contextual void construction

TODO.md

@@ -535,10 +535,26 @@
     (`match get()`) is a pre-existing gap (assign to a variable first, as the spec examples do);
     the rvalue pointer-capture guard is defensive for when that lands
 
-22.6. (`// ponytail:` follow-ups): contextual void construction (`e Event = .quit`) needs
-    enum-literal→union coercion. Separately, a **call expression directly as a match subject**
-    (`match get()`) is a pre-existing gap (assign to a variable first, as the spec examples do);
-    the rvalue pointer-capture guard is defensive for when that lands
+22.6. contextual void construction + call-as-match-subject (implemented; see below)
+  - **contextual void construction**: a bare enum literal in a tagged-union context constructs a
+    void-payload variant — `e Event = .quit` (and any expected-union position: `=`, return, call
+    argument) coerces `.quit` to the union, equivalent to `Event{ quit }`. Build-pass only: the
+    `.Enum_Literal` case, given a tagged-union `expected`, looks the variant up and emits the
+    tag-only union `.Struct` HIR for a void variant. A payload variant via a bare `.variant`
+    ("needs a payload") and an unknown variant are diagnosed; the payload-carrying contextual form
+    `.variant{...}` stays deferred to milestone 23 (error channel)
+  - **call expression directly as a match subject**: `match get() { … }` now specializes the call.
+    Root cause was that the inference/spec-request walker `infer_statements` had no `.Match` case,
+    so a match's subject and arm bodies were never visited and their calls never got a
+    specialization (`find_spec` → "could not resolve specialization"). Added a `.Match` case that
+    infers the subject and recurses into arm bodies (with the capture local typed from the variant
+    payload, mirroring the `.For`/unwrap-`.If` handling). This also covers value-`match` and calls
+    inside arm bodies. As a side effect the rvalue pointer-capture guard from 22.5 is now reachable
+    (`match make_box() { .v |@p|: … }` correctly errors "requires an addressable subject")
+  - checker-only; no parser/AST/HIR/IR/lowering/codegen change
+  - deferred: payload-carrying contextual construction (`.variant{…}`, milestone 23); a
+    `yield call()` inside a value-block/value-match arm still misses its spec (`infer_statements`
+    has no `.Yield` case either — a separate pre-existing gap)
 
 23. error types (see below)