LDC-E1345 — Parallel state with one region

What it means

A parallel state runs regions side by side, so it needs at least two: one region is just a sequential state wearing a heavier spelling, and the toolchain would emit a shape its own gates reject. A parallel block with a single region stops the compiler at the state.

A join faces the same honesty rule from the other side: a join with no regions joins nothing, and a quorum larger than the region count can never be reached. Either shape stops the compiler at the join.

The repair is to give the parallel state its plural meaning — two or more regions — or to write the sequential state plainly. Joins count only regions that exist.

Example

Arxo Law

language "law.core" version "0.2";
package demo.diagnostics version "0.1.0";
namespace "urn:law:demo:diagnostics";

entity Tenant;
event Filed {
    tenant: Tenant;
}
procedure Solo(t: Tenant) {
    state Start initial;
    state Work parallel {
        region Only {
            state A initial;
            state B terminal;
            transition Go {
                from A;
                to B;
                on Filed;
            }
        }
    }
    state Done terminal;
    transition Begin {
        from Start;
        to Work;
        on Filed;
    }
    transition End {
        from Work;
        to Done;
        on Filed;
    }
}

Fix

Arxo Law

language "law.core" version "0.2";
package demo.diagnostics version "0.1.0";
namespace "urn:law:demo:diagnostics";

entity Tenant;
event Filed {
    tenant: Tenant;
}
procedure Solo(t: Tenant) {
    state Start initial;
    state Work parallel {
        region Left {
            state A initial;
            state B terminal;
            transition Go {
                from A;
                to B;
                on Filed;
            }
        }
        region Right {
            state C initial;
            state D terminal;
            transition Go2 {
                from C;
                to D;
                on Filed;
            }
        }
    }
    state Done terminal;
    transition Begin {
        from Start;
        to Work;
        on Filed;
    }
    transition End {
        from Work;
        to Done;
        on Filed;
    }
}

Engine message

The engine reports this in its own wording:

Output

example.law:11:11: error LDC-E1345: состояние "Work": `parallel` с одной областью отвергается — составному состоянию нужно не меньше двух областей (§162.1); до выдачи IR не допускается

Related

• Procedures — states, transitions, and how a procedure runs.
• LDC-E1311 — a procedure needs exactly one initial state.