-do compile }
+! PR fortran/102332 - ICE in select_type_set_tmp
+! Contributed by G.Steinmetz
+
+program p
+  type t
+     real :: a, b
+  end type
+  class(t), allocatable :: x ! Valid
+  select type (y => x)
+  type is (t)
+     y%a = 0
+  end select
+end
+
+subroutine s0 (x)
+  type t
+     real :: a, b
+  end type
+  class(t) :: x ! Valid
+  select type (y => x)
+  type is (t)
+     y%a = 0
+  end select
+end
+
+subroutine s1
+  type t
+     real :: a, b
+  end type
+  class(t) :: x         ! { dg-error "must be dummy, allocatable or pointer" }
+  select type (y => x)
+  type is (t)
+     y%a = 0
+  end select
+end
+
+subroutine s3
+  type t
+     real :: a, b
+  end type
+  class(t) :: x         ! { dg-error "must be dummy, allocatable or pointer" }
+  select type (y => x)
+  class is (t)
+     y%a = 0
+  end select
+end
+
+subroutine s2
+  type t
+     real :: a, b
+  end type
+  class(t) :: x         ! { dg-error "must be dummy, allocatable or pointer" }
+  select type (y => x)
+  type default          ! { dg-error "Expected" }
+     y%a = 0
+  end select
+end
+
+subroutine s4
+  type t
+     real :: a, b
+  end type
+  class(t) :: x         ! { dg-error "must be dummy, allocatable or pointer" }
+  select type (y => x)
+  class default
+     y%a = 0
+  end select
+end