1 files changed, 119 insertions, 0 deletions
diff --git a/src/tools/clippy/tests/ui/identity_op.rs b/src/tools/clippy/tests/ui/identity_op.rs
new file mode 100644
index 000000000..ca799c9cf
--- /dev/null
+++ b/src/tools/clippy/tests/ui/identity_op.rs
@@ -0,0 +1,119 @@
+// run-rustfix
+
+#![warn(clippy::identity_op)]
+#![allow(
+    clippy::eq_op,
+    clippy::no_effect,
+    clippy::unnecessary_operation,
+    clippy::op_ref,
+    clippy::double_parens,
+    unused
+)]
+
+use std::fmt::Write as _;
+
+const ONE: i64 = 1;
+const NEG_ONE: i64 = -1;
+const ZERO: i64 = 0;
+
+struct A(String);
+
+impl std::ops::Shl<i32> for A {
+    type Output = A;
+    fn shl(mut self, other: i32) -> Self {
+        let _ = write!(self.0, "{}", other);
+        self
+    }
+}
+
+struct Length(u8);
+struct Meter;
+
+impl core::ops::Mul<Meter> for u8 {
+    type Output = Length;
+    fn mul(self, _: Meter) -> Length {
+        Length(self)
+    }
+}
+
+#[rustfmt::skip]
+fn main() {
+    let x = 0;
+
+    x + 0;
+    x + (1 - 1);
+    x + 1;
+    0 + x;
+    1 + x;
+    x - ZERO; //no error, as we skip lookups (for now)
+    x | (0);
+    ((ZERO)) | x; //no error, as we skip lookups (for now)
+
+    x * 1;
+    1 * x;
+    x / ONE; //no error, as we skip lookups (for now)
+
+    x / 2; //no false positive
+
+    x & NEG_ONE; //no error, as we skip lookups (for now)
+    -1 & x;
+
+    let u: u8 = 0;
+    u & 255;
+
+    1 << 0; // no error, this case is allowed, see issue 3430
+    42 << 0;
+    1 >> 0;
+    42 >> 0;
+    &x >> 0;
+    x >> &0;
+
+    let mut a = A("".into());
+    let b = a << 0; // no error: non-integer
+
+    1 * Meter; // no error: non-integer
+
+    2 % 3;
+    -2 % 3;
+    2 % -3 + x;
+    -2 % -3 + x;
+    x + 1 % 3;
+    (x + 1) % 3; // no error
+    4 % 3; // no error
+    4 % -3; // no error
+
+    // See #8724
+    let a = 0;
+    let b = true;
+    0 + if b { 1 } else { 2 };
+    0 + if b { 1 } else { 2 } + if b { 3 } else { 4 };
+    0 + match a { 0 => 10, _ => 20 };
+    0 + match a { 0 => 10, _ => 20 } + match a { 0 => 30, _ => 40 };
+    0 + if b { 1 } else { 2 } + match a { 0 => 30, _ => 40 };
+    0 + match a { 0 => 10, _ => 20 } + if b { 3 } else { 4 };
+    (if b { 1 } else { 2 }) + 0;
+
+    0 + { a } + 3;
+    0 + { a } * 2;
+    0 + loop { let mut c = 0; if c == 10 { break c; } c += 1; } + { a * 2 };
+
+    fn f(_: i32) {
+        todo!();
+    }
+    f(1 * a + { 8 * 5 });
+    f(0 + if b { 1 } else { 2 } + 3);
+    const _: i32 = { 2 * 4 } + 0 + 3;
+    const _: i32 = 0 + { 1 + 2 * 3 } + 3;
+
+    0 + a as usize;
+    let _ = 0 + a as usize;
+    0 + { a } as usize;
+
+    2 * (0 + { a });
+    1 * ({ a } + 4);
+    1 * 1;
+}
+
+pub fn decide(a: bool, b: bool) -> u32 {
+    0 + if a { 1 } else { 2 } + if b { 3 } else { 5 }
+}