feat(tvix/eval): emit instructions for dynamic var resolution r/4557

If an unknown variable is encountered and the with stack is not empty,
emit instructions for resolving the variable at runtime.

Change-Id: I752f4bd0025335744e4747364abd1bd34130374e
Reviewed-on: https://cl.tvl.fyi/c/depot/+/6223
Tested-by: BuildkiteCI
Reviewed-by: sterni <sternenseemann@systemli.org>
Reviewed-by: grfn <grfn@gws.fyi>

1 files changed, 11 insertions, 1 deletions

diff --git a/tvix/eval/src/compiler.rs b/tvix/eval/src/compiler.rs
index cb568bfc6fbd..970ad7a1b713 100644
--- a/tvix/eval/src/compiler.rs
+++ b/tvix/eval/src/compiler.rs
@@ -352,7 +352,17 @@ impl Compiler {
                 // features are not yet implemented.
                 match self.resolve_local(name) {
                     Some(idx) => self.chunk.push_op(OpCode::OpGetLocal(idx)),
-                    None => return Err(Error::UnknownStaticVariable(node)),
+                    None => {
+                        if self.scope.with_stack.is_empty() {
+                            return Err(Error::UnknownStaticVariable(node));
+                        }
+
+                        // Variable needs to be dynamically resolved
+                        // at runtime.
+                        let idx = self.chunk.push_constant(Value::String(name.into()));
+                        self.chunk.push_op(OpCode::OpConstant(idx));
+                        self.chunk.push_op(OpCode::OpResolveWith)
+                    }
                 }
             }
         };