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Diffstat (limited to 'crates/mbe/src/expander/transcriber.rs')
| -rw-r--r-- | crates/mbe/src/expander/transcriber.rs | 42 |
1 files changed, 41 insertions, 1 deletions
diff --git a/crates/mbe/src/expander/transcriber.rs b/crates/mbe/src/expander/transcriber.rs index 6161af1858..cdac2f1e3b 100644 --- a/crates/mbe/src/expander/transcriber.rs +++ b/crates/mbe/src/expander/transcriber.rs @@ -400,7 +400,8 @@ fn push_fragment(buf: &mut Vec<tt::TokenTree>, fragment: Fragment) { } buf.push(tt.into()) } - Fragment::Tokens(tt) | Fragment::Expr(tt) => buf.push(tt), + Fragment::Path(tt::TokenTree::Subtree(tt)) => fix_up_and_push_path_tt(buf, tt), + Fragment::Tokens(tt) | Fragment::Expr(tt) | Fragment::Path(tt) => buf.push(tt), } } @@ -411,6 +412,45 @@ fn push_subtree(buf: &mut Vec<tt::TokenTree>, tt: tt::Subtree) { } } +/// Inserts the path separator `::` between an identifier and its following generic +/// argument list, and then pushes into the buffer. See [`Fragment::Path`] for why +/// we need this fixup. +fn fix_up_and_push_path_tt(buf: &mut Vec<tt::TokenTree>, subtree: tt::Subtree) { + stdx::always!(matches!(subtree.delimiter.kind, tt::DelimiterKind::Invisible)); + let mut prev_was_ident = false; + // Note that we only need to fix up the top-level `TokenTree`s because the + // context of the paths in the descendant `Subtree`s won't be changed by the + // mbe transcription. + for tt in subtree.token_trees { + if prev_was_ident { + // Pedantically, `(T) -> U` in `FnOnce(T) -> U` is treated as a generic + // argument list and thus needs `::` between it and `FnOnce`. However in + // today's Rust this type of path *semantically* cannot appear as a + // top-level expression-context path, so we can safely ignore it. + if let tt::TokenTree::Leaf(tt::Leaf::Punct(tt::Punct { char: '<', .. })) = tt { + buf.push( + tt::Leaf::Punct(tt::Punct { + char: ':', + spacing: tt::Spacing::Joint, + span: tt::Span::unspecified(), + }) + .into(), + ); + buf.push( + tt::Leaf::Punct(tt::Punct { + char: ':', + spacing: tt::Spacing::Alone, + span: tt::Span::unspecified(), + }) + .into(), + ); + } + } + prev_was_ident = matches!(tt, tt::TokenTree::Leaf(tt::Leaf::Ident(_))); + buf.push(tt); + } +} + /// Handles `${count(t, depth)}`. `our_depth` is the recursion depth and `count_depth` is the depth /// defined by the metavar expression. fn count( |