remove use of hidden api in support procedural (#2383)

substrate/srml/support/procedural/tools/src/syn_ext.rs

@@ -23,7 +23,6 @@ use syn::parse::{
 	ParseStream,
 	Result,
 };
-use syn::token::CustomKeyword;
 use proc_macro2::TokenStream as T2;
 use quote::{ToTokens, quote};
 use std::iter::once;
@@ -72,32 +71,6 @@ groups_impl!(Braces, Brace, Brace, parse_braces);
 groups_impl!(Brackets, Bracket, Bracket, parse_brackets);
 groups_impl!(Parens, Paren, Parenthesis, parse_parens);
 
-#[derive(Debug, Clone)]
-pub struct CustomToken<T>(std::marker::PhantomData<T>);
-
-impl<T: CustomKeyword> Parse for CustomToken<T> {
-	fn parse(input: ParseStream) -> Result<Self> {
-		let ident: syn::Ident = input.parse()?;
-
-		if ident.to_string().as_str() != T::ident() {
-			return Err(syn::parse::Error::new_spanned(ident, "expected another custom token"))
-		}
-		Ok(CustomToken(std::marker::PhantomData))
-	}
-}
-
-impl<T: CustomKeyword> ToTokens for CustomToken<T> {
-	fn to_tokens(&self, tokens: &mut T2) {
-		use std::str::FromStr;
-		tokens.extend(T2::from_str(T::ident()).expect("custom keyword should parse to ident"));
-	}
-}
-
-impl<T: CustomKeyword> CustomKeyword for CustomToken<T> {
-	fn ident() -> &'static str { <T as CustomKeyword>::ident() }
-	fn display() -> &'static str { <T as CustomKeyword>::display() }
-}
-
 #[derive(Debug)]
 pub struct PunctuatedInner<P,T,V> {
 	pub inner: syn::punctuated::Punctuated<P,T>,