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Update len_zero to handle comparisions with one

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I have added test cases for comparisons with zero and one.
While implementing handling of one, incorrect handlings of zero
were also fixed.

fixes rust-lang-nursery/rust-clippy/#2554
This commit is contained in:
NiekGr 2018-05-05 15:01:51 +02:00
parent e6735dd327
commit e7a6b3e613
3 changed files with 158 additions and 58 deletions
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63
clippy_lints/src/len_zero.rs
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@ -1,7 +1,7 @@
use rustc::lint::*;
use rustc::hir::def_id::DefId;
use rustc::ty;
use rustc::hir::*;
use rustc::lint::*;
use rustc::ty;
use std::collections::HashSet;
use syntax::ast::{Lit, LitKind, Name};
use syntax::codemap::{Span, Spanned};
@ -81,8 +81,24 @@ impl<'a, 'tcx> LateLintPass<'a, 'tcx> for LenZero {
if let ExprBinary(Spanned { node: cmp, .. }, ref left, ref right) = expr.node {
match cmp {
BiEq => check_cmp(cx, expr.span, left, right, ""),
BiGt | BiNe => check_cmp(cx, expr.span, left, right, "!"),
BiEq => {
check_cmp(cx, expr.span, left, right, "", 0); // len == 0
check_cmp(cx, expr.span, right, left, "", 0); // 0 == len
},
BiNe => {
check_cmp(cx, expr.span, left, right, "!", 0); // len != 0
check_cmp(cx, expr.span, right, left, "!", 0); // 0 != len
},
BiGt => {
check_cmp(cx, expr.span, left, right, "!", 0); // len > 0
check_cmp(cx, expr.span, right, left, "", 1); // 1 > len
},
BiLt => {
check_cmp(cx, expr.span, left, right, "", 1); // len < 1
check_cmp(cx, expr.span, right, left, "!", 0); // 0 < len
},
BiGe => check_cmp(cx, expr.span, left, right, "!", 1), // len <= 1
BiLe => check_cmp(cx, expr.span, right, left, "!", 1), // 1 >= len
_ => (),
}
}
@ -168,40 +184,45 @@ fn check_impl_items(cx: &LateContext, item: &Item, impl_items: &[ImplItemRef]) {
cx,
LEN_WITHOUT_IS_EMPTY,
item.span,
&format!("item `{}` has a public `len` method but {} `is_empty` method", ty, is_empty),
&format!(
"item `{}` has a public `len` method but {} `is_empty` method",
ty, is_empty
),
);
}
}
}
fn check_cmp(cx: &LateContext, span: Span, left: &Expr, right: &Expr, op: &str) {
// check if we are in an is_empty() method
if let Some(name) = get_item_name(cx, left) {
if name == "is_empty" {
return;
fn check_cmp(cx: &LateContext, span: Span, method: &Expr, lit: &Expr, op: &str, compare_to: u32) {
if let (&ExprMethodCall(ref method_path, _, ref args), &ExprLit(ref lit)) = (&method.node, &lit.node) {
// check if we are in an is_empty() method
if let Some(name) = get_item_name(cx, method) {
if name == "is_empty" {
return;
}
}
}
match (&left.node, &right.node) {
(&ExprLit(ref lit), &ExprMethodCall(ref method_path, _, ref args)) |
(&ExprMethodCall(ref method_path, _, ref args), &ExprLit(ref lit)) => {
check_len_zero(cx, span, method_path.name, args, lit, op)
},
_ => (),
check_len(cx, span, method_path.name, args, lit, op, compare_to)
}
}
fn check_len_zero(cx: &LateContext, span: Span, name: Name, args: &[Expr], lit: &Lit, op: &str) {
fn check_len(cx: &LateContext, span: Span, method_name: Name, args: &[Expr], lit: &Lit, op: &str, compare_to: u32) {
if let Spanned {
node: LitKind::Int(0, _),
node: LitKind::Int(lit, _),
..
} = *lit
{
if name == "len" && args.len() == 1 && has_is_empty(cx, &args[0]) {
// check if length is compared to the specified number
if lit != u128::from(compare_to) {
return;
}
if method_name == "len" && args.len() == 1 && has_is_empty(cx, &args[0]) {
span_lint_and_sugg(
cx,
LEN_ZERO,
span,
"length comparison to zero",
&format!("length comparison to {}", if compare_to == 0 { "zero" } else { "one" }),
"using `is_empty` is more concise",
format!("{}{}.is_empty()", op, snippet(cx, args[0].span, "_")),
);