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Check if lhs < rhs in modulos and emit

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This commit is contained in:
Tianyi Song 2022-03-11 11:31:17 +08:00
parent 0c483f69db
commit a944ccb677
5 changed files with 75 additions and 29 deletions
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23
clippy_lints/src/identity_op.rs
View file

@ -5,7 +5,7 @@ use rustc_middle::ty;
use rustc_session::{declare_lint_pass, declare_tool_lint};
use rustc_span::source_map::Span;
use clippy_utils::consts::{constant_simple, Constant};
use clippy_utils::consts::{constant_full_int, constant_simple, Constant, FullInt};
use clippy_utils::diagnostics::span_lint;
use clippy_utils::{clip, unsext};
@ -54,6 +54,7 @@ impl<'tcx> LateLintPass<'tcx> for IdentityOp {
check(cx, left, -1, e.span, right.span);
check(cx, right, -1, e.span, left.span);
},
BinOpKind::Rem => check_modulo(cx, left, right, e.span, left.span),
_ => (),
}
}
@ -70,6 +71,18 @@ fn is_allowed(cx: &LateContext<'_>, cmp: BinOp, left: &Expr<'_>, right: &Expr<'_
&& constant_simple(cx, cx.typeck_results(), left) == Some(Constant::Int(1)))
}
fn check_modulo(cx: &LateContext<'_>, left: &Expr<'_>, right: &Expr<'_>, span: Span, arg: Span) {
let lhs_const = constant_full_int(cx, cx.typeck_results(), left);
let rhs_const = constant_full_int(cx, cx.typeck_results(), right);
if match (lhs_const, rhs_const) {
(Some(FullInt::S(lv)), Some(FullInt::S(rv))) => lv.abs() < rv,
(Some(FullInt::U(lv)), Some(FullInt::U(rv))) => lv < rv,
_ => return,
} {
span_ineffective_operation(cx, span, arg);
}
}
fn check(cx: &LateContext<'_>, e: &Expr<'_>, m: i8, span: Span, arg: Span) {
if let Some(Constant::Int(v)) = constant_simple(cx, cx.typeck_results(), e).map(Constant::peel_refs) {
let check = match *cx.typeck_results().expr_ty(e).peel_refs().kind() {
@ -83,6 +96,12 @@ fn check(cx: &LateContext<'_>, e: &Expr<'_>, m: i8, span: Span, arg: Span) {
1 => v == 1,
_ => unreachable!(),
} {
span_ineffective_operation(cx, span, arg);
}
}
}
fn span_ineffective_operation(cx: &LateContext<'_>, span: Span, arg: Span) {
span_lint(
cx,
IDENTITY_OP,
@ -93,5 +112,3 @@ fn check(cx: &LateContext<'_>, e: &Expr<'_>, m: i8, span: Span, arg: Span) {
),
);
}
}
}

6
tests/ui/identity_op.rs
View file

@ -66,4 +66,10 @@ fn main() {
let b = a << 0; // no error: non-integer
1 * Meter; // no error: non-integer
2 % 3;
-2 % 3;
x + 1 % 3;
(x + 1) % 3; // no error
4 % 3; // no error
}

20
tests/ui/identity_op.stderr
View file

@ -78,5 +78,23 @@ error: the operation is ineffective. Consider reducing it to `x`
LL | x >> &0;
| ^^^^^^^
error: aborting due to 13 previous errors
error: the operation is ineffective. Consider reducing it to `2`
--> $DIR/identity_op.rs:70:5
|
LL | 2 % 3;
| ^^^^^
error: the operation is ineffective. Consider reducing it to `-2`
--> $DIR/identity_op.rs:71:5
|
LL | -2 % 3;
| ^^^^^^
error: the operation is ineffective. Consider reducing it to `1`
--> $DIR/identity_op.rs:72:9
|
LL | x + 1 % 3;
| ^^^^^
error: aborting due to 16 previous errors

7
tests/ui/modulo_arithmetic_integral_const.rs
View file

@ -1,5 +1,10 @@
#![warn(clippy::modulo_arithmetic)]
#![allow(clippy::no_effect, clippy::unnecessary_operation, clippy::modulo_one)]
#![allow(
clippy::no_effect,
clippy::unnecessary_operation,
clippy::modulo_one,
clippy::identity_op
)]
fn main() {
// Lint when both sides are const and of the opposite sign

34
tests/ui/modulo_arithmetic_integral_const.stderr
View file

@ -1,5 +1,5 @@
error: you are using modulo operator on constants with different signs: `-1 % 2`
--> $DIR/modulo_arithmetic_integral_const.rs:6:5
--> $DIR/modulo_arithmetic_integral_const.rs:11:5
|
LL | -1 % 2;
| ^^^^^^
@ -9,7 +9,7 @@ LL | -1 % 2;
= note: or consider using `rem_euclid` or similar function
error: you are using modulo operator on constants with different signs: `1 % -2`
--> $DIR/modulo_arithmetic_integral_const.rs:7:5
--> $DIR/modulo_arithmetic_integral_const.rs:12:5
|
LL | 1 % -2;
| ^^^^^^
@ -18,7 +18,7 @@ LL | 1 % -2;
= note: or consider using `rem_euclid` or similar function
error: you are using modulo operator on constants with different signs: `-1 % 3`
--> $DIR/modulo_arithmetic_integral_const.rs:8:5
--> $DIR/modulo_arithmetic_integral_const.rs:13:5
|
LL | (1 - 2) % (1 + 2);
| ^^^^^^^^^^^^^^^^^
@ -27,7 +27,7 @@ LL | (1 - 2) % (1 + 2);
= note: or consider using `rem_euclid` or similar function
error: you are using modulo operator on constants with different signs: `3 % -1`
--> $DIR/modulo_arithmetic_integral_const.rs:9:5
--> $DIR/modulo_arithmetic_integral_const.rs:14:5
|
LL | (1 + 2) % (1 - 2);
| ^^^^^^^^^^^^^^^^^
@ -36,7 +36,7 @@ LL | (1 + 2) % (1 - 2);
= note: or consider using `rem_euclid` or similar function
error: you are using modulo operator on constants with different signs: `-35 % 300000`
--> $DIR/modulo_arithmetic_integral_const.rs:10:5
--> $DIR/modulo_arithmetic_integral_const.rs:15:5
|
LL | 35 * (7 - 4 * 2) % (-500 * -600);
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@ -45,7 +45,7 @@ LL | 35 * (7 - 4 * 2) % (-500 * -600);
= note: or consider using `rem_euclid` or similar function
error: you are using modulo operator on constants with different signs: `-1 % 2`
--> $DIR/modulo_arithmetic_integral_const.rs:12:5
--> $DIR/modulo_arithmetic_integral_const.rs:17:5
|
LL | -1i8 % 2i8;
| ^^^^^^^^^^
@ -54,7 +54,7 @@ LL | -1i8 % 2i8;
= note: or consider using `rem_euclid` or similar function
error: you are using modulo operator on constants with different signs: `1 % -2`
--> $DIR/modulo_arithmetic_integral_const.rs:13:5
--> $DIR/modulo_arithmetic_integral_const.rs:18:5
|
LL | 1i8 % -2i8;
| ^^^^^^^^^^
@ -63,7 +63,7 @@ LL | 1i8 % -2i8;
= note: or consider using `rem_euclid` or similar function
error: you are using modulo operator on constants with different signs: `-1 % 2`
--> $DIR/modulo_arithmetic_integral_const.rs:14:5
--> $DIR/modulo_arithmetic_integral_const.rs:19:5
|
LL | -1i16 % 2i16;
| ^^^^^^^^^^^^
@ -72,7 +72,7 @@ LL | -1i16 % 2i16;
= note: or consider using `rem_euclid` or similar function
error: you are using modulo operator on constants with different signs: `1 % -2`
--> $DIR/modulo_arithmetic_integral_const.rs:15:5
--> $DIR/modulo_arithmetic_integral_const.rs:20:5
|
LL | 1i16 % -2i16;
| ^^^^^^^^^^^^
@ -81,7 +81,7 @@ LL | 1i16 % -2i16;
= note: or consider using `rem_euclid` or similar function
error: you are using modulo operator on constants with different signs: `-1 % 2`
--> $DIR/modulo_arithmetic_integral_const.rs:16:5
--> $DIR/modulo_arithmetic_integral_const.rs:21:5
|
LL | -1i32 % 2i32;
| ^^^^^^^^^^^^
@ -90,7 +90,7 @@ LL | -1i32 % 2i32;
= note: or consider using `rem_euclid` or similar function
error: you are using modulo operator on constants with different signs: `1 % -2`
--> $DIR/modulo_arithmetic_integral_const.rs:17:5
--> $DIR/modulo_arithmetic_integral_const.rs:22:5
|
LL | 1i32 % -2i32;
| ^^^^^^^^^^^^
@ -99,7 +99,7 @@ LL | 1i32 % -2i32;
= note: or consider using `rem_euclid` or similar function
error: you are using modulo operator on constants with different signs: `-1 % 2`
--> $DIR/modulo_arithmetic_integral_const.rs:18:5
--> $DIR/modulo_arithmetic_integral_const.rs:23:5
|
LL | -1i64 % 2i64;
| ^^^^^^^^^^^^
@ -108,7 +108,7 @@ LL | -1i64 % 2i64;
= note: or consider using `rem_euclid` or similar function
error: you are using modulo operator on constants with different signs: `1 % -2`
--> $DIR/modulo_arithmetic_integral_const.rs:19:5
--> $DIR/modulo_arithmetic_integral_const.rs:24:5
|
LL | 1i64 % -2i64;
| ^^^^^^^^^^^^
@ -117,7 +117,7 @@ LL | 1i64 % -2i64;
= note: or consider using `rem_euclid` or similar function
error: you are using modulo operator on constants with different signs: `-1 % 2`
--> $DIR/modulo_arithmetic_integral_const.rs:20:5
--> $DIR/modulo_arithmetic_integral_const.rs:25:5
|
LL | -1i128 % 2i128;
| ^^^^^^^^^^^^^^
@ -126,7 +126,7 @@ LL | -1i128 % 2i128;
= note: or consider using `rem_euclid` or similar function
error: you are using modulo operator on constants with different signs: `1 % -2`
--> $DIR/modulo_arithmetic_integral_const.rs:21:5
--> $DIR/modulo_arithmetic_integral_const.rs:26:5
|
LL | 1i128 % -2i128;
| ^^^^^^^^^^^^^^
@ -135,7 +135,7 @@ LL | 1i128 % -2i128;
= note: or consider using `rem_euclid` or similar function
error: you are using modulo operator on constants with different signs: `-1 % 2`
--> $DIR/modulo_arithmetic_integral_const.rs:22:5
--> $DIR/modulo_arithmetic_integral_const.rs:27:5
|
LL | -1isize % 2isize;
| ^^^^^^^^^^^^^^^^
@ -144,7 +144,7 @@ LL | -1isize % 2isize;
= note: or consider using `rem_euclid` or similar function
error: you are using modulo operator on constants with different signs: `1 % -2`
--> $DIR/modulo_arithmetic_integral_const.rs:23:5
--> $DIR/modulo_arithmetic_integral_const.rs:28:5
|
LL | 1isize % -2isize;
| ^^^^^^^^^^^^^^^^