On 9/10/24 8:35 PM, Patrick Palka wrote:
Bootstrapped and regtested on x86_64-pc-linux-gnu, does this look OK for trunk/backports?
OK, though you might combine the new STMT_EXPR case with the existing LAMBDA_EXPR case; the principle is the same for both.
-- >8 -- r8-7538 for PR84968 made strip_typedefs_expr diagnose seeing STATEMENT_LIST, which effectively makes us reject statement-expressions noexcept-specifiers (we already diagnose them in template arguments at parse time). Later r11-7452 made decltype(auto) deduction do strip_typedefs_expr on the expression before deducing (as an implementation detail) and so ever since we inadvertently reject decltype(auto) deduction of a statement-expression. This patch just removes the diagnostic in strip_typedefs_expr; it doesn't seem like the right place for it. And it lets us accept more code using statement-expressions in various contexts. PR c++/116418 PR c++/84968 gcc/cp/ChangeLog: * tree.cc (strip_typedefs_expr) <case STATEMENT_LIST>: Replace with ... <case STMT_EXPR>: ... this non-diagnosing early exit. gcc/testsuite/ChangeLog: * g++.dg/eh/pr84968.C: No longer expect ah ahead of time diagnostic for the statement-expresssion. Instantiate the template and expect an incomplete type error instead. * g++.dg/ext/stmtexpr26.C: New test. --- gcc/cp/tree.cc | 5 ++--- gcc/testsuite/g++.dg/eh/pr84968.C | 4 +++- gcc/testsuite/g++.dg/ext/stmtexpr26.C | 10 ++++++++++ 3 files changed, 15 insertions(+), 4 deletions(-) create mode 100644 gcc/testsuite/g++.dg/ext/stmtexpr26.C diff --git a/gcc/cp/tree.cc b/gcc/cp/tree.cc index 31ecbb1ac79..a150a91f2fa 100644 --- a/gcc/cp/tree.cc +++ b/gcc/cp/tree.cc @@ -2011,9 +2011,8 @@ strip_typedefs_expr (tree t, bool *remove_attributes, unsigned int flags) case LAMBDA_EXPR: return t;- case STATEMENT_LIST:- error ("statement-expression in a constant expression"); - return error_mark_node; + case STMT_EXPR: + return t;default:break; diff --git a/gcc/testsuite/g++.dg/eh/pr84968.C b/gcc/testsuite/g++.dg/eh/pr84968.C index 23c49f477a8..a6e21914eed 100644 --- a/gcc/testsuite/g++.dg/eh/pr84968.C +++ b/gcc/testsuite/g++.dg/eh/pr84968.C @@ -9,7 +9,9 @@ struct S { void a() try { } catch (int () - noexcept (({ union b a; true; }))) // { dg-error "constant" } + noexcept (({ union b a; true; }))) // { dg-error "'b a' has incomplete type" } { } }; + +template void S::a<int>(); // { dg-message "required from here" } diff --git a/gcc/testsuite/g++.dg/ext/stmtexpr26.C b/gcc/testsuite/g++.dg/ext/stmtexpr26.C new file mode 100644 index 00000000000..498dd12ef10 --- /dev/null +++ b/gcc/testsuite/g++.dg/ext/stmtexpr26.C @@ -0,0 +1,10 @@ +// PR c++/116418 +// { dg-do compile { target c++14 } } + +void foo (); +template <typename> +void bar () +{ + decltype(auto) v = ({ foo (); 3; }); +} +
