Mark some functions as constant

http/src/body.rs

@@ -330,9 +330,7 @@ where
     B: Stream<Item = io::Result<&'b [u8]>>,
 {
     /// Use a [`Stream`] as HTTP body.
-    // TODO: make this a `const` fn once trait bounds (`FileSend`) on `const`
-    // functions are stable.
-    pub fn new(length: usize, stream: B) -> StreamingBody<'b, B> {
+    pub const fn new(length: usize, stream: B) -> StreamingBody<'b, B> {
         StreamingBody {
             length,
             body: stream,
@@ -402,9 +400,7 @@ where
     ///
     /// This uses the bytes `offset..end` from `file` as HTTP body and sends
     /// them using `sendfile(2)` (using [`TcpStream::send_file`]).
-    // TODO: make this a `const` fn once trait bounds (`FileSend`) on `const`
-    // functions are stable.
-    pub fn new(file: &'f F, offset: usize, end: NonZeroUsize) -> FileBody<'f, F> {
+    pub const fn new(file: &'f F, offset: usize, end: NonZeroUsize) -> FileBody<'f, F> {
         debug_assert!(end.get() >= offset);
         FileBody { file, offset, end }
     }

http/src/header.rs

@@ -130,7 +130,7 @@ impl Headers {
     /// Returns an iterator over all headers.
     ///
     /// The order is unspecified.
-    pub fn iter<'a>(&'a self) -> Iter<'a> {
+    pub const fn iter<'a>(&'a self) -> Iter<'a> {
         Iter {
             headers: self,
             pos: 0,
@@ -863,7 +863,7 @@ impl HeaderName<'static> {
     /// This is only header to test [`HeaderName::from_str`], not part of the
     /// stable API.
     #[doc(hidden)]
-    pub fn is_heap_allocated(&self) -> bool {
+    pub const fn is_heap_allocated(&self) -> bool {
         matches!(self.inner, Cow::Owned(_))
     }
 }

http/src/request.rs

@@ -59,7 +59,7 @@ impl<B> Request<B> {
     }
 
     /// Returns mutable access to the headers.
-    pub fn headers_mut(&mut self) -> &mut Headers {
+    pub const fn headers_mut(&mut self) -> &mut Headers {
         &mut self.headers
     }
 
@@ -69,7 +69,7 @@ impl<B> Request<B> {
     }
 
     /// Mutable access to the request body.
-    pub fn body_mut(&mut self) -> &mut B {
+    pub const fn body_mut(&mut self) -> &mut B {
         &mut self.body
     }
 }

http/src/response.rs

@@ -42,7 +42,7 @@ impl<B> Response<B> {
     }
 
     /// Returns mutable access to the headers.
-    pub fn headers_mut(&mut self) -> &mut Headers {
+    pub const fn headers_mut(&mut self) -> &mut Headers {
         &mut self.headers
     }
 
@@ -52,7 +52,7 @@ impl<B> Response<B> {
     }
 
     /// Returns a mutable reference to the body.
-    pub fn body_mut(&mut self) -> &mut B {
+    pub const fn body_mut(&mut self) -> &mut B {
         &mut self.body
     }