In order to be able to perform CTAD for a dependently-scoped template such as A<T>::B in the testcase below, we need to permit a typename-specifier to resolve to a template as per [dcl.type.simple]/2, at least when it appears in a CTAD-enabled context.
This patch implements this using a new tsubst flag tf_tst_ok to control when a TYPENAME_TYPE is allowed to name a template, and sets this flag when substituting into the type of a CAST_EXPR, CONSTRUCTOR or VAR_DECL (each of which is a CTAD-enabled context). Bootstrapped and regtested on x86_64-pc-linux-gnu, does this look OK for trunk perhaps? PR c++/104641 gcc/cp/ChangeLog: * cp-tree.h (tsubst_flags::tf_tst_ok): New flag. * decl.cc (make_typename_type): Allow a typename-specifier to resolve to a template when tf_tst_ok. * pt.cc (tsubst_decl) <case VAR_DECL>: Set tf_tst_ok when substituting the type. (tsubst): Clear tf_tst_ok and remember if it was set. <case TYPENAME_TYPE>: Pass tf_tst_ok to make_typename_type appropriately. Do make_template_placeholder when when make_typename_type returns a TEMPLATE_DECL. (tsubst_copy) <case CAST_EXPR>: Set tf_tst_ok when substituting the type. (tsubst_copy_and_build) <case CAST_EXPR>: Likewise. <case CONSTRUCTOR>: Likewise. gcc/testsuite/ChangeLog: * g++.dg/cpp1z/class-deduction107.C: New test. --- gcc/cp/cp-tree.h | 2 ++ gcc/cp/decl.cc | 14 +++++--- gcc/cp/pt.cc | 35 +++++++++++++++---- .../g++.dg/cpp1z/class-deduction107.C | 20 +++++++++++ 4 files changed, 61 insertions(+), 10 deletions(-) create mode 100644 gcc/testsuite/g++.dg/cpp1z/class-deduction107.C diff --git a/gcc/cp/cp-tree.h b/gcc/cp/cp-tree.h index da63d51d9bc..8a44218611f 100644 --- a/gcc/cp/cp-tree.h +++ b/gcc/cp/cp-tree.h @@ -5551,6 +5551,8 @@ enum tsubst_flags { (build_target_expr and friends) */ tf_norm = 1 << 11, /* Build diagnostic information during constraint normalization. */ + tf_tst_ok = 1 << 12, /* Allow a typename-specifier to name + a template. */ /* Convenient substitution flags combinations. */ tf_warning_or_error = tf_warning | tf_error }; diff --git a/gcc/cp/decl.cc b/gcc/cp/decl.cc index 7f80f9d4d7a..23c06655bde 100644 --- a/gcc/cp/decl.cc +++ b/gcc/cp/decl.cc @@ -4148,10 +4148,16 @@ make_typename_type (tree context, tree name, enum tag_types tag_type, } if (!want_template && TREE_CODE (t) != TYPE_DECL) { - if (complain & tf_error) - error ("%<typename %T::%D%> names %q#T, which is not a type", - context, name, t); - return error_mark_node; + if ((complain & tf_tst_ok) && DECL_TYPE_TEMPLATE_P (t)) + /* The caller permits this typename-specifier to name a template + (because it appears in a CTAD-enabled context). */; + else + { + if (complain & tf_error) + error ("%<typename %T::%D%> names %q#T, which is not a type", + context, name, t); + return error_mark_node; + } } if (!check_accessibility_of_qualified_id (t, /*object_type=*/NULL_TREE, diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc index 8fb17349ee1..18a21572ce3 100644 --- a/gcc/cp/pt.cc +++ b/gcc/cp/pt.cc @@ -14926,7 +14926,10 @@ tsubst_decl (tree t, tree args, tsubst_flags_t complain) && VAR_HAD_UNKNOWN_BOUND (t) && type != error_mark_node) type = strip_array_domain (type); - type = tsubst (type, args, complain, in_decl); + tsubst_flags_t tcomplain = complain; + if (VAR_P (t)) + tcomplain |= tf_tst_ok; + type = tsubst (type, args, tcomplain, in_decl); /* Substituting the type might have recursively instantiated this same alias (c++/86171). */ if (gen_tmpl && DECL_ALIAS_TEMPLATE_P (gen_tmpl) @@ -15612,6 +15615,9 @@ tsubst (tree t, tree args, tsubst_flags_t complain, tree in_decl) bool fndecl_type = (complain & tf_fndecl_type); complain &= ~tf_fndecl_type; + bool tst_ok = (complain & tf_tst_ok); + complain &= ~tf_tst_ok; + if (type && code != TYPENAME_TYPE && code != TEMPLATE_TYPE_PARM @@ -16199,8 +16205,10 @@ tsubst (tree t, tree args, tsubst_flags_t complain, tree in_decl) return error_mark_node; } - f = make_typename_type (ctx, f, typename_type, - complain | tf_keep_type_decl); + tsubst_flags_t tcomplain = complain | tf_keep_type_decl; + if (tst_ok) + tcomplain |= tf_tst_ok; + f = make_typename_type (ctx, f, typename_type, tcomplain); if (f == error_mark_node) return f; if (TREE_CODE (f) == TYPE_DECL) @@ -16229,6 +16237,12 @@ tsubst (tree t, tree args, tsubst_flags_t complain, tree in_decl) } } + if (TREE_CODE (f) == TEMPLATE_DECL) + { + gcc_checking_assert (tst_ok); + f = make_template_placeholder (f); + } + return cp_build_qualified_type_real (f, cp_type_quals (f) | cp_type_quals (t), complain); } @@ -17107,7 +17121,10 @@ tsubst_copy (tree t, tree args, tsubst_flags_t complain, tree in_decl) case CONVERT_EXPR: case NOP_EXPR: { - tree type = tsubst (TREE_TYPE (t), args, complain, in_decl); + tsubst_flags_t tcomplain = complain; + if (code == CAST_EXPR) + tcomplain |= tf_tst_ok; + tree type = tsubst (TREE_TYPE (t), args, tcomplain, in_decl); tree op0 = tsubst_copy (TREE_OPERAND (t, 0), args, complain, in_decl); return build1 (code, type, op0); } @@ -20130,7 +20147,10 @@ tsubst_copy_and_build (tree t, tree type; tree op, r = NULL_TREE; - type = tsubst (TREE_TYPE (t), args, complain, in_decl); + tsubst_flags_t tcomplain = complain; + if (TREE_CODE (t) == CAST_EXPR) + tcomplain |= tf_tst_ok; + type = tsubst (TREE_TYPE (t), args, tcomplain, in_decl); if (integral_constant_expression_p && !cast_valid_in_integral_constant_expression_p (type)) { @@ -21090,12 +21110,15 @@ tsubst_copy_and_build (tree t, vec<constructor_elt, va_gc> *n; constructor_elt *ce; unsigned HOST_WIDE_INT idx; - tree type = tsubst (TREE_TYPE (t), args, complain, in_decl); bool process_index_p; int newlen; bool need_copy_p = false; tree r; + tsubst_flags_t tcomplain = complain; + if (COMPOUND_LITERAL_P (t)) + tcomplain |= tf_tst_ok; + tree type = tsubst (TREE_TYPE (t), args, tcomplain, in_decl); if (type == error_mark_node) RETURN (error_mark_node); diff --git a/gcc/testsuite/g++.dg/cpp1z/class-deduction107.C b/gcc/testsuite/g++.dg/cpp1z/class-deduction107.C new file mode 100644 index 00000000000..462da1dcdc2 --- /dev/null +++ b/gcc/testsuite/g++.dg/cpp1z/class-deduction107.C @@ -0,0 +1,20 @@ +// PR c++/104641 +// { dg-do compile { target c++17 } } + +template<class T> +struct A { + template<class U> struct B { B(U); }; +private: + template<class U> struct C { C(U); }; +}; + +template<class T> +void f() { + typename A<T>::B x = 0; + auto y = typename A<T>::B(0); + auto z = typename A<T>::B{0}; + + typename A<T>::C w(0); // { dg-error "private" } +} + +template void f<void>(); -- 2.35.1.354.g715d08a9e5