Add missing_const_for_fn clippy lint (#8498)

crates/rpc/ipc/src/server/mod.rs

@@ -588,31 +588,31 @@ impl Default for Builder<Identity, Identity> {
 
 impl<HttpMiddleware, RpcMiddleware> Builder<HttpMiddleware, RpcMiddleware> {
     /// Set the maximum size of a request body in bytes. Default is 10 MiB.
-    pub fn max_request_body_size(mut self, size: u32) -> Self {
+    pub const fn max_request_body_size(mut self, size: u32) -> Self {
         self.settings.max_request_body_size = size;
         self
     }
 
     /// Set the maximum size of a response body in bytes. Default is 10 MiB.
-    pub fn max_response_body_size(mut self, size: u32) -> Self {
+    pub const fn max_response_body_size(mut self, size: u32) -> Self {
         self.settings.max_response_body_size = size;
         self
     }
 
     /// Set the maximum size of a log
-    pub fn max_log_length(mut self, size: u32) -> Self {
+    pub const fn max_log_length(mut self, size: u32) -> Self {
         self.settings.max_log_length = size;
         self
     }
 
     /// Set the maximum number of connections allowed. Default is 100.
-    pub fn max_connections(mut self, max: u32) -> Self {
+    pub const fn max_connections(mut self, max: u32) -> Self {
         self.settings.max_connections = max;
         self
     }
 
     /// Set the maximum number of connections allowed. Default is 1024.
-    pub fn max_subscriptions_per_connection(mut self, max: u32) -> Self {
+    pub const fn max_subscriptions_per_connection(mut self, max: u32) -> Self {
         self.settings.max_subscriptions_per_connection = max;
         self
     }
@@ -634,7 +634,7 @@ impl<HttpMiddleware, RpcMiddleware> Builder<HttpMiddleware, RpcMiddleware> {
     /// # Panics
     ///
     /// Panics if the buffer capacity is 0.
-    pub fn set_message_buffer_capacity(mut self, c: u32) -> Self {
+    pub const fn set_message_buffer_capacity(mut self, c: u32) -> Self {
         self.settings.message_buffer_capacity = c;
         self
     }

crates/rpc/ipc/src/server/rpc_service.rs

@@ -36,7 +36,7 @@ pub(crate) enum RpcServiceCfg {
 
 impl RpcService {
     /// Create a new service.
-    pub(crate) fn new(
+    pub(crate) const fn new(
         methods: Methods,
         max_response_body_size: usize,
         conn_id: usize,

crates/rpc/ipc/src/stream_codec.rs

@@ -61,13 +61,13 @@ impl StreamCodec {
     }
 
     /// New custom stream codec
-    pub fn new(incoming_separator: Separator, outgoing_separator: Separator) -> Self {
+    pub const fn new(incoming_separator: Separator, outgoing_separator: Separator) -> Self {
         Self { incoming_separator, outgoing_separator }
     }
 }
 
 #[inline]
-fn is_whitespace(byte: u8) -> bool {
+const fn is_whitespace(byte: u8) -> bool {
     matches!(byte, 0x0D | 0x0A | 0x20 | 0x09)
 }