1 use clippy_utils::diagnostics::span_lint_and_then;
2 use clippy_utils::macros::{is_panic, root_macro_call_first_node};
3 use clippy_utils::method_chain_args;
4 use clippy_utils::ty::is_type_diagnostic_item;
5 use if_chain::if_chain;
7 use rustc_lint::{LateContext, LateLintPass};
8 use rustc_middle::hir::map::Map;
10 use rustc_session::{declare_lint_pass, declare_tool_lint};
11 use rustc_span::{sym, Span};
13 declare_clippy_lint! {
15 /// Checks for impls of `From<..>` that contain `panic!()` or `unwrap()`
17 /// ### Why is this bad?
18 /// `TryFrom` should be used if there's a possibility of failure.
25 /// impl From<String> for Foo {
26 /// fn from(s: String) -> Self {
27 /// Foo(s.parse().unwrap())
36 /// use std::convert::TryFrom;
37 /// impl TryFrom<String> for Foo {
39 /// fn try_from(s: String) -> Result<Self, Self::Error> {
40 /// if let Ok(parsed) = s.parse() {
48 #[clippy::version = "pre 1.29.0"]
49 pub FALLIBLE_IMPL_FROM,
51 "Warn on impls of `From<..>` that contain `panic!()` or `unwrap()`"
54 declare_lint_pass!(FallibleImplFrom => [FALLIBLE_IMPL_FROM]);
56 impl<'tcx> LateLintPass<'tcx> for FallibleImplFrom {
57 fn check_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx hir::Item<'_>) {
58 // check for `impl From<???> for ..`
60 if let hir::ItemKind::Impl(impl_) = &item.kind;
61 if let Some(impl_trait_ref) = cx.tcx.impl_trait_ref(item.def_id);
62 if cx.tcx.is_diagnostic_item(sym::From, impl_trait_ref.def_id);
64 lint_impl_body(cx, item.span, impl_.items);
70 fn lint_impl_body<'tcx>(cx: &LateContext<'tcx>, impl_span: Span, impl_items: &[hir::ImplItemRef]) {
71 use rustc_hir::intravisit::{self, NestedVisitorMap, Visitor};
72 use rustc_hir::{Expr, ImplItemKind};
74 struct FindPanicUnwrap<'a, 'tcx> {
75 lcx: &'a LateContext<'tcx>,
76 typeck_results: &'tcx ty::TypeckResults<'tcx>,
80 impl<'a, 'tcx> Visitor<'tcx> for FindPanicUnwrap<'a, 'tcx> {
83 fn visit_expr(&mut self, expr: &'tcx Expr<'_>) {
84 if let Some(macro_call) = root_macro_call_first_node(self.lcx, expr) {
85 if is_panic(self.lcx, macro_call.def_id) {
86 self.result.push(expr.span);
91 if let Some(arglists) = method_chain_args(expr, &["unwrap"]) {
92 let reciever_ty = self.typeck_results.expr_ty(&arglists[0][0]).peel_refs();
93 if is_type_diagnostic_item(self.lcx, reciever_ty, sym::Option)
94 || is_type_diagnostic_item(self.lcx, reciever_ty, sym::Result)
96 self.result.push(expr.span);
100 // and check sub-expressions
101 intravisit::walk_expr(self, expr);
104 fn nested_visit_map(&mut self) -> NestedVisitorMap<Self::Map> {
105 NestedVisitorMap::None
109 for impl_item in impl_items {
111 if impl_item.ident.name == sym::from;
112 if let ImplItemKind::Fn(_, body_id) =
113 cx.tcx.hir().impl_item(impl_item.id).kind;
115 // check the body for `begin_panic` or `unwrap`
116 let body = cx.tcx.hir().body(body_id);
117 let mut fpu = FindPanicUnwrap {
119 typeck_results: cx.tcx.typeck(impl_item.id.def_id),
122 fpu.visit_expr(&body.value);
124 // if we've found one, lint
125 if !fpu.result.is_empty() {
130 "consider implementing `TryFrom` instead",
133 "`From` is intended for infallible conversions only. \
134 Use `TryFrom` if there's a possibility for the conversion to fail");
135 diag.span_note(fpu.result, "potential failure(s)");