1 extern crate rustc_typeck as typeck;
4 use std::cell::RefCell;
6 use rustc::lint::{Context, LintPass, LintArray, Lint};
7 use rustc::util::nodemap::DefIdMap;
8 use rustc::middle::ty::{self, TypeVariants, TypeAndMut, MethodTraitItemId, ImplOrTraitItemId};
9 use rustc::middle::def::{DefTy, DefStruct, DefTrait};
10 use syntax::codemap::{Span, Spanned};
12 use utils::{span_lint, walk_ptrs_ty};
14 declare_lint!(pub LEN_ZERO, Warn,
15 "Warn when .is_empty() could be used instead of checking .len()");
17 declare_lint!(pub LEN_WITHOUT_IS_EMPTY, Warn,
18 "Warn on traits and impls that have .len() but not .is_empty()");
23 impl LintPass for LenZero {
24 fn get_lints(&self) -> LintArray {
25 lint_array!(LEN_ZERO, LEN_WITHOUT_IS_EMPTY)
28 fn check_item(&mut self, cx: &Context, item: &Item) {
30 &ItemTrait(_, _, _, ref trait_items) =>
31 check_trait_items(cx, item, trait_items),
32 &ItemImpl(_, _, _, None, _, ref impl_items) => // only non-trait
33 check_impl_items(cx, item, impl_items),
38 fn check_expr(&mut self, cx: &Context, expr: &Expr) {
39 if let &ExprBinary(Spanned{node: cmp, ..}, ref left, ref right) =
42 BiEq => check_cmp(cx, expr.span, left, right, ""),
43 BiGt | BiNe => check_cmp(cx, expr.span, left, right, "!"),
50 fn check_trait_items(cx: &Context, item: &Item, trait_items: &[P<TraitItem>]) {
51 fn is_named_self(item: &TraitItem, name: &str) -> bool {
52 item.ident.name == name && if let MethodTraitItem(ref sig, _) =
53 item.node { is_self_sig(sig) } else { false }
56 if !trait_items.iter().any(|i| is_named_self(i, "is_empty")) {
57 //span_lint(cx, LEN_WITHOUT_IS_EMPTY, item.span, &format!("trait {}", item.ident.as_str()));
58 for i in trait_items {
59 if is_named_self(i, "len") {
60 span_lint(cx, LEN_WITHOUT_IS_EMPTY, i.span,
61 &format!("Trait '{}' has a '.len(_: &Self)' method, but no \
62 '.is_empty(_: &Self)' method. Consider adding one.",
69 fn check_impl_items(cx: &Context, item: &Item, impl_items: &[P<ImplItem>]) {
70 fn is_named_self(item: &ImplItem, name: &str) -> bool {
71 item.ident.name == name && if let MethodImplItem(ref sig, _) =
72 item.node { is_self_sig(sig) } else { false }
75 if !impl_items.iter().any(|i| is_named_self(i, "is_empty")) {
77 if is_named_self(i, "len") {
79 span_lint(cx, LEN_WITHOUT_IS_EMPTY,
80 Span{ lo: s.lo, hi: s.lo, expn_id: s.expn_id },
81 &format!("Item '{}' has a '.len(_: &Self)' method, but no \
82 '.is_empty(_: &Self)' method. Consider adding one.",
90 fn is_self_sig(sig: &MethodSig) -> bool {
91 if let SelfStatic = sig.explicit_self.node {
92 false } else { sig.decl.inputs.len() == 1 }
95 fn check_cmp(cx: &Context, span: Span, left: &Expr, right: &Expr, empty: &str) {
96 match (&left.node, &right.node) {
97 (&ExprLit(ref lit), &ExprMethodCall(ref method, _, ref args)) =>
98 check_len_zero(cx, span, method, args, lit, empty),
99 (&ExprMethodCall(ref method, _, ref args), &ExprLit(ref lit)) =>
100 check_len_zero(cx, span, method, args, lit, empty),
105 fn check_len_zero(cx: &Context, span: Span, method: &SpannedIdent,
106 args: &[P<Expr>], lit: &Lit, empty: &str) {
107 if let &Spanned{node: LitInt(0, _), ..} = lit {
108 if method.node.name == "len" && args.len() == 1 &&
109 has_is_empty(cx, &*args[0]) {
110 span_lint(cx, LEN_ZERO, span, &format!(
111 "Consider replacing the len comparison with '{}_.is_empty()'",
117 /// check if this type has an is_empty method
118 fn has_is_empty(cx: &Context, expr: &Expr) -> bool {
119 /// get a ImplOrTraitItem and return true if it matches is_empty(self)
120 fn is_is_empty(cx: &Context, id: &ImplOrTraitItemId) -> bool {
121 if let &MethodTraitItemId(def_id) = id {
122 if let ty::MethodTraitItem(ref method) =
123 cx.tcx.impl_or_trait_item(def_id) {
124 method.name.as_str() == "is_empty"
125 && method.fty.sig.skip_binder().inputs.len() == 1
130 /// check the inherent impl's items for an is_empty(self) method
131 fn has_is_empty_impl(cx: &Context, id: &DefId) -> bool {
132 let impl_items = cx.tcx.impl_items.borrow();
133 cx.tcx.inherent_impls.borrow().get(id).map_or(false,
134 |ids| ids.iter().any(|iid| impl_items.get(iid).map_or(false,
135 |iids| iids.iter().any(|i| is_is_empty(cx, i)))))
138 let ty = &walk_ptrs_ty(&cx.tcx.expr_ty(expr));
140 ty::TyTrait(_) => cx.tcx.trait_item_def_ids.borrow().get(
141 &ty.ty_to_def_id().expect("trait impl not found")).map_or(false,
142 |ids| ids.iter().any(|i| is_is_empty(cx, i))),
143 ty::TyProjection(_) => ty.ty_to_def_id().map_or(false,
144 |id| has_is_empty_impl(cx, &id)),
145 ty::TyEnum(ref id, _) | ty::TyStruct(ref id, _) =>
146 has_is_empty_impl(cx, &id.did),
147 ty::TyArray(..) => true,