Add tests for generic code

Author: HMPerson1

tests/ui/useless_asref.rs

@@ -1,5 +1,7 @@
 #![deny(useless_asref)]
 
+use std::fmt::Debug;
+
 struct FakeAsRef;
 
 #[allow(should_implement_trait)]
@@ -54,6 +56,9 @@ fn not_ok() {
         foo_rslice(mrrrrrslice);
     }
     foo_rrrrmr((&&&&MoreRef).as_ref());
+
+    generic_not_ok(mrslice);
+    generic_ok(mrslice);
 }
 
 fn ok() {
@@ -87,7 +92,26 @@ fn ok() {
     }
     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.as_mut());
+    foo_mrt(mrt);
+    foo_rt(mrt.as_ref());
+    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.stderr

@@ -1,7 +1,7 @@
 error: this call to `as_ref` does nothing
-  --> $DIR/useless_asref.rs:29:18
+  --> $DIR/useless_asref.rs:31:18
    |
-29 |         foo_rstr(rstr.as_ref());
+31 |         foo_rstr(rstr.as_ref());
    |                  ^^^^^^^^^^^^^ help: try this: `rstr`
    |
 note: lint level defined here
@@ -11,50 +11,62 @@ note: lint level defined here
    |         ^^^^^^^^^^^^^
 
 error: this call to `as_ref` does nothing
-  --> $DIR/useless_asref.rs:31:20
+  --> $DIR/useless_asref.rs:33:20
    |
-31 |         foo_rslice(rslice.as_ref());
+33 |         foo_rslice(rslice.as_ref());
    |                    ^^^^^^^^^^^^^^^ help: try this: `rslice`
 
 error: this call to `as_mut` does nothing
-  --> $DIR/useless_asref.rs:35:21
+  --> $DIR/useless_asref.rs:37:21
    |
-35 |         foo_mrslice(mrslice.as_mut());
+37 |         foo_mrslice(mrslice.as_mut());
    |                     ^^^^^^^^^^^^^^^^ help: try this: `mrslice`
 
 error: this call to `as_ref` does nothing
-  --> $DIR/useless_asref.rs:37:20
+  --> $DIR/useless_asref.rs:39:20
    |
-37 |         foo_rslice(mrslice.as_ref());
+39 |         foo_rslice(mrslice.as_ref());
    |                    ^^^^^^^^^^^^^^^^ help: try this: `mrslice`
 
 error: this call to `as_ref` does nothing
-  --> $DIR/useless_asref.rs:44:20
+  --> $DIR/useless_asref.rs:46:20
    |
-44 |         foo_rslice(rrrrrslice.as_ref());
+46 |         foo_rslice(rrrrrslice.as_ref());
    |                    ^^^^^^^^^^^^^^^^^^^ help: try this: `rrrrrslice`
 
 error: this call to `as_ref` does nothing
-  --> $DIR/useless_asref.rs:46:18
+  --> $DIR/useless_asref.rs:48:18
    |
-46 |         foo_rstr(rrrrrstr.as_ref());
+48 |         foo_rstr(rrrrrstr.as_ref());
    |                  ^^^^^^^^^^^^^^^^^ help: try this: `rrrrrstr`
 
 error: this call to `as_mut` does nothing
-  --> $DIR/useless_asref.rs:51:21
+  --> $DIR/useless_asref.rs:53:21
    |
-51 |         foo_mrslice(mrrrrrslice.as_mut());
+53 |         foo_mrslice(mrrrrrslice.as_mut());
    |                     ^^^^^^^^^^^^^^^^^^^^ help: try this: `mrrrrrslice`
 
 error: this call to `as_ref` does nothing
-  --> $DIR/useless_asref.rs:53:20
+  --> $DIR/useless_asref.rs:55:20
    |
-53 |         foo_rslice(mrrrrrslice.as_ref());
+55 |         foo_rslice(mrrrrrslice.as_ref());
    |                    ^^^^^^^^^^^^^^^^^^^^ help: try this: `mrrrrrslice`
 
 error: this call to `as_ref` does nothing
-  --> $DIR/useless_asref.rs:56:16
+  --> $DIR/useless_asref.rs:58:16
    |
-56 |     foo_rrrrmr((&&&&MoreRef).as_ref());
+58 |     foo_rrrrmr((&&&&MoreRef).as_ref());
    |                ^^^^^^^^^^^^^^^^^^^^^^ help: try this: `(&&&&MoreRef)`
 
+error: this call to `as_mut` does nothing
+   --> $DIR/useless_asref.rs:104:13
+    |
+104 |     foo_mrt(mrt.as_mut());
+    |             ^^^^^^^^^^^^ help: try this: `mrt`
+
+error: this call to `as_ref` does nothing
+   --> $DIR/useless_asref.rs:106:12
+    |
+106 |     foo_rt(mrt.as_ref());
+    |            ^^^^^^^^^^^^ help: try this: `mrt`
+