fix(tvix/eval): force exprs inside string interpolation r/4847

The expression inside ${…} may return arbitrary values, including
thunks, so we need to make sure to force them just in case.

Change-Id: Ic11ba00c4c92a10a83becd91233db5f57f6e59c8
Reviewed-on: https://cl.tvl.fyi/c/depot/+/6541
Autosubmit: sterni <sternenseemann@systemli.org>
Reviewed-by: grfn <grfn@gws.fyi>
Tested-by: BuildkiteCI
Reviewed-by: tazjin <tazjin@tvl.su>

1 files changed, 5 insertions, 1 deletions

diff --git a/tvix/eval/src/compiler/mod.rs b/tvix/eval/src/compiler/mod.rs
index 07086c72fc29..3830c01712f2 100644
--- a/tvix/eval/src/compiler/mod.rs
+++ b/tvix/eval/src/compiler/mod.rs
@@ -258,6 +258,7 @@ impl Compiler<'_, '_> {
     }
 
     fn compile_str(&mut self, slot: LocalIdx, node: ast::Str) {
+        // TODO: thunk string construction if it is not a literal
         let mut count = 0;
 
         // The string parts are produced in literal order, however
@@ -271,7 +272,10 @@ impl Compiler<'_, '_> {
                 // Interpolated expressions are compiled as normal and
                 // dealt with by the VM before being assembled into
                 // the final string.
-                ast::InterpolPart::Interpolation(node) => self.compile(slot, node.expr().unwrap()),
+                ast::InterpolPart::Interpolation(node) => {
+                    self.compile(slot, node.expr().unwrap());
+                    self.emit_force(&node);
+                }
 
                 ast::InterpolPart::Literal(lit) => {
                     self.emit_constant(Value::String(lit.into()), &node);