[C++ PATCH] Fix C++ ICE due to CONVERT_EXPR of error_mark_node (PR c++/84662)

[Jakub Jelinek]

Hi!

Various spots in the FE don't really like if error_mark_node is deeply
embedded in expression operands, in this case tsubst_copy_and_build
creates CONVERT_EXPR <some_type, error_mark_node> on which
is_bitfield_expr_with_lowered_type ICEs.

Fixed by just returning error_mark_node (various other spots in
tsubst_copy_and_build do the same).

While at it, I've discovered 3 spots in the function which were using
return instead of RETURN and thus wouldn't properly restore input_location;
I wonder if eventually this shouldn't be done through some sentinel class
where the destructor would restore input_location and just use return
instead of RETURN.

Anyway, bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?

2018-03-02  <ja...@redhat.com>

        PR c++/84662
        * pt.c (tsubst_copy_and_build) <case TEMPLATE_ID_EXPR>: Use
        RETURN instead of return.
        <case POINTER_PLUS_EXPR>: Likewise.
        <case CONVERT_EXPR>: If op0 is error_mark_node, just return
        it instead of wrapping it into CONVERT_EXPR.

        * g++.dg/cpp1y/pr84662.C: New test.

--- gcc/cp/pt.c.jj      2018-03-02 00:15:54.097781049 +0100
+++ gcc/cp/pt.c 2018-03-02 12:30:38.127232430 +0100
@@ -17318,14 +17318,14 @@ tsubst_copy_and_build (tree t,
        if (targs)
          targs = tsubst_template_args (targs, args, complain, in_decl);
        if (targs == error_mark_node)
-         return error_mark_node;
+         RETURN (error_mark_node);
 
        if (TREE_CODE (templ) == SCOPE_REF)
          {
            tree name = TREE_OPERAND (templ, 1);
            tree tid = lookup_template_function (name, targs);
            TREE_OPERAND (templ, 1) = tid;
-           return templ;
+           RETURN (templ);
          }
 
        if (variable_template_p (templ))
@@ -17401,6 +17401,8 @@ tsubst_copy_and_build (tree t,
       {
        tree type = tsubst (TREE_TYPE (t), args, complain, in_decl);
        tree op0 = RECUR (TREE_OPERAND (t, 0));
+       if (op0 == error_mark_node)
+         RETURN (error_mark_node);
        RETURN (build1 (CONVERT_EXPR, type, op0));
       }
 
@@ -17549,7 +17551,7 @@ tsubst_copy_and_build (tree t,
       {
        tree op0 = RECUR (TREE_OPERAND (t, 0));
        tree op1 = RECUR (TREE_OPERAND (t, 1));
-       return fold_build_pointer_plus (op0, op1);
+       RETURN (fold_build_pointer_plus (op0, op1));
       }
 
     case SCOPE_REF:
--- gcc/testsuite/g++.dg/cpp1y/pr84662.C.jj     2018-03-02 12:32:23.012209212 
+0100
+++ gcc/testsuite/g++.dg/cpp1y/pr84662.C        2018-03-02 12:32:59.159201202 
+0100
@@ -0,0 +1,6 @@
+// PR c++/84662
+// { dg-do compile { target c++14 } }
+// { dg-options "" }
+
+double b;
+a (__attribute__((c (0 && int() - ([] {} && b) || auto))));    // { dg-error 
"expected constructor, destructor, or type conversion before" }

        Jakub