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check for is_empty() method to get rid of false positives

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llogiq 2015-06-01 07:40:33 +02:00
parent 77838d6ba7
commit 21cd0c7e70
2 changed files with 32 additions and 7 deletions
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36
src/len_zero.rs
View file

@ -1,11 +1,15 @@
extern crate rustc_typeck as typeck;
use std::rc::Rc;
use std::cell::RefCell;
use syntax::ptr::P;
use syntax::ast::*;
use rustc::lint::{Context, LintPass, LintArray, Lint};
use rustc::middle::ty::{self, node_id_to_type, sty, ty_ptr, ty_rptr, mt, MethodTraitItemId};
use rustc::util::nodemap::DefIdMap;
use rustc::middle::ty::{self, node_id_to_type, sty, ty_ptr, ty_rptr, expr_ty,
mt, ty_to_def_id, impl_or_trait_item, MethodTraitItemId, ImplOrTraitItemId};
use rustc::middle::def::{DefTy, DefStruct, DefTrait};
use syntax::codemap::{Span, Spanned};
use syntax::ast::*;
declare_lint!(pub LEN_ZERO, Warn,
"Warn on usage of double-mut refs, e.g. '&mut &mut ...'");
@ -69,7 +73,9 @@ fn check_impl_items(cx: &Context, item: &Item, impl_items: &[P<ImplItem>]) {
if !impl_items.iter().any(|i| is_named_self(i, "is_empty")) {
for i in impl_items {
if is_named_self(i, "len") {
cx.span_lint(LEN_WITHOUT_IS_EMPTY, i.span,
let s = i.span;
cx.span_lint(LEN_WITHOUT_IS_EMPTY,
Span{ lo: s.lo, hi: s.lo, expn_id: s.expn_id },
&format!("Item '{}' has a '.len()' method, but no \
'.is_empty()' method. Consider adding one.",
item.ident.as_str()));
@ -92,10 +98,30 @@ fn check_cmp(cx: &Context, span: Span, left: &Expr, right: &Expr, empty: &str) {
fn check_len_zero(cx: &Context, span: Span, method: &SpannedIdent,
args: &[P<Expr>], lit: &Lit, empty: &str) {
if let &Spanned{node: LitInt(0, _), ..} = lit {
if method.node.as_str() == "len" && args.len() == 1 {
if method.node.as_str() == "len" && args.len() == 1 &&
has_is_empty(cx, &expr_ty(cx.tcx, &*args[0])) {
cx.span_lint(LEN_ZERO, span, &format!(
"Consider replacing the len comparison with '{}_.is_empty()' if available",
"Consider replacing the len comparison with \
'{}_.is_empty()' if available",
empty))
}
}
}
fn has_is_empty(cx: &Context, ty: &::rustc::middle::ty::Ty) -> bool {
fn check_item(cx: &Context, id: &ImplOrTraitItemId) -> bool {
if let &MethodTraitItemId(ref def_id) = id {
if let ty::MethodTraitItem(ref method) = ty::impl_or_trait_item(
cx.tcx, *def_id) {
method.name.as_str() == "is_empty"
} else { false }
} else { false }
}
::rustc::middle::ty::ty_to_def_id(ty).map_or(true, |id| {
cx.tcx.impl_items.borrow().get(&id).map_or(false, |item_ids| {
item_ids.iter().any(|i| check_item(cx, i))
}) || cx.tcx.trait_item_def_ids.borrow().get(&id).map_or(false,
|item_ids| { item_ids.iter().any(|i| check_item(cx, i)) })
})
}

3
tests/compile-fail/len_zero.rs
View file

@ -44,8 +44,7 @@ fn main() {
}
let y = One;
// false positives here
if y.len() == 0 { //~ERROR Consider replacing the len comparison
if y.len() == 0 { //no error because One does not have .is_empty()
println!("This should not happen either!");
}