scylla-macros: Replace derive macros docs with stubs

When both original item and re-export are documented, documentations are
merged. Before this commit, both original item and re-export were
documented - identically or at least very similarly. This caused docs
in scylla-cql crate to be copy-pasted twice. Replace docs with stubs
pointing to the scylla crate to avoid it and point users to proper
documentation.

Author: Lorak-mmk

scylla-macros/src/lib.rs

@@ -9,7 +9,9 @@ mod value_list;
 
 mod serialize;
 
-/// See the documentation for this item in the `scylla` crate.
+/// Documentation for this macro can only be found
+/// in `scylla` crate - not in scylla-macros nor in scylla-cql.
+/// This is because of rustdocs limitations that are hard to explain here.
 #[proc_macro_derive(SerializeCql, attributes(scylla))]
 pub fn serialize_cql_derive(tokens_input: TokenStream) -> TokenStream {
     match serialize::cql::derive_serialize_cql(tokens_input) {
@@ -18,7 +20,9 @@ pub fn serialize_cql_derive(tokens_input: TokenStream) -> TokenStream {
     }
 }
 
-/// See the documentation for this item in the `scylla` crate.
+/// Documentation for this macro can only be found
+/// in `scylla` crate - not in scylla-macros nor in scylla-cql.
+/// This is because of rustdocs limitations that are hard to explain here.
 #[proc_macro_derive(SerializeRow, attributes(scylla))]
 pub fn serialize_row_derive(tokens_input: TokenStream) -> TokenStream {
     match serialize::row::derive_serialize_row(tokens_input) {
@@ -27,32 +31,36 @@ pub fn serialize_row_derive(tokens_input: TokenStream) -> TokenStream {
     }
 }
 
-/// #[derive(FromRow)] derives FromRow for struct
-/// Works only on simple structs without generics etc
+/// Documentation for this macro can only be found
+/// in `scylla` crate - not in scylla-macros nor in scylla-cql.
+/// This is because of rustdocs limitations that are hard to explain here.
 #[proc_macro_derive(FromRow, attributes(scylla_crate))]
 pub fn from_row_derive(tokens_input: TokenStream) -> TokenStream {
     let res = from_row::from_row_derive(tokens_input);
     res.unwrap_or_else(|e| e.into_compile_error().into())
 }
 
-/// #[derive(FromUserType)] allows to parse a struct as User Defined Type
-/// Works only on simple structs without generics etc
+/// Documentation for this macro can only be found
+/// in `scylla` crate - not in scylla-macros nor in scylla-cql.
+/// This is because of rustdocs limitations that are hard to explain here.
 #[proc_macro_derive(FromUserType, attributes(scylla_crate))]
 pub fn from_user_type_derive(tokens_input: TokenStream) -> TokenStream {
     let res = from_user_type::from_user_type_derive(tokens_input);
     res.unwrap_or_else(|e| e.into_compile_error().into())
 }
 
-/// #[derive(IntoUserType)] allows to parse a struct as User Defined Type
-/// Works only on simple structs without generics etc
+/// Documentation for this macro can only be found
+/// in `scylla` crate - not in scylla-macros nor in scylla-cql.
+/// This is because of rustdocs limitations that are hard to explain here.
 #[proc_macro_derive(IntoUserType, attributes(scylla_crate))]
 pub fn into_user_type_derive(tokens_input: TokenStream) -> TokenStream {
     let res = into_user_type::into_user_type_derive(tokens_input);
     res.unwrap_or_else(|e| e.into_compile_error().into())
 }
 
-/// #[derive(ValueList)] derives ValueList for struct
-/// Works only on simple structs without generics etc
+/// Documentation for this macro can only be found
+/// in `scylla` crate - not in scylla-macros nor in scylla-cql.
+/// This is because of rustdocs limitations that are hard to explain here.
 #[proc_macro_derive(ValueList, attributes(scylla_crate))]
 pub fn value_list_derive(tokens_input: TokenStream) -> TokenStream {
     let res = value_list::value_list_derive(tokens_input);