feat(tvix/eval): add error contexts to annotate error kinds r/5706

This makes it possible for users to add additional context to an
error, which will then be rendered as an additional secondary span in
the formatted error output.

We should strive to do this basically anywhere errors are raised that
can occur multiple times, *especially* during type casts. This was
triggered by me debugging a type cast error attached to a fairly
large-ish span (a builtin invocation).

Change-Id: I51be41fabee00cf04de973935daf34fe6424e76f
Reviewed-on: https://cl.tvl.fyi/c/depot/+/7849
Tested-by: BuildkiteCI
Reviewed-by: flokli <flokli@flokli.de>

1 files changed, 3 insertions, 14 deletions

diff --git a/tvix/eval/src/vm.rs b/tvix/eval/src/vm.rs
index 3dece0641281..60006ea76f9c 100644
--- a/tvix/eval/src/vm.rs
+++ b/tvix/eval/src/vm.rs
@@ -134,12 +134,7 @@ macro_rules! fallible {
     ( $self:ident, $body:expr) => {
         match $body {
             Ok(result) => result,
-            Err(kind) => {
-                return Err(Error {
-                    kind,
-                    span: $self.current_span(),
-                })
-            }
+            Err(kind) => return Err(Error::new(kind, $self.current_span())),
         }
     };
 }
@@ -281,10 +276,7 @@ impl<'o> VM<'o> {
     /// Construct an error from the given ErrorKind and the source
     /// span of the current instruction.
     pub fn error(&self, kind: ErrorKind) -> Error {
-        Error {
-            kind,
-            span: self.current_span(),
-        }
+        Error::new(kind, self.current_span())
     }
 
     /// Push an already constructed warning.
@@ -1197,10 +1189,7 @@ pub fn run_lambda(
 
     value
         .deep_force(&mut vm, &mut Default::default())
-        .map_err(|kind| Error {
-            kind,
-            span: root_span,
-        })?;
+        .map_err(|kind| Error::new(kind, root_span))?;
 
     Ok(RuntimeResult {
         value,