diff options
| author | Patrick Palka <ppalka@redhat.com> | 2021-08-18 08:37:45 -0400 |
|---|---|---|
| committer | Patrick Palka <ppalka@redhat.com> | 2021-08-18 08:37:45 -0400 |
| commit | be4a4fb516688d7cfe28a80a4aa333f4ecf0b518 (patch) | |
| tree | 40bd7e48f685156136613ae9e09ddb5f805609e0 /gcc/cp/pt.c | |
| parent | a6b3db3e8625a3cba1240f0b5e1a29bd6c68b8ca (diff) | |
| download | gcc-be4a4fb516688d7cfe28a80a4aa333f4ecf0b518.zip gcc-be4a4fb516688d7cfe28a80a4aa333f4ecf0b518.tar.gz gcc-be4a4fb516688d7cfe28a80a4aa333f4ecf0b518.tar.bz2 | |
c++: aggregate CTAD and brace elision [PR101344]
Here the problem is ultimately that collect_ctor_idx_types always
recurses into an eligible sub-CONSTRUCTOR regardless of whether the
corresponding pair of braces was elided in the original initializer.
This causes us to reject some completely-braced forms of aggregate
CTAD as in the first testcase below, because collect_ctor_idx_types
effectively assumes that the original initializer is always minimally
braced (and so the aggregate deduction candidate is given a function
type that's incompatible with the original completely-braced initializer).
In order to fix this, collect_ctor_idx_types needs to somehow know the
shape of the original initializer when iterating over the reshaped
initializer. To that end this patch makes reshape_init flag sub-ctors
that were built to undo brace elision in the original ctor, so that
collect_ctor_idx_types that determine whether to recurse into a sub-ctor
by simply inspecting this flag.
This happens to also fix PR101820, which is about aggregate CTAD using
designated initializers, for much the same reasons.
A curious case is the "intermediately-braced" initialization of 'e3'
(which we reject) in the first testcase below. It seems to me we're
behaving as specified here (according to [over.match.class.deduct]/1)
because the initializer element x_1={1, 2, 3, 4} corresponds to the
subobject e_1=E::t, hence the type T_1 of the first function parameter
of the aggregate deduction candidate is T(&&)[2][2], but T can't be
deduced from x_1 using this parameter type (as opposed to say T(&&)[4]).
PR c++/101344
PR c++/101820
gcc/cp/ChangeLog:
* cp-tree.h (CONSTRUCTOR_BRACES_ELIDED_P): Define.
* decl.c (reshape_init_r): Set it.
* pt.c (collect_ctor_idx_types): Recurse into a sub-CONSTRUCTOR
iff CONSTRUCTOR_BRACES_ELIDED_P.
gcc/testsuite/ChangeLog:
* g++.dg/cpp2a/class-deduction-aggr11.C: New test.
* g++.dg/cpp2a/class-deduction-aggr12.C: New test.
Diffstat (limited to 'gcc/cp/pt.c')
| -rw-r--r-- | gcc/cp/pt.c | 7 |
1 files changed, 1 insertions, 6 deletions
diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c index 0c14966..020a4bf 100644 --- a/gcc/cp/pt.c +++ b/gcc/cp/pt.c @@ -28837,12 +28837,7 @@ collect_ctor_idx_types (tree ctor, tree list, tree elt = NULL_TREE) { tree ftype = elt ? elt : TREE_TYPE (idx); if (BRACE_ENCLOSED_INITIALIZER_P (val) - && CONSTRUCTOR_NELTS (val) - /* As in reshape_init_r, a non-aggregate or array-of-dependent-bound - type gets a single initializer. */ - && CP_AGGREGATE_TYPE_P (ftype) - && !(TREE_CODE (ftype) == ARRAY_TYPE - && uses_template_parms (TYPE_DOMAIN (ftype)))) + && CONSTRUCTOR_BRACES_ELIDED_P (val)) { tree subelt = NULL_TREE; if (TREE_CODE (ftype) == ARRAY_TYPE) |