https://gcc.gnu.org/bugzilla/show_bug.cgi?id=83035
--- Comment #2 from CVS Commits ---
The master branch has been updated by Patrick Palka :
https://gcc.gnu.org/g:bb2a7f80a98de3febefbb32b1e4898062bdb6af8
commit r12-6022-gbb2a7f80a98de3febefbb32b1e4898062bdb6af8
Author: Patrick Palka
Date: Thu Dec 16 13:40:42 2021 -0500
c++: two-stage name lookup for overloaded operators [PR51577]
In order to properly implement two-stage name lookup for dependent
operator expressions, we need to remember the result of unqualified
lookup of the operator at template definition time, and reuse that
result rather than performing another unqualified lookup at
instantiation time.
Ideally we could just store the lookup in the expression directly, but
as pointed out in r9-6405 this isn't really possible since we use the
standard tree codes to represent most dependent operator expressions.
We could perhaps create a new tree code to represent dependent operator
expressions, with enough operands to store the lookup along with
everything else, but that'd require a lot of careful work to make sure
we handle this new tree code properly across the frontend.
But currently type-dependent operator (and call) expressions are given
an empty TREE_TYPE, which dependent_type_p treats as dependent, so this
field is effectively unused except to signal that the expression is
type-dependent. It'd be convenient if we could store the lookup there
while preserving the dependent-ness of the expression.
To that end, this patch creates a new kind of type, called
DEPENDENT_OPERATOR_TYPE, which we give to dependent operator expressions
and into which we can store the result of operator lookup at template
definition time (DEPENDENT_OPERATOR_TYPE_SAVED_LOOKUPS). Since this
type is always dependent (by definition), and since the frontend doesn't
seem to care much about the exact type of a type-dependent expression,
using this type in place of a NULL_TREE type seems to "just work"; only
dependent_type_p and WILDCARD_TYPE_P need to be adjusted to return true
for this new type.
The rest of the patch mostly consists of adding the necessary plumbing
to pass DEPENDENT_OPERATOR_TYPE_SAVED_LOOKUPS to add_operator_candidates,
adjusting all callers of build_x_* appropriately, and removing the now
unnecessary push_operator_bindings mechanism.
In passing, this patch simplifies finish_constraint_binary_op to avoid
using build_x_binary_op for building a binary constraint-expr; we don't
need to consider operator overloads here, as the &&/|| inside a
constraint effectively always has the built-in meaning (since atomic
constraints must have bool type).
This patch also makes FOLD_EXPR_OP yield a tree_code instead of a raw
INTEGER_CST.
Finally, this patch adds the XFAILed test operator-8.C which is about
broken two-stage name lookup for rewritten non-dependent operator
expressions, an existing bug that's otherwise only documented in
build_new_op.
PR c++/51577
PR c++/83035
PR c++/100465
gcc/cp/ChangeLog:
* call.c (add_operator_candidates): Add lookups parameter.
Use it to avoid performing a second unqualified lookup when
instantiating a dependent operator expression.
(build_new_op): Add lookups parameter and pass it appropriately.
* constraint.cc (finish_constraint_binary_op): Use
build_min_nt_loc instead of build_x_binary_op.
* coroutines.cc (build_co_await): Adjust call to build_new_op.
* cp-objcp-common.c (cp_common_init_ts): Mark
DEPENDENT_OPERATOR_TYPE appropriately.
* cp-tree.def (DEPENDENT_OPERATOR_TYPE): Define.
* cp-tree.h (WILDCARD_TYPE_P): Accept DEPENDENT_OPERATOR_TYPE.
(FOLD_EXPR_OP_RAW): New, renamed from ...
(FOLD_EXPR_OP): ... this. Change this to return the tree_code
directly.
(DEPENDENT_OPERATOR_TYPE_SAVED_LOOKUPS): Define.
(templated_operator_saved_lookups): Define.
(build_new_op): Add lookups parameter.
(build_dependent_operator_type): Declare.
(build_x_indirect_ref): Add lookups parameter.
(build_x_binary_op): Likewise.
(build_x_unary_op): Likewise.
(build_x_compound_expr): Likewise.
(build_x_modify_expr): Likewise.
* cxx-pretty-print.c (get_fold_operator): Adjust after
FOLD_EXPR_OP change.
* decl.c (start_preparsed_function): Don't call
push_operator_bindings.
* decl2.c (grok_array_decl): Adjust calls to build_new_op.
* method.c (do_one_comp): Likewise.
(build_comparison_op): Likewise.
* module.cc (trees_out::type_node): Handle DEPENDENT_OPERATOR_TYPE.
