Implement MethodFilter via bitflags (#158)

Fixes https://github.com/tokio-rs/axum/issues/107

src/routing/method_filter.rs

@@ -0,0 +1,45 @@
+use bitflags::bitflags;
+use http::Method;
+
+bitflags! {
+    /// A filter that matches one or more HTTP methods.
+    pub struct MethodFilter: u16 {
+        /// Match `CONNECT` requests.
+        const CONNECT = 0b000000001;
+        /// Match `DELETE` requests.
+        const DELETE =  0b000000010;
+        /// Match `GET` requests.
+        const GET =     0b000000100;
+        /// Match `HEAD` requests.
+        const HEAD =    0b000001000;
+        /// Match `OPTIONS` requests.
+        const OPTIONS = 0b000010000;
+        /// Match `PATCH` requests.
+        const PATCH =   0b000100000;
+        /// Match `POSt` requests.
+        const POST =    0b001000000;
+        /// Match `PUT` requests.
+        const PUT =     0b010000000;
+        /// Match `TRACE` requests.
+        const TRACE =   0b100000000;
+    }
+}
+
+impl MethodFilter {
+    #[allow(clippy::match_like_matches_macro)]
+    pub(crate) fn matches(self, method: &Method) -> bool {
+        let method = match *method {
+            Method::CONNECT => Self::CONNECT,
+            Method::DELETE => Self::DELETE,
+            Method::GET => Self::GET,
+            Method::HEAD => Self::HEAD,
+            Method::OPTIONS => Self::OPTIONS,
+            Method::PATCH => Self::PATCH,
+            Method::POST => Self::POST,
+            Method::PUT => Self::PUT,
+            Method::TRACE => Self::TRACE,
+            _ => return false,
+        };
+        self.contains(method)
+    }
+}