Fortran: error recovery after invalid assumed type declaration

gcc/fortran/ChangeLog:

	PR fortran/104573
	* resolve.cc (resolve_structure_cons): Avoid NULL pointer
	dereference when there is no valid component.

gcc/testsuite/ChangeLog:

	PR fortran/104573
	* gfortran.dg/assumed_type_14.f90: New test.

gcc/fortran/resolve.cc

@@ -1288,15 +1288,19 @@ resolve_structure_cons (gfc_expr *expr, int init)
 	}
     }
 
-  cons = gfc_constructor_first (expr->value.constructor);
-
   /* A constructor may have references if it is the result of substituting a
      parameter variable.  In this case we just pull out the component we
      want.  */
   if (expr->ref)
     comp = expr->ref->u.c.sym->components;
-  else
+  else if ((expr->ts.type == BT_DERIVED || expr->ts.type == BT_CLASS
+	    || expr->ts.type == BT_UNION)
+	   && expr->ts.u.derived)
     comp = expr->ts.u.derived->components;
+  else
+    return false;
+
+  cons = gfc_constructor_first (expr->value.constructor);
 
   for (; comp && cons; comp = comp->next, cons = gfc_constructor_next (cons))
     {

gcc/testsuite/gfortran.dg/assumed_type_14.f90

@@ -0,0 +1,22 @@
+! { dg-do compile }
+! PR fortran/104573 - ICE in resolve_structure_cons
+! Contributed by G.Steinmetz
+! Contributed by M.Morin
+
+program p
+  type t
+  end type
+  type(*), parameter :: x = t() ! { dg-error "Assumed type of variable" }
+  print *, x
+end
+
+subroutine s
+  type t
+     integer :: a
+  end type
+  character(3), parameter :: x = t(2) ! { dg-error "Cannot convert" }
+  character(3), parameter :: y = x    ! { dg-error "Unclassifiable statement" }
+  print *, y
+end
+
+! { dg-prune-output "Cannot convert" }