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|
/// This module parses a raw `tt::TokenStream` into macro-by-example token
/// stream. This is a *mostly* identify function, expect for handling of
/// `$var:tt_kind` and `$(repeat),*` constructs.
use crate::ParseError;
use crate::tt_cursor::TtCursor;
pub(crate) fn parse(tt: &tt::Subtree) -> Result<crate::MacroRules, ParseError> {
let mut parser = TtCursor::new(tt);
let mut rules = Vec::new();
while !parser.is_eof() {
rules.push(parse_rule(&mut parser)?);
if let Err(e) = parser.expect_char(';') {
if !parser.is_eof() {
return Err(e);
}
break;
}
}
Ok(crate::MacroRules { rules })
}
fn parse_rule(p: &mut TtCursor) -> Result<crate::Rule, ParseError> {
let lhs = parse_subtree(p.eat_subtree()?, false)?;
p.expect_char('=')?;
p.expect_char('>')?;
let mut rhs = parse_subtree(p.eat_subtree()?, true)?;
rhs.delimiter = crate::Delimiter::None;
Ok(crate::Rule { lhs, rhs })
}
fn is_boolean_literal(lit: Option<&tt::TokenTree>) -> bool {
if let Some(tt::TokenTree::Leaf(tt::Leaf::Literal(lit))) = lit {
if lit.text == "true" || lit.text == "false" {
return true;
}
}
false
}
fn parse_subtree(tt: &tt::Subtree, transcriber: bool) -> Result<crate::Subtree, ParseError> {
let mut token_trees = Vec::new();
let mut p = TtCursor::new(tt);
while let Some(tt) = p.eat() {
let child: crate::TokenTree = match tt {
tt::TokenTree::Leaf(leaf) => match leaf {
tt::Leaf::Punct(tt::Punct { char: '$', spacing }) => {
// mbe var can be an ident or keyword, including `true` and `false`
if p.at_ident().is_some() || is_boolean_literal(p.current()) {
crate::Leaf::from(parse_var(&mut p, transcriber)?).into()
} else if let Some(tt::TokenTree::Subtree(_)) = p.current() {
parse_repeat(&mut p, transcriber)?.into()
} else {
// Treat it as normal punct
crate::Leaf::from(tt::Punct { char: '$', spacing: *spacing }).into()
}
}
tt::Leaf::Punct(punct) => crate::Leaf::from(*punct).into(),
tt::Leaf::Ident(tt::Ident { text, id: _ }) => {
crate::Leaf::from(crate::Ident { text: text.clone() }).into()
}
tt::Leaf::Literal(tt::Literal { text }) => {
crate::Leaf::from(crate::Literal { text: text.clone() }).into()
}
},
tt::TokenTree::Subtree(subtree) => parse_subtree(&subtree, transcriber)?.into(),
};
token_trees.push(child);
}
Ok(crate::Subtree { token_trees, delimiter: tt.delimiter })
}
fn parse_var(p: &mut TtCursor, transcriber: bool) -> Result<crate::Var, ParseError> {
let text = {
if is_boolean_literal(p.current()) {
let lit = p.eat_literal().unwrap();
lit.text.clone()
} else {
let ident = p.eat_ident().unwrap();
ident.text.clone()
}
};
let kind = if !transcriber && p.at_char(':') {
p.bump();
if let Some(ident) = p.eat_ident() {
Some(ident.text.clone())
} else {
p.rev_bump();
None
}
} else {
None
};
Ok(crate::Var { text, kind })
}
fn mk_repeat(
rep: char,
subtree: crate::Subtree,
separator: Option<crate::Separator>,
) -> Result<crate::Repeat, ParseError> {
let kind = match rep {
'*' => crate::RepeatKind::ZeroOrMore,
'+' => crate::RepeatKind::OneOrMore,
'?' => crate::RepeatKind::ZeroOrOne,
_ => return Err(ParseError::Expected(String::from("repeat"))),
};
Ok(crate::Repeat { subtree, kind, separator })
}
fn parse_repeat(p: &mut TtCursor, transcriber: bool) -> Result<crate::Repeat, ParseError> {
let subtree = p.eat_subtree()?;
let mut subtree = parse_subtree(subtree, transcriber)?;
subtree.delimiter = crate::Delimiter::None;
if let Some(rep) = p.at_punct() {
match rep.char {
'*' | '+' | '?' => {
p.bump();
return mk_repeat(rep.char, subtree, None);
}
_ => {}
}
}
let sep = p.eat_seperator().ok_or(ParseError::Expected(String::from("separator")))?;
let rep = p.eat_punct().ok_or(ParseError::Expected(String::from("repeat")))?;
mk_repeat(rep.char, subtree, Some(sep))
}
#[cfg(test)]
mod tests {
use ra_syntax::{ast, AstNode};
use super::*;
use crate::ast_to_token_tree;
#[test]
fn test_invalid_parse() {
expect_err("invalid", "subtree");
is_valid("($i:ident) => ()");
is_valid("($($i:ident)*) => ($_)");
is_valid("($($true:ident)*) => ($true)");
is_valid("($($false:ident)*) => ($false)");
expect_err("$i:ident => ()", "subtree");
expect_err("($i:ident) ()", "`=`");
expect_err("($($i:ident)_) => ()", "repeat");
}
fn expect_err(macro_body: &str, expected: &str) {
assert_eq!(
create_rules(&format_macro(macro_body)),
Err(ParseError::Expected(String::from(expected)))
);
}
fn is_valid(macro_body: &str) {
assert!(create_rules(&format_macro(macro_body)).is_ok());
}
fn format_macro(macro_body: &str) -> String {
format!(
"
macro_rules! foo {{
{}
}}
",
macro_body
)
}
fn create_rules(macro_definition: &str) -> Result<crate::MacroRules, ParseError> {
let source_file = ast::SourceFile::parse(macro_definition);
let macro_definition =
source_file.syntax().descendants().find_map(ast::MacroCall::cast).unwrap();
let (definition_tt, _) = ast_to_token_tree(macro_definition.token_tree().unwrap()).unwrap();
parse(&definition_tt)
}
}
|
