{"ast_node_type":"function","tokens":[{"end":72,"kind":"keyword","start":0,"text":"fn"}]}
    fn from((let_expr, hir_id): (&'a hir::LetExpr<'a>, HirId)) -> Self {
impl<'a> From<(&'a hir::LetExpr<'a>, HirId)> for Declaration<'a> {
        let hir::LetExpr { pat, ty, span, init, recovered: _ } = *let_expr;