diff --git a/compiler/rustc_parse/src/parser/attr_wrapper.rs b/compiler/rustc_parse/src/parser/attr_wrapper.rs index 8bd615e6d791..c85d0bd05cbd 100644 --- a/compiler/rustc_parse/src/parser/attr_wrapper.rs +++ b/compiler/rustc_parse/src/parser/attr_wrapper.rs @@ -136,8 +136,9 @@ impl ToAttrTokenStream for LazyAttrTokenStreamImpl { node_replacements.array_windows() { assert!( - node_range.0.end <= next_node_range.0.start, - "Node ranges should be disjoint: ({:?}, {:?}) ({:?}, {:?})", + node_range.0.end <= next_node_range.0.start + || node_range.0.end >= next_node_range.0.end, + "Node ranges should be disjoint or nested: ({:?}, {:?}) ({:?}, {:?})", node_range, tokens, next_node_range, @@ -145,8 +146,20 @@ impl ToAttrTokenStream for LazyAttrTokenStreamImpl { ); } - // Process the replace ranges. - for (node_range, target) in node_replacements.into_iter() { + // Process the replace ranges, starting from the highest start + // position and working our way back. If have tokens like: + // + // `#[cfg(FALSE)] struct Foo { #[cfg(FALSE)] field: bool }` + // + // Then we will generate replace ranges for both + // the `#[cfg(FALSE)] field: bool` and the entire + // `#[cfg(FALSE)] struct Foo { #[cfg(FALSE)] field: bool }` + // + // By starting processing from the replace range with the greatest + // start position, we ensure that any (outer) replace range which + // encloses another (inner) replace range will fully overwrite the + // inner range's replacement. + for (node_range, target) in node_replacements.into_iter().rev() { assert!( !node_range.0.is_empty(), "Cannot replace an empty node range: {:?}", @@ -383,9 +396,10 @@ impl<'a> Parser<'a> { // from `ParserRange` form to `NodeRange` form. We will perform the actual // replacement only when we convert the `LazyAttrTokenStream` to an // `AttrTokenStream`. - self.capture_state - .parser_replacements - .drain(parser_replacements_start..parser_replacements_end) + self.capture_state.parser_replacements + [parser_replacements_start..parser_replacements_end] + .iter() + .cloned() .chain(inner_attr_parser_replacements) .map(|(parser_range, data)| { (NodeRange::new(parser_range, collect_pos.start_pos), data)