Fix broken type comparison assert

In implementing Jason's suggested direction for 93933, the compiler
exploded in a surprising way.  Turns out an assert had been passing
NULLS to comptypes, and therefore not checking what it intended.

Further comptypes, could silently accept such nulls under most
circumstances.

	* class.c (adjust_clone_args): Correct arg-checking assert.
	* typeck.c (comptypes): Assert not nulls.

gcc/cp/ChangeLog

+2020-02-27  Nathan Sidwell  <nathan@acm.org>
+
+	* class.c (adjust_clone_args): Correct arg-checking assert.
+	* typeck.c (comptypes): Assert not nulls.
+
 2020-02-26  Marek Polacek  <polacek@redhat.com>
 
 	PR c++/93789 - ICE with invalid array bounds.

gcc/cp/class.c

@@ -4900,8 +4900,8 @@ adjust_clone_args (tree decl)
 	      break;
 	    }
 
-	  gcc_assert (same_type_p (TREE_TYPE (decl_parms),
-				   TREE_TYPE (clone_parms)));
+	  gcc_checking_assert (same_type_p (TREE_VALUE (decl_parms),
+					    TREE_VALUE (clone_parms)));
 
 	  if (TREE_PURPOSE (decl_parms) && !TREE_PURPOSE (clone_parms))
 	    {

gcc/cp/typeck.c

@@ -1483,10 +1483,13 @@ structural_comptypes (tree t1, tree t2, int strict)
 bool
 comptypes (tree t1, tree t2, int strict)
 {
+  gcc_checking_assert (t1 && t2);
+
   if (strict == COMPARE_STRICT && comparing_specializations
       && (t1 != TYPE_CANONICAL (t1) || t2 != TYPE_CANONICAL (t2)))
     /* If comparing_specializations, treat dependent aliases as distinct.  */
     strict = COMPARE_STRUCTURAL;
+
   if (strict == COMPARE_STRICT)
     {
       if (t1 == t2)