return newdecl;
}
+/* As rewrite_template_parm, but for the whole TREE_LIST representing a
+ template parameter. */
+
+static tree
+rewrite_tparm_list (tree oldelt, unsigned index, unsigned level,
+ tree targs, unsigned targs_index, tsubst_flags_t complain)
+{
+ tree olddecl = TREE_VALUE (oldelt);
+ tree newdecl = rewrite_template_parm (olddecl, index, level,
+ targs, complain);
+ if (newdecl == error_mark_node)
+ return error_mark_node;
+ tree newdef = tsubst_template_arg (TREE_PURPOSE (oldelt),
+ targs, complain, NULL_TREE);
+ tree list = build_tree_list (newdef, newdecl);
+ TEMPLATE_PARM_CONSTRAINTS (list)
+ = tsubst_constraint_info (TEMPLATE_PARM_CONSTRAINTS (oldelt),
+ targs, complain, NULL_TREE);
+ int depth = TMPL_ARGS_DEPTH (targs);
+ TMPL_ARG (targs, depth, targs_index) = template_parm_to_arg (list);
+ return list;
+}
+
/* Returns a C++17 class deduction guide template based on the constructor
CTOR. As a special case, CTOR can be a RECORD_TYPE for an implicit default
guide, REFERENCE_TYPE for an implicit copy/move guide, or TREE_LIST for an
unsigned index = i + clen;
unsigned level = 1;
tree oldelt = TREE_VEC_ELT (ftparms, i);
- tree olddecl = TREE_VALUE (oldelt);
- tree newdecl = rewrite_template_parm (olddecl, index, level,
- tsubst_args, complain);
- if (newdecl == error_mark_node)
+ tree newelt
+ = rewrite_tparm_list (oldelt, index, level,
+ tsubst_args, i, complain);
+ if (newelt == error_mark_node)
ok = false;
- tree newdef = tsubst_template_arg (TREE_PURPOSE (oldelt),
- tsubst_args, complain, ctor);
- tree list = build_tree_list (newdef, newdecl);
- TEMPLATE_PARM_CONSTRAINTS (list)
- = tsubst_constraint_info (TEMPLATE_PARM_CONSTRAINTS (oldelt),
- tsubst_args, complain, ctor);
- TREE_VEC_ELT (new_vec, index) = list;
- TMPL_ARG (tsubst_args, depth, i) = template_parm_to_arg (list);
+ TREE_VEC_ELT (new_vec, index) = newelt;
}
/* Now we have a final set of template parms to substitute into the
return list;
}
+/* Return whether ETYPE is, or is derived from, a specialization of TMPL. */
+
+static bool
+is_spec_or_derived (tree etype, tree tmpl)
+{
+ if (!etype || !CLASS_TYPE_P (etype))
+ return false;
+
+ tree type = TREE_TYPE (tmpl);
+ tree tparms = (INNERMOST_TEMPLATE_PARMS
+ (DECL_TEMPLATE_PARMS (tmpl)));
+ tree targs = make_tree_vec (TREE_VEC_LENGTH (tparms));
+ int err = unify (tparms, targs, type, etype,
+ UNIFY_ALLOW_DERIVED, /*explain*/false);
+ ggc_free (targs);
+ return !err;
+}
+
/* Return a C++20 aggregate deduction candidate for TYPE initialized from
INIT. */
static tree
-maybe_aggr_guide (tree type, tree init)
+maybe_aggr_guide (tree tmpl, tree init, vec<tree,va_gc> *args)
{
if (cxx_dialect < cxx2a)
return NULL_TREE;
if (init == NULL_TREE)
return NULL_TREE;
+
+ tree type = TREE_TYPE (tmpl);
if (!CP_AGGREGATE_TYPE_P (type))
return NULL_TREE;
+ /* No aggregate candidate for copy-initialization. */
+ if (args->length() == 1)
+ {
+ tree val = (*args)[0];
+ if (is_spec_or_derived (tmpl, TREE_TYPE (val)))
+ return NULL_TREE;
+ }
+
/* If we encounter a problem, we just won't add the candidate. */
tsubst_flags_t complain = tf_none;
return NULL_TREE;
}
-/* Return whether ETYPE is, or is derived from, a specialization of TMPL. */
+/* UGUIDES are the deduction guides for the underlying template of alias
+ template TMPL; adjust them to be deduction guides for TMPL. */
-static bool
-is_spec_or_derived (tree etype, tree tmpl)
-{
- if (!etype || !CLASS_TYPE_P (etype))
- return false;
+static tree
+alias_ctad_tweaks (tree tmpl, tree uguides)
+{
+ /* [over.match.class.deduct]: When resolving a placeholder for a deduced
+ class type (9.2.8.2) where the template-name names an alias template A,
+ the defining-type-id of A must be of the form
+
+ typename(opt) nested-name-specifier(opt) template(opt) simple-template-id
+
+ as specified in 9.2.8.2. The guides of A are the set of functions or
+ function templates formed as follows. For each function or function
+ template f in the guides of the template named by the simple-template-id
+ of the defining-type-id, the template arguments of the return type of f
+ are deduced from the defining-type-id of A according to the process in
+ 13.10.2.5 with the exception that deduction does not fail if not all
+ template arguments are deduced. Let g denote the result of substituting
+ these deductions into f. If substitution succeeds, form a function or
+ function template f' with the following properties and add it to the set
+ of guides of A:
+
+ * The function type of f' is the function type of g.
+
+ * If f is a function template, f' is a function template whose template
+ parameter list consists of all the template parameters of A (including
+ their default template arguments) that appear in the above deductions or
+ (recursively) in their default template arguments, followed by the
+ template parameters of f that were not deduced (including their default
+ template arguments), otherwise f' is not a function template.
+
+ * The associated constraints (13.5.2) are the conjunction of the
+ associated constraints of g and a constraint that is satisfied if and only
+ if the arguments of A are deducible (see below) from the return type.
+
+ * If f is a copy deduction candidate (12.4.1.8), then f' is considered to
+ be so as well.
+
+ * If f was generated from a deduction-guide (12.4.1.8), then f' is
+ considered to be so as well.
+
+ * The explicit-specifier of f' is the explicit-specifier of g (if
+ any). */
+
+ /* This implementation differs from the above in two significant ways:
+
+ 1) We include all template parameters of A, not just some.
+ 2) The added constraint is same_type instead of deducible.
+
+ I believe that while it's probably possible to construct a testcase that
+ behaves differently with this simplification, it should have the same
+ effect for real uses. Including all template parameters means that we
+ deduce all parameters of A when resolving the call, so when we're in the
+ constraint we don't need to deduce them again, we can just check whether
+ the deduction produced the desired result. */
+
+ tsubst_flags_t complain = tf_warning_or_error;
+ tree atype = TREE_TYPE (tmpl);
+ tree aguides = NULL_TREE;
+ tree atparms = INNERMOST_TEMPLATE_PARMS (DECL_TEMPLATE_PARMS (tmpl));
+ unsigned natparms = TREE_VEC_LENGTH (atparms);
+ tree utype = DECL_ORIGINAL_TYPE (DECL_TEMPLATE_RESULT (tmpl));
+ for (ovl_iterator iter (uguides); iter; ++iter)
+ {
+ tree f = *iter;
+ tree in_decl = f;
+ location_t loc = DECL_SOURCE_LOCATION (f);
+ tree ret = TREE_TYPE (TREE_TYPE (f));
+ tree fprime = f;
+ if (TREE_CODE (f) == TEMPLATE_DECL)
+ {
+ processing_template_decl_sentinel ptds (/*reset*/false);
+ ++processing_template_decl;
+
+ /* Deduce template arguments for f from the type-id of A. */
+ tree ftparms = INNERMOST_TEMPLATE_PARMS (DECL_TEMPLATE_PARMS (f));
+ unsigned len = TREE_VEC_LENGTH (ftparms);
+ tree targs = make_tree_vec (len);
+ int err = unify (ftparms, targs, ret, utype, UNIFY_ALLOW_NONE, false);
+ gcc_assert (!err);
+
+ /* The number of parms for f' is the number of parms for A plus
+ non-deduced parms of f. */
+ unsigned ndlen = 0;
+ unsigned j;
+ for (unsigned i = 0; i < len; ++i)
+ if (TREE_VEC_ELT (targs, i) == NULL_TREE)
+ ++ndlen;
+ tree gtparms = make_tree_vec (natparms + ndlen);
+
+ /* First copy over the parms of A. */
+ for (j = 0; j < natparms; ++j)
+ TREE_VEC_ELT (gtparms, j) = TREE_VEC_ELT (atparms, j);
+ /* Now rewrite the non-deduced parms of f. */
+ for (unsigned i = 0; ndlen && i < len; ++i)
+ if (TREE_VEC_ELT (targs, i) == NULL_TREE)
+ {
+ --ndlen;
+ unsigned index = j++;
+ unsigned level = 1;
+ tree oldlist = TREE_VEC_ELT (ftparms, i);
+ tree list = rewrite_tparm_list (oldlist, index, level,
+ targs, i, complain);
+ TREE_VEC_ELT (gtparms, index) = list;
+ }
+ gtparms = build_tree_list (size_one_node, gtparms);
+
+ /* Substitute the deduced arguments plus the rewritten template
+ parameters into f to get g. This covers the type, copyness,
+ guideness, and explicit-specifier. */
+ tree g = tsubst_decl (DECL_TEMPLATE_RESULT (f), targs, complain);
+ if (g == error_mark_node)
+ return error_mark_node;
+ DECL_USE_TEMPLATE (g) = 0;
+ fprime = build_template_decl (g, gtparms, false);
+ DECL_TEMPLATE_RESULT (fprime) = g;
+ TREE_TYPE (fprime) = TREE_TYPE (g);
+ tree gtargs = template_parms_to_args (gtparms);
+ DECL_TEMPLATE_INFO (g) = build_template_info (fprime, gtargs);
+ DECL_PRIMARY_TEMPLATE (fprime) = fprime;
+
+ /* Substitute the associated constraints. */
+ tree ci = get_constraints (f);
+ if (ci)
+ ci = tsubst_constraint_info (ci, targs, complain, in_decl);
+ if (ci == error_mark_node)
+ return error_mark_node;
+
+ /* Add a constraint that the return type matches the instantiation of
+ A with the same template arguments. */
+ ret = TREE_TYPE (TREE_TYPE (fprime));
+ if (!same_type_p (atype, ret)
+ /* FIXME this should mean they don't compare as equivalent. */
+ || dependent_alias_template_spec_p (atype, nt_opaque))
+ {
+ tree same = finish_trait_expr (loc, CPTK_IS_SAME_AS, atype, ret);
+ ci = append_constraint (ci, same);
+ }
+
+ if (ci)
+ set_constraints (fprime, ci);
+ }
+ else
+ {
+ /* For a non-template deduction guide, if the arguments of A aren't
+ deducible from the return type, don't add the candidate. */
+ tree targs = make_tree_vec (natparms);
+ int err = unify (atparms, targs, utype, ret, UNIFY_ALLOW_NONE, false);
+ for (unsigned i = 0; !err && i < natparms; ++i)
+ if (TREE_VEC_ELT (targs, i) == NULL_TREE)
+ err = true;
+ if (err)
+ continue;
+ }
+ aguides = lookup_add (fprime, aguides);
+ }
+
+ return aguides;
+}
+
+/* Return artificial deduction guides built from the constructors of class
+ template TMPL. */
+
+static tree
+ctor_deduction_guides_for (tree tmpl, tsubst_flags_t complain)
+{
tree type = TREE_TYPE (tmpl);
- tree tparms = (INNERMOST_TEMPLATE_PARMS
- (DECL_TEMPLATE_PARMS (tmpl)));
- tree targs = make_tree_vec (TREE_VEC_LENGTH (tparms));
- int err = unify (tparms, targs, type, etype,
- UNIFY_ALLOW_DERIVED, /*explain*/false);
- ggc_free (targs);
- return !err;
+ tree outer_args = NULL_TREE;
+ if (DECL_CLASS_SCOPE_P (tmpl)
+ && CLASSTYPE_TEMPLATE_INSTANTIATION (DECL_CONTEXT (tmpl)))
+ {
+ outer_args = CLASSTYPE_TI_ARGS (DECL_CONTEXT (tmpl));
+ type = TREE_TYPE (most_general_template (tmpl));
+ }
+
+ tree cands = NULL_TREE;
+
+ for (ovl_iterator iter (CLASSTYPE_CONSTRUCTORS (type)); iter; ++iter)
+ {
+ /* Skip inherited constructors. */
+ if (iter.using_p ())
+ continue;
+
+ tree guide = build_deduction_guide (type, *iter, outer_args, complain);
+ cands = lookup_add (guide, cands);
+ }
+
+ /* Add implicit default constructor deduction guide. */
+ if (!TYPE_HAS_USER_CONSTRUCTOR (type))
+ {
+ tree guide = build_deduction_guide (type, type, outer_args,
+ complain);
+ cands = lookup_add (guide, cands);
+ }
+
+ /* Add copy guide. */
+ {
+ tree gtype = build_reference_type (type);
+ tree guide = build_deduction_guide (type, gtype, outer_args,
+ complain);
+ cands = lookup_add (guide, cands);
+ }
+
+ return cands;
+}
+
+static GTY((deletable)) hash_map<tree, tree_pair_p> *dguide_cache;
+
+/* Return the non-aggregate deduction guides for deducible template TMPL. The
+ aggregate candidate is added separately because it depends on the
+ initializer. */
+
+static tree
+deduction_guides_for (tree tmpl, tsubst_flags_t complain)
+{
+ tree guides = NULL_TREE;
+ if (DECL_ALIAS_TEMPLATE_P (tmpl))
+ {
+ tree under = DECL_ORIGINAL_TYPE (DECL_TEMPLATE_RESULT (tmpl));
+ tree tinfo = get_template_info (under);
+ guides = deduction_guides_for (TI_TEMPLATE (tinfo), complain);
+ }
+ else
+ {
+ guides = lookup_qualified_name (CP_DECL_CONTEXT (tmpl),
+ dguide_name (tmpl),
+ /*type*/false, /*complain*/false,
+ /*hidden*/false);
+ if (guides == error_mark_node)
+ guides = NULL_TREE;
+ }
+
+ /* Cache the deduction guides for a template. We also remember the result of
+ lookup, and rebuild everything if it changes; should be very rare. */
+ tree_pair_p cache = NULL;
+ if (tree_pair_p &r
+ = hash_map_safe_get_or_insert<hm_ggc> (dguide_cache, tmpl))
+ {
+ cache = r;
+ if (cache->purpose == guides)
+ return cache->value;
+ }
+ else
+ {
+ r = cache = ggc_cleared_alloc<tree_pair_s> ();
+ cache->purpose = guides;
+ }
+
+ tree cands = NULL_TREE;
+ if (DECL_ALIAS_TEMPLATE_P (tmpl))
+ cands = alias_ctad_tweaks (tmpl, guides);
+ else
+ {
+ cands = ctor_deduction_guides_for (tmpl, complain);
+ for (ovl_iterator it (guides); it; ++it)
+ cands = lookup_add (*it, cands);
+ }
+
+ cache->value = cands;
+ return cands;
+}
+
+/* Return whether TMPL is a (class template argument-) deducible template. */
+
+bool
+ctad_template_p (tree tmpl)
+{
+ /* A deducible template is either a class template or is an alias template
+ whose defining-type-id is of the form
+
+ typename(opt) nested-name-specifier(opt) template(opt) simple-template-id
+
+ where the nested-name-specifier (if any) is non-dependent and the
+ template-name of the simple-template-id names a deducible template. */
+
+ if (DECL_CLASS_TEMPLATE_P (tmpl)
+ || DECL_TEMPLATE_TEMPLATE_PARM_P (tmpl))
+ return true;
+ if (!DECL_ALIAS_TEMPLATE_P (tmpl))
+ return false;
+ tree orig = DECL_ORIGINAL_TYPE (DECL_TEMPLATE_RESULT (tmpl));
+ if (tree tinfo = get_template_info (orig))
+ return ctad_template_p (TI_TEMPLATE (tinfo));
+ return false;
}
/* Deduce template arguments for the class template placeholder PTYPE for
type. */
static tree
-do_class_deduction (tree ptype, tree tmpl, tree init, int flags,
- tsubst_flags_t complain)
+do_class_deduction (tree ptype, tree tmpl, tree init,
+ int flags, tsubst_flags_t complain)
{
- if (!DECL_CLASS_TEMPLATE_P (tmpl))
+ /* We should have handled this in the caller. */
+ if (DECL_TEMPLATE_TEMPLATE_PARM_P (tmpl))
+ return ptype;
+
+ /* Look through alias templates that just rename another template. */
+ tmpl = get_underlying_template (tmpl);
+ if (!ctad_template_p (tmpl))
{
- /* We should have handled this in the caller. */
- if (DECL_TEMPLATE_TEMPLATE_PARM_P (tmpl))
- return ptype;
if (complain & tf_error)
- error ("non-class template %qT used without template arguments", tmpl);
+ error ("non-deducible template %qT used without template arguments", tmpl);
return error_mark_node;
}
+ else if (cxx_dialect < cxx2a && DECL_ALIAS_TEMPLATE_P (tmpl))
+ {
+ /* This doesn't affect conforming C++17 code, so just pedwarn. */
+ if (complain & tf_warning_or_error)
+ pedwarn (input_location, 0, "alias template deduction only available "
+ "with %<-std=c++2a%> or %<-std=gnu++2a%>");
+ }
+
if (init && TREE_TYPE (init) == ptype)
/* Using the template parm as its own argument. */
return ptype;
tree type = TREE_TYPE (tmpl);
bool try_list_ctor = false;
- bool copy_init = false;
releasing_vec rv_args = NULL;
vec<tree,va_gc> *&args = *&rv_args;
args = make_tree_vector ();
else if (BRACE_ENCLOSED_INITIALIZER_P (init))
{
- if (CONSTRUCTOR_NELTS (init) == 1)
+ try_list_ctor = TYPE_HAS_LIST_CTOR (type);
+ if (try_list_ctor && CONSTRUCTOR_NELTS (init) == 1)
{
/* As an exception, the first phase in 16.3.1.7 (considering the
initializer list as a single argument) is omitted if the
where U is a specialization of C or a class derived from a
specialization of C. */
tree elt = CONSTRUCTOR_ELT (init, 0)->value;
- copy_init = is_spec_or_derived (TREE_TYPE (elt), tmpl);
+ if (is_spec_or_derived (TREE_TYPE (elt), tmpl))
+ try_list_ctor = false;
}
- try_list_ctor = !copy_init && TYPE_HAS_LIST_CTOR (type);
if (try_list_ctor || is_std_init_list (type))
args = make_tree_vector_single (init);
else
args = make_tree_vector_from_ctor (init);
}
+ else if (TREE_CODE (init) == TREE_LIST)
+ args = make_tree_vector_from_list (init);
else
- {
- if (TREE_CODE (init) == TREE_LIST)
- args = make_tree_vector_from_list (init);
- else
- args = make_tree_vector_single (init);
+ args = make_tree_vector_single (init);
- if (args->length() == 1)
- copy_init = is_spec_or_derived (TREE_TYPE ((*args)[0]), tmpl);
- }
+ /* Do this now to avoid problems with erroneous args later on. */
+ args = resolve_args (args, complain);
+ if (args == NULL)
+ return error_mark_node;
- tree dname = dguide_name (tmpl);
- tree cands = lookup_qualified_name (CP_DECL_CONTEXT (tmpl), dname,
- /*type*/false, /*complain*/false,
- /*hidden*/false);
- bool elided = false;
+ tree cands = deduction_guides_for (tmpl, complain);
if (cands == error_mark_node)
- cands = NULL_TREE;
+ return error_mark_node;
/* Prune explicit deduction guides in copy-initialization context. */
+ bool elided = false;
if (flags & LOOKUP_ONLYCONVERTING)
{
for (lkp_iterator iter (cands); !elided && iter; ++iter)
}
}
- tree outer_args = NULL_TREE;
- if (DECL_CLASS_SCOPE_P (tmpl)
- && CLASSTYPE_TEMPLATE_INSTANTIATION (DECL_CONTEXT (tmpl)))
- {
- outer_args = CLASSTYPE_TI_ARGS (DECL_CONTEXT (tmpl));
- type = TREE_TYPE (most_general_template (tmpl));
- }
-
- bool saw_ctor = false;
- // FIXME cache artificial deduction guides
- for (ovl_iterator iter (CLASSTYPE_CONSTRUCTORS (type)); iter; ++iter)
- {
- /* Skip inherited constructors. */
- if (iter.using_p ())
- continue;
-
- tree guide = build_deduction_guide (type, *iter, outer_args, complain);
- if (guide == error_mark_node)
- return error_mark_node;
- if ((flags & LOOKUP_ONLYCONVERTING)
- && DECL_NONCONVERTING_P (STRIP_TEMPLATE (guide)))
- elided = true;
- else
- cands = lookup_add (guide, cands);
-
- saw_ctor = true;
- }
-
- if (!copy_init)
- if (tree guide = maybe_aggr_guide (type, init))
- cands = lookup_add (guide, cands);
+ if (tree guide = maybe_aggr_guide (tmpl, init, args))
+ cands = lookup_add (guide, cands);
tree call = error_mark_node;
}
}
- /* Maybe generate an implicit deduction guide. */
- if (call == error_mark_node && args->length () < 2)
- {
- tree gtype = NULL_TREE;
-
- if (args->length () == 1)
- /* Generate a copy guide. */
- gtype = build_reference_type (type);
- else if (!saw_ctor)
- /* Generate a default guide. */
- gtype = type;
-
- if (gtype)
- {
- tree guide = build_deduction_guide (type, gtype, outer_args,
- complain);
- if (guide == error_mark_node)
- return error_mark_node;
- cands = lookup_add (guide, cands);
- }
- }
-
if (elided && !cands)
{
error ("cannot deduce template arguments for copy-initialization"
--cp_unevaluated_operand;
}
- if (call == error_mark_node && (complain & tf_warning_or_error))
+ if (call == error_mark_node
+ && (complain & tf_warning_or_error))
{
error ("class template argument deduction failed:");
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