https://gcc.gnu.org/g:38c2679ff9330d3ac1d5d86459294446733a435a
commit r13-8608-g38c2679ff9330d3ac1d5d86459294446733a435a
Author: Patrick Palka <ppa...@redhat.com>
Date: Fri Feb 2 19:07:08 2024 -0500
c++: requires-exprs and partial constraint subst [PR110006]
In r11-3261-gb28b621ac67bee we made tsubst_requires_expr never partially
substitute into a requires-expression so as to avoid checking its
requirements out of order during e.g. generic lambda regeneration.
These PRs however illustrate that we still sometimes do need to
partially substitute into a requires-expression, in particular when it
appears in associated constraints that we're directly substituting for
sake of declaration matching or dguide constraint rewriting. In these
cases we're being called from tsubst_constraint during which
processing_constraint_expression_p is true, so this patch checks this
predicate to control whether we defer substitution or partially
substitute.
In turn, we now need to propagate semantic tsubst flags through
tsubst_requires_expr rather than just using tf_none, notably for sake of
dguide constraint rewriting which sets tf_dguide.
PR c++/110006
PR c++/112769
gcc/cp/ChangeLog:
* constraint.cc (subst_info::quiet): Accomodate non-diagnostic
tsubst flags.
(tsubst_valid_expression_requirement): Likewise.
(tsubst_simple_requirement): Return a substituted _REQ node when
processing_template_decl.
(tsubst_type_requirement_1): Accomodate non-diagnostic tsubst
flags.
(tsubst_type_requirement): Return a substituted _REQ node when
processing_template_decl.
(tsubst_compound_requirement): Likewise. Accomodate non-diagnostic
tsubst flags.
(tsubst_nested_requirement): Likewise.
(tsubst_requires_expr): Don't defer partial substitution when
processing_constraint_expression_p is true, in which case return
a substituted REQUIRES_EXPR.
* pt.cc (tsubst_expr) <case REQUIRES_EXPR>: Accomodate
non-diagnostic tsubst flags.
gcc/testsuite/ChangeLog:
* g++.dg/cpp2a/class-deduction-alias18.C: New test.
* g++.dg/cpp2a/concepts-friend16.C: New test.
Reviewed-by: Jason Merrill <ja...@redhat.com>
(cherry picked from commit 686b5eb9c9ee623a604dde5c49fa11c23f384c62)
Diff:
---
gcc/cp/constraint.cc | 56 +++++++++++++++++-----
gcc/cp/pt.cc | 3 +-
.../g++.dg/cpp2a/class-deduction-alias18.C | 13 +++++
gcc/testsuite/g++.dg/cpp2a/concepts-friend16.C | 25 ++++++++++
4 files changed, 84 insertions(+), 13 deletions(-)
diff --git a/gcc/cp/constraint.cc b/gcc/cp/constraint.cc
index 273d15ab097..971619eabea 100644
--- a/gcc/cp/constraint.cc
+++ b/gcc/cp/constraint.cc
@@ -85,7 +85,7 @@ struct subst_info
/* True if we should not diagnose errors. */
bool quiet() const
{
- return complain == tf_none;
+ return !(complain & tf_warning_or_error);
}
/* True if we should diagnose errors. */
@@ -1999,8 +1999,9 @@ hash_placeholder_constraint (tree c)
static tree
tsubst_valid_expression_requirement (tree t, tree args, sat_info info)
{
- tree r = tsubst_expr (t, args, tf_none, info.in_decl);
- if (convert_to_void (r, ICV_STATEMENT, tf_none) != error_mark_node)
+ tsubst_flags_t quiet = info.complain & ~tf_warning_or_error;
+ tree r = tsubst_expr (t, args, quiet, info.in_decl);
+ if (convert_to_void (r, ICV_STATEMENT, quiet) != error_mark_node)
return r;
if (info.diagnose_unsatisfaction_p ())
@@ -2036,6 +2037,8 @@ tsubst_simple_requirement (tree t, tree args, sat_info
info)
tree expr = tsubst_valid_expression_requirement (t0, args, info);
if (expr == error_mark_node)
return error_mark_node;
+ if (processing_template_decl)
+ return finish_simple_requirement (EXPR_LOCATION (t), expr);
return boolean_true_node;
}
@@ -2045,7 +2048,8 @@ tsubst_simple_requirement (tree t, tree args, sat_info
info)
static tree
tsubst_type_requirement_1 (tree t, tree args, sat_info info, location_t loc)
{
- tree r = tsubst (t, args, tf_none, info.in_decl);
+ tsubst_flags_t quiet = info.complain & ~tf_warning_or_error;
+ tree r = tsubst (t, args, quiet, info.in_decl);
if (r != error_mark_node)
return r;
@@ -2076,6 +2080,8 @@ tsubst_type_requirement (tree t, tree args, sat_info info)
tree type = tsubst_type_requirement_1 (t0, args, info, EXPR_LOCATION (t));
if (type == error_mark_node)
return error_mark_node;
+ if (processing_template_decl)
+ return finish_type_requirement (EXPR_LOCATION (t), type);
return boolean_true_node;
}
@@ -2132,9 +2138,11 @@ tsubst_compound_requirement (tree t, tree args, sat_info
info)
location_t loc = cp_expr_loc_or_input_loc (expr);
+ subst_info quiet (info.complain & ~tf_warning_or_error, info.in_decl);
+
/* Check the noexcept condition. */
bool noexcept_p = COMPOUND_REQ_NOEXCEPT_P (t);
- if (noexcept_p && !expr_noexcept_p (expr, tf_none))
+ if (noexcept_p && !expr_noexcept_p (expr, quiet.complain))
{
if (info.diagnose_unsatisfaction_p ())
inform (loc, "%qE is not %<noexcept%>", expr);
@@ -2147,8 +2155,6 @@ tsubst_compound_requirement (tree t, tree args, sat_info
info)
if (type == error_mark_node)
return error_mark_node;
- subst_info quiet (tf_none, info.in_decl);
-
/* Check expression against the result type. */
if (type)
{
@@ -2190,6 +2196,9 @@ tsubst_compound_requirement (tree t, tree args, sat_info
info)
}
}
+ if (processing_template_decl)
+ return finish_compound_requirement (EXPR_LOCATION (t),
+ expr, type, noexcept_p);
return boolean_true_node;
}
@@ -2198,7 +2207,16 @@ tsubst_compound_requirement (tree t, tree args, sat_info
info)
static tree
tsubst_nested_requirement (tree t, tree args, sat_info info)
{
- sat_info quiet (tf_none, info.in_decl);
+ if (processing_template_decl)
+ {
+ tree req = TREE_OPERAND (t, 0);
+ req = tsubst_constraint (req, args, info.complain, info.in_decl);
+ if (req == error_mark_node)
+ return error_mark_node;
+ return finish_nested_requirement (EXPR_LOCATION (t), req);
+ }
+
+ sat_info quiet (info.complain & ~tf_warning_or_error, info.in_decl);
tree result = constraint_satisfaction_value (t, args, quiet);
if (result == boolean_true_node)
return boolean_true_node;
@@ -2338,18 +2356,25 @@ tsubst_requires_expr (tree t, tree args, sat_info info)
args = add_extra_args (REQUIRES_EXPR_EXTRA_ARGS (t), args,
info.complain, info.in_decl);
- if (processing_template_decl)
+ if (processing_template_decl
+ && !processing_constraint_expression_p ())
{
/* We're partially instantiating a generic lambda. Substituting into
this requires-expression now may cause its requirements to get
checked out of order, so instead just remember the template
- arguments and wait until we can substitute them all at once. */
+ arguments and wait until we can substitute them all at once.
+
+ Except if this requires-expr is part of associated constraints
+ that we're substituting into directly (for e.g. declaration
+ matching or dguide constraint rewriting), in which case we need
+ to partially substitute. */
t = copy_node (t);
REQUIRES_EXPR_EXTRA_ARGS (t) = build_extra_args (t, args, info.complain);
return t;
}
- if (tree parms = REQUIRES_EXPR_PARMS (t))
+ tree parms = REQUIRES_EXPR_PARMS (t);
+ if (parms)
{
parms = tsubst_constraint_variables (parms, args, info);
if (parms == error_mark_node)
@@ -2357,10 +2382,13 @@ tsubst_requires_expr (tree t, tree args, sat_info info)
}
tree result = boolean_true_node;
+ if (processing_template_decl)
+ result = NULL_TREE;
for (tree reqs = REQUIRES_EXPR_REQS (t); reqs; reqs = TREE_CHAIN (reqs))
{
tree req = TREE_VALUE (reqs);
- if (tsubst_requirement (req, args, info) == error_mark_node)
+ req = tsubst_requirement (req, args, info);
+ if (req == error_mark_node)
{
result = boolean_false_node;
if (info.diagnose_unsatisfaction_p ())
@@ -2368,7 +2396,11 @@ tsubst_requires_expr (tree t, tree args, sat_info info)
else
break;
}
+ else if (processing_template_decl)
+ result = tree_cons (NULL_TREE, req, result);
}
+ if (processing_template_decl && result != boolean_false_node)
+ result = finish_requires_expr (EXPR_LOCATION (t), parms, nreverse
(result));
return result;
}
diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc
index f5e6541fd0f..a768d11c82f 100644
--- a/gcc/cp/pt.cc
+++ b/gcc/cp/pt.cc
@@ -21783,7 +21783,8 @@ tsubst_copy_and_build (tree t,
case REQUIRES_EXPR:
{
- tree r = tsubst_requires_expr (t, args, tf_none, in_decl);
+ complain &= ~tf_warning_or_error;
+ tree r = tsubst_requires_expr (t, args, complain, in_decl);
RETURN (r);
}
diff --git a/gcc/testsuite/g++.dg/cpp2a/class-deduction-alias18.C
b/gcc/testsuite/g++.dg/cpp2a/class-deduction-alias18.C
new file mode 100644
index 00000000000..0bb11bb944c
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp2a/class-deduction-alias18.C
@@ -0,0 +1,13 @@
+// PR c++/112769
+// { dg-do compile { target c++20 } }
+
+template<int I, typename T>
+struct type
+{
+ type(T) requires requires { T{0}; };
+};
+
+template <typename T>
+using alias = type<0, T>;
+
+alias foo{123};
diff --git a/gcc/testsuite/g++.dg/cpp2a/concepts-friend16.C
b/gcc/testsuite/g++.dg/cpp2a/concepts-friend16.C
new file mode 100644
index 00000000000..18974eeb172
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp2a/concepts-friend16.C
@@ -0,0 +1,25 @@
+// PR c++/110006
+// { dg-do compile { target c++20 } }
+
+template<typename T>
+class s;
+
+template<typename T>
+void constraint(s<T> const&, int&);
+
+template<typename U, typename T2>
+U function(s<T2> const x)
+ requires requires (U& u) { constraint(x, u); };
+
+template<typename T>
+class s
+{
+ template<typename U, typename T2>
+ friend U function(s<T2> const x)
+ requires requires (U& u) { constraint(x, u); };
+};
+
+int f(s<int> q)
+{
+ return function<int>(q); // { dg-bogus "ambiguous" }
+}
