Lint comparison to empty slice using PartialEq methods

tests/ui/comparison_to_empty.fixed

@@ -33,4 +33,12 @@ fn main() {
     if let [0] = &*s
         && s == [0]
     {}
+
+    // Also lint the `PartialEq` methods
+    let s = String::new();
+    let _ = s.is_empty();
+    let _ = !s.is_empty();
+    let v = vec![0];
+    let _ = v.is_empty();
+    let _ = !v.is_empty();
 }

tests/ui/comparison_to_empty.rs

@@ -33,4 +33,12 @@ fn main() {
     if let [0] = &*s
         && s == [0]
     {}
+
+    // Also lint the `PartialEq` methods
+    let s = String::new();
+    let _ = s.eq("");
+    let _ = s.ne("");
+    let v = vec![0];
+    let _ = v.eq(&[]);
+    let _ = v.ne(&[]);
 }

tests/ui/comparison_to_empty.stderr

@@ -55,5 +55,29 @@ error: comparison to empty slice
 LL |         && s == []
    |            ^^^^^^^ help: using `is_empty` is clearer and more explicit: `s.is_empty()`
 
-error: aborting due to 9 previous errors
+error: comparison to empty slice
+  --> tests/ui/comparison_to_empty.rs:39:13
+   |
+LL |     let _ = s.eq("");
+   |             ^^^^^^^^ help: using `is_empty` is clearer and more explicit: `s.is_empty()`
+
+error: comparison to empty slice
+  --> tests/ui/comparison_to_empty.rs:40:13
+   |
+LL |     let _ = s.ne("");
+   |             ^^^^^^^^ help: using `!is_empty` is clearer and more explicit: `!s.is_empty()`
+
+error: comparison to empty slice
+  --> tests/ui/comparison_to_empty.rs:42:13
+   |
+LL |     let _ = v.eq(&[]);
+   |             ^^^^^^^^^ help: using `is_empty` is clearer and more explicit: `v.is_empty()`
+
+error: comparison to empty slice
+  --> tests/ui/comparison_to_empty.rs:43:13
+   |
+LL |     let _ = v.ne(&[]);
+   |             ^^^^^^^^^ help: using `!is_empty` is clearer and more explicit: `!v.is_empty()`
+
+error: aborting due to 13 previous errors