{"ast_node_type":"function","tokens":[{"end":72,"kind":"keyword","start":0,"text":"pub(crate)"}]}
    pub(crate) fn instantiate(&mut self, vid: ty::TyVid, ty: Ty<'tcx>) {
    /// Precondition: `vid` must not have been previously instantiated.
        let vid = self.root_var(vid);