unknown-phrase

A sentence matches a phrase when it has the same number of items and the same words in the same places. A hole takes exactly one item, so a sentence of several words must be inside parentheses. If nothing matches, you get unknown-phrase. It is also the error for an event phrase that stands outside when, a record field that does not exist, and a message … with setting of more than two items.

A common cause is a missing pair of parentheses. Here if takes one condition, and n.Role is "leader" is three items.

# package p
Node has
  set Role to "follower"

define [n: Node] Demote
  if n.Role is "leader"
    set n.Role to "follower"

p/p.synod:6:3: error[unknown-phrase]: no phrase matches "if n.Role is "leader""
  hint: did you mean "if (n.Role is "leader")"?

# package p
Node has
  set Role to "follower"

define [n: Node] Demote
  if (n.Role is "leader")
    set n.Role to "follower"