https://gcc.gnu.org/g:c6cc6d4741a880109c4e0e64d5a189687fb526f6
commit r15-498-gc6cc6d4741a880109c4e0e64d5a189687fb526f6 Author: Patrick Palka <ppa...@redhat.com> Date: Tue May 14 22:55:16 2024 -0400 c++: lvalueness of non-dependent assignment expr [PR114994] r14-4111-g6e92a6a2a72d3b made us check non-dependent simple assignment expressions ahead of time and give them a type, as was already done for compound assignments. Unlike for compound assignments however, if a simple assignment resolves to an operator overload we represent it as a (typed) MODOP_EXPR instead of a CALL_EXPR to the selected overload. (I reckoned this was at worst a pessimization -- we'll just have to repeat overload resolution at instantiatiation time.) But this turns out to break the below testcase ultimately because MODOP_EXPR (of non-reference type) is always treated as an lvalue according to lvalue_kind, which is incorrect for the MODOP_EXPR representing x=42. We can fix this by representing such class assignment expressions as CALL_EXPRs as well, but this turns out to require some tweaking of our -Wparentheses warning logic and may introduce other fallout making it unsuitable for backporting. So this patch instead fixes lvalue_kind to consider the type of a MODOP_EXPR representing a class assignment. PR c++/114994 gcc/cp/ChangeLog: * tree.cc (lvalue_kind) <case MODOP_EXPR>: For a class assignment, consider the result type. gcc/testsuite/ChangeLog: * g++.dg/template/non-dependent32.C: New test. Reviewed-by: Jason Merrill <ja...@redhat.com> Diff: --- gcc/cp/tree.cc | 5 ++++- gcc/testsuite/g++.dg/template/non-dependent32.C | 18 ++++++++++++++++++ 2 files changed, 22 insertions(+), 1 deletion(-) diff --git a/gcc/cp/tree.cc b/gcc/cp/tree.cc index f1a23ffe8179..9d37d255d8d5 100644 --- a/gcc/cp/tree.cc +++ b/gcc/cp/tree.cc @@ -275,7 +275,10 @@ lvalue_kind (const_tree ref) /* We expect to see unlowered MODOP_EXPRs only during template processing. */ gcc_assert (processing_template_decl); - return clk_ordinary; + if (CLASS_TYPE_P (TREE_TYPE (TREE_OPERAND (ref, 0)))) + goto default_; + else + return clk_ordinary; case MODIFY_EXPR: case TYPEID_EXPR: diff --git a/gcc/testsuite/g++.dg/template/non-dependent32.C b/gcc/testsuite/g++.dg/template/non-dependent32.C new file mode 100644 index 000000000000..54252c7dfaf9 --- /dev/null +++ b/gcc/testsuite/g++.dg/template/non-dependent32.C @@ -0,0 +1,18 @@ +// PR c++/114994 +// { dg-do compile { target c++11 } } + +struct udl_arg { + udl_arg operator=(int); +}; + +void f(udl_arg&&); + +template<class> +void g() { + udl_arg x; + f(x=42); // { dg-bogus "cannot bind" } +} + +int main() { + g<int>(); +}