fix: print actual consts when shifting by them

this is kind of a side-effect of the next commit

Author: ada4a

clippy_lints/src/manual_rotate.rs

@@ -84,17 +84,18 @@ impl LateLintPass<'_> for ManualRotate {
         {
             let const_eval = ConstEvalCtxt::new(cx);
 
-            if let Some(Constant::Int(l_amount)) = const_eval.eval(l_amount)
-                && let Some(Constant::Int(r_amount)) = const_eval.eval(r_amount)
-                && l_amount + r_amount == u128::from(bit_width)
+            if let Some(Constant::Int(l_amount_val)) = const_eval.eval(l_amount)
+                && let Some(Constant::Int(r_amount_val)) = const_eval.eval(r_amount)
+                && l_amount_val + r_amount_val == u128::from(bit_width)
             {
-                let (shift_function, amount) = if l_amount < r_amount {
+                let (shift_function, amount) = if l_amount_val < r_amount_val {
                     (l_shift_dir, l_amount)
                 } else {
                     (r_shift_dir, r_amount)
                 };
                 let mut applicability = Applicability::MachineApplicable;
                 let expr_sugg = sugg::Sugg::hir_with_applicability(cx, l_expr, "_", &mut applicability).maybe_paren();
+                let amount = sugg::Sugg::hir_with_applicability(cx, amount, "_", &mut applicability);
                 span_lint_and_sugg(
                     cx,
                     MANUAL_ROTATE,

tests/ui/manual_rotate.fixed

@@ -4,6 +4,7 @@ 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;
+    const N: u32 = 5;
     // True positives
     let y_u8 = x_u8.rotate_right(3);
     //~^ manual_rotate
@@ -29,6 +30,9 @@ fn main() {
     //~^ manual_rotate
     let y_u64_as = (x_u32 as u64).rotate_right(8);
     //~^ manual_rotate
+    // shift by a const
+    let _ = x_i64.rotate_right(N);
+    //~^ manual_rotate
 
     // False positives - can't be replaced with a rotation
     let y_u8_false = (x_u8 >> 6) | (x_u8 << 3);

tests/ui/manual_rotate.rs

@@ -4,6 +4,7 @@ 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;
+    const N: u32 = 5;
     // True positives
     let y_u8 = (x_u8 >> 3) | (x_u8 << 5);
     //~^ manual_rotate
@@ -29,6 +30,9 @@ fn main() {
     //~^ manual_rotate
     let y_u64_as = (x_u32 as u64 >> 8) | ((x_u32 as u64) << 56);
     //~^ manual_rotate
+    // shift by a const
+    let _ = (x_i64 >> N) | (x_i64 << (64 - N));
+    //~^ manual_rotate
 
     // False positives - can't be replaced with a rotation
     let y_u8_false = (x_u8 >> 6) | (x_u8 << 3);

tests/ui/manual_rotate.stderr

@@ -1,5 +1,5 @@
 error: there is no need to manually implement bit rotation
-  --> tests/ui/manual_rotate.rs:8:16
+  --> tests/ui/manual_rotate.rs:9:16
    |
 LL |     let y_u8 = (x_u8 >> 3) | (x_u8 << 5);
    |                ^^^^^^^^^^^^^^^^^^^^^^^^^ help: this expression can be rewritten as: `x_u8.rotate_right(3)`
@@ -8,64 +8,70 @@ LL |     let y_u8 = (x_u8 >> 3) | (x_u8 << 5);
    = 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:10:17
+  --> tests/ui/manual_rotate.rs:11:17
    |
 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:12:17
+  --> tests/ui/manual_rotate.rs:13:17
    |
 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:14:17
+  --> tests/ui/manual_rotate.rs:15:17
    |
 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:16:16
+  --> tests/ui/manual_rotate.rs:17:16
    |
 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:18:17
+  --> tests/ui/manual_rotate.rs:19:17
    |
 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:20:17
+  --> tests/ui/manual_rotate.rs:21:17
    |
 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:22:17
+  --> tests/ui/manual_rotate.rs:23:17
    |
 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:25:22
+  --> tests/ui/manual_rotate.rs:26:22
    |
 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:28:25
+  --> tests/ui/manual_rotate.rs:29:25
    |
 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:30:20
+  --> tests/ui/manual_rotate.rs:31:20
    |
 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
+error: there is no need to manually implement bit rotation
+  --> tests/ui/manual_rotate.rs:34:13
+   |
+LL |     let _ = (x_i64 >> N) | (x_i64 << (64 - N));
+   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: this expression can be rewritten as: `x_i64.rotate_right(N)`
+
+error: aborting due to 12 previous errors