feat: expand composed error-set inline match arms

TODO.md

@@ -45,8 +45,8 @@ including runtime places and type-control updates without runtime reflection.
 arrays or tuples, including loop-filled producer storage and owned defaults.
 `inline for` expands constant ranges, fixed value/type arrays, heterogeneous
 value/type tuples and strings with immutable exact captures and compile-time-selected exits.
-final inline match arms expand nominal enums and tagged unions with static tags
-and exact by-value payloads, preserving runtime dispatch and scoped control flow.
+final inline match arms expand nominal enums, tagged unions and composed error sets
+with static tags and exact by-value payloads, preserving runtime dispatch and scoped control flow.
 general type-valued execution, metadata reflection and generic library acceptance remain open.
 the driver retains frontend storage and source provenance through
 `@source/compilation`, with compilation-wide AST node identities.
@@ -108,8 +108,9 @@ test discovery and FFI remain outside these completed slices.
   - [x] generated-record checkpoint: `struct_type!(layout, names, types, defaults)` builds ordinary records from constant fixed arrays or tuples with unique ASCII field names, concrete types and contextual optional defaults. literal heterogeneous collections, helper results and loop-filled producer arrays preserve exact types, owned defaults/copies and cached nominal identity through interpreter/native execution. `.auto` permits empty records; `.c` requires nonempty C-compatible fields and retains native field order/layout. malformed inputs, incomplete arrays, runtime dependencies, field/default validation, imported provenance, shared construction bounds and repeatable compilation retain diagnostics and isolation. metadata inspection, inline expansion, aggregate C calling conventions and storage-bearing defaults remain open.
   - [x] inline-loop checkpoint: `inline for` expands constant integer ranges, fixed arrays (including type-valued arrays) and strings into separately checked runtime bodies through interpreter/native execution. exact immutable captures, `usize` collection indices, narrow inclusive maxima, selected conditional/tagged-match bodies, static break/continue tail pruning, nested inline/ordinary loops, runtime returns/errors and scoped cleanup retain ordinary semantics. empty loops skip body elaboration; runtime-dependent inputs/transfers, pointer captures, storage-bearing escapes and shared expansion bounds retain diagnostics. imported producers/provenance and repeatable compilation are verified. heterogeneous tuples and inline-match syntax are covered below; metadata iteration remains open.
   - [x] heterogeneous inline-tuple checkpoint: `inline for` iterates constant tuples with exact per-field value/type captures and `usize` indices through interpreter/native execution. literal/helper/aliased tuples, erased generic inputs, nested tuple projections, generated storage, empty shapes, static exits, cleanup and aggregate copy isolation retain existing semantics. type-producing bodies borrow tuple places so later fields observe updates while saved copies remain isolated. runtime dependencies and storage-bearing escapes are rejected before iteration, including discarded captures and early exits; named records and ordinary tuple loops remain invalid. imported producers, nominal type leaves and repeatable compilation are verified. inline-match syntax is covered below; metadata collections remain open.
-  - [x] nominal inline-match checkpoint: final `inline |tag|:` enum arms and `inline |payload[, tag]|:` tagged-union arms expand remaining variants through interpreter/native execution. runtime subjects evaluate once; immutable static enum/tag captures specialize nested conditions, matches and generic calls while exact by-value scalar/aggregate/string/void payloads retain runtime semantics and copy isolation. statement/expression arms, ordinary loop/optional/match captures, scoped cleanup and return/break/continue work; type-producing bodies select generated storage and update outer type/value locals, including collection captures. invalid subjects/captures, redundant/nonfinal arms, ordinary pattern checks, imported provenance, shared expansion bounds and repeatable compilation retain diagnostics and ownership. composed error-set inline arms, pointer captures and metadata reflection remain open.
-  - [ ] remaining gate: general type-valued compile-time execution, composed error-set inline arms and metadata reflection (`typeinfo!` and metadata collections), broader constant materialization (including untagged unions and storage-bearing values), plus existing-library acceptance. required expression-valued control flow, compound updates, formatting parsing and imported C-binding support may interleave with later gates.
+  - [x] nominal inline-match checkpoint: final `inline |tag|:` enum arms and `inline |payload[, tag]|:` tagged-union arms expand remaining variants through interpreter/native execution. runtime subjects evaluate once; immutable static enum/tag captures specialize nested conditions, matches and generic calls while exact by-value scalar/aggregate/string/void payloads retain runtime semantics and copy isolation. statement/expression arms, ordinary loop/optional/match captures, scoped cleanup and return/break/continue work; type-producing bodies select generated storage and update outer type/value locals, including collection captures. invalid subjects/captures, redundant/nonfinal arms, ordinary pattern checks, imported provenance, shared expansion bounds and repeatable compilation retain diagnostics and ownership. composed error-set inline arms are covered below; pointer captures and metadata reflection remain open.
+  - [x] composed inline-match checkpoint: composed error sets expand remaining variants through interpreter/native execution, including nested/repeated/aliased enum, tagged-union and named struct members. all-void sets use one static tag capture; payload-bearing sets use exact immutable by-value payloads and optional static tags, including void members. catch captures, nested inline tag matches, generic calls, owned aggregate copies, deferred cleanup and error returns retain ordinary semantics. constant inputs and type-producing bodies select generated storage with cached nominal identity; struct variant names remain identifiers in generated constants rather than embedding declarations. invalid compositions/captures, narrow payload types, redundant arms, imported dependencies and repeatable compilation retain diagnostics and ownership. member discovery shares the type-control bound; pointer captures and metadata reflection remain open.
+  - [ ] remaining gate: general type-valued compile-time execution and metadata reflection (`typeinfo!` and metadata collections), broader constant materialization (including untagged unions and storage-bearing values), plus existing-library acceptance. required expression-valued control flow, compound updates, formatting parsing and imported C-binding support may interleave with later gates.
 - [ ] remaining source constructs: expression-valued control flow and `yield`, compound updates and multiline strings. examples: `source/parser/parse.hon`, `source/llvm/runtime.hon`.
 - [ ] standard-library milestone: compile/run a multi-package program exercising existing allocation and IO, including error cleanup; no replacement miniature standard library.
 - [ ] native driver integration: required C ABI declarations, `process.Init` startup arguments/IO, actual CLI exit statuses, file loading, temporary files and spawning Clang. Honey-generated programs currently accept only parameterless `main` and print its result; Bro's bootstrap startup support is not Honey backend support.