Refactor and fix state contexts in Rust backend #31
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Extracted helper functions from the transition code that generate each component of a state context, to be reused elsewhere where state contexts are needed.
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Whoops, forgot to commit my final changes. 😳 The PR should be updated now. |
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Sep 4, 2021
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This significantly refactors the generation of the state context initialization code in the Rust backend, making state contexts work correctly and consistently for all ways of entering a state (initial state, transitions, and change-states).
Previously, state contexts were only initialized correctly for transitions, which led to limitations in initial states described in #22 and in change-states, described in #27. Both of these issues are fixed.
For initial states, only state variables and exit parameters are allowed (i.e. not state parameters or enter parameters). It could be possible to also allow either state parameters or enter parameters by passing these in to the state machine constructor. However, it's not clear which of these should take precedence. Also, these features are usually only accessible in Frame, so it would be inconsistent to allow access to them from Rust for initial states. Thus, it seems like a reasonable limitation that these features are not available for initial states.
For change-states, enter and exit parameters are not allowed since these events are not triggered by a change-state.
This PR needs approval from @frame-lang since the PR includes a minor change to the parser to enable parsing state parameters on change-states.
Fixes #22
Fixes #27