Re: [PATCH] c++: fix tf_decltype manipulation for COMPOUND_EXPR

[Jason Merrill <jason@redhat.com>]

On 11/7/23 10:08, Patrick Palka wrote:
> bootstrapped and regtested on x86_64-pc-linxu-gnu, does this look OK for trunk?
> 
> -- >8 --
> 
> In the COMPOUND_EXPR case of tsubst_expr, we were redundantly clearing
> the tf_decltype flag when substituting the LHS and also neglecting to
> propagate it when substituting the RHS.  This patch corrects this flag
> manipulation, which allows us to accept the below testcase.
> 
> gcc/cp/ChangeLog:
> 
> 	* pt.cc (tsubst_expr) <case COMPOUND_EXPR>: Don't redundantly
> 	clear tf_decltype when substituting the LHS.  Propagate
> 	tf_decltype when substituting the RHS.
> 
> gcc/testsuite/ChangeLog:
> 
> 	* g++.dg/cpp0x/decltype-call7.C: New test.
> ---
>   gcc/cp/pt.cc                                | 9 ++++-----
>   gcc/testsuite/g++.dg/cpp0x/decltype-call7.C | 9 +++++++++
>   2 files changed, 13 insertions(+), 5 deletions(-)
>   create mode 100644 gcc/testsuite/g++.dg/cpp0x/decltype-call7.C
> 
> diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc
> index 521749df525..5f879287a58 100644
> --- a/gcc/cp/pt.cc
> +++ b/gcc/cp/pt.cc
> @@ -20382,11 +20382,10 @@ tsubst_expr (tree t, tree args, tsubst_flags_t complain, tree in_decl)
>   
>       case COMPOUND_EXPR:
>         {
> -	tree op0 = tsubst_expr (TREE_OPERAND (t, 0), args,
> -				complain & ~tf_decltype, in_decl);
> -	RETURN (build_x_compound_expr (EXPR_LOCATION (t),
> -				       op0,
> -				       RECUR (TREE_OPERAND (t, 1)),
> +	tree op0 = RECUR (TREE_OPERAND (t, 0));
> +	tree op1 = tsubst_expr (TREE_OPERAND (t, 1), args,
> +				complain|decltype_flag, in_decl);
> +	RETURN (build_x_compound_expr (EXPR_LOCATION (t), op0, op1,
>   				       templated_operator_saved_lookups (t),
>   				       complain|decltype_flag));

Hmm, passing decltype_flag to both op1 and the , is concerning.  Can you 
add a test with overloaded operator, where the RHS is a class with a 
destructor?

Jason