yeast: Delete the Cursor trait, inline its methods on AstCursor

The trait had a single implementor (`AstCursor`), three type parameters
of which one (`T`) was never used in any method signature, and one
external consumer that needed `use yeast::Cursor;` in scope just to
call methods on the cursor. The abstraction was overhead without a
second implementor to justify it.

Move the six trait methods to an inherent `impl AstCursor` block;
delete `shared/yeast/src/cursor.rs`, the `pub mod cursor;` and
`pub use cursor::Cursor;` lines in `lib.rs`, and the `use yeast::Cursor;`
in `tree-sitter-extractor`'s `traverse_yeast`.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: tausbn

shared/tree-sitter-extractor/src/extractor/mod.rs

@@ -882,7 +882,6 @@ fn emit_extras_in(visitor: &mut Visitor, node: Node<'_>) {
 }
 
 fn traverse_yeast(tree: &yeast::Ast, visitor: &mut Visitor) {
-    use yeast::Cursor;
     let mut cursor = tree.walk();
     visitor.enter_node(cursor.node());
     let mut recurse = true;

shared/yeast/src/cursor.rs

@@ -7,7 +7,6 @@ use serde_json::{json, Value};
 
 pub mod build;
 pub mod captures;
-pub mod cursor;
 pub mod dump;
 pub mod node_types_yaml;
 pub mod query;
@@ -19,7 +18,6 @@ mod visitor;
 pub use yeast_macros::{query, rule, tree, trees};
 
 use captures::Captures;
-pub use cursor::Cursor;
 use query::QueryNode;
 
 /// Node id: an index into the [`Ast`] arena. A newtype around `usize`
@@ -174,37 +172,16 @@ impl<'a> AstCursor<'a> {
         self.node_id
     }
 
-    fn goto_next_sibling_opt(&mut self) -> Option<()> {
-        self.node_id = self.parents.last_mut()?.1.next()?;
-        Some(())
-    }
-
-    fn goto_first_child_opt(&mut self) -> Option<()> {
-        let parent_id = self.node_id;
-        let parent = self.ast.get_node(parent_id)?;
-        let mut children = ChildrenIter::new(parent);
-        let first_child = children.next()?;
-        self.node_id = first_child;
-        self.parents.push((parent_id, children));
-        Some(())
-    }
-
-    fn goto_parent_opt(&mut self) -> Option<()> {
-        self.node_id = self.parents.pop()?.0;
-        Some(())
-    }
-}
-impl<'a> Cursor<'a, Ast, Node, FieldId> for AstCursor<'a> {
-    fn node(&self) -> &'a Node {
+    pub fn node(&self) -> &'a Node {
         &self.ast.nodes[self.node_id.0]
     }
 
-    fn field_id(&self) -> Option<FieldId> {
+    pub fn field_id(&self) -> Option<FieldId> {
         let (_, children) = self.parents.last()?;
         children.current_field()
     }
 
-    fn field_name(&self) -> Option<&'static str> {
+    pub fn field_name(&self) -> Option<&'static str> {
         if self.field_id() == Some(CHILD_FIELD) {
             None
         } else {
@@ -213,17 +190,37 @@ impl<'a> Cursor<'a, Ast, Node, FieldId> for AstCursor<'a> {
         }
     }
 
-    fn goto_first_child(&mut self) -> bool {
+    pub fn goto_first_child(&mut self) -> bool {
         self.goto_first_child_opt().is_some()
     }
 
-    fn goto_next_sibling(&mut self) -> bool {
+    pub fn goto_next_sibling(&mut self) -> bool {
         self.goto_next_sibling_opt().is_some()
     }
 
-    fn goto_parent(&mut self) -> bool {
+    pub fn goto_parent(&mut self) -> bool {
         self.goto_parent_opt().is_some()
     }
+
+    fn goto_next_sibling_opt(&mut self) -> Option<()> {
+        self.node_id = self.parents.last_mut()?.1.next()?;
+        Some(())
+    }
+
+    fn goto_first_child_opt(&mut self) -> Option<()> {
+        let parent_id = self.node_id;
+        let parent = self.ast.get_node(parent_id)?;
+        let mut children = ChildrenIter::new(parent);
+        let first_child = children.next()?;
+        self.node_id = first_child;
+        self.parents.push((parent_id, children));
+        Some(())
+    }
+
+    fn goto_parent_opt(&mut self) -> Option<()> {
+        self.node_id = self.parents.pop()?.0;
+        Some(())
+    }
 }
 
 /// An iterator over the child Ids of a node.