On 2/23/23 16:52, Patrick Palka wrote:
Here we're incorrectly treating the non-dependent variable template-id
tag<int> as dependent ever since r226642 gave variable TEMPLATE_ID_EXPR
an empty type which causes the call to finish_template_variable from
finish_id_expression_1 to be dead code at template parse time. Thus
we're led into treating tag<int>.var<void> as a dependent name at parse
time.
This patch fixes this by making finish_id_expression_1 instantiate a
variable template-id as long as the template and args are non-dependent
according to the dependence test in lookup_and_finish_template_variable
and not according to type_dependent_expression_p. This patch also moves
said dependence test into finish_template_variable.
bootstrapped and regtested on x86_64-pc-linux-gnu, does this look OK for
trunk?
PR c++/108848
gcc/cp/ChangeLog:
* pt.cc (finish_template_variable): Move dependence check
to here from ...
(lookup_and_finish_template_variable): ... here.
* semantics.cc (finish_id_expression_1): Call
finish_template_variable sooner and regardless of
type_dependent_expression_p.
gcc/testsuite/ChangeLog:
* g++.dg/cpp1y/noexcept1.C: Don't expect bogus "different
exception specifier" error. Expect a separate "not usable
in a constant expression" error.
* g++.dg/cpp1y/var-templ70.C: New test.
* g++.dg/cpp1y/var-templ71.C: New test.
---
gcc/cp/pt.cc | 18 ++++++++++--------
gcc/cp/semantics.cc | 14 +++++---------
gcc/testsuite/g++.dg/cpp1y/noexcept1.C | 4 ++--
gcc/testsuite/g++.dg/cpp1y/var-templ70.C | 20 ++++++++++++++++++++
gcc/testsuite/g++.dg/cpp1y/var-templ71.C | 10 ++++++++++
5 files changed, 47 insertions(+), 19 deletions(-)
create mode 100644 gcc/testsuite/g++.dg/cpp1y/var-templ70.C
create mode 100644 gcc/testsuite/g++.dg/cpp1y/var-templ71.C
diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc
index b1ac7d4beb4..11c0baa0119 100644
--- a/gcc/cp/pt.cc
+++ b/gcc/cp/pt.cc
@@ -10317,7 +10317,8 @@ lookup_template_variable (tree templ, tree arglist)
return build2 (TEMPLATE_ID_EXPR, NULL_TREE, templ, arglist);
}
-/* Instantiate a variable declaration from a TEMPLATE_ID_EXPR for use. */
+/* Instantiate a variable declaration from a TEMPLATE_ID_EXPR if it's
+ not dependent. */
tree
finish_template_variable (tree var, tsubst_flags_t complain)
@@ -10325,6 +10326,12 @@ finish_template_variable (tree var, tsubst_flags_t
complain)
tree templ = TREE_OPERAND (var, 0);
tree arglist = TREE_OPERAND (var, 1);
+ /* If the template or arguments are dependent, then we
+ can't instantiate yet. */
+ if (TMPL_PARMS_DEPTH (DECL_TEMPLATE_PARMS (templ)) != 1
+ || any_dependent_template_arguments_p (arglist))
+ return var;
+
tree parms = DECL_TEMPLATE_PARMS (templ);
arglist = coerce_template_parms (parms, arglist, templ, complain);
if (arglist == error_mark_node)
@@ -10352,13 +10359,8 @@ lookup_and_finish_template_variable (tree templ, tree
targs,
tsubst_flags_t complain)
{
tree var = lookup_template_variable (templ, targs);
- if (TMPL_PARMS_DEPTH (DECL_TEMPLATE_PARMS (templ)) == 1
- && !any_dependent_template_arguments_p (targs))
- {
- var = finish_template_variable (var, complain);
- mark_used (var);
- }
-
+ var = finish_template_variable (var, complain);
+ mark_used (var);
return convert_from_reference (var);
}
diff --git a/gcc/cp/semantics.cc b/gcc/cp/semantics.cc
index c2df0b69b30..a18364dda4f 100644
--- a/gcc/cp/semantics.cc
+++ b/gcc/cp/semantics.cc
@@ -4208,6 +4208,11 @@ finish_id_expression_1 (tree id_expression,
}
else
{
We could use a comment here about why this needs to come before checking
type_dep*. OK with that change.
+ if (TREE_CODE (decl) == TEMPLATE_ID_EXPR
+ && variable_template_p (TREE_OPERAND (decl, 0))
+ && !concept_check_p (decl))
+ decl = finish_template_variable (decl);
+
bool dependent_p = type_dependent_expression_p (decl);
/* If the declaration was explicitly qualified indicate
@@ -4275,15 +4280,6 @@ finish_id_expression_1 (tree id_expression,
/* Replace an evaluated use of the thread_local variable with
a call to its wrapper. */
decl = wrap;
- else if (TREE_CODE (decl) == TEMPLATE_ID_EXPR
- && !dependent_p
- && variable_template_p (TREE_OPERAND (decl, 0))
- && !concept_check_p (decl))
- {
- decl = finish_template_variable (decl);
- mark_used (decl);
- decl = convert_from_reference (decl);
- }
else if (concept_check_p (decl))
{
/* Nothing more to do. All of the analysis for concept checks
diff --git a/gcc/testsuite/g++.dg/cpp1y/noexcept1.C
b/gcc/testsuite/g++.dg/cpp1y/noexcept1.C
index 86e46c96148..caa4a056a2e 100644
--- a/gcc/testsuite/g++.dg/cpp1y/noexcept1.C
+++ b/gcc/testsuite/g++.dg/cpp1y/noexcept1.C
@@ -5,9 +5,9 @@ template <int> bool b;
template <typename>
struct C {
- template <typename> friend int foo() noexcept(b<1>); // { dg-error "not usable in
a constant expression|different exception specifier" }
+ template <typename> friend int foo() noexcept(b<1>); // { dg-error "not usable in
a constant expression" }
};
-template <typename> int foo() noexcept(b<1>);
+template <typename> int foo() noexcept(b<1>); // { dg-error "not usable in a
constant expression" }
auto a = C<int>();
diff --git a/gcc/testsuite/g++.dg/cpp1y/var-templ70.C
b/gcc/testsuite/g++.dg/cpp1y/var-templ70.C
new file mode 100644
index 00000000000..aed2db5de88
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp1y/var-templ70.C
@@ -0,0 +1,20 @@
+// PR c++/108848
+// { dg-do compile { target c++14 } }
+
+template<class T>
+struct tag_t {
+ template<class Sig>
+ static constexpr const Sig* var = nullptr;
+
+ template<class Sig>
+ static const Sig* fun();
+};
+
+template <class T>
+constexpr tag_t<T> tag {};
+
+template<class T>
+void f() {
+ tag<int>.var<void>; // { dg-bogus "expected 'template' keyword" }
+ tag<int>.fun<void>(); // { dg-bogus "expected 'template' keyword" }
+};
diff --git a/gcc/testsuite/g++.dg/cpp1y/var-templ71.C
b/gcc/testsuite/g++.dg/cpp1y/var-templ71.C
new file mode 100644
index 00000000000..df33c62ec3e
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp1y/var-templ71.C
@@ -0,0 +1,10 @@
+// Verify we can evaluate a non-dependent variable template-id ahead of time.
+// { dg-do compile { target c++14 } }
+
+template<class Sig>
+static constexpr int var = 0;
+
+template<class T>
+void f() {
+ static_assert(var<void>); // { dg-error "assert" }
+}
