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Merge pull request #1749 from Manishearth/cmp_owned

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Improve cmp_owned and stop suggestiong `self == other` inside a `PartialEq` impl
This commit is contained in:
Oliver Schneider 2017-05-12 07:27:03 +02:00 committed by GitHub
commit 2026f29fdf
4 changed files with 100 additions and 51 deletions
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77
clippy_lints/src/misc.rs
View file

@ -6,11 +6,12 @@ use rustc::middle::const_val::ConstVal;
use rustc::ty;
use rustc_const_eval::ConstContext;
use rustc_const_math::ConstFloat;
use syntax::codemap::{Span, Spanned, ExpnFormat};
use syntax::codemap::{Span, ExpnFormat};
use utils::{get_item_name, get_parent_expr, implements_trait, in_macro, is_integer_literal, match_path, snippet,
span_lint, span_lint_and_then, walk_ptrs_ty, last_path_segment, iter_input_pats, in_constant};
span_lint, span_lint_and_then, walk_ptrs_ty, last_path_segment, iter_input_pats, in_constant,
match_trait_method, paths};
use utils::sugg::Sugg;
use syntax::ast::LitKind;
use syntax::ast::{LitKind, CRATE_NODE_ID};
/// **What it does:** Checks for function arguments and let bindings denoted as `ref`.
///
@ -297,8 +298,8 @@ impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Pass {
if let ExprPath(QPath::Resolved(_, ref path)) = right.node {
check_nan(cx, path, expr);
}
check_to_owned(cx, left, right, true, cmp.span);
check_to_owned(cx, right, left, false, cmp.span)
check_to_owned(cx, left, right);
check_to_owned(cx, right, left);
}
if (op == BiEq || op == BiNe) && (is_float(cx, left) || is_float(cx, right)) {
if is_allowed(cx, left) || is_allowed(cx, right) {
@ -422,12 +423,11 @@ fn is_float(cx: &LateContext, expr: &Expr) -> bool {
matches!(walk_ptrs_ty(cx.tables.expr_ty(expr)).sty, ty::TyFloat(_))
}
fn check_to_owned(cx: &LateContext, expr: &Expr, other: &Expr, left: bool, op: Span) {
fn check_to_owned(cx: &LateContext, expr: &Expr, other: &Expr) {
let (arg_ty, snip) = match expr.node {
ExprMethodCall(Spanned { node: ref name, .. }, _, ref args) if args.len() == 1 => {
let name = name.as_str();
if name == "to_string" || name == "to_owned" && is_str_arg(cx, args) {
(cx.tables.expr_ty(&args[0]), snippet(cx, args[0].span, ".."))
ExprMethodCall(.., ref args) if args.len() == 1 => {
if match_trait_method(cx, expr, &paths::TO_STRING) || match_trait_method(cx, expr, &paths::TO_OWNED) {
(cx.tables.expr_ty_adjusted(&args[0]), snippet(cx, args[0].span, ".."))
} else {
return;
}
@ -435,7 +435,7 @@ fn check_to_owned(cx: &LateContext, expr: &Expr, other: &Expr, left: bool, op: S
ExprCall(ref path, ref v) if v.len() == 1 => {
if let ExprPath(ref path) = path.node {
if match_path(path, &["String", "from_str"]) || match_path(path, &["String", "from"]) {
(cx.tables.expr_ty(&v[0]), snippet(cx, v[0].span, ".."))
(cx.tables.expr_ty_adjusted(&v[0]), snippet(cx, v[0].span, ".."))
} else {
return;
}
@ -446,40 +446,43 @@ fn check_to_owned(cx: &LateContext, expr: &Expr, other: &Expr, left: bool, op: S
_ => return,
};
let other_ty = cx.tables.expr_ty(other);
let other_ty = cx.tables.expr_ty_adjusted(other);
let partial_eq_trait_id = match cx.tcx.lang_items.eq_trait() {
Some(id) => id,
None => return,
};
if !implements_trait(cx, arg_ty, partial_eq_trait_id, &[other_ty], None) {
// *arg impls PartialEq<other>
if !arg_ty
.builtin_deref(true, ty::LvaluePreference::NoPreference)
.map_or(false, |tam| implements_trait(cx, tam.ty, partial_eq_trait_id, &[other_ty], None))
// arg impls PartialEq<*other>
&& !other_ty
.builtin_deref(true, ty::LvaluePreference::NoPreference)
.map_or(false, |tam| implements_trait(cx, arg_ty, partial_eq_trait_id, &[tam.ty], None))
// arg impls PartialEq<other>
&& !implements_trait(cx, arg_ty, partial_eq_trait_id, &[other_ty], None) {
return;
}
if left {
span_lint(cx,
CMP_OWNED,
expr.span,
&format!("this creates an owned instance just for comparison. Consider using `{} {} {}` to \
compare without allocation",
snip,
snippet(cx, op, "=="),
snippet(cx, other.span, "..")));
} else {
span_lint(cx,
CMP_OWNED,
expr.span,
&format!("this creates an owned instance just for comparison. Consider using `{} {} {}` to \
compare without allocation",
snippet(cx, other.span, ".."),
snippet(cx, op, "=="),
snip));
}
}
fn is_str_arg(cx: &LateContext, args: &[Expr]) -> bool {
args.len() == 1 && matches!(walk_ptrs_ty(cx.tables.expr_ty(&args[0])).sty, ty::TyStr)
span_lint_and_then(cx, CMP_OWNED, expr.span, "this creates an owned instance just for comparison", |db| {
// this is as good as our recursion check can get, we can't prove that the current function is called by
// PartialEq::eq, but we can at least ensure that this code is not part of it
let parent_fn = cx.tcx.hir.get_parent(expr.id);
let parent_impl = cx.tcx.hir.get_parent(parent_fn);
if parent_impl != CRATE_NODE_ID {
if let map::NodeItem(item) = cx.tcx.hir.get(parent_impl) {
if let ItemImpl(.., Some(ref trait_ref), _, _) = item.node {
if trait_ref.path.def.def_id() == partial_eq_trait_id {
// we are implementing PartialEq, don't suggest not doing `to_owned`, otherwise we go into recursion
db.span_label(expr.span, "try calling implementing the comparison without allocating");
return;
}
}
}
}
db.span_suggestion(expr.span, "try", snip.to_string());
});
}
/// Heuristic to see if an expression is used. Should be compatible with `unused_variables`'s idea

2
clippy_lints/src/utils/paths.rs
View file

@ -71,6 +71,8 @@ pub const RESULT_OK: [&'static str; 4] = ["core", "result", "Result", "Ok"];
pub const SERDE_DE_VISITOR: [&'static str; 3] = ["serde", "de", "Visitor"];
pub const SLICE_INTO_VEC: [&'static str; 4] = ["collections", "slice", "<impl [T]>", "into_vec"];
pub const STRING: [&'static str; 3] = ["collections", "string", "String"];
pub const TO_OWNED: [&'static str; 3] = ["collections", "borrow", "ToOwned"];
pub const TO_STRING: [&'static str; 3] = ["collections", "string", "ToString"];
pub const TRANSMUTE: [&'static str; 4] = ["core", "intrinsics", "", "transmute"];
pub const VEC: [&'static str; 3] = ["collections", "vec", "Vec"];
pub const VEC_DEQUE: [&'static str; 3] = ["collections", "vec_deque", "VecDeque"];

36
tests/ui/cmp_owned.rs
View file

@ -16,10 +16,40 @@ fn main() {
x != "foo".to_owned();
// removed String::from_str(..), as it has finally been removed in 1.4.0
// as of 2015-08-14
x != String::from("foo");
42.to_string() == "42";
Foo.to_owned() == Foo;
}
struct Foo;
impl PartialEq for Foo {
fn eq(&self, other: &Self) -> bool {
self.to_owned() == *other
}
}
impl ToOwned for Foo {
type Owned = Bar;
fn to_owned(&self) -> Bar {
Bar
}
}
#[derive(PartialEq)]
struct Bar;
impl PartialEq<Foo> for Bar {
fn eq(&self, _: &Foo) -> bool {
true
}
}
impl std::borrow::Borrow<Foo> for Bar {
fn borrow(&self) -> &Foo {
static FOO: Foo = Foo;
&FOO
}
}

36
tests/ui/cmp_owned.stderr
View file

@ -1,8 +1,8 @@
error: this creates an owned instance just for comparison. Consider using `x != "foo"` to compare without allocation
error: this creates an owned instance just for comparison
--> $DIR/cmp_owned.rs:8:14
|
8 | x != "foo".to_string();
| ^^^^^^^^^^^^^^^^^
| ^^^^^^^^^^^^^^^^^ help: try `"foo"`
|
note: lint level defined here
--> $DIR/cmp_owned.rs:4:8
@ -10,23 +10,37 @@ note: lint level defined here
4 | #[deny(cmp_owned)]
| ^^^^^^^^^
error: this creates an owned instance just for comparison. Consider using `"foo" != x` to compare without allocation
error: this creates an owned instance just for comparison
--> $DIR/cmp_owned.rs:10:9
|
10 | "foo".to_string() != x;
| ^^^^^^^^^^^^^^^^^
| ^^^^^^^^^^^^^^^^^ help: try `"foo"`
error: this creates an owned instance just for comparison. Consider using `x != "foo"` to compare without allocation
error: this creates an owned instance just for comparison
--> $DIR/cmp_owned.rs:17:10
|
17 | x != "foo".to_owned();
| ^^^^^^^^^^^^^^^^
| ^^^^^^^^^^^^^^^^ help: try `"foo"`
error: this creates an owned instance just for comparison. Consider using `x != "foo"` to compare without allocation
--> $DIR/cmp_owned.rs:22:10
error: this creates an owned instance just for comparison
--> $DIR/cmp_owned.rs:19:10
|
22 | x != String::from("foo");
| ^^^^^^^^^^^^^^^^^^^
19 | x != String::from("foo");
| ^^^^^^^^^^^^^^^^^^^ help: try `"foo"`
error: aborting due to 4 previous errors
error: this creates an owned instance just for comparison
--> $DIR/cmp_owned.rs:23:5
|
23 | Foo.to_owned() == Foo;
| ^^^^^^^^^^^^^^ help: try `Foo`
warning: this creates an owned instance just for comparison
--> $DIR/cmp_owned.rs:30:9
|
30 | self.to_owned() == *other
| ^^^^^^^^^^^^^^^ try calling implementing the comparison without allocating
|
= note: #[warn(cmp_owned)] on by default
error: aborting due to 5 previous errors