fix(header): deprecate HeaderFormatter

Cargo.toml

@@ -11,6 +11,7 @@ license = "MIT"
 authors = ["Sean McArthur <sean.monstar@gmail.com>",
            "Jonathan Reem <jonathan.reem@gmail.com>"]
 keywords = ["http", "hyper", "hyperium"]
+build = "build.rs"
 
 [dependencies]
 httparse = "1.0"
@@ -28,5 +29,8 @@ url = "1.0"
 [dev-dependencies]
 env_logger = "0.3"
 
+[build-dependencies]
+rustc_version = "0.1"
+
 [features]
 nightly = []

build.rs

@@ -0,0 +1,7 @@
+extern crate rustc_version as rustc;
+
+fn main() {
+    if rustc::version_matches(">= 1.9") {
+        println!("cargo:rustc-cfg=has_deprecated");
+    }
+}

src/header/mod.rs

@@ -495,11 +495,14 @@ impl<'a> FromIterator<HeaderView<'a>> for Headers {
     }
 }
 
-impl<'a> fmt::Display for &'a (HeaderFormat + Send + Sync) {
-    #[inline]
-    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        let mut multi = MultilineFormatter(Multi::Join(true, f));
-        self.fmt_multi_header(&mut multi)
+deprecated! {
+    #[deprecated(note="The semantics of formatting a HeaderFormat directly are not clear")]
+    impl<'a> fmt::Display for &'a (HeaderFormat + Send + Sync) {
+        #[inline]
+        fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+            let mut multi = MultilineFormatter(Multi::Join(true, f));
+            self.fmt_multi_header(&mut multi)
+        }
     }
 }
 
@@ -510,8 +513,12 @@ impl<'a> fmt::Display for &'a (HeaderFormat + Send + Sync) {
 ///
 /// Note: This may not necessarily be the value written to stream, such
 /// as with the SetCookie header.
-pub struct HeaderFormatter<'a, H: HeaderFormat>(pub &'a H);
+deprecated! {
+    #[deprecated(note="The semantics of formatting a HeaderFormat directly are not clear")]
+    pub struct HeaderFormatter<'a, H: HeaderFormat>(pub &'a H);
+}
 
+#[allow(deprecated)]
 impl<'a, H: HeaderFormat> fmt::Display for HeaderFormatter<'a, H> {
     #[inline]
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
@@ -520,6 +527,7 @@ impl<'a, H: HeaderFormat> fmt::Display for HeaderFormatter<'a, H> {
     }
 }
 
+#[allow(deprecated)]
 impl<'a, H: HeaderFormat> fmt::Debug for HeaderFormatter<'a, H> {
     #[inline]
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {

src/lib.rs

@@ -172,6 +172,13 @@ macro_rules! inspect(
     })
 );
 
+macro_rules! deprecated {
+    (#[$note:meta] $i:item) => (
+        #[cfg_attr(has_deprecated, $note)]
+        $i
+    );
+}
+
 #[cfg(test)]
 #[macro_use]
 mod mock;