lookup and verify sha256 for kotlinc in bazel

I try migrating from Maven to Bazel and want to use another (newer) version of kotlinc than the standard default.

I have started from the example given on https://github.com/bazelbuild/rules_kotlin#custom-kotlinc-distribution-and-version:

load("@io_bazel_rules_kotlin//kotlin:repositories.bzl", "kotlin_repositories", "kotlinc_version")
kotlin_repositories(
    compiler_release = kotlinc_version(
        release = "1.6.21", # just the numeric version
        sha256 = "632166fed89f3f430482f5aa07f2e20b923b72ef688c8f5a7df3aa1502c6d8ba"
    )
)

However, the link and the example explain only the syntax. It is nice that the Bazel configuration is so concise, but on the downside it is hard to see what the effect of this rule is.

How can I know/verify what binary for kotlinc will be download and where from? Can I figure out which other kotlinc releases are available, and more importantly, what the correct sha256 should be?

(Since this seems to be an official part of Bazel (loading from @io_bazel…), maybe there is a public directory (like https://mvnrepository.com/ for mvn, https://www.npmjs.com/ for npm, etc.) to check?)

Both the hash and the download location for the kotlinc that are apparently used by Bazel kotlin_rule can currently be found on GitHub:

https://github.com/JetBrains/kotlin/releases

• hash for each release is printed at the end of the respective release note, next to kotlin-compiler-*.zip
• download URL follows under "Asset", which for older releases may be collapsed (not immediately visible)

(as for the last part of the question: a unified directory for dependencies (artifacts, plugins, toolchains) seems to be unfeasible for a general-purpose build automation tool such as Bazel; it works for specific-purpose tools like Maven, NPM and so on; but all these ecosystems use quite different approaches and conventions, its probably too much hassle to provide that in a unified way for a system like Bazel; at least some of these bounded ecosystems already started to provide configuration snippets for Bazel)