objc++: type/expr tsubst conflation [PR111920]

After r14-4796-g3e3d73ed5e85e7, tsubst_copy_and_build (now named
tsubst_expr) no longer dispatches to tsubst for type trees, and
callers have to do it themselves if appropriate.  This patch makes
some overlooked adjustments to Objective-C++-specific code paths.

	PR objc++/111920

gcc/cp/ChangeLog:

	* pt.cc (tsubst_expr) <case AT_ENCODE_EXPR>: Use tsubst instead
	of tsubst_expr.

gcc/objcp/ChangeLog:

	* objcp-lang.cc (objcp_tsubst_expr) <case CLASS_REFERENCE_EXPR>:
	Use tsubst instead of tsubst_expr for type operands.

Author: Patrick Palka

gcc/cp/pt.cc

@@ -20261,7 +20261,7 @@ tsubst_expr (tree t, tree args, tsubst_flags_t complain, tree in_decl)
 	op1 = TREE_OPERAND (t, 0);
 	++cp_unevaluated_operand;
 	++c_inhibit_evaluation_warnings;
-	op1 = tsubst_expr (op1, args, complain, in_decl);
+	op1 = tsubst (op1, args, complain, in_decl);
 	--cp_unevaluated_operand;
 	--c_inhibit_evaluation_warnings;
 	RETURN (objc_build_encode_expr (op1));

gcc/objcp/objcp-lang.cc

@@ -66,8 +66,14 @@ objcp_tsubst_expr (tree t, tree args, tsubst_flags_t complain, tree in_decl)
 	 RECURSE (TREE_OPERAND (t, 2)), NULL);
 
     case CLASS_REFERENCE_EXPR:
-      return objc_get_class_reference
-	(RECURSE (TREE_OPERAND (t, 0)));
+      {
+	tree ident = TREE_OPERAND (t, 0);
+	if (TYPE_P (ident))
+	  ident = tsubst (ident, args, complain, in_decl);
+	else
+	  ident = RECURSE (ident);
+	return objc_get_class_reference (ident);
+      }
 
     default:
       break;