1 use crate::utils::paths::{BEGIN_PANIC, BEGIN_PANIC_FMT, FROM_TRAIT};
3 is_expn_of, is_type_diagnostic_item, match_def_path, method_chain_args, span_lint_and_then, walk_ptrs_ty,
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};
13 declare_clippy_lint! {
14 /// **What it does:** Checks for impls of `From<..>` that contain `panic!()` or `unwrap()`
16 /// **Why is this bad?** `TryFrom` should be used if there's a possibility of failure.
18 /// **Known problems:** None.
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 pub FALLIBLE_IMPL_FROM,
50 "Warn on impls of `From<..>` that contain `panic!()` or `unwrap()`"
53 declare_lint_pass!(FallibleImplFrom => [FALLIBLE_IMPL_FROM]);
55 impl<'tcx> LateLintPass<'tcx> for FallibleImplFrom {
56 fn check_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx hir::Item<'_>) {
57 // check for `impl From<???> for ..`
58 let impl_def_id = cx.tcx.hir().local_def_id(item.hir_id);
60 if let hir::ItemKind::Impl{ items: impl_items, .. } = item.kind;
61 if let Some(impl_trait_ref) = cx.tcx.impl_trait_ref(impl_def_id);
62 if match_def_path(cx, impl_trait_ref.def_id, &FROM_TRAIT);
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, ExprKind, ImplItemKind, QPath};
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 // check for `begin_panic`
86 if let ExprKind::Call(ref func_expr, _) = expr.kind;
87 if let ExprKind::Path(QPath::Resolved(_, ref path)) = func_expr.kind;
88 if let Some(path_def_id) = path.res.opt_def_id();
89 if match_def_path(self.lcx, path_def_id, &BEGIN_PANIC) ||
90 match_def_path(self.lcx, path_def_id, &BEGIN_PANIC_FMT);
91 if is_expn_of(expr.span, "unreachable").is_none();
93 self.result.push(expr.span);
98 if let Some(arglists) = method_chain_args(expr, &["unwrap"]) {
99 let reciever_ty = walk_ptrs_ty(self.typeck_results.expr_ty(&arglists[0][0]));
100 if is_type_diagnostic_item(self.lcx, reciever_ty, sym!(option_type))
101 || is_type_diagnostic_item(self.lcx, reciever_ty, sym!(result_type))
103 self.result.push(expr.span);
107 // and check sub-expressions
108 intravisit::walk_expr(self, expr);
111 fn nested_visit_map(&mut self) -> NestedVisitorMap<Self::Map> {
112 NestedVisitorMap::None
116 for impl_item in impl_items {
118 if impl_item.ident.name == sym!(from);
119 if let ImplItemKind::Fn(_, body_id) =
120 cx.tcx.hir().impl_item(impl_item.id).kind;
122 // check the body for `begin_panic` or `unwrap`
123 let body = cx.tcx.hir().body(body_id);
124 let impl_item_def_id = cx.tcx.hir().local_def_id(impl_item.id.hir_id);
125 let mut fpu = FindPanicUnwrap {
127 typeck_results: cx.tcx.typeck(impl_item_def_id),
130 fpu.visit_expr(&body.value);
132 // if we've found one, lint
133 if !fpu.result.is_empty() {
138 "consider implementing `TryFrom` instead",
141 "`From` is intended for infallible conversions only. \
142 Use `TryFrom` if there's a possibility for the conversion to fail.");
143 diag.span_note(fpu.result, "potential failure(s)");