Evaluate type traits in valueflow

[pfultz2]

Right now it just evaluates is_void, is_lvalue_reference, and is_rvalue_reference. More work needed to handle library types in the type traits

[pfultz2]

@danmar @orbitcowboy @chrchr-github Any feedback?

[chrchr-github]

Is this something that can grow into a generalized type trait evaluation? Seems like a huge task in any case.
is_void, is_lvalue_reference, is_rvalue_reference don't seem like the most popular traits to me, but I guess you have to start somewhere.

[pfultz2]

This is just a start, but the idea is to handle more traits in the future, somewhat similar to how we do math evaluations. We can also add some library support in the future so we can handle the traits from other libraries that work the same as the std traits.

I started with is_void since there was already a ticket for it, and also did is_reference since that is a simple one as well. The other traits may take some more work, but can be incrementally added.

[chrchr-github]

In addition to {} and ::value, we should probably support C++17 _v helper variable templates as well, since new code is likely to use those,

[pfultz2]

In addition to {} and ::value, we should probably support C++17 _v helper variable templates as well, since new code is likely to use those,

Thats already supported with a ASSERT_EQUALS(true, testKnownValueOfTok("std::is_void_v<void>;", "::", 1)); test here: https://github.com/danmar/cppcheck/pull/7393/files#diff-0c918c64e1eee55c83249b2cbe2beb837af6dd0a5a4273a1ae9168cd0582ba8dR619

[chrchr-github]

Thats already supported with a ASSERT_EQUALS(true, testKnownValueOfTok("std::is_void_v<void>;", "::", 1)); test here: https://github.com/danmar/cppcheck/pull/7393/files#diff-0c918c64e1eee55c83249b2cbe2beb837af6dd0a5a4273a1ae9168cd0582ba8dR619

Ah ok, must have missed that test. Does that mean std::reference_v etc. are also supported?

[pfultz2]

Does that mean std::reference_v etc. are also supported?

Yes std::is_reference_v is supported as well.