Add erasing_op lint

For expressions that can be replaced by a zero.

tests/ui/bit_masks.stderr

@@ -6,6 +6,14 @@ error: &-masking with zero
    |
    = note: `-D bad-bit-mask` implied by `-D warnings`
 
+error: the operation is ineffective. Consider reducing it to `0`
+  --> $DIR/bit_masks.rs:12:5
+   |
+12 |     x & 0 == 0;
+   |     ^^^^^
+   |
+   = note: `-D erasing-op` implied by `-D warnings`
+
 error: incompatible bit mask: `_ & 2` can never be equal to `1`
   --> $DIR/bit_masks.rs:15:5
    |
@@ -48,6 +56,12 @@ error: &-masking with zero
 35 |     0 & x == 0;
    |     ^^^^^^^^^^
 
+error: the operation is ineffective. Consider reducing it to `0`
+  --> $DIR/bit_masks.rs:35:5
+   |
+35 |     0 & x == 0;
+   |     ^^^^^
+
 error: incompatible bit mask: `_ | 2` will always be higher than `1`
   --> $DIR/bit_masks.rs:39:5
    |

tests/ui/erasing_op.rs

@@ -0,0 +1,12 @@
+
+
+
+#[allow(no_effect)]
+#[warn(erasing_op)]
+fn main() {
+    let x: u8 = 0;
+
+    x * 0;
+    0 & x;
+    0 / x;
+}

tests/ui/erasing_op.stderr

@@ -0,0 +1,20 @@
+error: the operation is ineffective. Consider reducing it to `0`
+ --> $DIR/erasing_op.rs:9:5
+  |
+9 |     x * 0;
+  |     ^^^^^
+  |
+  = note: `-D erasing-op` implied by `-D warnings`
+
+error: the operation is ineffective. Consider reducing it to `0`
+  --> $DIR/erasing_op.rs:10:5
+   |
+10 |     0 & x;
+   |     ^^^^^
+
+error: the operation is ineffective. Consider reducing it to `0`
+  --> $DIR/erasing_op.rs:11:5
+   |
+11 |     0 / x;
+   |     ^^^^^
+