diff options
| -rw-r--r-- | tvix/eval/src/value/thunk.rs | 35 |
1 files changed, 34 insertions, 1 deletions
diff --git a/tvix/eval/src/value/thunk.rs b/tvix/eval/src/value/thunk.rs index 9c048d40b499..1ff5beb0d472 100644 --- a/tvix/eval/src/value/thunk.rs +++ b/tvix/eval/src/value/thunk.rs @@ -92,6 +92,28 @@ impl ThunkRepr { ThunkRepr::Suspended { lambda, .. } => format!("thunk({:p})", *lambda), } } + + /// Return the Value within a fully-evaluated ThunkRepr; panics + /// if the thunk is not fully-evaluated. + fn expect(self) -> Value { + match self { + ThunkRepr::Evaluated(value) => value, + ThunkRepr::Blackhole { .. } => panic!("Thunk::expect() called on a black-holed thunk"), + ThunkRepr::Suspended { .. } | ThunkRepr::Native(_) => { + panic!("Thunk::expect() called on a suspended thunk") + } + } + } + + fn expect_ref(&self) -> &Value { + match self { + ThunkRepr::Evaluated(value) => value, + ThunkRepr::Blackhole { .. } => panic!("Thunk::expect() called on a black-holed thunk"), + ThunkRepr::Suspended { .. } | ThunkRepr::Native(_) => { + panic!("Thunk::expect() called on a suspended thunk") + } + } + } } /// A thunk is created for any value which requires non-strict @@ -178,7 +200,7 @@ impl Thunk { // If the current thunk is already fully evaluated, return its evaluated // value. The VM will continue running the code that landed us here. if self.is_forced() { - return Ok(self.value().clone()); + return Ok(self.unwrap_or_clone()); } // Begin evaluation of this thunk by marking it as a blackhole, meaning @@ -280,6 +302,17 @@ impl Thunk { }) } + /// Returns the inner evaluated value of a thunk, cloning it if + /// the Rc has more than one strong reference. It is an error + /// to call this on a thunk that has not been forced, or is not + /// otherwise known to be fully evaluated. + fn unwrap_or_clone(self) -> Value { + match Rc::try_unwrap(self.0) { + Ok(refcell) => refcell.into_inner().expect(), + Err(rc) => Ref::map(rc.borrow(), |thunkrepr| thunkrepr.expect_ref()).clone(), + } + } + pub fn upvalues(&self) -> Ref<'_, Upvalues> { Ref::map(self.0.borrow(), |thunk| match thunk { ThunkRepr::Suspended { upvalues, .. } => upvalues.as_ref(), |