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feat(tvix/eval): implement capture of self-recursive upvalues

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With this change, it becomes possible for functions to call themselves
as they are being defined in local bindings.

Change-Id: Ib46a39ba17b1452b5673d96fa729d633d237241a
Reviewed-on: https://cl.tvl.fyi/c/depot/+/6314
Tested-by: BuildkiteCI
Reviewed-by: sterni <sternenseemann@systemli.org>
This commit is contained in:
Vincent Ambo 2022-08-27 22:58:39 +03:00 • committed by tazjin
parent 06b07f5c47
commit ae531a2245
4 changed files with 22 additions and 7 deletions
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12
tvix/eval/src/vm.rs
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@ -359,7 +359,15 @@ impl VM {
}
OpCode::OpClosure(idx) => {
let closure = self.chunk().constant(idx).clone().to_closure()?;
let value = self.chunk().constant(idx).clone();
self.push(value.clone());
// This refers to the same Rc, and from this point
// on internally mutates the closure objects
// upvalues. The closure is already in its stack
// slot, which means that it can capture itself as
// an upvalue for self-recursion.
let closure = value.to_closure()?;
debug_assert!(
closure.upvalue_count() > 0,
@ -387,8 +395,6 @@ impl VM {
_ => panic!("compiler error: missing closure operand"),
}
}
self.push(Value::Closure(closure));
}
// Data-carrying operands should never be executed,