We’ve written a blog post summarizing the changes in this patch release: Crystal 1.5.1 released! - The Crystal Programming Language . While we have tested it against several known and sizeable projects, that doesn’t preclude the existence of regressions. If you find an issue, please check the issue tracker and file a bug: it will be fixed in the following patch version.
The full changelog is here: Release 1.5.1 · crystal-lang/crystal · GitHub .