fix(tvix/eval): thunk let-expression r/5184

There are some rare scope cases with deferred access where this
doesn't behave correctly otherwise.

Change-Id: I6c774f5e62c1cb50b598026c54727017a52cd22d
Reviewed-on: https://cl.tvl.fyi/c/depot/+/7064
Tested-by: BuildkiteCI
Reviewed-by: sterni <sternenseemann@systemli.org>

1 files changed, 5 insertions, 1 deletions

diff --git a/tvix/eval/src/compiler/mod.rs b/tvix/eval/src/compiler/mod.rs
index 9c8f0078f36a..2ab76623864b 100644
--- a/tvix/eval/src/compiler/mod.rs
+++ b/tvix/eval/src/compiler/mod.rs
@@ -224,7 +224,11 @@ impl Compiler<'_> {
             ast::Expr::IfElse(if_else) => {
                 self.thunk(slot, if_else, move |c, s| c.compile_if_else(s, if_else))
             }
-            ast::Expr::LetIn(let_in) => self.compile_let_in(slot, let_in),
+
+            ast::Expr::LetIn(let_in) => {
+                self.thunk(slot, let_in, move |c, s| c.compile_let_in(s, let_in))
+            }
+
             ast::Expr::Ident(ident) => self.compile_ident(slot, ident),
             ast::Expr::With(with) => self.thunk(slot, with, |c, s| c.compile_with(s, with)),
             ast::Expr::Lambda(lambda) => {