feat(tvix/eval): improve panic!() messages in Thunk::value() r/5303

Change-Id: I3b1284e28c350bfed84d643ae7f922f3487e1f2a
Reviewed-on: https://cl.tvl.fyi/c/depot/+/7355
Autosubmit: Adam Joseph <adam@westernsemico.com>
Tested-by: BuildkiteCI
Reviewed-by: tazjin <tazjin@tvl.su>

1 files changed, 4 insertions, 4 deletions

diff --git a/tvix/eval/src/value/thunk.rs b/tvix/eval/src/value/thunk.rs
index 5eee07a9e7ac..5107c6328da4 100644
--- a/tvix/eval/src/value/thunk.rs
+++ b/tvix/eval/src/value/thunk.rs
@@ -144,8 +144,8 @@ impl Thunk {
     // difficult to represent in the type system without impacting the
     // API too much.
     pub fn value(&self) -> Ref<Value> {
-        Ref::map(self.0.borrow(), |thunk| {
-            if let ThunkRepr::Evaluated(value) = thunk {
+        Ref::map(self.0.borrow(), |thunk| match thunk {
+            ThunkRepr::Evaluated(value) => {
                 #[cfg(debug_assertions)]
                 if matches!(
                     value,
@@ -158,8 +158,8 @@ impl Thunk {
                 }
                 return value;
             }
-
-            panic!("Thunk::value called on non-evaluated thunk");
+            ThunkRepr::Blackhole => panic!("Thunk::value called on a black-holed thunk"),
+            ThunkRepr::Suspended { .. } => panic!("Thunk::value called on a suspended thunk"),
         })
     }