const_fn 0.4.3

An attribute for easy generation of const functions with conditional compilations.
Documentation 
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use proc_macro::{Ident, Literal, TokenStream, TokenTree};
use std::iter;

pub(crate) trait ToTokens {
    fn to_tokens(&self, tokens: &mut TokenStream);

    fn to_token_stream(&self) -> TokenStream {
        let mut tokens = TokenStream::new();
        self.to_tokens(&mut tokens);
        tokens
    }
}

impl ToTokens for Ident {
    fn to_tokens(&self, tokens: &mut TokenStream) {
        tokens.extend(iter::once(TokenTree::Ident(self.clone())));
    }
}

impl ToTokens for Literal {
    fn to_tokens(&self, tokens: &mut TokenStream) {
        tokens.extend(iter::once(TokenTree::Literal(self.clone())));
    }
}

impl ToTokens for TokenTree {
    fn to_tokens(&self, tokens: &mut TokenStream) {
        tokens.extend(iter::once(self.clone()));
    }
}

impl ToTokens for TokenStream {
    fn to_tokens(&self, tokens: &mut TokenStream) {
        tokens.extend(self.clone());
    }
}