refactor(header): add comment and lint allowing to panic in const context workaround

Author: tottoto

src/header/name.rs

@@ -1269,6 +1269,12 @@ impl HeaderName {
                 i += 1;
             }
         } {
+            // TODO: When msrv is bumped to larger than 1.57, this should be
+            // replaced with `panic!` macro.
+            // https://blog.rust-lang.org/2021/12/02/Rust-1.57.0.html#panic-in-const-contexts
+            //
+            // See the panics section of this method's document for details.
+            #[allow(clippy::no_effect)]
             ([] as [u8; 0])[0]; // Invalid header name
         }
 

src/header/value.rs

@@ -86,6 +86,12 @@ impl HeaderValue {
         let mut i = 0;
         while i < bytes.len() {
             if !is_visible_ascii(bytes[i]) {
+                // TODO: When msrv is bumped to larger than 1.57, this should be
+                // replaced with `panic!` macro.
+                // https://blog.rust-lang.org/2021/12/02/Rust-1.57.0.html#panic-in-const-contexts
+                //
+                // See the panics section of this method's document for details.
+                #[allow(clippy::no_effect)]
                 ([] as [u8; 0])[0]; // Invalid header value
             }
             i += 1;