* [PATCH] c++: Allow template lambdas without lambda-declarator [PR97839]
@ 2020-11-17 18:05 Marek Polacek
2020-11-18 18:16 ` Marek Polacek
2020-11-20 22:14 ` Jason Merrill
0 siblings, 2 replies; 4+ messages in thread
From: Marek Polacek @ 2020-11-17 18:05 UTC (permalink / raw)
To: GCC Patches, Jason Merrill
Our implementation of template lambdas incorrectly requires the optional
lambda-declarator. This was probably required by an early draft of
generic lambdas, but now the production is [expr.prim.lambda.general]:
lambda-expression:
lambda-introducer lambda-declarator [opt] compound-statement
lambda-introducer < template-parameter-list > requires-clause [opt]
lambda-declarator [opt] compound-statement
Therefore, we should accept the following test.
Incidentally, I noticed we give a terrible diagnostic when the user uses
'mutable', but forgets to type '()' before it, which sounds like a common
mistake. So it seems to me we should handle that specifically, rather
than to emit this:
lambda-generic8.C: In lambda function:
lambda-generic8.C:8:18: error: expected '{' before 'mutable'
8 | []<typename T> mutable {}.operator()<int>();
| ^~~~~~~
lambda-generic8.C: In function 'int main()':
lambda-generic8.C:8:17: error: expected ';' before 'mutable'
8 | []<typename T> mutable {}.operator()<int>();
| ^~~~~~~~
| ;
lambda-generic8.C:8:28: error: expected primary-expression before '.' token
8 | []<typename T> mutable {}.operator()<int>();
| ^
lambda-generic8.C:8:40: error: expected primary-expression before 'int'
8 | []<typename T> mutable {}.operator()<int>();
| ^~~
Is it okay to fix this in stage3?
Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk?
gcc/cp/ChangeLog:
PR c++/97839
* parser.c (cp_parser_lambda_declarator_opt): Don't require ().
gcc/testsuite/ChangeLog:
PR c++/97839
* g++.dg/cpp2a/lambda-generic8.C: New test.
---
gcc/cp/parser.c | 14 ++++++--------
gcc/testsuite/g++.dg/cpp2a/lambda-generic8.C | 9 +++++++++
2 files changed, 15 insertions(+), 8 deletions(-)
create mode 100644 gcc/testsuite/g++.dg/cpp2a/lambda-generic8.C
diff --git a/gcc/cp/parser.c b/gcc/cp/parser.c
index 42f705266bb..9f09c778c29 100644
--- a/gcc/cp/parser.c
+++ b/gcc/cp/parser.c
@@ -10604,6 +10604,8 @@ cp_parser_trait_expr (cp_parser* parser, enum rid keyword)
lambda-expression:
lambda-introducer lambda-declarator [opt] compound-statement
+ lambda-introducer < template-parameter-list > requires-clause [opt]
+ lambda-declarator [opt] compound-statement
Returns a representation of the expression. */
@@ -11061,13 +11063,11 @@ cp_parser_lambda_introducer (cp_parser* parser, tree lambda_expr)
/* Parse the (optional) middle of a lambda expression.
lambda-declarator:
- < template-parameter-list [opt] >
- requires-clause [opt]
- ( parameter-declaration-clause [opt] )
- attribute-specifier [opt]
+ ( parameter-declaration-clause )
decl-specifier-seq [opt]
- exception-specification [opt]
- lambda-return-type-clause [opt]
+ noexcept-specifier [opt]
+ attribute-specifier-seq [opt]
+ trailing-return-type [opt]
requires-clause [opt]
LAMBDA_EXPR is the current representation of the lambda expression. */
@@ -11217,8 +11217,6 @@ cp_parser_lambda_declarator_opt (cp_parser* parser, tree lambda_expr)
trailing-return-type in case of decltype. */
pop_bindings_and_leave_scope ();
}
- else if (template_param_list != NULL_TREE) // generate diagnostic
- cp_parser_require (parser, CPP_OPEN_PAREN, RT_OPEN_PAREN);
/* Create the function call operator.
diff --git a/gcc/testsuite/g++.dg/cpp2a/lambda-generic8.C b/gcc/testsuite/g++.dg/cpp2a/lambda-generic8.C
new file mode 100644
index 00000000000..f3c3809b36d
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp2a/lambda-generic8.C
@@ -0,0 +1,9 @@
+// PR c++/97839
+// { dg-do compile { target c++20 } }
+// Test that a lambda with <template-param-list> doesn't require
+// a lambda-declarator.
+
+int main()
+{
+ []<typename T>{}.operator()<int>();
+}
base-commit: 8661f4faa875f361cd22a197774c1fa04cd0580b
--
2.28.0
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] c++: Allow template lambdas without lambda-declarator [PR97839]
2020-11-17 18:05 [PATCH] c++: Allow template lambdas without lambda-declarator [PR97839] Marek Polacek
@ 2020-11-18 18:16 ` Marek Polacek
2020-11-20 22:15 ` Jason Merrill
2020-11-20 22:14 ` Jason Merrill
1 sibling, 1 reply; 4+ messages in thread
From: Marek Polacek @ 2020-11-18 18:16 UTC (permalink / raw)
To: GCC Patches, Jason Merrill
On Tue, Nov 17, 2020 at 01:05:20PM -0500, Marek Polacek via Gcc-patches wrote:
> Our implementation of template lambdas incorrectly requires the optional
> lambda-declarator. This was probably required by an early draft of
> generic lambdas, but now the production is [expr.prim.lambda.general]:
>
> lambda-expression:
> lambda-introducer lambda-declarator [opt] compound-statement
> lambda-introducer < template-parameter-list > requires-clause [opt]
> lambda-declarator [opt] compound-statement
>
> Therefore, we should accept the following test.
>
> Incidentally, I noticed we give a terrible diagnostic when the user uses
> 'mutable', but forgets to type '()' before it, which sounds like a common
> mistake. So it seems to me we should handle that specifically, rather
> than to emit this:
This might be necessary to handle <wg21.link/p1102> anyway.
> lambda-generic8.C: In lambda function:
> lambda-generic8.C:8:18: error: expected '{' before 'mutable'
> 8 | []<typename T> mutable {}.operator()<int>();
> | ^~~~~~~
> lambda-generic8.C: In function 'int main()':
> lambda-generic8.C:8:17: error: expected ';' before 'mutable'
> 8 | []<typename T> mutable {}.operator()<int>();
> | ^~~~~~~~
> | ;
> lambda-generic8.C:8:28: error: expected primary-expression before '.' token
> 8 | []<typename T> mutable {}.operator()<int>();
> | ^
> lambda-generic8.C:8:40: error: expected primary-expression before 'int'
> 8 | []<typename T> mutable {}.operator()<int>();
> | ^~~
>
> Is it okay to fix this in stage3?
>
> Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk?
>
> gcc/cp/ChangeLog:
>
> PR c++/97839
> * parser.c (cp_parser_lambda_declarator_opt): Don't require ().
>
> gcc/testsuite/ChangeLog:
>
> PR c++/97839
> * g++.dg/cpp2a/lambda-generic8.C: New test.
> ---
> gcc/cp/parser.c | 14 ++++++--------
> gcc/testsuite/g++.dg/cpp2a/lambda-generic8.C | 9 +++++++++
> 2 files changed, 15 insertions(+), 8 deletions(-)
> create mode 100644 gcc/testsuite/g++.dg/cpp2a/lambda-generic8.C
>
> diff --git a/gcc/cp/parser.c b/gcc/cp/parser.c
> index 42f705266bb..9f09c778c29 100644
> --- a/gcc/cp/parser.c
> +++ b/gcc/cp/parser.c
> @@ -10604,6 +10604,8 @@ cp_parser_trait_expr (cp_parser* parser, enum rid keyword)
>
> lambda-expression:
> lambda-introducer lambda-declarator [opt] compound-statement
> + lambda-introducer < template-parameter-list > requires-clause [opt]
> + lambda-declarator [opt] compound-statement
>
> Returns a representation of the expression. */
>
> @@ -11061,13 +11063,11 @@ cp_parser_lambda_introducer (cp_parser* parser, tree lambda_expr)
> /* Parse the (optional) middle of a lambda expression.
>
> lambda-declarator:
> - < template-parameter-list [opt] >
> - requires-clause [opt]
> - ( parameter-declaration-clause [opt] )
> - attribute-specifier [opt]
> + ( parameter-declaration-clause )
> decl-specifier-seq [opt]
> - exception-specification [opt]
> - lambda-return-type-clause [opt]
> + noexcept-specifier [opt]
> + attribute-specifier-seq [opt]
> + trailing-return-type [opt]
> requires-clause [opt]
>
> LAMBDA_EXPR is the current representation of the lambda expression. */
> @@ -11217,8 +11217,6 @@ cp_parser_lambda_declarator_opt (cp_parser* parser, tree lambda_expr)
> trailing-return-type in case of decltype. */
> pop_bindings_and_leave_scope ();
> }
> - else if (template_param_list != NULL_TREE) // generate diagnostic
> - cp_parser_require (parser, CPP_OPEN_PAREN, RT_OPEN_PAREN);
>
> /* Create the function call operator.
>
> diff --git a/gcc/testsuite/g++.dg/cpp2a/lambda-generic8.C b/gcc/testsuite/g++.dg/cpp2a/lambda-generic8.C
> new file mode 100644
> index 00000000000..f3c3809b36d
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/cpp2a/lambda-generic8.C
> @@ -0,0 +1,9 @@
> +// PR c++/97839
> +// { dg-do compile { target c++20 } }
> +// Test that a lambda with <template-param-list> doesn't require
> +// a lambda-declarator.
> +
> +int main()
> +{
> + []<typename T>{}.operator()<int>();
> +}
>
> base-commit: 8661f4faa875f361cd22a197774c1fa04cd0580b
> --
> 2.28.0
>
Marek
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] c++: Allow template lambdas without lambda-declarator [PR97839]
2020-11-17 18:05 [PATCH] c++: Allow template lambdas without lambda-declarator [PR97839] Marek Polacek
2020-11-18 18:16 ` Marek Polacek
@ 2020-11-20 22:14 ` Jason Merrill
1 sibling, 0 replies; 4+ messages in thread
From: Jason Merrill @ 2020-11-20 22:14 UTC (permalink / raw)
To: Marek Polacek, GCC Patches
On 11/17/20 1:05 PM, Marek Polacek wrote:
> Our implementation of template lambdas incorrectly requires the optional
> lambda-declarator. This was probably required by an early draft of
> generic lambdas, but now the production is [expr.prim.lambda.general]:
>
> lambda-expression:
> lambda-introducer lambda-declarator [opt] compound-statement
> lambda-introducer < template-parameter-list > requires-clause [opt]
> lambda-declarator [opt] compound-statement
>
> Therefore, we should accept the following test.
>
> Incidentally, I noticed we give a terrible diagnostic when the user uses
> 'mutable', but forgets to type '()' before it, which sounds like a common
> mistake. So it seems to me we should handle that specifically, rather
> than to emit this:
>
> lambda-generic8.C: In lambda function:
> lambda-generic8.C:8:18: error: expected '{' before 'mutable'
> 8 | []<typename T> mutable {}.operator()<int>();
> | ^~~~~~~
> lambda-generic8.C: In function 'int main()':
> lambda-generic8.C:8:17: error: expected ';' before 'mutable'
> 8 | []<typename T> mutable {}.operator()<int>();
> | ^~~~~~~~
> | ;
> lambda-generic8.C:8:28: error: expected primary-expression before '.' token
> 8 | []<typename T> mutable {}.operator()<int>();
> | ^
> lambda-generic8.C:8:40: error: expected primary-expression before 'int'
> 8 | []<typename T> mutable {}.operator()<int>();
> | ^~~
>
> Is it okay to fix this in stage3?
Yes: this is a bugfix, not new functionality.
> Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk?
OK.
> gcc/cp/ChangeLog:
>
> PR c++/97839
> * parser.c (cp_parser_lambda_declarator_opt): Don't require ().
>
> gcc/testsuite/ChangeLog:
>
> PR c++/97839
> * g++.dg/cpp2a/lambda-generic8.C: New test.
> ---
> gcc/cp/parser.c | 14 ++++++--------
> gcc/testsuite/g++.dg/cpp2a/lambda-generic8.C | 9 +++++++++
> 2 files changed, 15 insertions(+), 8 deletions(-)
> create mode 100644 gcc/testsuite/g++.dg/cpp2a/lambda-generic8.C
>
> diff --git a/gcc/cp/parser.c b/gcc/cp/parser.c
> index 42f705266bb..9f09c778c29 100644
> --- a/gcc/cp/parser.c
> +++ b/gcc/cp/parser.c
> @@ -10604,6 +10604,8 @@ cp_parser_trait_expr (cp_parser* parser, enum rid keyword)
>
> lambda-expression:
> lambda-introducer lambda-declarator [opt] compound-statement
> + lambda-introducer < template-parameter-list > requires-clause [opt]
> + lambda-declarator [opt] compound-statement
>
> Returns a representation of the expression. */
>
> @@ -11061,13 +11063,11 @@ cp_parser_lambda_introducer (cp_parser* parser, tree lambda_expr)
> /* Parse the (optional) middle of a lambda expression.
>
> lambda-declarator:
> - < template-parameter-list [opt] >
> - requires-clause [opt]
> - ( parameter-declaration-clause [opt] )
> - attribute-specifier [opt]
> + ( parameter-declaration-clause )
> decl-specifier-seq [opt]
> - exception-specification [opt]
> - lambda-return-type-clause [opt]
> + noexcept-specifier [opt]
> + attribute-specifier-seq [opt]
> + trailing-return-type [opt]
> requires-clause [opt]
>
> LAMBDA_EXPR is the current representation of the lambda expression. */
> @@ -11217,8 +11217,6 @@ cp_parser_lambda_declarator_opt (cp_parser* parser, tree lambda_expr)
> trailing-return-type in case of decltype. */
> pop_bindings_and_leave_scope ();
> }
> - else if (template_param_list != NULL_TREE) // generate diagnostic
> - cp_parser_require (parser, CPP_OPEN_PAREN, RT_OPEN_PAREN);
>
> /* Create the function call operator.
>
> diff --git a/gcc/testsuite/g++.dg/cpp2a/lambda-generic8.C b/gcc/testsuite/g++.dg/cpp2a/lambda-generic8.C
> new file mode 100644
> index 00000000000..f3c3809b36d
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/cpp2a/lambda-generic8.C
> @@ -0,0 +1,9 @@
> +// PR c++/97839
> +// { dg-do compile { target c++20 } }
> +// Test that a lambda with <template-param-list> doesn't require
> +// a lambda-declarator.
> +
> +int main()
> +{
> + []<typename T>{}.operator()<int>();
> +}
>
> base-commit: 8661f4faa875f361cd22a197774c1fa04cd0580b
>
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] c++: Allow template lambdas without lambda-declarator [PR97839]
2020-11-18 18:16 ` Marek Polacek
@ 2020-11-20 22:15 ` Jason Merrill
0 siblings, 0 replies; 4+ messages in thread
From: Jason Merrill @ 2020-11-20 22:15 UTC (permalink / raw)
To: Marek Polacek, GCC Patches
On 11/18/20 1:16 PM, Marek Polacek wrote:
> On Tue, Nov 17, 2020 at 01:05:20PM -0500, Marek Polacek via Gcc-patches wrote:
>> Our implementation of template lambdas incorrectly requires the optional
>> lambda-declarator. This was probably required by an early draft of
>> generic lambdas, but now the production is [expr.prim.lambda.general]:
>>
>> lambda-expression:
>> lambda-introducer lambda-declarator [opt] compound-statement
>> lambda-introducer < template-parameter-list > requires-clause [opt]
>> lambda-declarator [opt] compound-statement
>>
>> Therefore, we should accept the following test.
>>
>> Incidentally, I noticed we give a terrible diagnostic when the user uses
>> 'mutable', but forgets to type '()' before it, which sounds like a common
>> mistake. So it seems to me we should handle that specifically, rather
>> than to emit this:
>
> This might be necessary to handle <wg21.link/p1102> anyway.
Agreed.
>> lambda-generic8.C: In lambda function:
>> lambda-generic8.C:8:18: error: expected '{' before 'mutable'
>> 8 | []<typename T> mutable {}.operator()<int>();
>> | ^~~~~~~
>> lambda-generic8.C: In function 'int main()':
>> lambda-generic8.C:8:17: error: expected ';' before 'mutable'
>> 8 | []<typename T> mutable {}.operator()<int>();
>> | ^~~~~~~~
>> | ;
>> lambda-generic8.C:8:28: error: expected primary-expression before '.' token
>> 8 | []<typename T> mutable {}.operator()<int>();
>> | ^
>> lambda-generic8.C:8:40: error: expected primary-expression before 'int'
>> 8 | []<typename T> mutable {}.operator()<int>();
>> | ^~~
>>
>> Is it okay to fix this in stage3?
>>
>> Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk?
>>
>> gcc/cp/ChangeLog:
>>
>> PR c++/97839
>> * parser.c (cp_parser_lambda_declarator_opt): Don't require ().
>>
>> gcc/testsuite/ChangeLog:
>>
>> PR c++/97839
>> * g++.dg/cpp2a/lambda-generic8.C: New test.
>> ---
>> gcc/cp/parser.c | 14 ++++++--------
>> gcc/testsuite/g++.dg/cpp2a/lambda-generic8.C | 9 +++++++++
>> 2 files changed, 15 insertions(+), 8 deletions(-)
>> create mode 100644 gcc/testsuite/g++.dg/cpp2a/lambda-generic8.C
>>
>> diff --git a/gcc/cp/parser.c b/gcc/cp/parser.c
>> index 42f705266bb..9f09c778c29 100644
>> --- a/gcc/cp/parser.c
>> +++ b/gcc/cp/parser.c
>> @@ -10604,6 +10604,8 @@ cp_parser_trait_expr (cp_parser* parser, enum rid keyword)
>>
>> lambda-expression:
>> lambda-introducer lambda-declarator [opt] compound-statement
>> + lambda-introducer < template-parameter-list > requires-clause [opt]
>> + lambda-declarator [opt] compound-statement
>>
>> Returns a representation of the expression. */
>>
>> @@ -11061,13 +11063,11 @@ cp_parser_lambda_introducer (cp_parser* parser, tree lambda_expr)
>> /* Parse the (optional) middle of a lambda expression.
>>
>> lambda-declarator:
>> - < template-parameter-list [opt] >
>> - requires-clause [opt]
>> - ( parameter-declaration-clause [opt] )
>> - attribute-specifier [opt]
>> + ( parameter-declaration-clause )
>> decl-specifier-seq [opt]
>> - exception-specification [opt]
>> - lambda-return-type-clause [opt]
>> + noexcept-specifier [opt]
>> + attribute-specifier-seq [opt]
>> + trailing-return-type [opt]
>> requires-clause [opt]
>>
>> LAMBDA_EXPR is the current representation of the lambda expression. */
>> @@ -11217,8 +11217,6 @@ cp_parser_lambda_declarator_opt (cp_parser* parser, tree lambda_expr)
>> trailing-return-type in case of decltype. */
>> pop_bindings_and_leave_scope ();
>> }
>> - else if (template_param_list != NULL_TREE) // generate diagnostic
>> - cp_parser_require (parser, CPP_OPEN_PAREN, RT_OPEN_PAREN);
>>
>> /* Create the function call operator.
>>
>> diff --git a/gcc/testsuite/g++.dg/cpp2a/lambda-generic8.C b/gcc/testsuite/g++.dg/cpp2a/lambda-generic8.C
>> new file mode 100644
>> index 00000000000..f3c3809b36d
>> --- /dev/null
>> +++ b/gcc/testsuite/g++.dg/cpp2a/lambda-generic8.C
>> @@ -0,0 +1,9 @@
>> +// PR c++/97839
>> +// { dg-do compile { target c++20 } }
>> +// Test that a lambda with <template-param-list> doesn't require
>> +// a lambda-declarator.
>> +
>> +int main()
>> +{
>> + []<typename T>{}.operator()<int>();
>> +}
>>
>> base-commit: 8661f4faa875f361cd22a197774c1fa04cd0580b
>> --
>> 2.28.0
>>
>
> Marek
>
^ permalink raw reply [flat|nested] 4+ messages in thread
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2020-11-17 18:05 [PATCH] c++: Allow template lambdas without lambda-declarator [PR97839] Marek Polacek
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