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len_without_is_empty false positive #1740

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This commit is contained in:
Tim Nielens 2017-08-28 23:13:56 +02:00
parent 73d87d966d
commit ec79970771
3 changed files with 70 additions and 25 deletions
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55
clippy_lints/src/len_zero.rs
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@ -2,6 +2,7 @@ use rustc::lint::*;
use rustc::hir::def_id::DefId;
use rustc::ty;
use rustc::hir::*;
use std::collections::HashSet;
use syntax::ast::{Lit, LitKind, Name};
use syntax::codemap::{Span, Spanned};
use utils::{get_item_name, in_macro, snippet, span_lint, span_lint_and_sugg, walk_ptrs_ty};
@ -88,7 +89,7 @@ impl<'a, 'tcx> LateLintPass<'a, 'tcx> for LenZero {
}
}
fn check_trait_items(cx: &LateContext, item: &Item, trait_items: &[TraitItemRef]) {
fn check_trait_items(cx: &LateContext, visited_trait: &Item, trait_items: &[TraitItemRef]) {
fn is_named_self(cx: &LateContext, item: &TraitItemRef, name: &str) -> bool {
item.name == name &&
if let AssociatedItemKind::Method { has_self } = item.kind {
@ -102,18 +103,52 @@ fn check_trait_items(cx: &LateContext, item: &Item, trait_items: &[TraitItemRef]
}
}
if !trait_items.iter().any(|i| is_named_self(cx, i, "is_empty")) {
if let Some(i) = trait_items.iter().find(|i| is_named_self(cx, i, "len")) {
if cx.access_levels.is_exported(i.id.node_id) {
span_lint(
cx,
LEN_WITHOUT_IS_EMPTY,
item.span,
&format!("trait `{}` has a `len` method but no `is_empty` method", item.name),
);
// fill the set with current and super traits
fn fill_trait_set<'a, 'b: 'a>(traitt: &'b Item, set: &'a mut HashSet<&'b Item>, cx: &'b LateContext) {
if set.insert(traitt) {
if let ItemTrait(.., ref ty_param_bounds, _) = traitt.node {
for ty_param_bound in ty_param_bounds {
if let TraitTyParamBound(ref poly_trait_ref, _) = *ty_param_bound {
let super_trait_node_id = cx.tcx
.hir
.as_local_node_id(poly_trait_ref.trait_ref.path.def.def_id())
.expect("the DefId is local, the NodeId should be available");
let super_trait = cx.tcx.hir.expect_item(super_trait_node_id);
fill_trait_set(super_trait, set, cx);
}
}
}
}
}
if cx.access_levels.is_exported(visited_trait.id) &&
trait_items
.iter()
.any(|i| is_named_self(cx, i, "len"))
{
let mut current_and_super_traits = HashSet::new();
fill_trait_set(visited_trait, &mut current_and_super_traits, cx);
let is_empty_method_found = current_and_super_traits
.iter()
.flat_map(|i| match i.node {
ItemTrait(.., ref trait_items) => trait_items.iter(),
_ => bug!("should only handle traits"),
})
.any(|i| is_named_self(cx, i, "is_empty"));
if !is_empty_method_found {
span_lint(
cx,
LEN_WITHOUT_IS_EMPTY,
visited_trait.span,
&format!(
"trait `{}` has a `len` method but no (possibly inherited) `is_empty` method",
visited_trait.name
),
);
}
}
}
fn check_impl_items(cx: &LateContext, item: &Item, impl_items: &[ImplItemRef]) {