Errors

Errors have the form file:line:col: error: message. The output below is real: it was produced by drumlin during this site’s build, without the file prefix.

Unknown names

drumlin suggests the closest declared name.

component Scheduler
component Worker
Scheduelr --> Worker

drumlin says:

3:1: error: unknown element `Scheduelr`; did you mean `Scheduler`?

Duplicate declarations

component Worker
component Worker

drumlin says:

2:11: error: `Worker` is already declared

Unclosed blocks

component Outer {
  component Inner

drumlin says:

2:1: error: missing `}` for `Outer`

Unmatched braces

component Lonely
}

drumlin says:

2:1: error: unmatched `}`

Invalid nesting

diagram package
package Outer { class Inner }
Outer +-- Inner

drumlin says:

3:1: error: `Inner` is drawn inside `Outer`, so containment needs no line; declare `Inner` outside the `Outer` block

Misplaced statements

provides IFoo

drumlin says:

1:1: error: `provides` and `requires` belong inside a component

Ambiguous ports

component A { port data }
component B { port data }
component C
data --> C

drumlin says:

4:1: error: port `data` is ambiguous; write `<component>.data`

Unimplemented diagram kinds

diagram timing "Handshake"

drumlin says:

1:1: error: diagram kind `timing` is not implemented; this prototype supports `component`, `package`, `sequence`, `state`, `activity`

Sequence diagrams

Names must be declared before use, so a typo is caught where it happens.

diagram sequence
participant Server
Servre -> Server : ping

drumlin says:

3:1: error: unknown participant `Servre`; did you mean `Server`?; declare it with `participant` before its first use

A return needs a message block to return from.

diagram sequence
participant A
return done

drumlin says:

3:1: error: `return` belongs inside a message block

A fragment continuation must match its opener.

diagram sequence
participant A
participant B
opt "x" {
  A -> B : y
} else {
  B -> A : z
}

drumlin says:

6:3: error: `else` must follow the `}` of an `alt`

State diagrams

Rules from UML 2.5.1 clause 14 are checked. A fork, for example, needs one incoming and at least two outgoing transitions.

diagram state
fork f
A --> f
f --> B

drumlin says:

2:6: error: fork `f` needs exactly one incoming and at least two outgoing transitions

A name used only once, close to another name, is reported as a likely typo. Write state Idel first if the state really has that name.

diagram state
state Idle
[*] --> Idle
Idle --> Idel : wait

drumlin says:

4:10: error: unknown state `Idel`; did you mean `Idle`? declare it with `state Idel` if intended

A transition leaving a pseudostate cannot have a trigger.

diagram state
choice c
A --> c
c --> B : go

drumlin says:

4:7: error: a transition leaving a pseudostate cannot have a trigger; use `[guard] / effect`

A transition cannot join two orthogonal regions of one state.

diagram state
state A {
  region {
    [*] --> B
  }
  region {
    [*] --> C
    C --> B
  }
}

drumlin says:

8:5: error: a transition cannot join two orthogonal regions of `A`

Activity diagrams

Statements after the end of a flow can never run.

diagram activity
start
stop
action "Late"

drumlin says:

4:1: error: this statement can never run: the flow already ended with `stop` on line 3; remove it, or move it before the end

Every branch of a fork needs a step.

diagram activity
start
fork {
  action "A"
} and {
}
stop

drumlin says:

5:3: error: this `fork` branch is empty; each branch needs a step, or remove the branch

A flow must not end on a merge, because a merge has one outgoing flow.

diagram activity
start
if "x" {
  action "A"
}

drumlin says:

3:1: error: the flow continues after this `if` but nothing follows; add a step, or end it with `stop` or `end`

When a diagram uses lanes, every action must be in one.

diagram activity
lane "A" {
}
start
action "B"
stop

drumlin says:

5:1: error: this diagram uses lanes, so this `action` must be inside a `lane` block