https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103403
--- Comment #5 from CVS Commits <cvs-commit at gcc dot gnu.org> --- The trunk branch has been updated by Marek Polacek <mpola...@gcc.gnu.org>: https://gcc.gnu.org/g:abd7712f91c99690f8b0046ea168b2782afbac69 commit r12-5778-gabd7712f91c99690f8b0046ea168b2782afbac69 Author: Marek Polacek <pola...@redhat.com> Date: Tue Nov 30 21:07:25 2021 -0500 c++: Fix for decltype(auto) and parenthesized expr [PR103403] In r11-4758, I tried to fix this problem: int &&i = 0; decltype(auto) j = i; // should behave like int &&j = i; error wherein do_auto_deduction was getting confused with a REFERENCE_REF_P and it didn't realize its operand was a name, not an expression, and deduced the wrong type. Unfortunately that fix broke this: int&& r = 1; decltype(auto) rr = (r); where 'rr' should be 'int &' since '(r)' is an expression, not a name. But because I stripped the INDIRECT_REF with the r11-4758 change, we deduced 'rr's type as if decltype had gotten a name, resulting in 'int &&'. I suspect I thought that the REF_PARENTHESIZED_P check when setting 'bool id' in do_auto_deduction would handle the (r) case, but that's not the case; while the documentation for REF_PARENTHESIZED_P specifically says it can be set in INDIRECT_REF, we don't actually do so. This patch sets REF_PARENTHESIZED_P even on REFERENCE_REF_P, so that do_auto_deduction can use it. It also removes code in maybe_undo_parenthesized_ref that I think is dead -- and we don't hit it while running dg.exp. To adduce more data, it also looks dead here: https://splichal.eu/lcov/gcc/cp/semantics.c.gcov.html (It's dead since r9-1417.) Also add a fixed test for c++/81176. PR c++/103403 gcc/cp/ChangeLog: * cp-gimplify.c (cp_fold): Don't recurse if maybe_undo_parenthesized_ref doesn't change its argument. * pt.c (do_auto_deduction): Don't strip REFERENCE_REF_P trees if they are REF_PARENTHESIZED_P. Use stripped_init when checking for id-expression. * semantics.c (force_paren_expr): Set REF_PARENTHESIZED_P on REFERENCE_REF_P trees too. (maybe_undo_parenthesized_ref): Remove dead code. gcc/testsuite/ChangeLog: * g++.dg/cpp1y/decltype-auto2.C: New test. * g++.dg/cpp1y/decltype-auto3.C: New test. * g++.dg/cpp1y/decltype-auto4.C: New test. * g++.dg/cpp1z/decomp-decltype1.C: New test.
