Auto merge of #12983 - frp:manual_rotate, r=llogiq

Implement a lint to replace manual bit rotations with rotate_left/rot…

Fixes #6861

r? `@llogiq`

---

changelog: add [`manual_rotate`] lint

3 files changed, 133 insertions, 0 deletions

diff --git a/tests/ui/manual_rotate.fixed b/tests/ui/manual_rotate.fixed
new file mode 100644
index 00000000000..5d33838a318
--- /dev/null
+++ b/tests/ui/manual_rotate.fixed
@@ -0,0 +1,31 @@
+#![warn(clippy::manual_rotate)]
+#![allow(unused)]
+fn main() {
+    let (x_u8, x_u16, x_u32, x_u64) = (1u8, 1u16, 1u32, 1u64);
+    let (x_i8, x_i16, x_i32, x_i64) = (1i8, 1i16, 1i32, 1i64);
+    let a_u32 = 1u32;
+    // True positives
+    let y_u8 = x_u8.rotate_right(3);
+    let y_u16 = x_u16.rotate_right(7);
+    let y_u32 = x_u32.rotate_right(8);
+    let y_u64 = x_u64.rotate_right(9);
+    let y_i8 = x_i8.rotate_right(3);
+    let y_i16 = x_i16.rotate_right(7);
+    let y_i32 = x_i32.rotate_right(8);
+    let y_i64 = x_i64.rotate_right(9);
+    // Plus also works instead of |
+    let y_u32_plus = x_u32.rotate_right(8);
+    // Complex expression
+    let y_u32_complex = (x_u32 | 3256).rotate_right(8);
+    let y_u64_as = (x_u32 as u64).rotate_right(8);
+
+    // False positives - can't be replaced with a rotation
+    let y_u8_false = (x_u8 >> 6) | (x_u8 << 3);
+    let y_u32_false = (x_u32 >> 8) | (x_u32 >> 24);
+    let y_u64_false2 = (x_u64 >> 9) & (x_u64 << 55);
+    // Variable mismatch
+    let y_u32_wrong_vars = (x_u32 >> 8) | (a_u32 << 24);
+    // Has side effects and therefore should not be matched
+    let mut l = vec![12_u8, 34];
+    let y = (l.pop().unwrap() << 3) + (l.pop().unwrap() >> 5);
+}
diff --git a/tests/ui/manual_rotate.rs b/tests/ui/manual_rotate.rs
new file mode 100644
index 00000000000..5377491fb1a
--- /dev/null
+++ b/tests/ui/manual_rotate.rs
@@ -0,0 +1,31 @@
+#![warn(clippy::manual_rotate)]
+#![allow(unused)]
+fn main() {
+    let (x_u8, x_u16, x_u32, x_u64) = (1u8, 1u16, 1u32, 1u64);
+    let (x_i8, x_i16, x_i32, x_i64) = (1i8, 1i16, 1i32, 1i64);
+    let a_u32 = 1u32;
+    // True positives
+    let y_u8 = (x_u8 >> 3) | (x_u8 << 5);
+    let y_u16 = (x_u16 >> 7) | (x_u16 << 9);
+    let y_u32 = (x_u32 >> 8) | (x_u32 << 24);
+    let y_u64 = (x_u64 >> 9) | (x_u64 << 55);
+    let y_i8 = (x_i8 >> 3) | (x_i8 << 5);
+    let y_i16 = (x_i16 >> 7) | (x_i16 << 9);
+    let y_i32 = (x_i32 >> 8) | (x_i32 << 24);
+    let y_i64 = (x_i64 >> 9) | (x_i64 << 55);
+    // Plus also works instead of |
+    let y_u32_plus = (x_u32 >> 8) + (x_u32 << 24);
+    // Complex expression
+    let y_u32_complex = ((x_u32 | 3256) >> 8) | ((x_u32 | 3256) << 24);
+    let y_u64_as = (x_u32 as u64 >> 8) | ((x_u32 as u64) << 56);
+
+    // False positives - can't be replaced with a rotation
+    let y_u8_false = (x_u8 >> 6) | (x_u8 << 3);
+    let y_u32_false = (x_u32 >> 8) | (x_u32 >> 24);
+    let y_u64_false2 = (x_u64 >> 9) & (x_u64 << 55);
+    // Variable mismatch
+    let y_u32_wrong_vars = (x_u32 >> 8) | (a_u32 << 24);
+    // Has side effects and therefore should not be matched
+    let mut l = vec![12_u8, 34];
+    let y = (l.pop().unwrap() << 3) + (l.pop().unwrap() >> 5);
+}
diff --git a/tests/ui/manual_rotate.stderr b/tests/ui/manual_rotate.stderr
new file mode 100644
index 00000000000..52da0861f70
--- /dev/null
+++ b/tests/ui/manual_rotate.stderr
@@ -0,0 +1,71 @@
+error: there is no need to manually implement bit rotation
+  --> tests/ui/manual_rotate.rs:8:16
+   |
+LL |     let y_u8 = (x_u8 >> 3) | (x_u8 << 5);
+   |                ^^^^^^^^^^^^^^^^^^^^^^^^^ help: this expression can be rewritten as: `x_u8.rotate_right(3)`
+   |
+   = note: `-D clippy::manual-rotate` implied by `-D warnings`
+   = help: to override `-D warnings` add `#[allow(clippy::manual_rotate)]`
+
+error: there is no need to manually implement bit rotation
+  --> tests/ui/manual_rotate.rs:9:17
+   |
+LL |     let y_u16 = (x_u16 >> 7) | (x_u16 << 9);
+   |                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: this expression can be rewritten as: `x_u16.rotate_right(7)`
+
+error: there is no need to manually implement bit rotation
+  --> tests/ui/manual_rotate.rs:10:17
+   |
+LL |     let y_u32 = (x_u32 >> 8) | (x_u32 << 24);
+   |                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: this expression can be rewritten as: `x_u32.rotate_right(8)`
+
+error: there is no need to manually implement bit rotation
+  --> tests/ui/manual_rotate.rs:11:17
+   |
+LL |     let y_u64 = (x_u64 >> 9) | (x_u64 << 55);
+   |                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: this expression can be rewritten as: `x_u64.rotate_right(9)`
+
+error: there is no need to manually implement bit rotation
+  --> tests/ui/manual_rotate.rs:12:16
+   |
+LL |     let y_i8 = (x_i8 >> 3) | (x_i8 << 5);
+   |                ^^^^^^^^^^^^^^^^^^^^^^^^^ help: this expression can be rewritten as: `x_i8.rotate_right(3)`
+
+error: there is no need to manually implement bit rotation
+  --> tests/ui/manual_rotate.rs:13:17
+   |
+LL |     let y_i16 = (x_i16 >> 7) | (x_i16 << 9);
+   |                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: this expression can be rewritten as: `x_i16.rotate_right(7)`
+
+error: there is no need to manually implement bit rotation
+  --> tests/ui/manual_rotate.rs:14:17
+   |
+LL |     let y_i32 = (x_i32 >> 8) | (x_i32 << 24);
+   |                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: this expression can be rewritten as: `x_i32.rotate_right(8)`
+
+error: there is no need to manually implement bit rotation
+  --> tests/ui/manual_rotate.rs:15:17
+   |
+LL |     let y_i64 = (x_i64 >> 9) | (x_i64 << 55);
+   |                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: this expression can be rewritten as: `x_i64.rotate_right(9)`
+
+error: there is no need to manually implement bit rotation
+  --> tests/ui/manual_rotate.rs:17:22
+   |
+LL |     let y_u32_plus = (x_u32 >> 8) + (x_u32 << 24);
+   |                      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: this expression can be rewritten as: `x_u32.rotate_right(8)`
+
+error: there is no need to manually implement bit rotation
+  --> tests/ui/manual_rotate.rs:19:25
+   |
+LL |     let y_u32_complex = ((x_u32 | 3256) >> 8) | ((x_u32 | 3256) << 24);
+   |                         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: this expression can be rewritten as: `(x_u32 | 3256).rotate_right(8)`
+
+error: there is no need to manually implement bit rotation
+  --> tests/ui/manual_rotate.rs:20:20
+   |
+LL |     let y_u64_as = (x_u32 as u64 >> 8) | ((x_u32 as u64) << 56);
+   |                    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: this expression can be rewritten as: `(x_u32 as u64).rotate_right(8)`
+
+error: aborting due to 11 previous errors
+