2 use crate::utils::{match_type, method_chain_args, paths, snippet, span_help_and_lint};
3 use if_chain::if_chain;
5 use rustc::lint::{LateContext, LateLintPass, LintArray, LintPass};
6 use rustc::{declare_lint_pass, declare_tool_lint};
9 /// **What it does:*** Checks for unnecessary `ok()` in if let.
11 /// **Why is this bad?** Calling `ok()` in if let is unnecessary, instead match
14 /// **Known problems:** None.
18 /// for result in iter {
19 /// if let Some(bench) = try!(result).parse().ok() {
27 /// for result in iter {
28 /// if let Ok(bench) = try!(result).parse() {
33 pub IF_LET_SOME_RESULT,
35 "usage of `ok()` in `if let Some(pat)` statements is unnecessary, match on `Ok(pat)` instead"
38 declare_lint_pass!(OkIfLet => [IF_LET_SOME_RESULT]);
40 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for OkIfLet {
41 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
42 if_chain! { //begin checking variables
43 if let ExprKind::Match(ref op, ref body, ref source) = expr.node; //test if expr is a match
44 if let MatchSource::IfLetDesugar { .. } = *source; //test if it is an If Let
45 if let ExprKind::MethodCall(_, _, ref result_types) = op.node; //check is expr.ok() has type Result<T,E>.ok()
46 if let PatKind::TupleStruct(QPath::Resolved(_, ref x), ref y, _) = body[0].pats[0].node; //get operation
47 if method_chain_args(op, &[*sym::ok]).is_some(); //test to see if using ok() methoduse std::marker::Sized;
50 let is_result_type = match_type(cx, cx.tables.expr_ty(&result_types[0]), &*paths::RESULT);
51 let some_expr_string = snippet(cx, y[0].span, "");
52 if print::to_string(print::NO_ANN, |s| s.print_path(x, false)) == "Some" && is_result_type {
53 span_help_and_lint(cx, IF_LET_SOME_RESULT, expr.span,
54 "Matching on `Some` with `ok()` is redundant",
55 &format!("Consider matching on `Ok({})` and removing the call to `ok` instead", some_expr_string));