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_tool_lint, lint_array};
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 #[derive(Copy, Clone)]
40 impl LintPass for Pass {
41 fn get_lints(&self) -> LintArray {
42 lint_array!(IF_LET_SOME_RESULT)
45 fn name(&self) -> &'static str {
50 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Pass {
51 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
52 if_chain! { //begin checking variables
53 if let ExprKind::Match(ref op, ref body, ref source) = expr.node; //test if expr is a match
54 if let MatchSource::IfLetDesugar { .. } = *source; //test if it is an If Let
55 if let ExprKind::MethodCall(_, _, ref result_types) = op.node; //check is expr.ok() has type Result<T,E>.ok()
56 if let PatKind::TupleStruct(QPath::Resolved(_, ref x), ref y, _) = body[0].pats[0].node; //get operation
57 if method_chain_args(op, &["ok"]).is_some(); //test to see if using ok() methoduse std::marker::Sized;
60 let is_result_type = match_type(cx, cx.tables.expr_ty(&result_types[0]), &paths::RESULT);
61 let some_expr_string = snippet(cx, y[0].span, "");
62 if print::to_string(print::NO_ANN, |s| s.print_path(x, false)) == "Some" && is_result_type {
63 span_help_and_lint(cx, IF_LET_SOME_RESULT, expr.span,
64 "Matching on `Some` with `ok()` is redundant",
65 &format!("Consider matching on `Ok({})` and removing the call to `ok` instead", some_expr_string));