pawarser: Implement CompletedMarker::precede

crates/pawarser/src/parser/marker.rs

@@ -69,6 +69,17 @@ pub struct CompletedMarker<SyntaxKind: SyntaxElement, SyntaxErr: SyntaxError> {
 
 impl<SyntaxKind: SyntaxElement, SyntaxErr: SyntaxError> CompletedMarker<SyntaxKind, SyntaxErr> {
     pub fn precede(self, p: &mut Parser<SyntaxKind, SyntaxErr>, name: &str) -> Marker {
-        todo!()
+        let new_pos = p.start(name);
+
+        match &mut p.events[self.pos] {
+            Event::Start { forward_parent, .. } => {
+                // point forward parent of the node this marker completed to the new node
+                // will later be used to make the new node a parent of the current node.
+                *forward_parent = Some(new_pos.pos - self.pos)
+            }
+            _ => unreachable!(),
+        }
+
+        new_pos
     }
 }