Use NodeId for Binding source (#4234)

crates/ruff_python_semantic/src/binding.rs

@@ -3,8 +3,8 @@ use std::ops::{Deref, Index, IndexMut};
 
 use bitflags::bitflags;
 use ruff_text_size::TextRange;
-use rustpython_parser::ast::Stmt;
 
+use crate::node::NodeId;
 use crate::scope::ScopeId;
 
 #[derive(Debug, Clone)]
@@ -14,7 +14,7 @@ pub struct Binding<'a> {
     /// The context in which the binding was created.
     pub context: ExecutionContext,
     /// The statement in which the [`Binding`] was defined.
-    pub source: Option<&'a Stmt>,
+    pub source: Option<NodeId>,
     /// Tuple of (scope index, range) indicating the scope and range at which
     /// the binding was last used in a runtime context.
     pub runtime_usage: Option<(ScopeId, TextRange)>,