refactor(tvix/eval): after calling, the caller has to pop r/5094

Previously the various call functions either returned `EvalResult<()>`
or `EvalResult<Value>`, which was confusing.

Now only vm::call_with returns a Value directly, and other parts of
the API just leave the stack top in the post-call state.

This makes it easier to reason about what's going on in non-tail-call
cases (which are making a comeback).

Change-Id: I264ffc683a11aca72dd06e2220a5ff6e7c5fc2b0
Reviewed-on: https://cl.tvl.fyi/c/depot/+/6936
Tested-by: BuildkiteCI
Reviewed-by: grfn <grfn@gws.fyi>

1 files changed, 3 insertions, 4 deletions

diff --git a/tvix/eval/src/value/thunk.rs b/tvix/eval/src/value/thunk.rs
index ed994ebd7d57..7cb79dedc84a 100644
--- a/tvix/eval/src/value/thunk.rs
+++ b/tvix/eval/src/value/thunk.rs
@@ -87,10 +87,9 @@ impl Thunk {
                         std::mem::replace(&mut *thunk_mut, ThunkRepr::Blackhole)
                     {
                         drop(thunk_mut);
-                        let evaluated = ThunkRepr::Evaluated(
-                            vm.call(lambda, upvalues, 0)
-                                .map_err(|e| ErrorKind::ThunkForce(Box::new(e)))?,
-                        );
+                        vm.enter_frame(lambda, upvalues, 0)
+                            .map_err(|e| ErrorKind::ThunkForce(Box::new(e)))?;
+                        let evaluated = ThunkRepr::Evaluated(vm.pop());
                         (*self.0.borrow_mut()) = evaluated;
                     }
                 }