Auto merge of #3886 - phansch:rustfix_useless_asref, r=flip1995

Enable rustfix for `useless_asref` lint tests

cc #3630

tests/ui/useless_asref.fixed

@@ -0,0 +1,136 @@
+// run-rustfix
+
+#![deny(clippy::useless_asref)]
+#![allow(clippy::trivially_copy_pass_by_ref)]
+
+use std::fmt::Debug;
+
+struct FakeAsRef;
+
+#[allow(clippy::should_implement_trait)]
+impl FakeAsRef {
+    fn as_ref(&self) -> &Self {
+        self
+    }
+}
+
+struct MoreRef;
+
+impl<'a, 'b, 'c> AsRef<&'a &'b &'c MoreRef> for MoreRef {
+    fn as_ref(&self) -> &&'a &'b &'c MoreRef {
+        &&&&MoreRef
+    }
+}
+
+fn foo_rstr(x: &str) {
+    println!("{:?}", x);
+}
+fn foo_rslice(x: &[i32]) {
+    println!("{:?}", x);
+}
+fn foo_mrslice(x: &mut [i32]) {
+    println!("{:?}", x);
+}
+fn foo_rrrrmr(_: &&&&MoreRef) {
+    println!("so many refs");
+}
+
+fn not_ok() {
+    let rstr: &str = "hello";
+    let mut mrslice: &mut [i32] = &mut [1, 2, 3];
+
+    {
+        let rslice: &[i32] = &*mrslice;
+        foo_rstr(rstr);
+        foo_rstr(rstr);
+        foo_rslice(rslice);
+        foo_rslice(rslice);
+    }
+    {
+        foo_mrslice(mrslice);
+        foo_mrslice(mrslice);
+        foo_rslice(mrslice);
+        foo_rslice(mrslice);
+    }
+
+    {
+        let rrrrrstr = &&&&rstr;
+        let rrrrrslice = &&&&&*mrslice;
+        foo_rslice(rrrrrslice);
+        foo_rslice(rrrrrslice);
+        foo_rstr(rrrrrstr);
+        foo_rstr(rrrrrstr);
+    }
+    {
+        let mrrrrrslice = &mut &mut &mut &mut mrslice;
+        foo_mrslice(mrrrrrslice);
+        foo_mrslice(mrrrrrslice);
+        foo_rslice(mrrrrrslice);
+        foo_rslice(mrrrrrslice);
+    }
+    #[allow(unused_parens, clippy::double_parens)]
+    foo_rrrrmr((&&&&MoreRef));
+
+    generic_not_ok(mrslice);
+    generic_ok(mrslice);
+}
+
+fn ok() {
+    let string = "hello".to_owned();
+    let mut arr = [1, 2, 3];
+    let mut vec = vec![1, 2, 3];
+
+    {
+        foo_rstr(string.as_ref());
+        foo_rslice(arr.as_ref());
+        foo_rslice(vec.as_ref());
+    }
+    {
+        foo_mrslice(arr.as_mut());
+        foo_mrslice(vec.as_mut());
+    }
+
+    {
+        let rrrrstring = &&&&string;
+        let rrrrarr = &&&&arr;
+        let rrrrvec = &&&&vec;
+        foo_rstr(rrrrstring.as_ref());
+        foo_rslice(rrrrarr.as_ref());
+        foo_rslice(rrrrvec.as_ref());
+    }
+    {
+        let mrrrrarr = &mut &mut &mut &mut arr;
+        let mrrrrvec = &mut &mut &mut &mut vec;
+        foo_mrslice(mrrrrarr.as_mut());
+        foo_mrslice(mrrrrvec.as_mut());
+    }
+    FakeAsRef.as_ref();
+    foo_rrrrmr(MoreRef.as_ref());
+
+    generic_not_ok(arr.as_mut());
+    generic_ok(&mut arr);
+}
+
+fn foo_mrt<T: Debug + ?Sized>(t: &mut T) {
+    println!("{:?}", t);
+}
+fn foo_rt<T: Debug + ?Sized>(t: &T) {
+    println!("{:?}", t);
+}
+
+fn generic_not_ok<T: AsMut<T> + AsRef<T> + Debug + ?Sized>(mrt: &mut T) {
+    foo_mrt(mrt);
+    foo_mrt(mrt);
+    foo_rt(mrt);
+    foo_rt(mrt);
+}
+
+fn generic_ok<U: AsMut<T> + AsRef<T> + ?Sized, T: Debug + ?Sized>(mru: &mut U) {
+    foo_mrt(mru.as_mut());
+    foo_rt(mru.as_ref());
+}
+
+fn main() {
+    not_ok();
+    ok();
+}

tests/ui/useless_asref.rs

@@ -1,5 +1,8 @@
+// run-rustfix
+
 #![deny(clippy::useless_asref)]
 #![allow(clippy::trivially_copy_pass_by_ref)]
+
 use std::fmt::Debug;
 
 struct FakeAsRef;
@@ -65,6 +68,7 @@ fn not_ok() {
         foo_rslice(mrrrrrslice.as_ref());
         foo_rslice(mrrrrrslice);
     }
+    #[allow(unused_parens, clippy::double_parens)]
     foo_rrrrmr((&&&&MoreRef).as_ref());
 
     generic_not_ok(mrslice);

tests/ui/useless_asref.stderr

@@ -1,71 +1,71 @@
 error: this call to `as_ref` does nothing
-  --> $DIR/useless_asref.rs:41:18
+  --> $DIR/useless_asref.rs:44:18
    |
 LL |         foo_rstr(rstr.as_ref());
    |                  ^^^^^^^^^^^^^ help: try this: `rstr`
    |
 note: lint level defined here
-  --> $DIR/useless_asref.rs:1:9
+  --> $DIR/useless_asref.rs:3:9
    |
 LL | #![deny(clippy::useless_asref)]
    |         ^^^^^^^^^^^^^^^^^^^^^
 
 error: this call to `as_ref` does nothing
-  --> $DIR/useless_asref.rs:43:20
+  --> $DIR/useless_asref.rs:46:20
    |
 LL |         foo_rslice(rslice.as_ref());
    |                    ^^^^^^^^^^^^^^^ help: try this: `rslice`
 
 error: this call to `as_mut` does nothing
-  --> $DIR/useless_asref.rs:47:21
+  --> $DIR/useless_asref.rs:50:21
    |
 LL |         foo_mrslice(mrslice.as_mut());
    |                     ^^^^^^^^^^^^^^^^ help: try this: `mrslice`
 
 error: this call to `as_ref` does nothing
-  --> $DIR/useless_asref.rs:49:20
+  --> $DIR/useless_asref.rs:52:20
    |
 LL |         foo_rslice(mrslice.as_ref());
    |                    ^^^^^^^^^^^^^^^^ help: try this: `mrslice`
 
 error: this call to `as_ref` does nothing
-  --> $DIR/useless_asref.rs:56:20
+  --> $DIR/useless_asref.rs:59:20
    |
 LL |         foo_rslice(rrrrrslice.as_ref());
    |                    ^^^^^^^^^^^^^^^^^^^ help: try this: `rrrrrslice`
 
 error: this call to `as_ref` does nothing
-  --> $DIR/useless_asref.rs:58:18
+  --> $DIR/useless_asref.rs:61:18
    |
 LL |         foo_rstr(rrrrrstr.as_ref());
    |                  ^^^^^^^^^^^^^^^^^ help: try this: `rrrrrstr`
 
 error: this call to `as_mut` does nothing
-  --> $DIR/useless_asref.rs:63:21
+  --> $DIR/useless_asref.rs:66:21
    |
 LL |         foo_mrslice(mrrrrrslice.as_mut());
    |                     ^^^^^^^^^^^^^^^^^^^^ help: try this: `mrrrrrslice`
 
 error: this call to `as_ref` does nothing
-  --> $DIR/useless_asref.rs:65:20
+  --> $DIR/useless_asref.rs:68:20
    |
 LL |         foo_rslice(mrrrrrslice.as_ref());
    |                    ^^^^^^^^^^^^^^^^^^^^ help: try this: `mrrrrrslice`
 
 error: this call to `as_ref` does nothing
-  --> $DIR/useless_asref.rs:68:16
+  --> $DIR/useless_asref.rs:72:16
    |
 LL |     foo_rrrrmr((&&&&MoreRef).as_ref());
    |                ^^^^^^^^^^^^^^^^^^^^^^ help: try this: `(&&&&MoreRef)`
 
 error: this call to `as_mut` does nothing
-  --> $DIR/useless_asref.rs:118:13
+  --> $DIR/useless_asref.rs:122:13
    |
 LL |     foo_mrt(mrt.as_mut());
    |             ^^^^^^^^^^^^ help: try this: `mrt`
 
 error: this call to `as_ref` does nothing
-  --> $DIR/useless_asref.rs:120:12
+  --> $DIR/useless_asref.rs:124:12
    |
 LL |     foo_rt(mrt.as_ref());
    |            ^^^^^^^^^^^^ help: try this: `mrt`