From 7e52f8b1e03776575b92574252d9b6bbed9f1af4 Mon Sep 17 00:00:00 2001 From: Patrick Palka Date: Wed, 13 May 2020 16:40:10 -0400 Subject: [PATCH] c++: premature requires-expression folding [PR95020] In the testcase below we're prematurely folding away the requires-expression to 'true' after substituting in the function's template arguments, but before substituting in the lambda's deduced template arguments. This patch removes the uses_template_parms check when deciding in tsubst_requires_expr whether to keep around a new requires-expression. Regardless of whether the template arguments are dependent, there still might be more template parameters to later substitute in (as in the below testcase) and even if not, tsubst_expr doesn't perform full semantic processing unless !processing_template_decl, so we should still wait until then to fold away the requires-expression. gcc/cp/ChangeLog: PR c++/95020 * constraint.c (tsubst_requires_expr): Produce a new requires-expression when processing_template_decl, even if template arguments are not dependent. gcc/testsuite/ChangeLog: PR c++/95020 * g++/cpp2a/concepts-lambda7.C: New test. --- gcc/cp/ChangeLog | 7 +++++++ gcc/cp/constraint.cc | 4 +--- gcc/testsuite/ChangeLog | 5 +++++ gcc/testsuite/g++.dg/cpp2a/concepts-lambda7.C | 14 ++++++++++++++ 4 files changed, 27 insertions(+), 3 deletions(-) create mode 100644 gcc/testsuite/g++.dg/cpp2a/concepts-lambda7.C diff --git a/gcc/cp/ChangeLog b/gcc/cp/ChangeLog index 145a5d5..73a6500 100644 --- a/gcc/cp/ChangeLog +++ b/gcc/cp/ChangeLog @@ -1,3 +1,10 @@ +2020-05-13 Patrick Palka + + PR c++/95020 + * constraint.c (tsubst_requires_expr): Produce a new + requires-expression when processing_template_decl, even if + template arguments are not dependent. + 2020-05-13 Marek Polacek PR c++/95066 diff --git a/gcc/cp/constraint.cc b/gcc/cp/constraint.cc index 3a17005..eb72bfe 100644 --- a/gcc/cp/constraint.cc +++ b/gcc/cp/constraint.cc @@ -2173,9 +2173,7 @@ tsubst_requires_expr (tree t, tree args, if (reqs == error_mark_node) return boolean_false_node; - /* In certain cases, produce a new requires-expression. - Otherwise the value of the expression is true. */ - if (processing_template_decl && uses_template_parms (args)) + if (processing_template_decl) return finish_requires_expr (cp_expr_location (t), parms, reqs); return boolean_true_node; diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog index e2dea4d..b88e182 100644 --- a/gcc/testsuite/ChangeLog +++ b/gcc/testsuite/ChangeLog @@ -1,3 +1,8 @@ +2020-05-13 Patrick Palka + + PR c++/95020 + * g++/cpp2a/concepts-lambda7.C: New test. + 2020-05-13 Marek Polacek PR c++/95066 diff --git a/gcc/testsuite/g++.dg/cpp2a/concepts-lambda7.C b/gcc/testsuite/g++.dg/cpp2a/concepts-lambda7.C new file mode 100644 index 0000000..50746b7 --- /dev/null +++ b/gcc/testsuite/g++.dg/cpp2a/concepts-lambda7.C @@ -0,0 +1,14 @@ +// PR c++/95020 +// { dg-do compile { target c++2a } } + +template +void foo() { + auto t = [](auto v) { + static_assert(requires { *v; }); // { dg-error "static assertion failed" } + }; + t(0); +} + +void bar() { + foo(); +} -- 2.7.4