On Wed, 25 Mar 2020, Marek Polacek wrote:
> On Wed, Mar 25, 2020 at 12:17:41PM -0400, Patrick Palka via Gcc-patches wrote:
> > diff --git a/gcc/cp/parser.c b/gcc/cp/parser.c
> > index 03ecd7838f6..14a22b85318 100644
> > --- a/gcc/cp/parser.c
> > +++ b/gcc/cp/parser.c
> > @@ -27689,7 +27689,12 @@ cp_parser_requires_expression (cp_parser *parser)
> > else
> > parms = NULL_TREE;
> >
> > - /* Parse the requirement body. */
> > + /* Always parse the requirement body as if we're inside a template so
> > that
> > + we always do full semantic processing only during evaluation of this
> > + requires-expression and not also now during parsing. */
> > + processing_template_decl_sentinel ptds;
>
> This looks weird; this sentinel will always set processing_template_decl to 0,
> right? So...
>
> > + if (!processing_template_decl)
> > + processing_template_decl = 1;
>
> ...this will always be true? Did you mean to use temp_override instead?
Oops, good point. The intention was to set processing_template_decl to
1 when it is 0, and to otherwise not change it. So it looks like I
should pass false to processing_template_decl_sentinel's ctor here, like
so.
>
> I don't dare to say if this approach is OK or not, but I've certainly had
> my share of fun with CALL_EXPRs in templates :).
Hehe :)
-- >8 --
gcc/cp/ChangeLog:
PR c++/94252
* parser.c (cp_parser_requires_expression): Always parse the requirement
body as if we're processing a template, by temporarily setting
processing_template_decl to non-zero.
* semantics.c (finish_static_assert): Also explain an assertion failure
when the condition is a REQUIRES_EXPR.
gcc/testsuite/ChangeLog:
PR c++/94252
* g++.dg/concepts/diagnostic7.C: New test.
* g++.dg/concepts/pr94252.C: New test.
---
gcc/cp/parser.c | 7 ++++++-
gcc/cp/semantics.c | 6 ++++--
gcc/testsuite/g++.dg/concepts/diagnostic7.C | 12 ++++++++++++
gcc/testsuite/g++.dg/concepts/pr94252.C | 14 ++++++++++++++
4 files changed, 36 insertions(+), 3 deletions(-)
create mode 100644 gcc/testsuite/g++.dg/concepts/diagnostic7.C
create mode 100644 gcc/testsuite/g++.dg/concepts/pr94252.C
diff --git a/gcc/cp/parser.c b/gcc/cp/parser.c
index 03ecd7838f6..6150814ea9e 100644
--- a/gcc/cp/parser.c
+++ b/gcc/cp/parser.c
@@ -27689,7 +27689,12 @@ cp_parser_requires_expression (cp_parser *parser)
else
parms = NULL_TREE;
- /* Parse the requirement body. */
+ /* Always parse the requirement body as if we're inside a template so that
+ we always do full semantic processing only during evaluation of this
+ requires-expression and not also now during parsing. */
+ processing_template_decl_sentinel ptds (false);
+ if (!processing_template_decl)
+ processing_template_decl = 1;
reqs = cp_parser_requirement_body (parser);
if (reqs == error_mark_node)
return error_mark_node;
diff --git a/gcc/cp/semantics.c b/gcc/cp/semantics.c
index bcb2e72fbb5..e998b373af4 100644
--- a/gcc/cp/semantics.c
+++ b/gcc/cp/semantics.c
@@ -9691,8 +9691,10 @@ finish_static_assert (tree condition, tree message,
location_t location,
error ("static assertion failed: %s",
TREE_STRING_POINTER (message));
- /* Actually explain the failure if this is a concept check. */
- if (concept_check_p (orig_condition))
+ /* Actually explain the failure if this is a concept check or a
+ requires-expression. */
+ if (concept_check_p (orig_condition)
+ || TREE_CODE (orig_condition) == REQUIRES_EXPR)
diagnose_constraints (location, orig_condition, NULL_TREE);
}
else if (condition && condition != error_mark_node)
diff --git a/gcc/testsuite/g++.dg/concepts/diagnostic7.C
b/gcc/testsuite/g++.dg/concepts/diagnostic7.C
new file mode 100644
index 00000000000..f78e9bb8240
--- /dev/null
+++ b/gcc/testsuite/g++.dg/concepts/diagnostic7.C
@@ -0,0 +1,12 @@
+// { dg-do compile { target c++2a } }
+
+template<typename A, typename B>
+ concept same_as = __is_same(A, B); // { dg-message ".void. is not the same
as .int." }
+
+void f();
+
+static_assert(requires { { f() } noexcept -> same_as<int>; });
+// { dg-error "static assertion failed" "" { target *-*-* } .-1 }
+// { dg-message "not .noexcept." "" { target *-*-* } .-2 }
+// { dg-message "return-type-requirement" "" { target *-*-* } .-3 }
+// { dg-error "does not satisfy placeholder constraints" "" { target *-*-* }
.-4 }
diff --git a/gcc/testsuite/g++.dg/concepts/pr94252.C
b/gcc/testsuite/g++.dg/concepts/pr94252.C
new file mode 100644
index 00000000000..7b93997363a
--- /dev/null
+++ b/gcc/testsuite/g++.dg/concepts/pr94252.C
@@ -0,0 +1,14 @@
+// PR c++/94252
+// { dg-do compile { target c++2a } }
+
+auto f = []{ return 0; };
+static_assert(requires { f(); });
+
+template<typename A, typename B>
+ concept same_as = __is_same(A, B);
+
+struct S { int f(int) noexcept; };
+static_assert(requires(S o, int i) {
+ o.f(i);
+ { o.f(i) } noexcept -> same_as<int>;
+});
--
2.26.0.rc1.11.g30e9940356
