On 9/8/19 11:47 AM, Marek Polacek wrote:
[dcl.type.auto.deduct]/5 "If the placeholder-type-specifier is of the form type-constraintopt decltype(auto), T shall be the placeholder alone."So, only plain decltype(auto) is allowed. But we aren't diagnosing it in function declarations, because do_auto_deduction is never called for those. Bootstrapped/regtested on x86_64-linux, ok for trunk? 2019-09-08 Marek Polacek <pola...@redhat.com> PR c++/84374 - diagnose invalid uses of decltype(auto). * decl.c (grokdeclarator): Diagnose wrong usage of decltype(auto) in a function declaration. * g++.dg/cpp1y/auto-fn57.C: New test. diff --git gcc/cp/decl.c gcc/cp/decl.c index 88e2c3beb2b..b1777730934 100644 --- gcc/cp/decl.c +++ gcc/cp/decl.c @@ -11560,6 +11560,14 @@ grokdeclarator (const cp_declarator *declarator, "cannot have deduced return type"); virtualp = false; } + else if (is_auto (auto_node) + && AUTO_IS_DECLTYPE (auto_node) + && type != auto_node) + { + error_at (typespec_loc, "%qT as type rather than " + "plain %<decltype(auto)%>", type); + return error_mark_node; + } } else if (!is_auto (type) && sfk != sfk_conversion) { @@ -11580,6 +11588,16 @@ grokdeclarator (const cp_declarator *declarator, "invalid use of %<decltype(auto)%>"); return error_mark_node; } + else if (tree a = type_uses_auto (late_return_type)) + { + if (AUTO_IS_DECLTYPE (a) && a != late_return_type) + { + error_at (typespec_loc, "%qT as type rather than " + "plain %<decltype(auto)%>", + late_return_type); + return error_mark_node; + } + }
Maybe check this in one place, after splice_late_return_type? Jason
