if let ExprKind::Cast(cast_exp, _) = expr.kind {
let pre_cast_ty = cx.typeck_results().expr_ty(cast_exp);
let cast_ty = cx.typeck_results().expr_ty(expr);
if let ExprKind::Cast(cast_exp, _) = expr.kind {
let pre_cast_ty = cx.typeck_results().expr_ty(cast_exp);
let cast_ty = cx.typeck_results().expr_ty(expr);