Make AST borrowed

1 files changed, 18 insertions, 5 deletions

diff --git a/crates/typst-syntax/src/node.rs b/crates/typst-syntax/src/node.rs
index f949b4dd..8e4e056e 100644
--- a/crates/typst-syntax/src/node.rs
+++ b/crates/typst-syntax/src/node.rs
@@ -105,22 +105,22 @@ impl SyntaxNode {
     }
 
     /// Whether the node can be cast to the given AST node.
-    pub fn is<T: AstNode>(&self) -> bool {
+    pub fn is<'a, T: AstNode<'a>>(&'a self) -> bool {
         self.cast::<T>().is_some()
     }
 
     /// Try to convert the node to a typed AST node.
-    pub fn cast<T: AstNode>(&self) -> Option<T> {
+    pub fn cast<'a, T: AstNode<'a>>(&'a self) -> Option<T> {
         T::from_untyped(self)
     }
 
     /// Cast the first child that can cast to the AST type `T`.
-    pub fn cast_first_match<T: AstNode>(&self) -> Option<T> {
+    pub fn cast_first_match<'a, T: AstNode<'a>>(&'a self) -> Option<T> {
         self.children().find_map(Self::cast)
     }
 
     /// Cast the last child that can cast to the AST type `T`.
-    pub fn cast_last_match<T: AstNode>(&self) -> Option<T> {
+    pub fn cast_last_match<'a, T: AstNode<'a>>(&'a self) -> Option<T> {
         self.children().rev().find_map(Self::cast)
     }
 
@@ -273,6 +273,17 @@ impl SyntaxNode {
             Repr::Error(node) => node.error.span.number() + 1,
         }
     }
+
+    /// An arbitrary node just for filling a slot in memory.
+    ///
+    /// In contrast to `default()`, this is a const fn.
+    pub(super) const fn arbitrary() -> Self {
+        Self(Repr::Leaf(LeafNode {
+            kind: SyntaxKind::Eof,
+            text: EcoString::new(),
+            span: Span::detached(),
+        }))
+    }
 }
 
 impl Debug for SyntaxNode {
@@ -287,7 +298,7 @@ impl Debug for SyntaxNode {
 
 impl Default for SyntaxNode {
     fn default() -> Self {
-        Self::error("", "")
+        Self::arbitrary()
     }
 }
 
@@ -802,6 +813,8 @@ impl<'a> LinkedNode<'a> {
 impl Deref for LinkedNode<'_> {
     type Target = SyntaxNode;
 
+    /// Dereference to a syntax node. Note that this shortens the lifetime, so
+    /// you may need to use [`get()`](Self::get) instead in some situations.
     fn deref(&self) -> &Self::Target {
         self.get()
     }