needless_borrow: allow other lints, make fixable

Author: Manishearth

tests/ui/needless_borrow.fixed

@@ -0,0 +1,62 @@
+// run-rustfix
+
+#![allow(clippy::needless_borrowed_reference)]
+
+#[allow(clippy::trivially_copy_pass_by_ref)]
+fn x(y: &i32) -> i32 {
+    *y
+}
+
+#[warn(clippy::all, clippy::needless_borrow)]
+#[allow(unused_variables)]
+fn main() {
+    let a = 5;
+    let b = x(&a);
+    let c = x(&a);
+    let s = &String::from("hi");
+    let s_ident = f(&s); // should not error, because `&String` implements Copy, but `String` does not
+    let g_val = g(&Vec::new()); // should not error, because `&Vec<T>` derefs to `&[T]`
+    let vec = Vec::new();
+    let vec_val = g(&vec); // should not error, because `&Vec<T>` derefs to `&[T]`
+    h(&"foo"); // should not error, because the `&&str` is required, due to `&Trait`
+    if let Some(cake) = Some(&5) {}
+    let garbl = match 42 {
+        44 => &a,
+        45 => {
+            println!("foo");
+            &&a // FIXME: this should lint, too
+        },
+        46 => &a,
+        _ => panic!(),
+    };
+}
+
+fn f<T: Copy>(y: &T) -> T {
+    *y
+}
+
+fn g(y: &[u8]) -> u8 {
+    y[0]
+}
+
+trait Trait {}
+
+impl<'a> Trait for &'a str {}
+
+fn h(_: &dyn Trait) {}
+#[warn(clippy::needless_borrow)]
+#[allow(dead_code)]
+fn issue_1432() {
+    let mut v = Vec::<String>::new();
+    let _ = v.iter_mut().filter(|&ref a| a.is_empty());
+    let _ = v.iter().filter(|&a| a.is_empty());
+
+    let _ = v.iter().filter(|&a| a.is_empty());
+}
+
+#[allow(dead_code)]
+#[warn(clippy::needless_borrow)]
+#[derive(Debug)]
+enum Foo<'a> {
+    Str(&'a str),
+}

tests/ui/needless_borrow.rs

@@ -1,4 +1,6 @@
-use std::borrow::Cow;
+// run-rustfix
+
+#![allow(clippy::needless_borrowed_reference)]
 
 #[allow(clippy::trivially_copy_pass_by_ref)]
 fn x(y: &i32) -> i32 {

tests/ui/needless_borrow.stderr

@@ -1,42 +1,28 @@
 error: this expression borrows a reference that is immediately dereferenced by the compiler
-  --> $DIR/needless_borrow.rs:13:15
+  --> $DIR/needless_borrow.rs:15:15
    |
 LL |     let c = x(&&a);
    |               ^^^ help: change this to: `&a`
    |
    = note: `-D clippy::needless-borrow` implied by `-D warnings`
 
 error: this pattern creates a reference to a reference
-  --> $DIR/needless_borrow.rs:20:17
+  --> $DIR/needless_borrow.rs:22:17
    |
 LL |     if let Some(ref cake) = Some(&5) {}
    |                 ^^^^^^^^ help: change this to: `cake`
 
 error: this expression borrows a reference that is immediately dereferenced by the compiler
-  --> $DIR/needless_borrow.rs:27:15
+  --> $DIR/needless_borrow.rs:29:15
    |
 LL |         46 => &&a,
    |               ^^^ help: change this to: `&a`
 
-error: this pattern takes a reference on something that is being de-referenced
-  --> $DIR/needless_borrow.rs:49:34
-   |
-LL |     let _ = v.iter_mut().filter(|&ref a| a.is_empty());
-   |                                  ^^^^^^ help: try removing the `&ref` part and just keep: `a`
-   |
-   = note: `-D clippy::needless-borrowed-reference` implied by `-D warnings`
-
-error: this pattern takes a reference on something that is being de-referenced
-  --> $DIR/needless_borrow.rs:50:30
-   |
-LL |     let _ = v.iter().filter(|&ref a| a.is_empty());
-   |                              ^^^^^^ help: try removing the `&ref` part and just keep: `a`
-
 error: this pattern creates a reference to a reference
-  --> $DIR/needless_borrow.rs:50:31
+  --> $DIR/needless_borrow.rs:52:31
    |
 LL |     let _ = v.iter().filter(|&ref a| a.is_empty());
    |                               ^^^^^ help: change this to: `a`
 
-error: aborting due to 6 previous errors
+error: aborting due to 4 previous errors