Add closure test

tests/ui/needless_borrow.fixed

@@ -300,3 +300,16 @@ mod meets_msrv {
         let _ = std::process::Command::new("ls").args(["-a", "-l"]).status().unwrap();
     }
 }
+
+#[allow(dead_code)]
+fn closure_test() {
+    let env = "env".to_owned();
+    let arg = "arg".to_owned();
+    let f = |arg| {
+        let loc = "loc".to_owned();
+        let _ = std::fs::write("x", &env); // Don't lint. In environment
+        let _ = std::fs::write("x", arg);
+        let _ = std::fs::write("x", loc);
+    };
+    f(arg);
+}

tests/ui/needless_borrow.rs

@@ -300,3 +300,16 @@ mod meets_msrv {
         let _ = std::process::Command::new("ls").args(&["-a", "-l"]).status().unwrap();
     }
 }
+
+#[allow(dead_code)]
+fn closure_test() {
+    let env = "env".to_owned();
+    let arg = "arg".to_owned();
+    let f = |arg| {
+        let loc = "loc".to_owned();
+        let _ = std::fs::write("x", &env); // Don't lint. In environment
+        let _ = std::fs::write("x", &arg);
+        let _ = std::fs::write("x", &loc);
+    };
+    f(arg);
+}

tests/ui/needless_borrow.stderr

@@ -186,5 +186,17 @@ error: the borrowed expression implements the required traits
 LL |         let _ = std::process::Command::new("ls").args(&["-a", "-l"]).status().unwrap();
    |                                                       ^^^^^^^^^^^^^ help: change this to: `["-a", "-l"]`
 
-error: aborting due to 31 previous errors
+error: the borrowed expression implements the required traits
+  --> $DIR/needless_borrow.rs:311:37
+   |
+LL |         let _ = std::fs::write("x", &arg);
+   |                                     ^^^^ help: change this to: `arg`
+
+error: the borrowed expression implements the required traits
+  --> $DIR/needless_borrow.rs:312:37
+   |
+LL |         let _ = std::fs::write("x", &loc);
+   |                                     ^^^^ help: change this to: `loc`
+
+error: aborting due to 33 previous errors