Fix arrow parsing; avoid extra block nodes in AST

quantified-uncertainty / squiggle

An estimation language

https://squiggle-language.com

MIT License

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Fix arrow parsing; avoid extra block nodes in AST #3136

Closed berekuk closed 3 months ago

berekuk commented 3 months ago

This fixes #3110, and also fixes #2670, and also simplifies grammar and AST (see tests in diff for examples).

Previously:

$ node dist/cli/index.js parse -e 'x=5'
(Program
  (LetStatement
    :x
    (Block 5)
  )
)

Now:

$ node dist/cli/index.js parse -e 'x=5'
(Program
  (LetStatement :x 5)
)

The arrow bug in particular was caused by parsing let statements as lambdas first, before falling back on arbitrary expressions. I don't know why it was there; there might be some obscure case where this is a technically breaking change, but all tests are parsed and I hope it's fine.

Note that this doesn't give us any significant performance improvements; I already unwrap single-expression blocks during compilation.

(Which is good because otherwise I'd be worried about this change; I remember that some time ago skipping these block nodes wasn't safe).

changeset-bot[bot] commented 3 months ago

🦋 Changeset detected

Latest commit: 4ce0af0ecee10e3eb0e3dcbba2bef1ddfa33840e

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 6 packages

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