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From: "ich.freak at gmx dot net" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug c++/103540] diagnosting concept depends on itself Date: Sun, 05 Dec 2021 16:04:26 +0000 [thread overview] Message-ID: <bug-103540-4-laBghBYIow@http.gcc.gnu.org/bugzilla/> (raw) In-Reply-To: <bug-103540-4@http.gcc.gnu.org/bugzilla/> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103540 --- Comment #2 from Igel <ich.freak at gmx dot net> --- Ah thanks for copying the relevant code here. The error that you're referring to is: <source>: In instantiation of 'struct X<0>': <source>:5:14: required by substitution of 'template<class N> requires StrictNodeType<N> using Int = int [with N = X<0>]' <source>:15:27: required from here <source>:12:11: error: template constraint failure for 'template<class N> requires StrictNodeType<N> using Int = int' 12 | using something = Int<X>; | ^~~~~~~~~ <source>:12:11: note: constraints not satisfied I guess technically, you're right that it points to the correct spot and it is the programmers duty to translate this into "the concept StrictNodeType<X<0>> depends on itself because the type X<0>::something (also known as Int<X<0>>) declared in line 12 depends on the concept StrictNodeType<X<0>>". However, this information can be buried arbitrarily deep in the error messages. Consider, for example, the following adaptation: #include <type_traits> template<typename N> concept StrictNodeType = requires { typename N::something; }; template<StrictNodeType N> using Int = int; template<template<class> class P, class Q> using chooser = P<Q>; template<int> struct X { using something = chooser<Int, X>; }; using ThisBreaks = Int<X<0>>; The only hint towards the real problem (gcc cannot tell if X<0> has a type called 'something' or not) is now this: <source>:14:18: required from 'struct X<0>' I guess all I'm saying is that extracting the site of the problematic code is currently very hard for "depends on itself"-errors.
prev parent reply other threads:[~2021-12-05 16:04 UTC|newest] Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top 2021-12-03 14:05 [Bug c++/103540] New: " ich.freak at gmx dot net 2021-12-03 22:10 ` [Bug c++/103540] " redi at gcc dot gnu.org 2021-12-05 16:04 ` ich.freak at gmx dot net [this message]
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