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|
/// `tt` crate defines a `TokenTree` data structure: this is the interface (both
/// input and output) of macros. It closely mirrors `proc_macro` crate's
/// `TokenTree`.
macro_rules! impl_froms {
($e:ident: $($v:ident), *) => {
$(
impl From<$v> for $e {
fn from(it: $v) -> $e {
$e::$v(it)
}
}
)*
}
}
use std::fmt;
use smol_str::SmolStr;
/// Represents identity of the token.
///
/// For hygiene purposes, we need to track which expanded tokens originated from
/// which source tokens. We do it by assigning an distinct identity to each
/// source token and making sure that identities are preserved during macro
/// expansion.
#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
pub struct TokenId(pub u32);
impl TokenId {
pub const fn unspecified() -> TokenId {
TokenId(!0)
}
}
#[derive(Debug, Clone)]
pub enum TokenTree {
Leaf(Leaf),
Subtree(Subtree),
}
impl_froms!(TokenTree: Leaf, Subtree);
#[derive(Debug, Clone)]
pub enum Leaf {
Literal(Literal),
Punct(Punct),
Ident(Ident),
}
impl_froms!(Leaf: Literal, Punct, Ident);
#[derive(Debug, Clone)]
pub struct Subtree {
pub delimiter: Delimiter,
pub token_trees: Vec<TokenTree>,
}
#[derive(Clone, Copy, Debug, PartialEq, Eq)]
pub enum Delimiter {
Parenthesis,
Brace,
Bracket,
None,
}
#[derive(Debug, Clone)]
pub struct Literal {
pub text: SmolStr,
}
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub struct Punct {
pub char: char,
pub spacing: Spacing,
}
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum Spacing {
Alone,
Joint,
}
#[derive(Debug, Clone)]
pub struct Ident {
pub text: SmolStr,
pub id: TokenId,
}
impl fmt::Display for TokenTree {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
match self {
TokenTree::Leaf(it) => fmt::Display::fmt(it, f),
TokenTree::Subtree(it) => fmt::Display::fmt(it, f),
}
}
}
impl fmt::Display for Subtree {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
let (l, r) = match self.delimiter {
Delimiter::Parenthesis => ("(", ")"),
Delimiter::Brace => ("{", "}"),
Delimiter::Bracket => ("[", "]"),
Delimiter::None => ("", ""),
};
f.write_str(l)?;
let mut needs_space = false;
for tt in self.token_trees.iter() {
if needs_space {
f.write_str(" ")?;
}
needs_space = true;
match tt {
TokenTree::Leaf(Leaf::Punct(p)) => {
needs_space = p.spacing == Spacing::Alone;
fmt::Display::fmt(p, f)?
}
tt => fmt::Display::fmt(tt, f)?,
}
}
f.write_str(r)?;
Ok(())
}
}
impl fmt::Display for Leaf {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
match self {
Leaf::Ident(it) => fmt::Display::fmt(it, f),
Leaf::Literal(it) => fmt::Display::fmt(it, f),
Leaf::Punct(it) => fmt::Display::fmt(it, f),
}
}
}
impl fmt::Display for Ident {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
fmt::Display::fmt(&self.text, f)
}
}
impl fmt::Display for Literal {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
fmt::Display::fmt(&self.text, f)
}
}
impl fmt::Display for Punct {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
fmt::Display::fmt(&self.char, f)
}
}
|
