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| 1 | +use if_chain::if_chain; |
| 2 | +use rustc::declare_lint_pass; |
| 3 | +use rustc::hir::intravisit::*; |
| 4 | +use rustc::lint::{LateContext, LateLintPass, LintArray, LintPass}; |
| 5 | +use rustc_hir::*; |
| 6 | +use rustc_session::declare_tool_lint; |
| 7 | + |
| 8 | +use crate::utils::span_lint; |
| 9 | + |
| 10 | +declare_clippy_lint! { |
| 11 | + /// **What it does:** Checks for lifetime annotations on return values |
| 12 | + /// which might not always get bound. |
| 13 | + /// |
| 14 | + /// **Why is this bad?** If the function contains unsafe code which |
| 15 | + /// transmutes to the lifetime, the resulting lifetime may live longer |
| 16 | + /// than was intended. |
| 17 | + /// |
| 18 | + /// **Known problems*: None. |
| 19 | + /// |
| 20 | + /// **Example:** |
| 21 | + /// ```rust |
| 22 | + /// struct WrappedStr(str); |
| 23 | + /// |
| 24 | + /// // Bad: unbound return lifetime causing unsoundness (e.g. when x is String) |
| 25 | + /// fn unbound<'a>(x: impl AsRef<str> + 'a) -> &'a WrappedStr { |
| 26 | + /// let s = x.as_ref(); |
| 27 | + /// unsafe { &*(s as *const str as *const WrappedStr) } |
| 28 | + /// } |
| 29 | + /// |
| 30 | + /// // Good: bound return lifetime is sound |
| 31 | + /// fn bound<'a>(x: &'a str) -> &'a WrappedStr { |
| 32 | + /// unsafe { &*(x as *const str as *const WrappedStr) } |
| 33 | + /// } |
| 34 | + /// ``` |
| 35 | + pub UNBOUND_RETURN_LIFETIMES, |
| 36 | + correctness, |
| 37 | + "unbound lifetimes in function return values" |
| 38 | +} |
| 39 | + |
| 40 | +declare_lint_pass!(UnboundReturnLifetimes => [UNBOUND_RETURN_LIFETIMES]); |
| 41 | + |
| 42 | +impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnboundReturnLifetimes { |
| 43 | + fn check_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx Item<'tcx>) { |
| 44 | + if let ItemKind::Fn(ref sig, ref generics, _id) = item.kind { |
| 45 | + check_fn_inner(cx, &sig.decl, generics, None); |
| 46 | + } |
| 47 | + } |
| 48 | + |
| 49 | + fn check_impl_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx ImplItem<'tcx>) { |
| 50 | + if let ImplItemKind::Method(ref sig, _) = item.kind { |
| 51 | + let parent_generics = impl_generics(cx, item.hir_id); |
| 52 | + check_fn_inner(cx, &sig.decl, &item.generics, parent_generics); |
| 53 | + } |
| 54 | + } |
| 55 | +} |
| 56 | + |
| 57 | +fn check_fn_inner<'a, 'tcx>( |
| 58 | + cx: &LateContext<'a, 'tcx>, |
| 59 | + decl: &'tcx FnDecl<'tcx>, |
| 60 | + generics: &'tcx Generics<'tcx>, |
| 61 | + parent_data: Option<(&'tcx Generics<'tcx>, &'tcx Ty<'tcx>)>, |
| 62 | +) { |
| 63 | + let output_type = if let FunctionRetTy::Return(ref output_type) = decl.output { |
| 64 | + output_type |
| 65 | + } else { |
| 66 | + return; |
| 67 | + }; |
| 68 | + |
| 69 | + let lt = if let TyKind::Rptr(ref lt, _) = output_type.kind { |
| 70 | + lt |
| 71 | + } else { |
| 72 | + return; |
| 73 | + }; |
| 74 | + |
| 75 | + if matches!(lt.name, LifetimeName::Param(_)) { |
| 76 | + let target_lt = lt; |
| 77 | + |
| 78 | + // check function generics |
| 79 | + // the target lifetime parameter must appear on the left of some outlives relation |
| 80 | + if lifetime_outlives_something(target_lt, generics) { |
| 81 | + return; |
| 82 | + } |
| 83 | + |
| 84 | + // check parent generics |
| 85 | + // the target lifetime parameter must appear on the left of some outlives relation |
| 86 | + if let Some((ref parent_generics, _)) = parent_data { |
| 87 | + if lifetime_outlives_something(target_lt, parent_generics) { |
| 88 | + return; |
| 89 | + } |
| 90 | + } |
| 91 | + |
| 92 | + // check type generics |
| 93 | + // the target lifetime parameter must be included in the type |
| 94 | + if let Some((_, ref parent_ty)) = parent_data { |
| 95 | + if TypeVisitor::type_contains_lifetime(parent_ty, target_lt) { |
| 96 | + return; |
| 97 | + } |
| 98 | + } |
| 99 | + |
| 100 | + // check arguments the target lifetime parameter must be included as a |
| 101 | + // lifetime of a reference, either directly or through the gneric |
| 102 | + // parameters of the argument type. |
| 103 | + for input in decl.inputs.iter() { |
| 104 | + if TypeVisitor::type_contains_lifetime(input, target_lt) { |
| 105 | + return; |
| 106 | + } |
| 107 | + } |
| 108 | + |
| 109 | + span_lint( |
| 110 | + cx, |
| 111 | + UNBOUND_RETURN_LIFETIMES, |
| 112 | + target_lt.span, |
| 113 | + "lifetime is unconstrained", |
| 114 | + ); |
| 115 | + } |
| 116 | +} |
| 117 | + |
| 118 | +struct TypeVisitor<'tcx> { |
| 119 | + found: bool, |
| 120 | + target_lt: &'tcx Lifetime, |
| 121 | +} |
| 122 | + |
| 123 | +impl<'tcx> TypeVisitor<'tcx> { |
| 124 | + fn type_contains_lifetime(ty: &Ty<'_>, target_lt: &'tcx Lifetime) -> bool { |
| 125 | + let mut visitor = TypeVisitor { |
| 126 | + found: false, |
| 127 | + target_lt, |
| 128 | + }; |
| 129 | + walk_ty(&mut visitor, ty); |
| 130 | + visitor.found |
| 131 | + } |
| 132 | +} |
| 133 | + |
| 134 | +impl<'tcx> Visitor<'tcx> for TypeVisitor<'tcx> { |
| 135 | + fn visit_lifetime(&mut self, lt: &'tcx Lifetime) { |
| 136 | + if lt.name == self.target_lt.name { |
| 137 | + self.found = true; |
| 138 | + } |
| 139 | + } |
| 140 | + |
| 141 | + fn visit_ty(&mut self, ty: &'tcx Ty<'_>) { |
| 142 | + match ty.kind { |
| 143 | + TyKind::Rptr(ref lt, _) => { |
| 144 | + if lt.name == self.target_lt.name { |
| 145 | + self.found = true; |
| 146 | + } |
| 147 | + }, |
| 148 | + TyKind::Path(ref qpath) => { |
| 149 | + if !self.found { |
| 150 | + walk_qpath(self, qpath, ty.hir_id, ty.span); |
| 151 | + } |
| 152 | + }, |
| 153 | + _ => (), |
| 154 | + } |
| 155 | + } |
| 156 | + |
| 157 | + fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> { |
| 158 | + NestedVisitorMap::None |
| 159 | + } |
| 160 | +} |
| 161 | + |
| 162 | +fn lifetime_outlives_something<'tcx>(target_lt: &'tcx Lifetime, generics: &'tcx Generics<'tcx>) -> bool { |
| 163 | + if let Some(param) = generics.get_named(target_lt.name.ident().name) { |
| 164 | + if param.bounds.iter().any(|b| matches!(b, GenericBound::Outlives(_))) { |
| 165 | + return true; |
| 166 | + } |
| 167 | + } |
| 168 | + false |
| 169 | +} |
| 170 | + |
| 171 | +fn impl_generics<'tcx>(cx: &LateContext<'_, 'tcx>, hir_id: HirId) -> Option<(&'tcx Generics<'tcx>, &'tcx Ty<'tcx>)> { |
| 172 | + let parent_impl = cx.tcx.hir().get_parent_item(hir_id); |
| 173 | + if_chain! { |
| 174 | + if parent_impl != CRATE_HIR_ID; |
| 175 | + if let Node::Item(item) = cx.tcx.hir().get(parent_impl); |
| 176 | + if let ItemKind::Impl(_, _, _, ref parent_generics, _, ref ty, _) = item.kind; |
| 177 | + then { |
| 178 | + return Some((parent_generics, ty)) |
| 179 | + } |
| 180 | + } |
| 181 | + None |
| 182 | +} |
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