Rework `Vt` into `Engine`

- Moves as much data out of the `Vm`
- Removes duplication with call_vm and call_vt flavours
- Uses tracked chain instead of fixed int for determining max nesting depth
- This means that nesting checks now generalizes to layout and realization, to detect crashing show rules and overly nested layouts

1 files changed, 10 insertions, 0 deletions

diff --git a/crates/typst-syntax/src/span.rs b/crates/typst-syntax/src/span.rs
index 14e5e216..8138a316 100644
--- a/crates/typst-syntax/src/span.rs
+++ b/crates/typst-syntax/src/span.rs
@@ -2,6 +2,8 @@ use std::fmt::{self, Debug, Formatter};
 use std::num::NonZeroU64;
 use std::ops::Range;
 
+use ecow::EcoString;
+
 use crate::FileId;
 
 /// A unique identifier for a syntax node.
@@ -80,6 +82,14 @@ impl Span {
     pub const fn number(self) -> u64 {
         self.0.get() & ((1 << Self::BITS) - 1)
     }
+
+    /// Resolve a file location relative to this span's source.
+    pub fn resolve_path(self, path: &str) -> Result<FileId, EcoString> {
+        let Some(file) = self.id() else {
+            return Err("cannot access file system from here".into());
+        };
+        Ok(file.join(path))
+    }
 }
 
 /// A value with a span locating it in the source code.