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use proc_macro2::TokenStream;
use quote::ToTokens;
use syn::token;
pub enum Fragment {
/// Tokens that can be used as an expression.
Expr(TokenStream),
/// Tokens that can be used inside a block. The surrounding curly braces are
/// not part of these tokens.
Block(TokenStream),
}
macro_rules! quote_expr {
($($tt:tt)*) => {
$crate::fragment::Fragment::Expr(quote!($($tt)*))
}
}
macro_rules! quote_block {
($($tt:tt)*) => {
$crate::fragment::Fragment::Block(quote!($($tt)*))
}
}
/// Interpolate a fragment in place of an expression. This involves surrounding
/// Block fragments in curly braces.
pub struct Expr(pub Fragment);
impl ToTokens for Expr {
fn to_tokens(&self, out: &mut TokenStream) {
match &self.0 {
Fragment::Expr(expr) => expr.to_tokens(out),
Fragment::Block(block) => {
token::Brace::default().surround(out, |out| block.to_tokens(out));
}
}
}
}
/// Interpolate a fragment as the statements of a block.
pub struct Stmts(pub Fragment);
impl ToTokens for Stmts {
fn to_tokens(&self, out: &mut TokenStream) {
match &self.0 {
Fragment::Expr(expr) => expr.to_tokens(out),
Fragment::Block(block) => block.to_tokens(out),
}
}
}
/// Interpolate a fragment as the value part of a `match` expression. This
/// involves putting a comma after expressions and curly braces around blocks.
pub struct Match(pub Fragment);
impl ToTokens for Match {
fn to_tokens(&self, out: &mut TokenStream) {
match &self.0 {
Fragment::Expr(expr) => {
expr.to_tokens(out);
<Token![,]>::default().to_tokens(out);
}
Fragment::Block(block) => {
token::Brace::default().surround(out, |out| block.to_tokens(out));
}
}
}
}
impl AsRef<TokenStream> for Fragment {
fn as_ref(&self) -> &TokenStream {
match self {
Fragment::Expr(expr) => expr,
Fragment::Block(block) => block,
}
}
}
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