1 use crate::utils::{is_type_diagnostic_item, method_chain_args, snippet_with_applicability, span_lint_and_sugg};
2 use if_chain::if_chain;
3 use rustc_errors::Applicability;
4 use rustc_hir::{Expr, ExprKind, MatchSource, PatKind, QPath};
5 use rustc_lint::{LateContext, LateLintPass};
6 use rustc_session::{declare_lint_pass, declare_tool_lint};
10 /// **What it does:*** Checks for unnecessary `ok()` in if let.
12 /// **Why is this bad?** Calling `ok()` in if let is unnecessary, instead match
15 /// **Known problems:** None.
20 /// if let Some(value) = i.parse().ok() {
29 /// if let Ok(value) = i.parse() {
34 pub IF_LET_SOME_RESULT,
36 "usage of `ok()` in `if let Some(pat)` statements is unnecessary, match on `Ok(pat)` instead"
39 declare_lint_pass!(OkIfLet => [IF_LET_SOME_RESULT]);
41 impl<'tcx> LateLintPass<'tcx> for OkIfLet {
42 fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
43 if_chain! { //begin checking variables
44 if let ExprKind::Match(ref op, ref body, source) = expr.kind; //test if expr is a match
45 if let MatchSource::IfLetDesugar { .. } = source; //test if it is an If Let
46 if let ExprKind::MethodCall(_, ok_span, ref result_types, _) = op.kind; //check is expr.ok() has type Result<T,E>.ok(, _)
47 if let PatKind::TupleStruct(QPath::Resolved(_, ref x), ref y, _) = body[0].pat.kind; //get operation
48 if method_chain_args(op, &["ok"]).is_some(); //test to see if using ok() methoduse std::marker::Sized;
49 if is_type_diagnostic_item(cx, cx.typeck_results().expr_ty(&result_types[0]), sym::result_type);
50 if rustc_hir_pretty::to_string(rustc_hir_pretty::NO_ANN, |s| s.print_path(x, false)) == "Some";
53 let mut applicability = Applicability::MachineApplicable;
54 let some_expr_string = snippet_with_applicability(cx, y[0].span, "", &mut applicability);
55 let trimmed_ok = snippet_with_applicability(cx, op.span.until(ok_span), "", &mut applicability);
59 trimmed_ok.trim().trim_end_matches('.'),
64 expr.span.with_hi(op.span.hi()),
65 "matching on `Some` with `ok()` is redundant",
66 &format!("consider matching on `Ok({})` and removing the call to `ok` instead", some_expr_string),