2 use rustc::{declare_lint, lint_array};
4 use crate::utils::{match_type, method_chain_args, paths, snippet, span_help_and_lint};
6 /// **What it does:*** Checks for unnecessary `ok()` in if let.
8 /// **Why is this bad?** Calling `ok()` in if let is unnecessary, instead match
11 /// **Known problems:** None.
15 /// for result in iter {
16 /// if let Some(bench) = try!(result).parse().ok() {
24 /// for result in iter {
25 /// if let Ok(bench) = try!(result).parse() {
30 declare_clippy_lint! {
31 pub IF_LET_SOME_RESULT,
33 "usage of `ok()` in `if let Some(pat)` statements is unnecessary, match on `Ok(pat)` instead"
36 #[derive(Copy, Clone)]
39 impl LintPass for Pass {
40 fn get_lints(&self) -> LintArray {
41 lint_array!(IF_LET_SOME_RESULT)
45 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Pass {
46 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
47 if_chain! { //begin checking variables
48 if let ExprKind::Match(ref op, ref body, ref source) = expr.node; //test if expr is a match
49 if let MatchSource::IfLetDesugar { .. } = *source; //test if it is an If Let
50 if let ExprKind::MethodCall(_, _, ref result_types) = op.node; //check is expr.ok() has type Result<T,E>.ok()
51 if let PatKind::TupleStruct(QPath::Resolved(_, ref x), ref y, _) = body[0].pats[0].node; //get operation
52 if method_chain_args(op, &["ok"]).is_some(); //test to see if using ok() methoduse std::marker::Sized;
55 let is_result_type = match_type(cx, cx.tables.expr_ty(&result_types[0]), &paths::RESULT);
56 let some_expr_string = snippet(cx, y[0].span, "");
57 if print::to_string(print::NO_ANN, |s| s.print_path(x, false)) == "Some" && is_result_type {
58 span_help_and_lint(cx, IF_LET_SOME_RESULT, expr.span,
59 "Matching on `Some` with `ok()` is redundant",
60 &format!("Consider matching on `Ok({})` and removing the call to `ok` instead", some_expr_string));