Clarify message for erasing_op lint

Author: Yury Krivopalov

clippy_lints/src/erasing_op.rs

@@ -7,7 +7,8 @@ use utils::{in_macro, span_lint};
 /// **What it does:** Checks for erasing operations, e.g. `x * 0`.
 ///
 /// **Why is this bad?** The whole expression can be replaced by zero.
-/// Most likely mistake was made and code should be reviewed or simplified.
+/// This is most likely not the intended outcome and should probably be
+/// corrected
 ///
 /// **Known problems:** None.
 ///
@@ -55,7 +56,7 @@ fn check(cx: &LateContext, e: &Expr, span: Span) {
                 cx,
                 ERASING_OP,
                 span,
-                "the operation is ineffective. Consider reducing it to `0`",
+                "this operation will always return zero. This is likely not the intended outcome",
             );
         }
     }

tests/ui/bit_masks.stderr

@@ -6,7 +6,7 @@ error: &-masking with zero
    |
    = note: `-D bad-bit-mask` implied by `-D warnings`
 
-error: the operation is ineffective. Consider reducing it to `0`
+error: this operation will always return zero. This is likely not the intended outcome
   --> $DIR/bit_masks.rs:12:5
    |
 12 |     x & 0 == 0;
@@ -56,7 +56,7 @@ error: &-masking with zero
 35 |     0 & x == 0;
    |     ^^^^^^^^^^
 
-error: the operation is ineffective. Consider reducing it to `0`
+error: this operation will always return zero. This is likely not the intended outcome
   --> $DIR/bit_masks.rs:35:5
    |
 35 |     0 & x == 0;

tests/ui/erasing_op.stderr

@@ -1,18 +1,18 @@
-error: the operation is ineffective. Consider reducing it to `0`
+error: this operation will always return zero. This is likely not the intended outcome
  --> $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`
+error: this operation will always return zero. This is likely not the intended outcome
   --> $DIR/erasing_op.rs:10:5
    |
 10 |     0 & x;
    |     ^^^^^
 
-error: the operation is ineffective. Consider reducing it to `0`
+error: this operation will always return zero. This is likely not the intended outcome
   --> $DIR/erasing_op.rs:11:5
    |
 11 |     0 / x;