5 use utils::{method_chain_args, match_def_path, span_lint_and_then, walk_ptrs_ty};
6 use utils::paths::{BEGIN_PANIC, BEGIN_PANIC_FMT, FROM_TRAIT, OPTION, RESULT};
8 /// **What it does:** Checks for impls of `From<..>` that contain `panic!()` or `unwrap()`
10 /// **Why is this bad?** `TryFrom` should be used if there's a possibility of failure.
12 /// **Known problems:** None.
17 /// impl From<String> for Foo {
18 /// fn from(s: String) -> Self {
19 /// Foo(s.parse().unwrap())
24 pub FALLIBLE_IMPL_FROM, Allow,
25 "Warn on impls of `From<..>` that contain `panic!()` or `unwrap()`"
28 pub struct FallibleImplFrom;
30 impl LintPass for FallibleImplFrom {
31 fn get_lints(&self) -> LintArray {
32 lint_array!(FALLIBLE_IMPL_FROM)
36 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for FallibleImplFrom {
37 fn check_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx hir::Item) {
38 // check for `impl From<???> for ..`
39 let impl_def_id = cx.tcx.hir.local_def_id(item.id);
41 if let hir::ItemImpl(.., ref impl_items) = item.node;
42 if let Some(impl_trait_ref) = cx.tcx.impl_trait_ref(impl_def_id);
43 if match_def_path(cx.tcx, impl_trait_ref.def_id, &FROM_TRAIT);
45 lint_impl_body(cx, item.span, impl_items);
51 fn lint_impl_body<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, impl_span: Span, impl_items: &hir::HirVec<hir::ImplItemRef>) {
53 use rustc::hir::intravisit::{self, NestedVisitorMap, Visitor};
55 struct FindPanicUnwrap<'a, 'tcx: 'a> {
56 tcx: ty::TyCtxt<'a, 'tcx, 'tcx>,
57 tables: &'tcx ty::TypeckTables<'tcx>,
61 impl<'a, 'tcx: 'a> Visitor<'tcx> for FindPanicUnwrap<'a, 'tcx> {
62 fn visit_expr(&mut self, expr: &'tcx Expr) {
63 // check for `begin_panic`
65 if let ExprCall(ref func_expr, _) = expr.node;
66 if let ExprPath(QPath::Resolved(_, ref path)) = func_expr.node;
67 if match_def_path(self.tcx, path.def.def_id(), &BEGIN_PANIC) ||
68 match_def_path(self.tcx, path.def.def_id(), &BEGIN_PANIC_FMT);
70 self.result.push(expr.span);
75 if let Some(arglists) = method_chain_args(expr, &["unwrap"]) {
76 let reciever_ty = walk_ptrs_ty(self.tables.expr_ty(&arglists[0][0]));
77 if match_type(self.tcx, reciever_ty, &OPTION) ||
78 match_type(self.tcx, reciever_ty, &RESULT)
80 self.result.push(expr.span);
84 // and check sub-expressions
85 intravisit::walk_expr(self, expr);
88 fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
89 NestedVisitorMap::None
93 for impl_item in impl_items {
95 if impl_item.name == "from";
96 if let ImplItemKind::Method(_, body_id) =
97 cx.tcx.hir.impl_item(impl_item.id).node;
99 // check the body for `begin_panic` or `unwrap`
100 let body = cx.tcx.hir.body(body_id);
101 let impl_item_def_id = cx.tcx.hir.local_def_id(impl_item.id.node_id);
102 let mut fpu = FindPanicUnwrap {
104 tables: cx.tcx.typeck_tables_of(impl_item_def_id),
107 fpu.visit_expr(&body.value);
109 // if we've found one, lint
110 if !fpu.result.is_empty() {
115 "consider implementing `TryFrom` instead",
118 "`From` is intended for infallible conversions only. \
119 Use `TryFrom` if there's a possibility for the conversion to fail.");
120 db.span_note(fpu.result, "potential failure(s)");
128 fn match_type(tcx: ty::TyCtxt, ty: ty::Ty, path: &[&str]) -> bool {
130 ty::TyAdt(adt, _) => match_def_path(tcx, adt.did, path),