[llvm-bugs] [Bug 45115] New: concepts-related information does not propogated through precompiled headers

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=45115

            Bug ID: 45115
           Summary: concepts-related information does not propogated
                    through precompiled headers
           Product: clang
           Version: 10.0
          Hardware: PC
                OS: Linux
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: C++2a
          Assignee: unassignedclangbugs at nondot.org
          Reporter: vopl at bk.ru
                CC: blitzrakete at gmail.com, erik.pilkington at gmail.com,
                    llvm-bugs at lists.llvm.org, richard-llvm at metafoo.co.uk

$ cat pch.hpp
#pragma once

template <class T> concept CncChar = sizeof(char)==sizeof(T);
template <class T> concept CncInt = sizeof(int)==sizeof(T);

template <class T> void f() requires CncInt<T> {}
template <class T> void f() requires CncChar<T> {}

$ cat main.cpp
//clang++ -std=gnu++2a pch.hpp -o pch.hpp.pch
//clang++ -std=gnu++2a -include-pch pch.hpp.pch -c main.cpp

#include "pch.hpp"

int main()
{
    f<int>();
    return 0;
}

# try compile main.cpp WITHOUT precompiled headers
$ clang++ -std=gnu++2a -c main.cpp && echo OK
OK
$
$
$# try compile main.cpp WITH precompiled headers - fail
$ clang++ -std=gnu++2a pch.hpp -o pch.hpp.pch
$ clang++ -std=gnu++2a -include-pch pch.hpp.pch -c main.cpp
main.cpp:8:5: error: no matching function for call to 'f'
    f<int>();
    ^~~~~~
./pch.hpp:7:25: note: candidate template ignored: constraints not satisfied
[with T = int]
template <class T> void f() requires CncChar<T> {}
                        ^
./pch.hpp:7:38: note: because 'int' does not satisfy 'CncChar'
template <class T> void f() requires CncChar<T> {}
                                     ^
./pch.hpp:3:38: note: because 'sizeof(char) == sizeof(int)' (1 == 4) evaluated
to false
template <class T> concept CncChar = sizeof(char)==sizeof(T);
                                     ^
1 error generated.

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