Derive Copy trait to SizeHint struct (#164)

The struct has only a size of 24 bytes and is trivially copy-able.

Author: cgzones

http-body/src/size_hint.rs

@@ -4,7 +4,7 @@
 ///
 /// * 0 for `lower`
 /// * `None` for `upper`.
-#[derive(Debug, Default, Clone)]
+#[derive(Debug, Default, Clone, Copy)]
 pub struct SizeHint {
     lower: u64,
     upper: Option<u64>,
@@ -178,7 +178,7 @@ fn size_hint_addition_basic() {
     let exact_l = SizeHint::with_exact(20);
     let exact_r = SizeHint::with_exact(5);
 
-    assert_eq!(Some(25), (exact_l.clone() + exact_r).exact());
+    assert_eq!(Some(25), (exact_l + exact_r).exact());
 
     let inexact_l = SizeHint {
         lower: 25,
@@ -189,12 +189,12 @@ fn size_hint_addition_basic() {
         upper: Some(50),
     };
 
-    let inexact = inexact_l + inexact_r.clone();
+    let inexact = inexact_l + inexact_r;
 
     assert_eq!(inexact.lower(), 35);
     assert_eq!(inexact.upper(), None);
 
-    let exact_inexact = exact_l.clone() + inexact_r.clone();
+    let exact_inexact = exact_l + inexact_r;
 
     assert_eq!(exact_inexact.lower(), 30);
     assert_eq!(exact_inexact.upper(), Some(70));

http-body/tests/is_end_stream.rs

@@ -18,7 +18,7 @@ impl Body for Mock {
     }
 
     fn size_hint(&self) -> SizeHint {
-        self.size_hint.clone()
+        self.size_hint
     }
 }