fix(tvix/eval): fix b/281 by adding Value::Catchable r/6650

This commit makes catchable errors a variant of Value.

The main downside of this approach is that we lose the ability to
use Rust's `?` syntax for propagating catchable errors.

Change-Id: Ibe89438d8a70dcec29e016df692b5bf88a5cad13
Reviewed-on: https://cl.tvl.fyi/c/depot/+/9289
Reviewed-by: tazjin <tazjin@tvl.su>
Autosubmit: Adam Joseph <adam@westernsemico.com>
Tested-by: BuildkiteCI

2 files changed, 9 insertions, 9 deletions

diff --git a/tvix/eval/src/compiler/import.rs b/tvix/eval/src/compiler/import.rs
index 59e3d92e81..94a6602e9d 100644
--- a/tvix/eval/src/compiler/import.rs
+++ b/tvix/eval/src/compiler/import.rs
@@ -25,7 +25,10 @@ async fn import_impl(
     mut args: Vec<Value>,
 ) -> Result<Value, ErrorKind> {
     // TODO(sterni): canon_path()?
-    let mut path = coerce_value_to_path(&co, args.pop().unwrap()).await?;
+    let mut path = match coerce_value_to_path(&co, args.pop().unwrap()).await? {
+        Err(cek) => return Ok(Value::Catchable(cek)),
+        Ok(path) => path,
+    };
 
     if path.is_dir() {
         path.push("default.nix");
@@ -36,11 +39,8 @@ async fn import_impl(
     }
 
     // TODO(tazjin): make this return a string directly instead
-    let contents = generators::request_read_to_string(&co, path.clone())
-        .await
-        .to_str()?
-        .as_str()
-        .to_string();
+    let contents: Value = generators::request_read_to_string(&co, path.clone()).await;
+    let contents = contents.to_str()?.as_str().to_string();
 
     let parsed = rnix::ast::Root::parse(&contents);
     let errors = parsed.errors();
diff --git a/tvix/eval/src/compiler/mod.rs b/tvix/eval/src/compiler/mod.rs
index 5c2825507f..cfd50bec57 100644
--- a/tvix/eval/src/compiler/mod.rs
+++ b/tvix/eval/src/compiler/mod.rs
@@ -396,11 +396,11 @@ impl Compiler<'_> {
         } else if raw_path.starts_with('<') {
             // TODO: decide what to do with findFile
             if raw_path.len() == 2 {
-                return self.emit_error(
-                    node,
-                    ErrorKind::CatchableErrorKind(CatchableErrorKind::NixPathResolution(
+                return self.emit_constant(
+                    Value::Catchable(CatchableErrorKind::NixPathResolution(
                         "Empty <> path not allowed".into(),
                     )),
+                    node,
                 );
             }
             let path = &raw_path[1..(raw_path.len() - 1)];