fix(tvix/eval): force condition of an assert r/4937

Change-Id: I3ad2234e8a8e4280e498c6d7af8ea0733ed4c7ea
Reviewed-on: https://cl.tvl.fyi/c/depot/+/6699
Autosubmit: sterni <sternenseemann@systemli.org>
Reviewed-by: tazjin <tazjin@tvl.su>
Tested-by: BuildkiteCI

3 files changed, 9 insertions, 0 deletions

diff --git a/tvix/eval/src/compiler/mod.rs b/tvix/eval/src/compiler/mod.rs
index 160433904d..793f0566e9 100644
--- a/tvix/eval/src/compiler/mod.rs
+++ b/tvix/eval/src/compiler/mod.rs
@@ -471,6 +471,7 @@ impl Compiler<'_> {
     fn compile_assert(&mut self, slot: LocalIdx, node: ast::Assert) {
         // Compile the assertion condition to leave its value on the stack.
         self.compile(slot, node.condition().unwrap());
+        self.emit_force(&node.condition().unwrap());
         self.push_op(OpCode::OpAssert, &node.condition().unwrap());
 
         // The runtime will abort evaluation at this point if the
diff --git a/tvix/eval/src/tests/tvix_tests/eval-okay-assert-thunk-condition.exp b/tvix/eval/src/tests/tvix_tests/eval-okay-assert-thunk-condition.exp
new file mode 100644
index 0000000000..aabe6ec390
--- /dev/null
+++ b/tvix/eval/src/tests/tvix_tests/eval-okay-assert-thunk-condition.exp
@@ -0,0 +1 @@
+21
diff --git a/tvix/eval/src/tests/tvix_tests/eval-okay-assert-thunk-condition.nix b/tvix/eval/src/tests/tvix_tests/eval-okay-assert-thunk-condition.nix
new file mode 100644
index 0000000000..8934b3d8cf
--- /dev/null
+++ b/tvix/eval/src/tests/tvix_tests/eval-okay-assert-thunk-condition.nix
@@ -0,0 +1,7 @@
+let
+  condition = x: y: x < y;
+in
+
+# The function application here will become a thunk which verifies that
+# assert forces the condition expression correctly.
+assert condition 21 42; 21