Stream: compiler development

Topic: parse error with -> and lambda

Anton (Feb 23 2026 at 14:28):

Piping into a lambda with -> should work right?

» lst.map(|_| "zzz ").join_with(" ").trim()->(|trimmed_str| {if trimmed_str.is_empty() "" else "bla"})
**PARSE ERROR**
A parsing error occurred: `expr_arrow_expects_ident`
This is an unexpected parsing error. Please check your syntax.

Richard Feldman (Feb 23 2026 at 14:50):

it should!

Richard Feldman (Feb 23 2026 at 14:51):

but we probably never supported it

Anton (Feb 23 2026 at 15:06):

#9195

Luke Boswell (Feb 23 2026 at 20:15):

I can implement this later today.

Luke Boswell (Feb 24 2026 at 02:23):

fixed in https://github.com/roc-lang/roc/pull/9197

Anton (Feb 24 2026 at 11:10):

Thanks Luke :)

Anton (Feb 24 2026 at 11:10):

I added a complex pipeline demo to the all syntax example: #9199

Last updated: Mar 20 2026 at 12:28 UTC