fix(tvix/eval): type check function argument with set pattern r/6243

C++ Nix forces and typechecks the passed argument even if it is not
necessary in order to compute the return value of the function. I
discovered this when I thought our formals miscompilation might be that
we are too strict, but doesn't look like it in this case.

Change-Id: Ifb3c92592293052c489d1e3ae8c7c54e4b6b4dc6
Reviewed-on: https://cl.tvl.fyi/c/depot/+/8701
Tested-by: BuildkiteCI
Autosubmit: sterni <sternenseemann@systemli.org>
Reviewed-by: tazjin <tazjin@tvl.su>

1 files changed, 13 insertions, 0 deletions

diff --git a/tvix/eval/src/vm/mod.rs b/tvix/eval/src/vm/mod.rs
index 4af23a72d73b..9f973eb120e9 100644
--- a/tvix/eval/src/vm/mod.rs
+++ b/tvix/eval/src/vm/mod.rs
@@ -638,6 +638,19 @@ impl<'o> VM<'o> {
                     }
                 }
 
+                OpCode::OpAssertAttrs => {
+                    let val = self.stack_peek(0);
+                    if !val.is_attrs() {
+                        return frame.error(
+                            self,
+                            ErrorKind::TypeError {
+                                expected: "set",
+                                actual: val.type_of(),
+                            },
+                        );
+                    }
+                }
+
                 OpCode::OpAttrs(Count(count)) => self.run_attrset(&frame, count)?,
 
                 OpCode::OpAttrsUpdate => {