julia

0275d1e9 - [JuliaLowering] Syntax versioning and macro-expansion improvements (#62221)

[JuliaLowering] Syntax versioning and macro-expansion improvements (#62221) Attach a new SyntaxContext to all syntax, which is shared between all nodes of the same macro expansion (with some exceptions for `escape`, etc.). ## New stuff Macros can now be syntax-version-aware, so the following is now possible: ```julia macro some_versioned_macro(arg) if syntax_version(__context__.macrocall) < v"1.14" # ... elseif syntax_version(arg) < v"1.14" # ... else # ... end end ``` ## Design TL;DR: Racket does it right. The following should be equivalent: | JL | Racket | | :----------- | :------- | | `SyntaxTree` | syntax object | | `Expr`/`Symbol`/etc | plain data | | `K"inert"`/`QuoteNode` | `'()` (quote) | | `K"quote"`/`:()` | `` `() `` (quasiquote) | | `K"$"` | `` ,() `` (unquote) | | `syntaxinert` (formerly inert_syntaxtree) | `` #'() `` (syntax) | | `syntaxquote` (new, no surface syntax yet) | `` #`() `` (quasisyntax) | | `syntaxunquote`(new, no surface syntax yet) | `` #,() `` (unsyntax) | This PR doesn't implement the full sets-of-scopes resolution, though it does make it easier to implement if we wanted that. No local macros makes it less important. We miss out on some cross-toplevel-thunk resolution, which I think is OK or desirable for now. After each macro expands, we want to apply a new scope layer to all new syntax (that wasn't passed as a macro argument at some point). Racket applies the new scope to all argument syntax, expands, then inverts that scope throughout the expansion. This PR expands, then applies the new layer to all syntax whose existing layer is not known to be "under" that new layer.