Fix clippy warnings

mlua_derive/src/token.rs

@@ -175,8 +175,7 @@ impl Tokens {
     pub(crate) fn retokenize(tt: TokenStream) -> Tokens {
         Tokens(
             tt.into_iter()
-                .map(Tokens::from)
-                .flatten()
+                .flat_map(Tokens::from)
                 .peekable()
                 .batching(|iter| {
                     // Find variable tokens
@@ -217,7 +216,7 @@ impl From<TokenTree> for Tokens {
 
                 vec![Token::new_delim(b, tt.clone(), true)]
                     .into_iter()
-                    .chain(g.stream().into_iter().map(Tokens::from).flatten())
+                    .chain(g.stream().into_iter().flat_map(Tokens::from))
                     .chain(vec![Token::new_delim(e, tt, false)])
                     .collect()
             }

src/lua.rs

@@ -180,6 +180,7 @@ impl LuaOptions {
     /// Sets [`catch_rust_panics`] option.
     ///
     /// [`catch_rust_panics`]: #structfield.catch_rust_panics
+    #[must_use]
     pub const fn catch_rust_panics(mut self, enabled: bool) -> Self {
         self.catch_rust_panics = enabled;
         self
@@ -190,6 +191,7 @@ impl LuaOptions {
     /// [`thread_cache_size`]: #structfield.thread_cache_size
     #[cfg(feature = "async")]
     #[cfg_attr(docsrs, doc(cfg(feature = "async")))]
+    #[must_use]
     pub const fn thread_cache_size(mut self, size: usize) -> Self {
         self.thread_cache_size = size;
         self

src/serde/de.rs

@@ -61,6 +61,7 @@ impl Options {
     /// Sets [`deny_unsupported_types`] option.
     ///
     /// [`deny_unsupported_types`]: #structfield.deny_unsupported_types
+    #[must_use]
     pub const fn deny_unsupported_types(mut self, enabled: bool) -> Self {
         self.deny_unsupported_types = enabled;
         self
@@ -69,6 +70,7 @@ impl Options {
     /// Sets [`deny_recursive_tables`] option.
     ///
     /// [`deny_recursive_tables`]: #structfield.deny_recursive_tables
+    #[must_use]
     pub fn deny_recursive_tables(mut self, enabled: bool) -> Self {
         self.deny_recursive_tables = enabled;
         self

src/serde/ser.rs

@@ -69,6 +69,7 @@ impl Options {
     /// Sets [`set_array_metatable`] option.
     ///
     /// [`set_array_metatable`]: #structfield.set_array_metatable
+    #[must_use]
     pub const fn set_array_metatable(mut self, enabled: bool) -> Self {
         self.set_array_metatable = enabled;
         self
@@ -77,6 +78,7 @@ impl Options {
     /// Sets [`serialize_none_to_null`] option.
     ///
     /// [`serialize_none_to_null`]: #structfield.serialize_none_to_null
+    #[must_use]
     pub const fn serialize_none_to_null(mut self, enabled: bool) -> Self {
         self.serialize_none_to_null = enabled;
         self
@@ -85,6 +87,7 @@ impl Options {
     /// Sets [`serialize_unit_to_null`] option.
     ///
     /// [`serialize_unit_to_null`]: #structfield.serialize_unit_to_null
+    #[must_use]
     pub const fn serialize_unit_to_null(mut self, enabled: bool) -> Self {
         self.serialize_unit_to_null = enabled;
         self