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author | Jason Merrill <jason@redhat.com> | 2024-01-17 17:29:33 -0500 |
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committer | Jason Merrill <jason@redhat.com> | 2024-01-19 13:35:04 -0500 |
commit | f1e5bf0d83ee4da81b6317c6d7f1278fe7eaa5a0 (patch) | |
tree | aa8ae41f486fca7101c25e70c7eb3aac1c88190f /gcc/cp | |
parent | e04376b336502016456eaf4e90c3ea792c77c8df (diff) | |
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c++: alias template argument conversion [PR112632]
We've had a problem with lost conversions to template parameter types for a
while now; looking at this PR, it occurred to me that the problem is really
with alias (and concept) templates, since we do substitution of dependent
arguments into them in a way that we don't for other templates. And fixing
that specific problem is a lot simpler than adding IMPLICIT_CONV_EXPR around
all dependent template arguments the way I gave up on for 111357.
The other part of the fix was changing tsubst_expr to actually call
convert_nontype_argument instead of assuming it will eventually happen.
I waffled about stripping the forced conversion when !force_conv
vs. skipping them in iterative_hash_template_arg and
template_args_equal (like we already do for some other conversions) and
decided to go with the former, but that isn't a strong preference if it
turns out to be somehow problematic.
PR c++/112632
PR c++/112594
PR c++/111357
PR c++/104594
PR c++/67898
gcc/cp/ChangeLog:
* cp-tree.h (IMPLICIT_CONV_EXPR_FORCED): New.
* pt.cc (expand_integer_pack): Remove 111357 workaround.
(maybe_convert_nontype_argument): Add force parm.
(convert_template_argument): Handle alias template args
specially.
(tsubst_expr): Don't ignore IMPLICIT_CONV_EXPR_NONTYPE_ARG.
* error.cc (dump_expr) [CASE_CONVERT]: Handle null optype.
gcc/testsuite/ChangeLog:
* g++.dg/cpp0x/alias-decl-nontype1.C: New test.
* g++.dg/cpp2a/concepts-narrowing1.C: New test.
* g++.dg/cpp2a/nontype-class63.C: New test.
* g++.dg/cpp2a/nontype-class63a.C: New test.
Diffstat (limited to 'gcc/cp')
-rw-r--r-- | gcc/cp/cp-tree.h | 5 | ||||
-rw-r--r-- | gcc/cp/error.cc | 4 | ||||
-rw-r--r-- | gcc/cp/pt.cc | 48 |
3 files changed, 41 insertions, 16 deletions
diff --git a/gcc/cp/cp-tree.h b/gcc/cp/cp-tree.h index d9b14d7..60e6daf 100644 --- a/gcc/cp/cp-tree.h +++ b/gcc/cp/cp-tree.h @@ -4717,6 +4717,11 @@ get_vec_init_expr (tree t) #define IMPLICIT_CONV_EXPR_BRACED_INIT(NODE) \ (TREE_LANG_FLAG_2 (IMPLICIT_CONV_EXPR_CHECK (NODE))) +/* True if NODE represents a conversion forced to be represented in + maybe_convert_nontype_argument, i.e. for an alias template. */ +#define IMPLICIT_CONV_EXPR_FORCED(NODE) \ + (TREE_LANG_FLAG_3 (IMPLICIT_CONV_EXPR_CHECK (NODE))) + /* Nonzero means that an object of this type cannot be initialized using an initializer list. */ #define CLASSTYPE_NON_AGGREGATE(NODE) \ diff --git a/gcc/cp/error.cc b/gcc/cp/error.cc index 52e24fb..d3fcac7 100644 --- a/gcc/cp/error.cc +++ b/gcc/cp/error.cc @@ -2673,6 +2673,8 @@ dump_expr (cxx_pretty_printer *pp, tree t, int flags) tree ttype = TREE_TYPE (t); tree optype = TREE_TYPE (op); + if (!optype) + optype = unknown_type_node; if (TREE_CODE (ttype) != TREE_CODE (optype) && INDIRECT_TYPE_P (ttype) @@ -2691,7 +2693,7 @@ dump_expr (cxx_pretty_printer *pp, tree t, int flags) else dump_unary_op (pp, "&", t, flags); } - else if (!same_type_p (TREE_TYPE (op), TREE_TYPE (t))) + else if (!same_type_p (optype, ttype)) { /* It is a cast, but we cannot tell whether it is a reinterpret or static cast. Use the C style notation. */ diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc index f82d018..fbbca46 100644 --- a/gcc/cp/pt.cc +++ b/gcc/cp/pt.cc @@ -3760,13 +3760,6 @@ expand_integer_pack (tree call, tree args, tsubst_flags_t complain, { if (hi != ohi) { - /* Work around maybe_convert_nontype_argument not doing this for - dependent arguments. Don't use IMPLICIT_CONV_EXPR_NONTYPE_ARG - because that will make tsubst_expr ignore it. */ - tree type = tsubst (TREE_TYPE (ohi), args, complain, in_decl); - if (!TREE_TYPE (hi) || !same_type_p (type, TREE_TYPE (hi))) - hi = build1 (IMPLICIT_CONV_EXPR, type, hi); - call = copy_node (call); CALL_EXPR_ARG (call, 0) = hi; } @@ -8457,23 +8450,30 @@ convert_wildcard_argument (tree parm, tree arg) conversion for the benefit of cp_tree_equal. */ static tree -maybe_convert_nontype_argument (tree type, tree arg) +maybe_convert_nontype_argument (tree type, tree arg, bool force) { /* Auto parms get no conversion. */ if (type_uses_auto (type)) return arg; + /* ??? Do we need to push the IMPLICIT_CONV_EXPR into the pack expansion? + That would complicate other things, and it doesn't seem necessary. */ + if (TREE_CODE (arg) == EXPR_PACK_EXPANSION) + return arg; /* We don't need or want to add this conversion now if we're going to use the argument for deduction. */ - if (value_dependent_expression_p (arg)) + if (!value_dependent_expression_p (arg)) + force = false; + else if (!force) return arg; type = cv_unqualified (type); tree argtype = TREE_TYPE (arg); - if (same_type_p (type, argtype)) + if (argtype && same_type_p (type, argtype)) return arg; arg = build1 (IMPLICIT_CONV_EXPR, type, arg); IMPLICIT_CONV_EXPR_NONTYPE_ARG (arg) = true; + IMPLICIT_CONV_EXPR_FORCED (arg) = force; return arg; } @@ -8741,6 +8741,22 @@ convert_template_argument (tree parm, if (t != TREE_TYPE (parm)) t = canonicalize_type_argument (t, complain); + /* We need to handle arguments for alias or concept templates + differently: we need to force building an IMPLICIT_CONV_EXPR, because + these arguments are going to be substituted directly into the + dependent type; they might not get another chance at + convert_nontype_argument. But if the argument ends up here again for + a template that isn't one of those, remove the conversion for + consistency between naming the same dependent type directly or through + an alias. */ + bool force_conv = in_decl && (DECL_ALIAS_TEMPLATE_P (in_decl) + || concept_definition_p (in_decl)); + if (!force_conv + && TREE_CODE (orig_arg) == IMPLICIT_CONV_EXPR + && IMPLICIT_CONV_EXPR_FORCED (orig_arg) + && same_type_p (TREE_TYPE (orig_arg), t)) + orig_arg = TREE_OPERAND (orig_arg, 0); + if (!type_dependent_expression_p (orig_arg) && !uses_template_parms (t)) /* We used to call digest_init here. However, digest_init @@ -8757,10 +8773,9 @@ convert_template_argument (tree parm, else { val = canonicalize_expr_argument (orig_arg, complain); - val = maybe_convert_nontype_argument (t, val); + val = maybe_convert_nontype_argument (t, val, force_conv); } - if (val == NULL_TREE) val = error_mark_node; else if (val == error_mark_node && (complain & tf_error)) @@ -20056,9 +20071,12 @@ tsubst_expr (tree t, tree args, tsubst_flags_t complain, tree in_decl) RETURN (retval); } if (IMPLICIT_CONV_EXPR_NONTYPE_ARG (t)) - /* We'll pass this to convert_nontype_argument again, we don't need - to actually perform any conversion here. */ - RETURN (expr); + { + tree r = convert_nontype_argument (type, expr, complain); + if (r == NULL_TREE) + r = error_mark_node; + RETURN (r); + } int flags = LOOKUP_IMPLICIT; if (IMPLICIT_CONV_EXPR_DIRECT_INIT (t)) flags = LOOKUP_NORMAL; |