Unnamed repository; edit this file 'description' to name the repository.
Diffstat (limited to 'crates/mbe/src/parser.rs')
| -rw-r--r-- | crates/mbe/src/parser.rs | 32 |
1 files changed, 28 insertions, 4 deletions
diff --git a/crates/mbe/src/parser.rs b/crates/mbe/src/parser.rs index 0fbf832b06..7a143e7466 100644 --- a/crates/mbe/src/parser.rs +++ b/crates/mbe/src/parser.rs @@ -52,7 +52,8 @@ impl MetaTemplate { pub(crate) enum Op { Var { name: SmolStr, kind: Option<MetaVarKind>, id: tt::TokenId }, Ignore { name: SmolStr, id: tt::TokenId }, - Index { depth: u32 }, + Index { depth: usize }, + Count { name: SmolStr, depth: Option<usize> }, Repeat { tokens: MetaTemplate, kind: RepeatKind, separator: Option<Separator> }, Subtree { tokens: MetaTemplate, delimiter: tt::Delimiter }, Literal(tt::Literal), @@ -295,9 +296,13 @@ fn parse_metavar_expr(src: &mut TtIter<'_>) -> Result<Op, ()> { let ident = args.expect_ident()?; Op::Ignore { name: ident.text.clone(), id: ident.span } } - "index" => { - let depth = if args.len() == 0 { 0 } else { args.expect_u32_literal()? }; - Op::Index { depth } + "index" => Op::Index { depth: parse_depth(&mut args)? }, + "count" => { + let ident = args.expect_ident()?; + // `${count(t)}` and `${count(t,)}` have different meanings. Not sure if this is a bug + // but that's how it's implemented in rustc as of this writing. See rust-lang/rust#111904. + let depth = if try_eat_comma(&mut args) { Some(parse_depth(&mut args)?) } else { None }; + Op::Count { name: ident.text.clone(), depth } } _ => return Err(()), }; @@ -308,3 +313,22 @@ fn parse_metavar_expr(src: &mut TtIter<'_>) -> Result<Op, ()> { Ok(op) } + +fn parse_depth(src: &mut TtIter<'_>) -> Result<usize, ()> { + if src.len() == 0 { + Ok(0) + } else if let tt::Leaf::Literal(lit) = src.expect_literal()? { + // Suffixes are not allowed. + lit.text.parse().map_err(|_| ()) + } else { + Err(()) + } +} + +fn try_eat_comma(src: &mut TtIter<'_>) -> bool { + if let Some(tt::TokenTree::Leaf(tt::Leaf::Punct(tt::Punct { char: ',', .. }))) = src.peek_n(0) { + let _ = src.next(); + return true; + } + false +} |