feat(tvix/eval): Box Value::Catchable

This is now the only enum variant for Value that is larger than 8
bytes (it's 16 bytes), so boxing it (especially since it's not
perf-critical) allows us to get the Value size down to only 16 bytes!

Change-Id: I98598e2b762944448bef982e8ff7da6d6683c4aa
Reviewed-on: https://cl.tvl.fyi/c/depot/+/10798
Tested-by: BuildkiteCI
Reviewed-by: raitobezarius <tvl@lahfa.xyz>
Autosubmit: aspen <root@gws.fyi>

tvix/eval/src/value/attrs.rs

@@ -375,7 +375,7 @@ impl NixAttrs {
                     continue;
                 }
 
-                Value::Catchable(err) => return Ok(Err(err)),
+                Value::Catchable(err) => return Ok(Err(*err)),
 
                 other => return Err(ErrorKind::InvalidAttributeName(other)),
             }

tvix/eval/src/value/json.rs

@@ -61,7 +61,7 @@ impl Value {
                         )
                         .await?
                     {
-                        Value::Catchable(cek) => return Ok(Err(cek)),
+                        Value::Catchable(cek) => return Ok(Err(*cek)),
                         Value::String(s) => return Ok(Ok(Json::String(s.to_str()?.to_owned()))),
                         _ => panic!("Value::coerce_to_string_() returned a non-string!"),
                     }
@@ -88,7 +88,7 @@ impl Value {
                 Json::Object(out)
             }
 
-            Value::Catchable(c) => return Ok(Err(c)),
+            Value::Catchable(c) => return Ok(Err(*c)),
 
             val @ Value::Closure(_)
             | val @ Value::Thunk(_)
@@ -110,7 +110,7 @@ impl Value {
     /// Value::Json.
     pub(crate) async fn into_json_generator(self, co: GenCo) -> Result<Value, ErrorKind> {
         match self.into_json(&co).await? {
-            Err(cek) => Ok(Value::Catchable(cek)),
+            Err(cek) => Ok(Value::from(cek)),
             Ok(json) => Ok(Value::Json(Box::new(json))),
         }
     }

tvix/eval/src/value/mod.rs

@@ -84,12 +84,13 @@ pub enum Value {
     FinaliseRequest(bool),
 
     #[serde(skip)]
-    Catchable(CatchableErrorKind),
+    Catchable(Box<CatchableErrorKind>),
 }
 
 impl From<CatchableErrorKind> for Value {
+    #[inline]
     fn from(c: CatchableErrorKind) -> Value {
-        Value::Catchable(c)
+        Value::Catchable(Box::new(c))
     }
 }
 
@@ -97,8 +98,12 @@ impl<V> From<Result<V, CatchableErrorKind>> for Value
 where
     Value: From<V>,
 {
+    #[inline]
     fn from(v: Result<V, CatchableErrorKind>) -> Value {
-        v.map_or_else(Value::Catchable, |v| v.into())
+        match v {
+            Ok(v) => v.into(),
+            Err(e) => Value::Catchable(Box::new(e)),
+        }
     }
 }
 
@@ -776,8 +781,8 @@ impl Value {
                 b = b.force(&co, span.clone()).await?;
             }
             let result = match (a, b) {
-                (Value::Catchable(c), _) => return Ok(Err(c)),
-                (_, Value::Catchable(c)) => return Ok(Err(c)),
+                (Value::Catchable(c), _) => return Ok(Err(*c)),
+                (_, Value::Catchable(c)) => return Ok(Err(*c)),
                 // same types
                 (Value::Integer(i1), Value::Integer(i2)) => i1.cmp(&i2),
                 (Value::Float(f1), Value::Float(f2)) => f1.total_cmp(&f2),