`context`

A statement is not allowed in the context it runs in.

compile error, shown by synod check.

Every statement runs in one of four contexts: node, main, check and look (spec/05 section 5.4). Each context has its own list of what it may read, write and use. A receiver phrase is node code, so it cannot be called from define main. Main reaches node state through p.Node values instead.

Example

Check this program to see the diagnostic.

# package main
use example.com/explain/p
use std/sim

define main
  set nodes to (sim.Cluster of 2 running p)
  each n in nodes
    n.p.Bump

# package p
Node has
  set Count to 0

define [n: Node] Bump
  set n.Count to (n.Count plus 1)

Diagnostic

p/main.synod:8:5: error[context]: "n.Bump" is node code; it cannot run in main context

Fix

Write the setup in main with a phrase that takes the node as a hole.

# package main
use example.com/explain/p
use std/sim

define main
  set nodes to (sim.Cluster of 2 running p)
  each n in nodes
    p.Bump n

# package p
Node has
  set Count to 0

define Bump [n: Node]
  set n.Count to (n.Count plus 1)