Added more tests

Author: botahamec

tests/ui/unused_box.rs

@@ -1,9 +1,31 @@
 #![warn(clippy::unused_box)]
 
-fn foo() -> Box<usize> {
+struct Foo {}
+
+// lint
+fn boxed_usize() -> Box<usize> {
     Box::new(5)
 }
 
+// lint
+fn boxed_string() -> Box<Foo> {
+    Box::new(Foo {})
+}
+
+// don't lint: str is unsized
+fn boxed_str() -> Box<str> {
+    "Hello, world!".to_string().into_boxed_str()
+}
+
+// don't lint: this has an unspecified return type
+fn default() {}
+
+// don't lint: this doesn't return a Box
+fn string() -> String {
+    String::from("Hello, world")
+}
+
 fn main() {
-    // test code goes here
+    // don't lint: this is a closure
+    let a = || -> Box<usize> { Box::new(5) };
 }

tests/ui/unused_box.stderr

@@ -1,10 +1,16 @@
 error: function returns `Box<usize>` when `usize` implements `Sized`
-  --> $DIR/unused_box.rs:3:13
+  --> $DIR/unused_box.rs:6:21
    |
-LL | fn foo() -> Box<usize> {
-   |             ^^^^^^^^^^ help: change the return type to: `usize`
+LL | fn boxed_usize() -> Box<usize> {
+   |                     ^^^^^^^^^^ help: change the return type to: `usize`
    |
    = note: `-D clippy::unused-box` implied by `-D warnings`
 
-error: aborting due to previous error
+error: function returns `Box<Foo>` when `Foo` implements `Sized`
+  --> $DIR/unused_box.rs:11:22
+   |
+LL | fn boxed_string() -> Box<Foo> {
+   |                      ^^^^^^^^ help: change the return type to: `Foo`
+
+error: aborting due to 2 previous errors