1 // Copyright 2014-2018 The Rust Project Developers. See the COPYRIGHT
2 // file at the top-level directory of this distribution.
4 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
5 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
6 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
7 // option. This file may not be copied, modified, or distributed
8 // except according to those terms.
10 use crate::rustc::hir::*;
11 use crate::rustc::lint::{LateContext, LateLintPass, LintArray, LintPass};
12 use crate::rustc::{declare_tool_lint, lint_array};
13 use crate::utils::{match_type, method_chain_args, paths, snippet, span_help_and_lint};
14 use if_chain::if_chain;
16 /// **What it does:*** Checks for unnecessary `ok()` in if let.
18 /// **Why is this bad?** Calling `ok()` in if let is unnecessary, instead match
21 /// **Known problems:** None.
25 /// for result in iter {
26 /// if let Some(bench) = try!(result).parse().ok() {
34 /// for result in iter {
35 /// if let Ok(bench) = try!(result).parse() {
40 declare_clippy_lint! {
41 pub IF_LET_SOME_RESULT,
43 "usage of `ok()` in `if let Some(pat)` statements is unnecessary, match on `Ok(pat)` instead"
46 #[derive(Copy, Clone)]
49 impl LintPass for Pass {
50 fn get_lints(&self) -> LintArray {
51 lint_array!(IF_LET_SOME_RESULT)
55 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Pass {
56 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
57 if_chain! { //begin checking variables
58 if let ExprKind::Match(ref op, ref body, ref source) = expr.node; //test if expr is a match
59 if let MatchSource::IfLetDesugar { .. } = *source; //test if it is an If Let
60 if let ExprKind::MethodCall(_, _, ref result_types) = op.node; //check is expr.ok() has type Result<T,E>.ok()
61 if let PatKind::TupleStruct(QPath::Resolved(_, ref x), ref y, _) = body[0].pats[0].node; //get operation
62 if method_chain_args(op, &["ok"]).is_some(); //test to see if using ok() methoduse std::marker::Sized;
65 let is_result_type = match_type(cx, cx.tables.expr_ty(&result_types[0]), &paths::RESULT);
66 let some_expr_string = snippet(cx, y[0].span, "");
67 if print::to_string(print::NO_ANN, |s| s.print_path(x, false)) == "Some" && is_result_type {
68 span_help_and_lint(cx, IF_LET_SOME_RESULT, expr.span,
69 "Matching on `Some` with `ok()` is redundant",
70 &format!("Consider matching on `Ok({})` and removing the call to `ok` instead", some_expr_string));