fix: guard eta-reduction against mismatched arg counts#272
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The eta-reduction pass simplified `Lambda(a, b): App(f, a)` to `f`, silently dropping `b`. The `zip` iterator stopped at the shorter list without verifying both sides had the same length. Add an `args.len() == app_args.len()` guard so eta-reduction only fires when the lambda forwards all of its arguments.
maplant
approved these changes
Jun 1, 2026
Two unit tests that construct CPS directly: - Lambda(a, b): App(f, a) must NOT be eta-reduced (drops b) - Lambda(a, b): App(f, a, b) SHOULD be eta-reduced to f The first test fails without the args-length guard, confirming the fix prevents silent argument dropping.
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Added a small rust test |
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Thanks! |
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CPS eta-reduction pass simplifies
Lambda(a, b): App(f, a)tof, silently droppingb. Add anargs.len() == app_args.len()guard so eta-reduction only fires when the lambda forwards all of its arguments.Test plan
cargo test --features async,tokio)(value, remaining)that only passesvalueto its continuation)