feat(tvix/eval): allow external users to construct native thunks r/8605

This interface is the only way to construct lazy builtins outside of eval, which
is actually a useful feature to have.

Change-Id: I386323af20aa3134bb4f669fa66fbb21e9b05fd4
Reviewed-on: https://cl.tvl.fyi/c/depot/+/12386
Reviewed-by: flokli <flokli@flokli.de>
Tested-by: BuildkiteCI
Autosubmit: tazjin <tazjin@tvl.su>
Reviewed-by: Yury Shvedov <yury.shvedov@kaspersky.com>

1 files changed, 6 insertions, 0 deletions

diff --git a/tvix/eval/src/value/mod.rs b/tvix/eval/src/value/mod.rs
index aaa052306027..2e78f20b49a0 100644
--- a/tvix/eval/src/value/mod.rs
+++ b/tvix/eval/src/value/mod.rs
@@ -888,6 +888,12 @@ impl Value {
             | Value::FinaliseRequest(_) => "an internal Tvix evaluator value".into(),
         }
     }
+
+    /// Constructs a thunk that will be evaluated lazily at runtime. This lets
+    /// users of Tvix implement their own lazy builtins and so on.
+    pub fn suspended_native_thunk(native: Box<dyn Fn() -> Result<Value, ErrorKind>>) -> Self {
+        Value::Thunk(Thunk::new_suspended_native(native))
+    }
 }
 
 trait TotalDisplay {