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