S0004: effect is not a valid ingress effect

Generated from rellum-diagnostics/src/db.rs.

Explanation

Only ingress effects can appear inside event(...). Output effects run during Fire and do not produce event payloads during Observe, so they cannot define reactive event sources.

Common causes

• using print!, write!, send!, sleep!, or another output effect in event(...)
• confusing an effect binding with an event source

Canonical fixes

• use an ingress effect for the event

Before:

line = event(print!("ready"))

After:

line = event(stdin_line!())

• move output effects into a ! binding

Before:

done = event(write!("build/out.txt", "ready"))

After:

main! = write!("build/out.txt", "ready")

Code example

line = event(print!("ready"))

Links

• RellC diagnostic overview