c++: refine dependent_alias_template_spec_p [PR90679]
For a (complex) alias template-id, dependent_alias_template_spec_p returns true if any template argument of the template-id is dependent. This predicate indicates that substitution into the template-id may behave differently with respect to SFINAE than substitution into the expanded alias, and so the alias is in a way non-transparent. For example, 'first_t<T, T&>' in template<class T, class...> using first_t = T; template<class T> first_t<T, T&> f(); is such an alias template-id since first_t doesn't use its second template parameter and so the substitution into the expanded alias would discard the SFINAE effects of the corresponding (dependent) argument 'T&'. But this predicate is overly conservative since what really matters for sake of SFINAE equivalence is whether a template argument corresponding to an _unused_ template parameter is dependent. So the predicate should return false for e.g. 'first_t<T&, int>'. This patch refines the predicate appropriately. We need to be able to efficiently determine which template parameters of a complex alias template are unused, so to that end we add a new out parameter to complex_alias_template_p and cache its result in an on-the-side hash_map that replaces the existing TEMPLATE_DECL_COMPLEX_ALIAS_P flag. PR c++/90679 gcc/cp/ChangeLog: * cp-tree.h (TEMPLATE_DECL_COMPLEX_ALIAS_P): Remove. (most_general_template): Constify parameter. * pt.cc (push_template_decl): Adjust after removing TEMPLATE_DECL_COMPLEX_ALIAS_P. (complex_alias_tmpl_info): New hash_map. (uses_all_template_parms_data::seen): Change type to tree* from bool*. (complex_alias_template_r): Adjust accordingly. (complex_alias_template_p): Add 'seen_out' out parameter. Call most_general_template and check PRIMARY_TEMPLATE_P. Use complex_alias_tmpl_info to cache the result and set '*seen_out' accordigly. (dependent_alias_template_spec_p): Add !processing_template_decl early exit test. Consider dependence of only template arguments corresponding to seen template parameters as per gcc/testsuite/ChangeLog: * g++.dg/cpp0x/alias-decl-76.C: New test.
This commit is contained in:
Patrick Palka
parent
c37159d2e5
commit
6d27ee7fcc
3 changed files with 103 additions and 32 deletions
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@ -552,7 +552,6 @@ extern GTY(()) tree cp_global_trees[CPTI_MAX];
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2: DECL_THIS_EXTERN (in VAR_DECL, FUNCTION_DECL or PARM_DECL)
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DECL_IMPLICIT_TYPEDEF_P (in a TYPE_DECL)
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DECL_CONSTRAINT_VAR_P (in a PARM_DECL)
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TEMPLATE_DECL_COMPLEX_ALIAS_P (in TEMPLATE_DECL)
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DECL_INSTANTIATING_NSDMI_P (in a FIELD_DECL)
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USING_DECL_UNRELATED_P (in USING_DECL)
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3: DECL_IN_AGGR_P.
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@ -3700,10 +3699,6 @@ struct GTY(()) lang_decl {
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#define TYPE_DECL_ALIAS_P(NODE) \
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DECL_LANG_FLAG_6 (TYPE_DECL_CHECK (NODE))
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/* Nonzero for TEMPLATE_DECL means that it is a 'complex' alias template. */
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#define TEMPLATE_DECL_COMPLEX_ALIAS_P(NODE) \
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DECL_LANG_FLAG_2 (TEMPLATE_DECL_CHECK (NODE))
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/* Nonzero for a type which is an alias for another type; i.e, a type
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which declaration was written 'using name-of-type =
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another-type'. */
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@ -7528,7 +7523,7 @@ extern tree tsubst_argument_pack (tree, tree, tsubst_flags_t, tree);
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extern tree tsubst_template_args (tree, tree, tsubst_flags_t, tree);
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extern tree tsubst_template_arg (tree, tree, tsubst_flags_t, tree);
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extern tree tsubst_function_parms (tree, tree, tsubst_flags_t, tree);
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extern tree most_general_template (tree);
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extern tree most_general_template (const_tree);
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extern tree get_mostly_instantiated_function_type (tree);
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extern bool problematic_instantiation_changed (void);
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extern void record_last_problematic_instantiation (void);
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104
gcc/cp/pt.cc
104
gcc/cp/pt.cc
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@ -213,7 +213,6 @@ static tree listify (tree);
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static tree listify_autos (tree, tree);
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static tree tsubst_template_parm (tree, tree, tsubst_flags_t);
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static tree instantiate_alias_template (tree, tree, tsubst_flags_t);
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static bool complex_alias_template_p (const_tree tmpl);
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static tree get_underlying_template (tree);
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static tree tsubst_attributes (tree, tree, tsubst_flags_t, tree);
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static tree canonicalize_expr_argument (tree, tsubst_flags_t);
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@ -6208,8 +6207,6 @@ push_template_decl (tree decl, bool is_friend)
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constr = build_constraints (constr, NULL_TREE);
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set_constraints (decl, constr);
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}
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if (complex_alias_template_p (tmpl))
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TEMPLATE_DECL_COMPLEX_ALIAS_P (tmpl) = true;
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}
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}
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@ -6499,12 +6496,16 @@ alias_template_specialization_p (const_tree t,
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return NULL_TREE;
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}
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/* A cache of the result of complex_alias_template_p. */
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static GTY((deletable)) hash_map<const_tree, tree> *complex_alias_tmpl_info;
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/* Data structure for complex_alias_template_*. */
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struct uses_all_template_parms_data
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{
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int level;
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bool *seen;
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tree *seen;
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};
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/* walk_tree callback for complex_alias_template_p. */
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@ -6524,7 +6525,7 @@ complex_alias_template_r (tree *tp, int *walk_subtrees, void *data_)
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{
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tree idx = get_template_parm_index (t);
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if (TEMPLATE_PARM_LEVEL (idx) == data.level)
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data.seen[TEMPLATE_PARM_IDX (idx)] = true;
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data.seen[TEMPLATE_PARM_IDX (idx)] = boolean_true_node;
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}
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default:;
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@ -6549,7 +6550,7 @@ complex_alias_template_r (tree *tp, int *walk_subtrees, void *data_)
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return t;
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/* Consider the expanded packs to be used outside the expansion... */
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data.seen[idx] = true;
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data.seen[idx] = boolean_true_node;
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}
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/* ...but don't walk into the pattern. Consider PR104008:
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@ -6571,12 +6572,17 @@ complex_alias_template_r (tree *tp, int *walk_subtrees, void *data_)
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using that alias can be ill-formed when the expansion is not, as with
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the void_t template.
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Returns 1 if always complex, 0 if not complex, -1 if complex iff any of the
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template arguments are empty packs. */
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If this predicate returns true in the ordinary case, the out parameter
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SEEN_OUT is set to a TREE_VEC containing boolean_true_node at element I if
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the I'th template parameter of the alias template is used in the alias. */
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static bool
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complex_alias_template_p (const_tree tmpl)
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complex_alias_template_p (const_tree tmpl, tree *seen_out)
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{
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tmpl = most_general_template (tmpl);
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if (!PRIMARY_TEMPLATE_P (tmpl))
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return false;
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/* A renaming alias isn't complex. */
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if (get_underlying_template (CONST_CAST_TREE (tmpl)) != tmpl)
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return false;
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@ -6585,26 +6591,55 @@ complex_alias_template_p (const_tree tmpl)
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if (get_constraints (tmpl))
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return true;
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if (!complex_alias_tmpl_info)
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complex_alias_tmpl_info = hash_map<const_tree, tree>::create_ggc (13);
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if (tree *slot = complex_alias_tmpl_info->get (tmpl))
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{
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tree result = *slot;
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if (result == boolean_false_node)
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return false;
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if (result == boolean_true_node)
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return true;
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gcc_assert (TREE_CODE (result) == TREE_VEC);
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if (seen_out)
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*seen_out = result;
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return true;
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}
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struct uses_all_template_parms_data data;
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tree pat = DECL_ORIGINAL_TYPE (DECL_TEMPLATE_RESULT (tmpl));
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tree parms = DECL_TEMPLATE_PARMS (tmpl);
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data.level = TMPL_PARMS_DEPTH (parms);
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int len = TREE_VEC_LENGTH (INNERMOST_TEMPLATE_PARMS (parms));
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data.seen = XALLOCAVEC (bool, len);
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tree seen = make_tree_vec (len);
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data.seen = TREE_VEC_BEGIN (seen);
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for (int i = 0; i < len; ++i)
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data.seen[i] = false;
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data.seen[i] = boolean_false_node;
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if (cp_walk_tree_without_duplicates (&pat, complex_alias_template_r, &data))
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return true;
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for (int i = 0; i < len; ++i)
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if (!data.seen[i])
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{
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complex_alias_tmpl_info->put (tmpl, boolean_true_node);
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return true;
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}
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for (int i = 0; i < len; ++i)
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if (data.seen[i] != boolean_true_node)
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{
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complex_alias_tmpl_info->put (tmpl, seen);
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if (seen_out)
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*seen_out = seen;
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return true;
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}
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complex_alias_tmpl_info->put (tmpl, boolean_false_node);
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return false;
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}
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/* If T is a specialization of a complex alias template with dependent
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template-arguments, return it; otherwise return NULL_TREE. If T is a
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typedef to such a specialization, return the specialization. */
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/* If T is a specialization of a complex alias template with a dependent
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argument for an unused template parameter, return it; otherwise return
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NULL_TREE. If T is a typedef to such a specialization, return the
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specialization. */
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tree
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dependent_alias_template_spec_p (const_tree t, bool transparent_typedefs)
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@ -6613,15 +6648,32 @@ dependent_alias_template_spec_p (const_tree t, bool transparent_typedefs)
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return NULL_TREE;
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gcc_assert (TYPE_P (t));
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if (!typedef_variant_p (t))
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if (!processing_template_decl || !typedef_variant_p (t))
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return NULL_TREE;
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tree tinfo = TYPE_ALIAS_TEMPLATE_INFO (t);
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if (tinfo
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&& TEMPLATE_DECL_COMPLEX_ALIAS_P (TI_TEMPLATE (tinfo))
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&& (any_dependent_template_arguments_p
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(INNERMOST_TEMPLATE_ARGS (TI_ARGS (tinfo)))))
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return CONST_CAST_TREE (t);
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if (tree tinfo = TYPE_ALIAS_TEMPLATE_INFO (t))
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{
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tree seen = NULL_TREE;
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if (complex_alias_template_p (TI_TEMPLATE (tinfo), &seen))
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{
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tree args = INNERMOST_TEMPLATE_ARGS (TI_ARGS (tinfo));
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if (!seen)
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{
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if (any_dependent_template_arguments_p (args))
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return CONST_CAST_TREE (t);
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}
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else
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{
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gcc_assert (TREE_VEC_LENGTH (args) == TREE_VEC_LENGTH (seen));
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for (int i = 0, len = TREE_VEC_LENGTH (args); i < len; ++i)
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if (TREE_VEC_ELT (seen, i) != boolean_true_node
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&& dependent_template_arg_p (TREE_VEC_ELT (args, i)))
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return CONST_CAST_TREE (t);
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}
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return NULL_TREE;
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}
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}
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if (transparent_typedefs)
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{
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@ -25817,7 +25869,7 @@ most_specialized_instantiation (tree templates)
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`template <class T> template <class U> S<T*>::f(U)'. */
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tree
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most_general_template (tree decl)
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most_general_template (const_tree decl)
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{
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if (TREE_CODE (decl) != TEMPLATE_DECL)
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{
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@ -25854,7 +25906,7 @@ most_general_template (tree decl)
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decl = DECL_TI_TEMPLATE (decl);
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}
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return decl;
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return CONST_CAST_TREE (decl);
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}
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/* Return the most specialized of the template partial specializations
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24
gcc/testsuite/g++.dg/cpp0x/alias-decl-76.C
Normal file
24
gcc/testsuite/g++.dg/cpp0x/alias-decl-76.C
Normal file
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@ -0,0 +1,24 @@
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// PR c++/90679
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// { dg-do compile { target c++11 } }
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template<class T, class...>
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using first_t = T;
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template<class T>
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struct A;
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template<class T>
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struct traits;
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template<class T>
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struct traits<A<first_t<T>>> {
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static constexpr int value = 1;
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};
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template<class T>
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struct traits<A<first_t<const T>>> {
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static constexpr int value = 2;
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};
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static_assert(traits<A<int>>::value == 1, "");
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static_assert(traits<A<const int>>::value == 2, ""); // { dg-bogus "ambiguous" }
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