Re: [PATCH] c++: Diagnose when "requires" is used instead of "requires requires" [PR94306]
On 3/26/20 11:49 PM, Patrick Palka wrote:
On Thu, 26 Mar 2020, Jason Merrill wrote:
On 3/26/20 6:36 PM, Patrick Palka wrote:
On Thu, 26 Mar 2020, Jason Merrill wrote:
On 3/26/20 5:28 PM, Patrick Palka wrote:
This adds support to detect and recover from the case where an opening
brace
immediately follows the start of a requires-clause. So rather than
emitting
the
error
error: expected primary-expression before '{' token
followed by a slew of irrevelant errors, we now assume the user had
intended
to
write "requires requires {" and diagnose and recover accordingly.
Tested on x86_64-pc-linux-gnu, does this look OK?
gcc/cp/ChangeLog:
PR c++/94306
* parser.c (cp_parser_requires_clause_opt): Diagnose and recover from
"requires {" when "requires requires {" was probably intended.
gcc/testsuite/ChangeLog:
PR c++/94306
* g++.dg/concepts/diagnostic8.C: New test.
---
gcc/cp/parser.c | 17 -
gcc/testsuite/g++.dg/concepts/diagnostic8.C | 6 ++
2 files changed, 22 insertions(+), 1 deletion(-)
create mode 100644 gcc/testsuite/g++.dg/concepts/diagnostic8.C
diff --git a/gcc/cp/parser.c b/gcc/cp/parser.c
index 05363653691..73c2c2cb010 100644
--- a/gcc/cp/parser.c
+++ b/gcc/cp/parser.c
@@ -27639,7 +27639,22 @@ cp_parser_requires_clause_opt (cp_parser
*parser,
bool lambda_p)
}
return NULL_TREE;
}
- cp_lexer_consume_token (parser->lexer);
+
+ cp_token *tok2 = cp_lexer_peek_nth_token (parser->lexer, 2);
+ if (tok2->type == CPP_OPEN_BRACE)
Do we want to handle an open paren the same way?
Hmm, wouldn't the error recovery be significantly different for an open
paren here? Just pretending that there's another "requires" token would
mean we proceed as if we got "requires requires (" but that is still
ill-formed I think.
Not ill-formed; a requires-expression can have a parameter-list.
Ah, of course.. But then again, wouldn't "requires (" be not
necessarily ill-formed, since the open paren could possibly be a part of
the constraint-expression e.g. "requires (a || b)"?
Ah, yes.
We could perhaps look ahead of the open paren and check if we match the
ill-formed pattern "requires (...) {...}" and if so, handle the open
paren the same way. Oh, but even that pattern is not necessarily
ill-formed, at least when parsing a lambda: the following
"[] () -> void requires (true) { }"
is apparently a well-formed lambda-expression whose tokens starting from
its requires-clause would match that pattern. So we would probably have
to condition this open-paren handling on !lambda_p.
Yeah, this is too much trouble. Your patch is OK as is.
+{
+ /* An opening brace following the start of a requires-clause is
+ill-formed; the user likely forgot the second `requires' that
+would start a requires-expression. */
+ gcc_rich_location richloc (tok2->location);
+ richloc.add_fixit_insert_before (" requires");
+ error_at (, "missing additional % to start "
+ "a requires-expression");
+ /* Don't consume the `requires', so that it's reused as the start
of
a
+requires-expression. */
+}
+ else
+cp_lexer_consume_token (parser->lexer);
if (!flag_concepts_ts)
return cp_parser_requires_clause_expression (parser, lambda_p);
diff --git a/gcc/testsuite/g++.dg/concepts/diagnostic8.C
b/gcc/testsuite/g++.dg/concepts/diagnostic8.C
new file mode 100644
index 000..70d7e4a9cc1
--- /dev/null
+++ b/gcc/testsuite/g++.dg/concepts/diagnostic8.C
@@ -0,0 +1,6 @@
+// PR c++/94306
+// { dg-do compile { target c++2a } }
+
+template struct S { };
+template requires { typename T::type; } struct S { };
+// { dg-error "missing additional .requires." "" { target *-*-* } .-1 }
Re: [PATCH] c++: Diagnose when "requires" is used instead of "requires requires" [PR94306]
On Thu, 26 Mar 2020, Jason Merrill wrote:
> On 3/26/20 6:36 PM, Patrick Palka wrote:
> > On Thu, 26 Mar 2020, Jason Merrill wrote:
> >
> > > On 3/26/20 5:28 PM, Patrick Palka wrote:
> > > > This adds support to detect and recover from the case where an opening
> > > > brace
> > > > immediately follows the start of a requires-clause. So rather than
> > > > emitting
> > > > the
> > > > error
> > > >
> > > > error: expected primary-expression before '{' token
> > > >
> > > > followed by a slew of irrevelant errors, we now assume the user had
> > > > intended
> > > > to
> > > > write "requires requires {" and diagnose and recover accordingly.
> > > >
> > > > Tested on x86_64-pc-linux-gnu, does this look OK?
> > > >
> > > > gcc/cp/ChangeLog:
> > > >
> > > > PR c++/94306
> > > > * parser.c (cp_parser_requires_clause_opt): Diagnose and
> > > > recover from
> > > > "requires {" when "requires requires {" was probably intended.
> > > >
> > > > gcc/testsuite/ChangeLog:
> > > >
> > > > PR c++/94306
> > > > * g++.dg/concepts/diagnostic8.C: New test.
> > > > ---
> > > >gcc/cp/parser.c | 17 -
> > > >gcc/testsuite/g++.dg/concepts/diagnostic8.C | 6 ++
> > > >2 files changed, 22 insertions(+), 1 deletion(-)
> > > >create mode 100644 gcc/testsuite/g++.dg/concepts/diagnostic8.C
> > > >
> > > > diff --git a/gcc/cp/parser.c b/gcc/cp/parser.c
> > > > index 05363653691..73c2c2cb010 100644
> > > > --- a/gcc/cp/parser.c
> > > > +++ b/gcc/cp/parser.c
> > > > @@ -27639,7 +27639,22 @@ cp_parser_requires_clause_opt (cp_parser
> > > > *parser,
> > > > bool lambda_p)
> > > > }
> > > > return NULL_TREE;
> > > >}
> > > > - cp_lexer_consume_token (parser->lexer);
> > > > +
> > > > + cp_token *tok2 = cp_lexer_peek_nth_token (parser->lexer, 2);
> > > > + if (tok2->type == CPP_OPEN_BRACE)
> > >
> > > Do we want to handle an open paren the same way?
> >
> > Hmm, wouldn't the error recovery be significantly different for an open
> > paren here? Just pretending that there's another "requires" token would
> > mean we proceed as if we got "requires requires (" but that is still
> > ill-formed I think.
>
> Not ill-formed; a requires-expression can have a parameter-list.
Ah, of course.. But then again, wouldn't "requires (" be not
necessarily ill-formed, since the open paren could possibly be a part of
the constraint-expression e.g. "requires (a || b)"?
We could perhaps look ahead of the open paren and check if we match the
ill-formed pattern "requires (...) {...}" and if so, handle the open
paren the same way. Oh, but even that pattern is not necessarily
ill-formed, at least when parsing a lambda: the following
"[] () -> void requires (true) { }"
is apparently a well-formed lambda-expression whose tokens starting from
its requires-clause would match that pattern. So we would probably have
to condition this open-paren handling on !lambda_p.
>
> > >
> > > > +{
> > > > + /* An opening brace following the start of a requires-clause is
> > > > +ill-formed; the user likely forgot the second `requires' that
> > > > +would start a requires-expression. */
> > > > + gcc_rich_location richloc (tok2->location);
> > > > + richloc.add_fixit_insert_before (" requires");
> > > > + error_at (, "missing additional % to start "
> > > > + "a requires-expression");
> > > > + /* Don't consume the `requires', so that it's reused as the start
> > > > of
> > > > a
> > > > +requires-expression. */
> > > > +}
> > > > + else
> > > > +cp_lexer_consume_token (parser->lexer);
> > > >if (!flag_concepts_ts)
> > > >return cp_parser_requires_clause_expression (parser, lambda_p);
> > > > diff --git a/gcc/testsuite/g++.dg/concepts/diagnostic8.C
> > > > b/gcc/testsuite/g++.dg/concepts/diagnostic8.C
> > > > new file mode 100644
> > > > index 000..70d7e4a9cc1
> > > > --- /dev/null
> > > > +++ b/gcc/testsuite/g++.dg/concepts/diagnostic8.C
> > > > @@ -0,0 +1,6 @@
> > > > +// PR c++/94306
> > > > +// { dg-do compile { target c++2a } }
> > > > +
> > > > +template struct S { };
> > > > +template requires { typename T::type; } struct S { };
> > > > +// { dg-error "missing additional .requires." "" { target *-*-* } .-1 }
> > > >
> > >
> > >
> >
>
>
Re: [PATCH] c++: Diagnose when "requires" is used instead of "requires requires" [PR94306]
On 3/26/20 6:36 PM, Patrick Palka wrote:
On Thu, 26 Mar 2020, Jason Merrill wrote:
On 3/26/20 5:28 PM, Patrick Palka wrote:
This adds support to detect and recover from the case where an opening brace
immediately follows the start of a requires-clause. So rather than emitting
the
error
error: expected primary-expression before '{' token
followed by a slew of irrevelant errors, we now assume the user had intended
to
write "requires requires {" and diagnose and recover accordingly.
Tested on x86_64-pc-linux-gnu, does this look OK?
gcc/cp/ChangeLog:
PR c++/94306
* parser.c (cp_parser_requires_clause_opt): Diagnose and recover from
"requires {" when "requires requires {" was probably intended.
gcc/testsuite/ChangeLog:
PR c++/94306
* g++.dg/concepts/diagnostic8.C: New test.
---
gcc/cp/parser.c | 17 -
gcc/testsuite/g++.dg/concepts/diagnostic8.C | 6 ++
2 files changed, 22 insertions(+), 1 deletion(-)
create mode 100644 gcc/testsuite/g++.dg/concepts/diagnostic8.C
diff --git a/gcc/cp/parser.c b/gcc/cp/parser.c
index 05363653691..73c2c2cb010 100644
--- a/gcc/cp/parser.c
+++ b/gcc/cp/parser.c
@@ -27639,7 +27639,22 @@ cp_parser_requires_clause_opt (cp_parser *parser,
bool lambda_p)
}
return NULL_TREE;
}
- cp_lexer_consume_token (parser->lexer);
+
+ cp_token *tok2 = cp_lexer_peek_nth_token (parser->lexer, 2);
+ if (tok2->type == CPP_OPEN_BRACE)
Do we want to handle an open paren the same way?
Hmm, wouldn't the error recovery be significantly different for an open
paren here? Just pretending that there's another "requires" token would
mean we proceed as if we got "requires requires (" but that is still
ill-formed I think.
Not ill-formed; a requires-expression can have a parameter-list.
+{
+ /* An opening brace following the start of a requires-clause is
+ill-formed; the user likely forgot the second `requires' that
+would start a requires-expression. */
+ gcc_rich_location richloc (tok2->location);
+ richloc.add_fixit_insert_before (" requires");
+ error_at (, "missing additional % to start "
+ "a requires-expression");
+ /* Don't consume the `requires', so that it's reused as the start of
a
+requires-expression. */
+}
+ else
+cp_lexer_consume_token (parser->lexer);
if (!flag_concepts_ts)
return cp_parser_requires_clause_expression (parser, lambda_p);
diff --git a/gcc/testsuite/g++.dg/concepts/diagnostic8.C
b/gcc/testsuite/g++.dg/concepts/diagnostic8.C
new file mode 100644
index 000..70d7e4a9cc1
--- /dev/null
+++ b/gcc/testsuite/g++.dg/concepts/diagnostic8.C
@@ -0,0 +1,6 @@
+// PR c++/94306
+// { dg-do compile { target c++2a } }
+
+template struct S { };
+template requires { typename T::type; } struct S { };
+// { dg-error "missing additional .requires." "" { target *-*-* } .-1 }
Re: [PATCH] c++: Diagnose when "requires" is used instead of "requires requires" [PR94306]
On Thu, 26 Mar 2020, David Malcolm wrote:
> On Thu, 2020-03-26 at 17:28 -0400, Patrick Palka via Gcc-patches wrote:
> > This adds support to detect and recover from the case where an
> > opening brace
> > immediately follows the start of a requires-clause. So rather than
> > emitting the
> > error
> >
> > error: expected primary-expression before '{' token
> >
> > followed by a slew of irrevelant errors, we now assume the user had
> > intended to
> > write "requires requires {" and diagnose and recover accordingly.
> >
> > Tested on x86_64-pc-linux-gnu, does this look OK?
> >
> > gcc/cp/ChangeLog:
> >
> > PR c++/94306
> > * parser.c (cp_parser_requires_clause_opt): Diagnose and
> > recover from
> > "requires {" when "requires requires {" was probably intended.
> >
> > gcc/testsuite/ChangeLog:
> >
> > PR c++/94306
> > * g++.dg/concepts/diagnostic8.C: New test.
> > ---
> > gcc/cp/parser.c | 17 -
> > gcc/testsuite/g++.dg/concepts/diagnostic8.C | 6 ++
> > 2 files changed, 22 insertions(+), 1 deletion(-)
> > create mode 100644 gcc/testsuite/g++.dg/concepts/diagnostic8.C
> >
> > diff --git a/gcc/cp/parser.c b/gcc/cp/parser.c
> > index 05363653691..73c2c2cb010 100644
> > --- a/gcc/cp/parser.c
> > +++ b/gcc/cp/parser.c
> > @@ -27639,7 +27639,22 @@ cp_parser_requires_clause_opt (cp_parser
> > *parser, bool lambda_p)
> > }
> >return NULL_TREE;
> > }
> > - cp_lexer_consume_token (parser->lexer);
> > +
> > + cp_token *tok2 = cp_lexer_peek_nth_token (parser->lexer, 2);
> > + if (tok2->type == CPP_OPEN_BRACE)
> > +{
> > + /* An opening brace following the start of a requires-clause
> > is
> > +ill-formed; the user likely forgot the second `requires' that
> > +would start a requires-expression. */
> > + gcc_rich_location richloc (tok2->location);
> > + richloc.add_fixit_insert_before (" requires");
>
> Thanks for adding a fix-it hint. That said, is this spacing here
> correct? If I'm reading it right, this adds " requires" immediately
> before the open brace, leading to a suggestion of:
> "requires {"
> becoming:
> "requires requires{"
>
> Perhaps adding it immediately after the first requires via:
> richloc.add_fixit_insert_after (first_requires_location,
> " requires");
> would be better, which ought to lead to a suggestion of:
> "requires {"
> becoming:
> "requires requires {"
>
> (assuming I'm reading the patch right)
>
> Might be an idea to test the effect of the fix-it hint e.g. via
> -fdiagnostics-generate-patch.
>
> Hope this is constructive
> Dave
That makes a lot of sense, thanks. Luckily we have the location of the
first "requires" already handy. Here's the updated patch which
incorporates the improved fix-it hint:
-- >8 --
gcc/cp/ChangeLog:
PR c++/94306
* parser.c (cp_parser_requires_clause_opt): Diagnose and recover from
"requires {" when "requires requires {" was probably intended.
gcc/testsuite/ChangeLog:
PR c++/94306
* g++.dg/concepts/diagnostic8.C: New test.
---
gcc/cp/parser.c | 17 -
gcc/testsuite/g++.dg/concepts/diagnostic8.C | 6 ++
2 files changed, 22 insertions(+), 1 deletion(-)
create mode 100644 gcc/testsuite/g++.dg/concepts/diagnostic8.C
diff --git a/gcc/cp/parser.c b/gcc/cp/parser.c
index 05363653691..5bc1ecd102e 100644
--- a/gcc/cp/parser.c
+++ b/gcc/cp/parser.c
@@ -27639,7 +27639,22 @@ cp_parser_requires_clause_opt (cp_parser *parser, bool
lambda_p)
}
return NULL_TREE;
}
- cp_lexer_consume_token (parser->lexer);
+
+ cp_token *tok2 = cp_lexer_peek_nth_token (parser->lexer, 2);
+ if (tok2->type == CPP_OPEN_BRACE)
+{
+ /* An opening brace following the start of a requires-clause is
+ill-formed; the user likely forgot the second `requires' that
+would start a requires-expression. */
+ gcc_rich_location richloc (tok2->location);
+ richloc.add_fixit_insert_after (tok->location, " requires");
+ error_at (, "missing additional % to start "
+ "a requires-expression");
+ /* Don't consume the `requires', so that it's reused as the start of a
+requires-expression. */
+}
+ else
+cp_lexer_consume_token (parser->lexer);
if (!flag_concepts_ts)
return cp_parser_requires_clause_expression (parser, lambda_p);
diff --git a/gcc/testsuite/g++.dg/concepts/diagnostic8.C
b/gcc/testsuite/g++.dg/concepts/diagnostic8.C
new file mode 100644
index 000..70d7e4a9cc1
--- /dev/null
+++ b/gcc/testsuite/g++.dg/concepts/diagnostic8.C
@@ -0,0 +1,6 @@
+// PR c++/94306
+// { dg-do compile { target c++2a } }
+
+template struct S { };
+template requires { typename T::type; } struct S { };
+// { dg-error "missing additional .requires." "" { target *-*-* } .-1 }
--
2.26.0.rc1.11.g30e9940356
Re: [PATCH] c++: Diagnose when "requires" is used instead of "requires requires" [PR94306]
On Thu, 26 Mar 2020, Jason Merrill wrote:
> On 3/26/20 5:28 PM, Patrick Palka wrote:
> > This adds support to detect and recover from the case where an opening brace
> > immediately follows the start of a requires-clause. So rather than emitting
> > the
> > error
> >
> >error: expected primary-expression before '{' token
> >
> > followed by a slew of irrevelant errors, we now assume the user had intended
> > to
> > write "requires requires {" and diagnose and recover accordingly.
> >
> > Tested on x86_64-pc-linux-gnu, does this look OK?
> >
> > gcc/cp/ChangeLog:
> >
> > PR c++/94306
> > * parser.c (cp_parser_requires_clause_opt): Diagnose and recover from
> > "requires {" when "requires requires {" was probably intended.
> >
> > gcc/testsuite/ChangeLog:
> >
> > PR c++/94306
> > * g++.dg/concepts/diagnostic8.C: New test.
> > ---
> > gcc/cp/parser.c | 17 -
> > gcc/testsuite/g++.dg/concepts/diagnostic8.C | 6 ++
> > 2 files changed, 22 insertions(+), 1 deletion(-)
> > create mode 100644 gcc/testsuite/g++.dg/concepts/diagnostic8.C
> >
> > diff --git a/gcc/cp/parser.c b/gcc/cp/parser.c
> > index 05363653691..73c2c2cb010 100644
> > --- a/gcc/cp/parser.c
> > +++ b/gcc/cp/parser.c
> > @@ -27639,7 +27639,22 @@ cp_parser_requires_clause_opt (cp_parser *parser,
> > bool lambda_p)
> > }
> > return NULL_TREE;
> > }
> > - cp_lexer_consume_token (parser->lexer);
> > +
> > + cp_token *tok2 = cp_lexer_peek_nth_token (parser->lexer, 2);
> > + if (tok2->type == CPP_OPEN_BRACE)
>
> Do we want to handle an open paren the same way?
Hmm, wouldn't the error recovery be significantly different for an open
paren here? Just pretending that there's another "requires" token would
mean we proceed as if we got "requires requires (" but that is still
ill-formed I think.
>
> > +{
> > + /* An opening brace following the start of a requires-clause is
> > +ill-formed; the user likely forgot the second `requires' that
> > +would start a requires-expression. */
> > + gcc_rich_location richloc (tok2->location);
> > + richloc.add_fixit_insert_before (" requires");
> > + error_at (, "missing additional % to start "
> > + "a requires-expression");
> > + /* Don't consume the `requires', so that it's reused as the start of
> > a
> > +requires-expression. */
> > +}
> > + else
> > +cp_lexer_consume_token (parser->lexer);
> > if (!flag_concepts_ts)
> > return cp_parser_requires_clause_expression (parser, lambda_p);
> > diff --git a/gcc/testsuite/g++.dg/concepts/diagnostic8.C
> > b/gcc/testsuite/g++.dg/concepts/diagnostic8.C
> > new file mode 100644
> > index 000..70d7e4a9cc1
> > --- /dev/null
> > +++ b/gcc/testsuite/g++.dg/concepts/diagnostic8.C
> > @@ -0,0 +1,6 @@
> > +// PR c++/94306
> > +// { dg-do compile { target c++2a } }
> > +
> > +template struct S { };
> > +template requires { typename T::type; } struct S { };
> > +// { dg-error "missing additional .requires." "" { target *-*-* } .-1 }
> >
>
>
Re: [PATCH] c++: Diagnose when "requires" is used instead of "requires requires" [PR94306]
On Thu, 2020-03-26 at 17:28 -0400, Patrick Palka via Gcc-patches wrote:
> This adds support to detect and recover from the case where an
> opening brace
> immediately follows the start of a requires-clause. So rather than
> emitting the
> error
>
> error: expected primary-expression before '{' token
>
> followed by a slew of irrevelant errors, we now assume the user had
> intended to
> write "requires requires {" and diagnose and recover accordingly.
>
> Tested on x86_64-pc-linux-gnu, does this look OK?
>
> gcc/cp/ChangeLog:
>
> PR c++/94306
> * parser.c (cp_parser_requires_clause_opt): Diagnose and
> recover from
> "requires {" when "requires requires {" was probably intended.
>
> gcc/testsuite/ChangeLog:
>
> PR c++/94306
> * g++.dg/concepts/diagnostic8.C: New test.
> ---
> gcc/cp/parser.c | 17 -
> gcc/testsuite/g++.dg/concepts/diagnostic8.C | 6 ++
> 2 files changed, 22 insertions(+), 1 deletion(-)
> create mode 100644 gcc/testsuite/g++.dg/concepts/diagnostic8.C
>
> diff --git a/gcc/cp/parser.c b/gcc/cp/parser.c
> index 05363653691..73c2c2cb010 100644
> --- a/gcc/cp/parser.c
> +++ b/gcc/cp/parser.c
> @@ -27639,7 +27639,22 @@ cp_parser_requires_clause_opt (cp_parser
> *parser, bool lambda_p)
> }
>return NULL_TREE;
> }
> - cp_lexer_consume_token (parser->lexer);
> +
> + cp_token *tok2 = cp_lexer_peek_nth_token (parser->lexer, 2);
> + if (tok2->type == CPP_OPEN_BRACE)
> +{
> + /* An opening brace following the start of a requires-clause
> is
> + ill-formed; the user likely forgot the second `requires' that
> + would start a requires-expression. */
> + gcc_rich_location richloc (tok2->location);
> + richloc.add_fixit_insert_before (" requires");
Thanks for adding a fix-it hint. That said, is this spacing here
correct? If I'm reading it right, this adds " requires" immediately
before the open brace, leading to a suggestion of:
"requires {"
becoming:
"requires requires{"
Perhaps adding it immediately after the first requires via:
richloc.add_fixit_insert_after (first_requires_location,
" requires");
would be better, which ought to lead to a suggestion of:
"requires {"
becoming:
"requires requires {"
(assuming I'm reading the patch right)
Might be an idea to test the effect of the fix-it hint e.g. via
-fdiagnostics-generate-patch.
Hope this is constructive
Dave
> + error_at (, "missing additional % to start
> "
> + "a requires-expression");
> + /* Don't consume the `requires', so that it's reused as the
> start of a
> + requires-expression. */
> +}
> + else
> +cp_lexer_consume_token (parser->lexer);
>
>if (!flag_concepts_ts)
> return cp_parser_requires_clause_expression (parser, lambda_p);
> diff --git a/gcc/testsuite/g++.dg/concepts/diagnostic8.C
> b/gcc/testsuite/g++.dg/concepts/diagnostic8.C
> new file mode 100644
> index 000..70d7e4a9cc1
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/concepts/diagnostic8.C
> @@ -0,0 +1,6 @@
> +// PR c++/94306
> +// { dg-do compile { target c++2a } }
> +
> +template struct S { };
> +template requires { typename T::type; } struct S { };
> +// { dg-error "missing additional .requires." "" { target *-*-* } .-
> 1 }
Re: [PATCH] c++: Diagnose when "requires" is used instead of "requires requires" [PR94306]
On 3/26/20 5:28 PM, Patrick Palka wrote:
This adds support to detect and recover from the case where an opening brace
immediately follows the start of a requires-clause. So rather than emitting the
error
error: expected primary-expression before '{' token
followed by a slew of irrevelant errors, we now assume the user had intended to
write "requires requires {" and diagnose and recover accordingly.
Tested on x86_64-pc-linux-gnu, does this look OK?
gcc/cp/ChangeLog:
PR c++/94306
* parser.c (cp_parser_requires_clause_opt): Diagnose and recover from
"requires {" when "requires requires {" was probably intended.
gcc/testsuite/ChangeLog:
PR c++/94306
* g++.dg/concepts/diagnostic8.C: New test.
---
gcc/cp/parser.c | 17 -
gcc/testsuite/g++.dg/concepts/diagnostic8.C | 6 ++
2 files changed, 22 insertions(+), 1 deletion(-)
create mode 100644 gcc/testsuite/g++.dg/concepts/diagnostic8.C
diff --git a/gcc/cp/parser.c b/gcc/cp/parser.c
index 05363653691..73c2c2cb010 100644
--- a/gcc/cp/parser.c
+++ b/gcc/cp/parser.c
@@ -27639,7 +27639,22 @@ cp_parser_requires_clause_opt (cp_parser *parser, bool
lambda_p)
}
return NULL_TREE;
}
- cp_lexer_consume_token (parser->lexer);
+
+ cp_token *tok2 = cp_lexer_peek_nth_token (parser->lexer, 2);
+ if (tok2->type == CPP_OPEN_BRACE)
Do we want to handle an open paren the same way?
+{
+ /* An opening brace following the start of a requires-clause is
+ill-formed; the user likely forgot the second `requires' that
+would start a requires-expression. */
+ gcc_rich_location richloc (tok2->location);
+ richloc.add_fixit_insert_before (" requires");
+ error_at (, "missing additional % to start "
+ "a requires-expression");
+ /* Don't consume the `requires', so that it's reused as the start of a
+requires-expression. */
+}
+ else
+cp_lexer_consume_token (parser->lexer);
if (!flag_concepts_ts)
return cp_parser_requires_clause_expression (parser, lambda_p);
diff --git a/gcc/testsuite/g++.dg/concepts/diagnostic8.C
b/gcc/testsuite/g++.dg/concepts/diagnostic8.C
new file mode 100644
index 000..70d7e4a9cc1
--- /dev/null
+++ b/gcc/testsuite/g++.dg/concepts/diagnostic8.C
@@ -0,0 +1,6 @@
+// PR c++/94306
+// { dg-do compile { target c++2a } }
+
+template struct S { };
+template requires { typename T::type; } struct S { };
+// { dg-error "missing additional .requires." "" { target *-*-* } .-1 }
[PATCH] c++: Diagnose when "requires" is used instead of "requires requires" [PR94306]
This adds support to detect and recover from the case where an opening brace
immediately follows the start of a requires-clause. So rather than emitting the
error
error: expected primary-expression before '{' token
followed by a slew of irrevelant errors, we now assume the user had intended to
write "requires requires {" and diagnose and recover accordingly.
Tested on x86_64-pc-linux-gnu, does this look OK?
gcc/cp/ChangeLog:
PR c++/94306
* parser.c (cp_parser_requires_clause_opt): Diagnose and recover from
"requires {" when "requires requires {" was probably intended.
gcc/testsuite/ChangeLog:
PR c++/94306
* g++.dg/concepts/diagnostic8.C: New test.
---
gcc/cp/parser.c | 17 -
gcc/testsuite/g++.dg/concepts/diagnostic8.C | 6 ++
2 files changed, 22 insertions(+), 1 deletion(-)
create mode 100644 gcc/testsuite/g++.dg/concepts/diagnostic8.C
diff --git a/gcc/cp/parser.c b/gcc/cp/parser.c
index 05363653691..73c2c2cb010 100644
--- a/gcc/cp/parser.c
+++ b/gcc/cp/parser.c
@@ -27639,7 +27639,22 @@ cp_parser_requires_clause_opt (cp_parser *parser, bool
lambda_p)
}
return NULL_TREE;
}
- cp_lexer_consume_token (parser->lexer);
+
+ cp_token *tok2 = cp_lexer_peek_nth_token (parser->lexer, 2);
+ if (tok2->type == CPP_OPEN_BRACE)
+{
+ /* An opening brace following the start of a requires-clause is
+ill-formed; the user likely forgot the second `requires' that
+would start a requires-expression. */
+ gcc_rich_location richloc (tok2->location);
+ richloc.add_fixit_insert_before (" requires");
+ error_at (, "missing additional % to start "
+ "a requires-expression");
+ /* Don't consume the `requires', so that it's reused as the start of a
+requires-expression. */
+}
+ else
+cp_lexer_consume_token (parser->lexer);
if (!flag_concepts_ts)
return cp_parser_requires_clause_expression (parser, lambda_p);
diff --git a/gcc/testsuite/g++.dg/concepts/diagnostic8.C
b/gcc/testsuite/g++.dg/concepts/diagnostic8.C
new file mode 100644
index 000..70d7e4a9cc1
--- /dev/null
+++ b/gcc/testsuite/g++.dg/concepts/diagnostic8.C
@@ -0,0 +1,6 @@
+// PR c++/94306
+// { dg-do compile { target c++2a } }
+
+template struct S { };
+template requires { typename T::type; } struct S { };
+// { dg-error "missing additional .requires." "" { target *-*-* } .-1 }
--
2.26.0.rc1.11.g30e9940356
