Upgrade bux-lsp to 0.2.0 with a richer lightweight symbol index:
func signatures, typed let/var/const, struct/enum/interface/type/module.
Skip comments and strings while scanning. Hover shows markdown Bux
code fences; definition resolves in-file and across workspace .bux files;
documentSymbol provides outline. Fix responses writing to stdout (stdin
was a broken pipe). didChange refreshes symbols; diagnostics still run
via buxc on open/save.
Sessions 10–12 from QUALITY_PLAN:
- Pattern payload bindings (Some(value) => value) in bootstrap and selfhost
- Empty-param closures via || (tkPipePipe) with loop/return bodies
- Expression-form match: let x = match …; newline before arms
- f"…" string interpolation desugared to String_Concat + conversions
- Lexer preserves \{ \} for literal braces in f-strings
- Bootstrap fix: f"plain" strips the f prefix after escape processing
- Examples: pattern_matching, closure_control, match_let, string_interp
Selfhost-loop remains binary-identical; all examples and error goldens pass.
Lower match to if-else for literals, ranges, enum tags, and wildcards.
Fix bootstrap literal arms that always matched; port real arm AST/parser
and Lcx_LowerMatch to selfhost with last-expression return. Expand
pattern_matching example and add parse/use-after-move/double-mut golden
diagnostics. Selfhost-loop remains binary-identical.
Add int-specialized higher-order Iter helpers that accept fat function
pointers, plus an example using named funcs and capturing closures.
Fix selfhost C backend pointer field access and Array Push indexing.
Introduce fat function pointers (BuxFn {code, env}) so capturing closures
are heap-allocated per value in both bootstrap and selfhost. Expand
Array/Map/Set/String/Test/Result APIs, add proper tuple codegen and
error snippets with multi-char underlines, golden diagnostic tests, and
LSP diagnostics via buxc check.