Add a reason to/remove some //@no-rustfix annotations

tests/ui/assign_ops.fixed

@@ -1,7 +1,9 @@
+#![allow(clippy::useless_vec)]
+#![warn(clippy::assign_op_pattern)]
+
 use core::num::Wrapping;
+use std::ops::{Mul, MulAssign};
 
-#[allow(dead_code, unused_assignments, clippy::useless_vec)]
-#[warn(clippy::assign_op_pattern)]
 fn main() {
     let mut a = 5;
     a += 1;
@@ -39,3 +41,35 @@ fn main() {
     v[0] = v[0] + v[1];
     let _ = || v[0] = v[0] + v[1];
 }
+
+fn cow_add_assign() {
+    use std::borrow::Cow;
+    let mut buf = Cow::Owned(String::from("bar"));
+    let cows = Cow::Borrowed("foo");
+
+    // this can be linted
+    buf += cows.clone();
+    //~^ assign_op_pattern
+
+    // this should not as cow<str> Add is not commutative
+    buf = cows + buf;
+}
+
+// check that we don't lint on op assign impls, because that's just the way to impl them
+
+#[derive(Copy, Clone, Debug, PartialEq, Eq)]
+pub struct Wrap(i64);
+
+impl Mul<i64> for Wrap {
+    type Output = Self;
+
+    fn mul(self, rhs: i64) -> Self {
+        Wrap(self.0 * rhs)
+    }
+}
+
+impl MulAssign<i64> for Wrap {
+    fn mul_assign(&mut self, rhs: i64) {
+        *self = *self * rhs
+    }
+}

tests/ui/assign_ops.rs

@@ -1,7 +1,9 @@
+#![allow(clippy::useless_vec)]
+#![warn(clippy::assign_op_pattern)]
+
 use core::num::Wrapping;
+use std::ops::{Mul, MulAssign};
 
-#[allow(dead_code, unused_assignments, clippy::useless_vec)]
-#[warn(clippy::assign_op_pattern)]
 fn main() {
     let mut a = 5;
     a = a + 1;
@@ -39,3 +41,35 @@ fn main() {
     v[0] = v[0] + v[1];
     let _ = || v[0] = v[0] + v[1];
 }
+
+fn cow_add_assign() {
+    use std::borrow::Cow;
+    let mut buf = Cow::Owned(String::from("bar"));
+    let cows = Cow::Borrowed("foo");
+
+    // this can be linted
+    buf = buf + cows.clone();
+    //~^ assign_op_pattern
+
+    // this should not as cow<str> Add is not commutative
+    buf = cows + buf;
+}
+
+// check that we don't lint on op assign impls, because that's just the way to impl them
+
+#[derive(Copy, Clone, Debug, PartialEq, Eq)]
+pub struct Wrap(i64);
+
+impl Mul<i64> for Wrap {
+    type Output = Self;
+
+    fn mul(self, rhs: i64) -> Self {
+        Wrap(self.0 * rhs)
+    }
+}
+
+impl MulAssign<i64> for Wrap {
+    fn mul_assign(&mut self, rhs: i64) {
+        *self = *self * rhs
+    }
+}

tests/ui/assign_ops.stderr

@@ -1,5 +1,5 @@
 error: manual implementation of an assign operation
-  --> tests/ui/assign_ops.rs:7:5
+  --> tests/ui/assign_ops.rs:9:5
    |
 LL |     a = a + 1;
    |     ^^^^^^^^^ help: replace it with: `a += 1`
@@ -8,64 +8,70 @@ LL |     a = a + 1;
    = help: to override `-D warnings` add `#[allow(clippy::assign_op_pattern)]`
 
 error: manual implementation of an assign operation
-  --> tests/ui/assign_ops.rs:9:5
+  --> tests/ui/assign_ops.rs:11:5
    |
 LL |     a = 1 + a;
    |     ^^^^^^^^^ help: replace it with: `a += 1`
 
 error: manual implementation of an assign operation
-  --> tests/ui/assign_ops.rs:11:5
+  --> tests/ui/assign_ops.rs:13:5
    |
 LL |     a = a - 1;
    |     ^^^^^^^^^ help: replace it with: `a -= 1`
 
 error: manual implementation of an assign operation
-  --> tests/ui/assign_ops.rs:13:5
+  --> tests/ui/assign_ops.rs:15:5
    |
 LL |     a = a * 99;
    |     ^^^^^^^^^^ help: replace it with: `a *= 99`
 
 error: manual implementation of an assign operation
-  --> tests/ui/assign_ops.rs:15:5
+  --> tests/ui/assign_ops.rs:17:5
    |
 LL |     a = 42 * a;
    |     ^^^^^^^^^^ help: replace it with: `a *= 42`
 
 error: manual implementation of an assign operation
-  --> tests/ui/assign_ops.rs:17:5
+  --> tests/ui/assign_ops.rs:19:5
    |
 LL |     a = a / 2;
    |     ^^^^^^^^^ help: replace it with: `a /= 2`
 
 error: manual implementation of an assign operation
-  --> tests/ui/assign_ops.rs:19:5
+  --> tests/ui/assign_ops.rs:21:5
    |
 LL |     a = a % 5;
    |     ^^^^^^^^^ help: replace it with: `a %= 5`
 
 error: manual implementation of an assign operation
-  --> tests/ui/assign_ops.rs:21:5
+  --> tests/ui/assign_ops.rs:23:5
    |
 LL |     a = a & 1;
    |     ^^^^^^^^^ help: replace it with: `a &= 1`
 
 error: manual implementation of an assign operation
-  --> tests/ui/assign_ops.rs:28:5
+  --> tests/ui/assign_ops.rs:30:5
    |
 LL |     s = s + "bla";
    |     ^^^^^^^^^^^^^ help: replace it with: `s += "bla"`
 
 error: manual implementation of an assign operation
-  --> tests/ui/assign_ops.rs:33:5
+  --> tests/ui/assign_ops.rs:35:5
    |
 LL |     a = a + Wrapping(1u32);
    |     ^^^^^^^^^^^^^^^^^^^^^^ help: replace it with: `a += Wrapping(1u32)`
 
 error: manual implementation of an assign operation
-  --> tests/ui/assign_ops.rs:36:5
+  --> tests/ui/assign_ops.rs:38:5
    |
 LL |     v[0] = v[0] + v[1];
    |     ^^^^^^^^^^^^^^^^^^ help: replace it with: `v[0] += v[1]`
 
-error: aborting due to 11 previous errors
+error: manual implementation of an assign operation
+  --> tests/ui/assign_ops.rs:51:5
+   |
+LL |     buf = buf + cows.clone();
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^ help: replace it with: `buf += cows.clone()`
+
+error: aborting due to 12 previous errors
 

tests/ui/cast.rs

@@ -1,4 +1,4 @@
-//@no-rustfix
+//@no-rustfix: only some diagnostics have suggestions
 
 #![feature(repr128)]
 #![allow(incomplete_features)]

tests/ui/cast_size.rs

@@ -1,7 +1,7 @@
 //@revisions: 32bit 64bit
 //@[32bit]ignore-bitwidth: 64
 //@[64bit]ignore-bitwidth: 32
-//@no-rustfix
+//@no-rustfix: only some diagnostics have suggestions
 
 #![warn(
     clippy::cast_precision_loss,

tests/ui/checked_unwrap/complex_conditionals_nested.rs

@@ -4,7 +4,7 @@
     clippy::branches_sharing_code,
     clippy::unnecessary_literal_unwrap
 )]
-//@no-rustfix
+//@no-rustfix: has placeholders
 fn test_nested() {
     fn nested() {
         let x = Some(());

tests/ui/checked_unwrap/simple_conditionals.rs

@@ -1,4 +1,4 @@
-//@no-rustfix: overlapping suggestions
+//@no-rustfix: has placeholders
 #![deny(clippy::panicking_unwrap, clippy::unnecessary_unwrap)]
 #![allow(
     clippy::if_same_then_else,

tests/ui/comparison_chain.rs

@@ -1,4 +1,4 @@
-//@no-rustfix
+//@no-rustfix: has placeholders
 #![allow(dead_code)]
 #![warn(clippy::comparison_chain)]
 

tests/ui/dbg_macro/dbg_macro_unfixable.rs

@@ -1,4 +1,4 @@
-//@no-rustfix
+//@no-rustfix: overlapping suggestions
 //@error-in-other-file:
 #![warn(clippy::dbg_macro)]
 

tests/ui/double_ended_iterator_last_unfixable.rs

@@ -1,4 +1,4 @@
-//@no-rustfix
+//@no-rustfix: requires manual changes
 #![warn(clippy::double_ended_iterator_last)]
 
 // Should not be linted because applying the lint would move the original iterator. This can only be

tests/ui/entry_unfixable.rs

@@ -1,6 +1,5 @@
-#![allow(unused, clippy::needless_pass_by_value, clippy::collapsible_if)]
+#![allow(clippy::needless_pass_by_value, clippy::collapsible_if)]
 #![warn(clippy::map_entry)]
-//@no-rustfix
 
 use std::collections::HashMap;
 use std::hash::Hash;

tests/ui/entry_unfixable.stderr

@@ -1,5 +1,5 @@
 error: usage of `contains_key` followed by `insert` on a `HashMap`
-  --> tests/ui/entry_unfixable.rs:28:13
+  --> tests/ui/entry_unfixable.rs:27:13
    |
 LL | /             if !self.values.contains_key(&name) {
 LL | |
@@ -14,7 +14,7 @@ LL | |             }
    = help: to override `-D warnings` add `#[allow(clippy::map_entry)]`
 
 error: usage of `contains_key` followed by `insert` on a `HashMap`
-  --> tests/ui/entry_unfixable.rs:43:5
+  --> tests/ui/entry_unfixable.rs:42:5
    |
 LL | /     if hm.contains_key(&key) {
 LL | |
@@ -26,7 +26,7 @@ LL | |     }
    | |_____^
 
 error: usage of `contains_key` followed by `insert` on a `HashMap`
-  --> tests/ui/entry_unfixable.rs:81:13
+  --> tests/ui/entry_unfixable.rs:80:13
    |
 LL | /             if self.globals.contains_key(&name) {
 LL | |

tests/ui/explicit_counter_loop.rs

@@ -1,6 +1,6 @@
 #![warn(clippy::explicit_counter_loop)]
 #![allow(clippy::uninlined_format_args, clippy::useless_vec)]
-//@no-rustfix
+//@no-rustfix: suggestion does not remove the `+= 1`
 fn main() {
     let mut vec = vec![1, 2, 3, 4];
     let mut _index = 0;

tests/ui/filter_map_bool_then_unfixable.rs

@@ -1,6 +1,5 @@
-#![allow(clippy::question_mark, unused)]
+#![allow(clippy::question_mark)]
 #![warn(clippy::filter_map_bool_then)]
-//@no-rustfix
 
 fn issue11617() {
     let mut x: Vec<usize> = vec![0; 10];