1 use clippy_utils::diagnostics::span_lint_and_then;
2 use clippy_utils::ty::is_type_diagnostic_item;
3 use clippy_utils::{method_chain_args, return_ty};
4 use if_chain::if_chain;
6 use rustc_hir::intravisit::{self, Visitor};
7 use rustc_hir::{Expr, ImplItemKind};
8 use rustc_lint::{LateContext, LateLintPass};
10 use rustc_session::{declare_lint_pass, declare_tool_lint};
11 use rustc_span::{sym, Span};
13 declare_clippy_lint! {
15 /// Checks for functions of type `Result` that contain `expect()` or `unwrap()`
17 /// ### Why is this bad?
18 /// These functions promote recoverable errors to non-recoverable errors which may be undesirable in code bases which wish to avoid panics.
20 /// ### Known problems
21 /// This can cause false positives in functions that handle both recoverable and non recoverable errors.
26 /// fn divisible_by_3(i_str: String) -> Result<(), String> {
29 /// .expect("cannot divide the input by three");
32 /// Err("Number is not divisible by 3")?
41 /// fn divisible_by_3(i_str: String) -> Result<(), String> {
44 /// .map_err(|e| format!("cannot divide the input by three: {}", e))?;
47 /// Err("Number is not divisible by 3")?
53 #[clippy::version = "1.48.0"]
56 "functions of type `Result<..>` or `Option`<...> that contain `expect()` or `unwrap()`"
59 declare_lint_pass!(UnwrapInResult=> [UNWRAP_IN_RESULT]);
61 impl<'tcx> LateLintPass<'tcx> for UnwrapInResult {
62 fn check_impl_item(&mut self, cx: &LateContext<'tcx>, impl_item: &'tcx hir::ImplItem<'_>) {
64 // first check if it's a method or function
65 if let hir::ImplItemKind::Fn(ref _signature, _) = impl_item.kind;
66 // checking if its return type is `result` or `option`
67 if is_type_diagnostic_item(cx, return_ty(cx, impl_item.hir_id()), sym::Result)
68 || is_type_diagnostic_item(cx, return_ty(cx, impl_item.hir_id()), sym::Option);
70 lint_impl_body(cx, impl_item.span, impl_item);
76 struct FindExpectUnwrap<'a, 'tcx> {
77 lcx: &'a LateContext<'tcx>,
78 typeck_results: &'tcx ty::TypeckResults<'tcx>,
82 impl<'a, 'tcx> Visitor<'tcx> for FindExpectUnwrap<'a, 'tcx> {
83 fn visit_expr(&mut self, expr: &'tcx Expr<'_>) {
85 if let Some(arglists) = method_chain_args(expr, &["expect"]) {
86 let receiver_ty = self.typeck_results.expr_ty(&arglists[0][0]).peel_refs();
87 if is_type_diagnostic_item(self.lcx, receiver_ty, sym::Option)
88 || is_type_diagnostic_item(self.lcx, receiver_ty, sym::Result)
90 self.result.push(expr.span);
95 if let Some(arglists) = method_chain_args(expr, &["unwrap"]) {
96 let receiver_ty = self.typeck_results.expr_ty(&arglists[0][0]).peel_refs();
97 if is_type_diagnostic_item(self.lcx, receiver_ty, sym::Option)
98 || is_type_diagnostic_item(self.lcx, receiver_ty, sym::Result)
100 self.result.push(expr.span);
104 // and check sub-expressions
105 intravisit::walk_expr(self, expr);
109 fn lint_impl_body<'tcx>(cx: &LateContext<'tcx>, impl_span: Span, impl_item: &'tcx hir::ImplItem<'_>) {
110 if let ImplItemKind::Fn(_, body_id) = impl_item.kind {
111 let body = cx.tcx.hir().body(body_id);
112 let mut fpu = FindExpectUnwrap {
114 typeck_results: cx.tcx.typeck(impl_item.def_id),
117 fpu.visit_expr(&body.value);
119 // if we've found one, lint
120 if !fpu.result.is_empty() {
125 "used unwrap or expect in a function that returns result or option",
127 diag.help("unwrap and expect should not be used in a function that returns result or option");
128 diag.span_note(fpu.result, "potential non-recoverable error(s)");