assert: allow comparing time.Time

[torkelrogstad]

Summary

Add support for comparing time>Time and custom types derived from it.

Changes

When comparing types, see if we're comparing time.Time, or a custom type based on time.Time. If that's the case, compare their Unix timestamps, with the smallest possible resolution.

Motivation

This now allows sticking a time.Time into assert.Greater and assert.Less, which is nice. Time stamps have a natural ordering, so I'd expect this to work.

[torkelrogstad]

Had to fiddle a bit with build tags to get this working across versions. Nw tests pass locally for me with both a new (1.17.6) and old (1.14.15). Looks like CI is fine as well.

[boyan-soubachov]

Why are we converting to timeType (i.e. time), then interface, then back to time?

[torkelrogstad]

Convert() returns a reflect.Value, Interface() takes us out of the reflection wrappers, and then finally we do a type assertion. It looks a bit convoluted, but it's all necessary!

[torkelrogstad]

Rebased, and added doc comments. Assumed you meant 1.16, as that's what's holding up the build tag stuff.

[torkelrogstad]

Okay, this is a bit awkward... go fmt wants me to use a syntax that's not supported by earlier versions of Go, so I don't quite know how to make all Go versions happy here

[torkelrogstad]

Nvm, got it working. Let's go 🚀

[boyan-soubachov]

Thank you :)