fix: lambdas capture their defining environment#883
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The JVM's FuncValue.eval returns a closure over the env it was created in
(values.scala): each application evaluates the body in that captured env
extended with the argument binding. sigma-rust's Value::Lambda carried
only args + body, and every invocation site (Apply and the HOF evals)
bound arguments into the CALLER's env with a save/restore dance — correct
for lambdas applied where they were created, wrong for lambdas that
escape: the inner lambda of add = (a: Int) => (b: Int) => a + b lost a
the moment the outer Apply returned, so the curried add(3)(1) errored
where the JVM evaluates 4.
Lambda gains the captured bindings (snapshotted by FuncValue::eval), and
a shared LambdaInvoker materializes the captured env once per lambda
value and binds the argument slot per call — replacing the save/restore
dance in Apply, Coll.{map,filter,fold,exists,forAll,flatMap} and
Option.{map,filter}. The capture must hold uniformly: an escaped lambda
fed to a HOF (val f = mk(3); coll.map(f)) hits the same root cause.
Surfaced by SANTA's v6 HOF vectors (HOF_currying_Apply_of_Apply,
blessed Int 4).
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
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The JVM's
FuncValue.evalreturns a closure over its defining env (values.scala); each application evaluates the body in that captured env plus the argument binding. sigma-rust'sValue::Lambdacarried onlyargs+body, and every invocation site (Apply, theColl/OptionHOF evals) bound arguments into the CALLER's env with a save/restore dance — wrong for lambdas that escape: the inner lambda ofadd = (a: Int) => (b: Int) => a + blostawhen the outer Apply returned, so the curriedadd(3)(1)errored where the JVM evaluates 4.Lambdanow captures its defining bindings and a sharedLambdaInvokerevaluates bodies in the captured env — uniformly, since an escaped lambda fed to a HOF hits the same root cause.Surfaced by SANTA's v6 HOF vectors (
add(3)(1)→ Int 4).