[MSVC][std:c++latest] Boost\libs\utility run tests failed due to error C2666: 'comparible_UDT::operator ==': overloaded functions have similar conversions

[Zhaojun-Liu]

Description:
After the MSVC team implented P2468R2 The Equality Operator You Are Looking For, we got a compiler error with /std:c++latest like below, the error is due to the equality operator here

utility/test/call_traits_test.cpp

Line 204 in 3aa25c9

bool operator == (const comparible_UDT& v){ return v.i_ == i_; }

is missing 'const'. Could you please look this issue? Thanks.

libs\utility\test\call_traits_test.cpp(131): error C2666: 'comparible_UDT::operator ==': overloaded functions have similar conversions
libs\utility\test\call_traits_test.cpp(204): note: could be 'bool comparible_UDT::operator ==(const comparible_UDT &)'
libs\utility\test\call_traits_test.cpp(204): note: or 'bool comparible_UDT::operator ==(const comparible_UDT &)' [synthesized expression 'y == x']

Note: this issue will be reproduced on next release version of VS (VS17.6 or later)

Repro steps:

1. open VS2019 x64 tools command
2. git clone ​https://github.com/boostorg/boost.git F:\gitP\boostorg\boost
3. git -C "F:\gitP\boostorg\boost" fetch --recurse-submodules=no --force
4. git -C "F:\gitP\boostorg\boost" reset --hard 0c4090b
5. git -C "F:\gitP\boostorg\boost" submodule sync
6. git -C "F:\gitP\boostorg\boost" submodule foreach git reset --hard
7. git -C "F:\gitP\boostorg\boost" submodule foreach git clean -xdf
8. git -C "F:\gitP\boostorg\boost" submodule update -f --init --recursive
9. set CL= /std:c++latest
10. cd F:\gitP\boostorg\boost
11. .\bootstrap
12. .\b2 headers variant=release --build-dir=F:\gitP\boostorg\boost\out\amd64rel address-model=64
13. .\b2 variant=release --build-dir=F:\gitP\boostorg\boost\out\amd64rel address-model=64
14. set CL=/D_SILENCE_EXPERIMENTAL_FILESYSTEM_DEPRECATION_WARNING /D_HAS_DEPRECATED_ADAPTOR_TYPEDEFS=1 /D_HAS_AUTO_PTR_ETC=1 /D_HAS_DEPRECATED_RAW_STORAGE_ITERATOR=1 /D_HAS_DEPRECATED_TEMPORARY_BUFFER=1 /D_HAS_DEPRECATED_NEGATORS=1 /Zc:enumTypes %CL%
15. set related reference path (in my environment like below):
    set OPENSSL_ROOT=F:\tools\OpenSSL\64
    set path=F:\tools\OpenSSL\64\bin;%path%
    set path=C:\Python\Python27;%path%
16. .\b2 -j16 variant=release --build-dir=F:\gitP\boostorg\boost\out\amd64rel libs\utility\test address-model=64 > utility_test.log

Detailed log:
utility_test.log

[Lastique]

Seems related to #65.