Please see the documentation on working with pre-releases as it explains the behavior you are seeing.

Many tools and libraries in this space require you to opt-in to using pre-releases. They do this out of experience in this space as pre-releases may (and sometimes) are not compatible with the stable release guarantees. The constraint needs to opt-in to pre-releases. You'll find the same behavior in other places like JavaScript and Rust.

For what is documented in the semver:

<valid semver> ::= <version core>
                 | <version core> "-" <pre-release>
                 | <version core> "+" <build>
                 | <version core> "-" <pre-release> "+" <build>

What about this one:

<valid semver> ::= <version core> "+" <build>

How to identify builds from releases without build in it? Which have the exact same issue here.

I will start with build metadata. The spec says...

Build metadata MUST be ignored when determining version precedence. Thus two versions that differ only in the build metadata, have the same precedence.

When comparing versions they are considered the same.

On pre-releases the spec states...

A pre-release version indicates that the version is unstable and might not satisfy the intended compatibility requirements as denoted by its associated normal version.

In the past, this library did not opt-in for pre-releases and that caused problems. Many other tools opt-in to pre-releases.

Just because pre-release is a valid semver does not mean comparison systems MUST handle them along stable release versions by default. There is no spec for filtering tooling.

@mattfarina Hello.
I have a linked question, so let more bother you in this thread, please.
My question is about prerelease versions. We couldn't compare a few prereleases of a one core version, that's understandable, but what about different core versions?

	c, _ := semver.NewConstraint("> 1.1.1")
	v, _ := semver.NewVersion("v2.2.2-alpha1")
	a := c.Check(v)
        // Output: false

meanwhile the constraint "> 1.1.1-0" gives the output true.

I guess, we can affirm, that the prerelease v1.1.1-XXXX satisfies two statements:

1. v1.1.1-XXXX < v.1.1.1
2. v1.1.1-XXXX > v1.1.0

What I might have missed in this logic?
Thank you