Hello,
Attached is a patch that adds parsing of the optional requires-clause in a
lambda-expression and lambda-declarator. Additionally, shorthand constraints
from the template-parameter-list are now actually applied and constrain the
synthesized operator().
Previously we were not parsing the requires clauses at all and not saving the
shorthand constraints in the place expected by grokfndecl.
The trailing requires-clause is now also used to suppress synthesis of the
conversion to function pointer for non-capturing non-generic lambdas as per
expr.prim.lambda.closure/7.
This includes a fix to template_class_depth. Previously it was computing the
wrong depth for lambdas in the initializer of a static member of a class
template, exhibited by the concepts-lambda4 test which currently fails on
trunk. The bug was causing grokfndecl to use the constraints from the template
class for the lambda.
gcc/cp/
2019-10-30 Jeff Chapman II
PR c++/84810 - constraints on lambdas
* lambda.c (maybe_add_lambda_conv_op): Do not synthesize
conversion if the call operator does not satisfy its constraints.
* parser.c (cp_parser_lambda_declarator_opt): Parse
requires-clause on generic lambdas; combine with shorthand
constraints. Parse trailing requires-clause and attach to the
synthesized call operator.
* pt.c (template_class_depth): Only inspect
LAMBDA_TYPE_EXTRA_SCOPE if it is present. This fixes an
incorrect depth calculation for lambdas inside the initializer
of a static data member of a template class.
gcc/testsuite/
2019-10-30 Jeff Chapman II
PR c++/84810 - constraints on lambdas
* g++.dg/cpp2a/concepts-lambda2.C: New test.
* g++.dg/cpp2a/concepts-lambda3.C: Ditto.
* g++.dg/cpp2a/concepts-lambda4.C: Ditto.
* g++.dg/cpp2a/concepts-pr84810.C: Ditto.
Bootstrapped and tested on x86_64-pc-linux-gnu.
Please let me know if there's any issues.
Thanks,
Jeff Chapman II
From d196b03e6f6924935a521a8d140d621d03ae18f2 Mon Sep 17 00:00:00 2001
From: Jeff Chapman II
Date: Mon, 28 Oct 2019 12:57:36 -0400
Subject: [PATCH 1/1] PR c++/84810 - constraints on lambdas
gcc/cp/
2019-10-30 Jeff Chapman II
PR c++/84810 - constraints on lambdas
* lambda.c (maybe_add_lambda_conv_op): Do not synthesize
conversion if the call operator does not satisfy its constraints.
* parser.c (cp_parser_lambda_declarator_opt): Parse
requires-clause on generic lambdas; combine with shorthand
constraints. Parse trailing requires-clause and attach to the
synthesized call operator.
* pt.c (template_class_depth): Only inspect
LAMBDA_TYPE_EXTRA_SCOPE if it is present. This fixes an
incorrect depth calculation for lambdas inside the initializer
of a static data member of a template class.
gcc/testsuite/
2019-10-30 Jeff Chapman II
PR c++/84810 - constraints on lambdas
* g++.dg/cpp2a/concepts-lambda2.C: New test.
* g++.dg/cpp2a/concepts-lambda3.C: Ditto.
* g++.dg/cpp2a/concepts-lambda4.C: Ditto.
* g++.dg/cpp2a/concepts-pr84810.C: Ditto.
---
gcc/cp/lambda.c | 6 +
gcc/cp/parser.c | 21 ++-
gcc/cp/pt.c | 2 +-
gcc/testsuite/g++.dg/cpp2a/concepts-lambda2.C | 153 ++
gcc/testsuite/g++.dg/cpp2a/concepts-lambda3.C | 64
gcc/testsuite/g++.dg/cpp2a/concepts-lambda4.C | 14 ++
gcc/testsuite/g++.dg/cpp2a/concepts-pr84810.C | 13 ++
7 files changed, 270 insertions(+), 3 deletions(-)
create mode 100644 gcc/testsuite/g++.dg/cpp2a/concepts-lambda2.C
create mode 100644 gcc/testsuite/g++.dg/cpp2a/concepts-lambda3.C
create mode 100644 gcc/testsuite/g++.dg/cpp2a/concepts-lambda4.C
create mode 100644 gcc/testsuite/g++.dg/cpp2a/concepts-pr84810.C
diff --git a/gcc/cp/lambda.c b/gcc/cp/lambda.c
index f128ed800f6..d621beca2eb 100644
--- a/gcc/cp/lambda.c
+++ b/gcc/cp/lambda.c
@@ -1046,6 +1046,12 @@ maybe_add_lambda_conv_op (tree type)
return;
}
+ /* Non-generic non-capturing lambdas only have a conversion function to
+ pointer to function when the trailing requires-clause's constraints are
+ satisfied. */
+ if (!generic_lambda_p && !constraints_satisfied_p (callop))
+return;
+
/* Non-template conversion operators are defined directly with build_call_a
and using DIRECT_ARGVEC for arguments (including 'this'). Templates are
deferred and the CALL is built in-place. In the case of a deduced return
diff --git a/gcc/cp/parser.c b/gcc/cp/parser.c
index 3857fe47d67..bbdf8d69077 100644
--- a/gcc/cp/parser.c
+++ b/gcc/cp/parser.c
@@ -10854,11 +10854,13 @@ cp_parser_lambda_introducer (cp_parser* parser, tree lambda_expr)
lambda-declarator:
< template-parameter-list [opt] >
+ requires-clause [opt]
( parameter-declaration-clause [opt] )
attribute-specifier [opt]
decl-specifier-seq [opt]
exception-specification [opt]
l
