1 // Copyright 2014-2018 The Rust Project Developers. See the COPYRIGHT
2 // file at the top-level directory of this distribution.
4 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
5 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
6 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
7 // option. This file may not be copied, modified, or distributed
8 // except according to those terms.
10 use crate::rustc::hir;
11 use crate::rustc::lint::{LateContext, LateLintPass, LintArray, LintPass};
13 use crate::rustc::{declare_tool_lint, lint_array};
14 use crate::syntax_pos::Span;
15 use crate::utils::paths::{BEGIN_PANIC, BEGIN_PANIC_FMT, FROM_TRAIT, OPTION, RESULT};
16 use crate::utils::{is_expn_of, match_def_path, method_chain_args, opt_def_id, span_lint_and_then, walk_ptrs_ty};
17 use if_chain::if_chain;
19 /// **What it does:** Checks for impls of `From<..>` that contain `panic!()` or `unwrap()`
21 /// **Why is this bad?** `TryFrom` should be used if there's a possibility of failure.
23 /// **Known problems:** None.
28 /// impl From<String> for Foo {
29 /// fn from(s: String) -> Self {
30 /// Foo(s.parse().unwrap())
34 declare_clippy_lint! {
35 pub FALLIBLE_IMPL_FROM,
37 "Warn on impls of `From<..>` that contain `panic!()` or `unwrap()`"
40 pub struct FallibleImplFrom;
42 impl LintPass for FallibleImplFrom {
43 fn get_lints(&self) -> LintArray {
44 lint_array!(FALLIBLE_IMPL_FROM)
48 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for FallibleImplFrom {
49 fn check_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx hir::Item) {
50 // check for `impl From<???> for ..`
51 let impl_def_id = cx.tcx.hir().local_def_id(item.id);
53 if let hir::ItemKind::Impl(.., ref impl_items) = item.node;
54 if let Some(impl_trait_ref) = cx.tcx.impl_trait_ref(impl_def_id);
55 if match_def_path(cx.tcx, impl_trait_ref.def_id, &FROM_TRAIT);
57 lint_impl_body(cx, item.span, impl_items);
63 fn lint_impl_body<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, impl_span: Span, impl_items: &hir::HirVec<hir::ImplItemRef>) {
64 use crate::rustc::hir::intravisit::{self, NestedVisitorMap, Visitor};
65 use crate::rustc::hir::*;
67 struct FindPanicUnwrap<'a, 'tcx: 'a> {
68 tcx: ty::TyCtxt<'a, 'tcx, 'tcx>,
69 tables: &'tcx ty::TypeckTables<'tcx>,
73 impl<'a, 'tcx: 'a> Visitor<'tcx> for FindPanicUnwrap<'a, 'tcx> {
74 fn visit_expr(&mut self, expr: &'tcx Expr) {
75 // check for `begin_panic`
77 if let ExprKind::Call(ref func_expr, _) = expr.node;
78 if let ExprKind::Path(QPath::Resolved(_, ref path)) = func_expr.node;
79 if let Some(path_def_id) = opt_def_id(path.def);
80 if match_def_path(self.tcx, path_def_id, &BEGIN_PANIC) ||
81 match_def_path(self.tcx, path_def_id, &BEGIN_PANIC_FMT);
82 if is_expn_of(expr.span, "unreachable").is_none();
84 self.result.push(expr.span);
89 if let Some(arglists) = method_chain_args(expr, &["unwrap"]) {
90 let reciever_ty = walk_ptrs_ty(self.tables.expr_ty(&arglists[0][0]));
91 if match_type(self.tcx, reciever_ty, &OPTION) || match_type(self.tcx, reciever_ty, &RESULT) {
92 self.result.push(expr.span);
96 // and check sub-expressions
97 intravisit::walk_expr(self, expr);
100 fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
101 NestedVisitorMap::None
105 for impl_item in impl_items {
107 if impl_item.ident.name == "from";
108 if let ImplItemKind::Method(_, body_id) =
109 cx.tcx.hir().impl_item(impl_item.id).node;
111 // check the body for `begin_panic` or `unwrap`
112 let body = cx.tcx.hir().body(body_id);
113 let impl_item_def_id = cx.tcx.hir().local_def_id(impl_item.id.node_id);
114 let mut fpu = FindPanicUnwrap {
116 tables: cx.tcx.typeck_tables_of(impl_item_def_id),
119 fpu.visit_expr(&body.value);
121 // if we've found one, lint
122 if !fpu.result.is_empty() {
127 "consider implementing `TryFrom` instead",
130 "`From` is intended for infallible conversions only. \
131 Use `TryFrom` if there's a possibility for the conversion to fail.");
132 db.span_note(fpu.result, "potential failure(s)");
140 fn match_type(tcx: ty::TyCtxt<'_, '_, '_>, ty: ty::Ty<'_>, path: &[&str]) -> bool {
142 ty::Adt(adt, _) => match_def_path(tcx, adt.did, path),