E036: You tried to transition into a state that belongs to a different machine

Turf’s machine construct lets you declare a set of states and the moves allowed between them, like machine ConnectionState { Idle -> Connecting, Connecting -> Connected }. When you call .transition(...), the thing inside the parentheses has to be one of THAT SAME machine’s own states.

Here’s a valid transition:

machine ConnectionState {    Idle -> Connecting,    Connecting -> Connected,}mut conn: ConnectionState = ConnectionState::Idle;conn.transition(ConnectionState::Connecting);   // ConnectionState -> ConnectionState, matches

If you pass a state from a totally different machine, or something that isn’t a state at all:

machine LightState {    Off -> On,}conn.transition(LightState::On);   // conn is a ConnectionState, not a LightState!

…Turf stops you, because conn can never actually become a LightState – the two machines are unrelated types, even if their state names happen to look similar.

To fix it, double-check which machine’s state you meant to use, and make sure it’s a state defined on the exact machine type your variable was declared with. If the state name has a typo or doesn’t exist on any machine at all, you’ll actually see a different error first (an “unknown variant” error) – this one specifically means the state exists, just on the wrong machine.

The same error is reported when the target has the right machine type but is a value rather than a written state, such as a parameter or variable that holds one:

fn go(c: ConnectionState, next: ConnectionState): ConnectionState {    mut conn: ConnectionState = c;    conn.transition(next);             // which edge is this? It can't be known here    return conn;}

A transition names its target, so the edge it takes is known where it is written. To move to a state chosen at run time, compare the value that chooses it and write one .transition(ConnectionState::X) per arm.

This kind of mix-up is easy to make once you have a couple of machines in the same file – Turf catching it here means you find out immediately, not while debugging a confusing runtime issue later.

Run turf --explain E036 in a terminal to read this again.