go: types.sx — func-decl + stmt-level dispatch + 7 tests [nothing]

Phase 3 cont. Adds:

  * go-check-func-decl — binds the function in the outer ctx (recursive
    self-reference will work once call-checking lands), extends the
    body's ctx with each :field param group via go-ctx-extend-field
    (the binding-group shape's *third* consumer in the type checker;
    five total across parser+typer when counted with struct fields,
    var-decls, const-decls, func params, method receivers).
  * go-check-stmt — dispatches on :return / :assign / :var-decl /
    :const-decl / :short-decl / :type-decl / :block; falls back to
    go-synth for expression statements.
  * go-check-block — threads ctx through stmts so that decls inside
    the block extend the ctx for subsequent stmts.
  * go-check-return-list — each return expr assignable to the
    corresponding declared result type; mismatch counts are typed.
  * go-check-assign / go-check-assign-pairs — RHS assignable to LHS
    synthesised type, count mismatch typed.
  * Helpers: go-decl-params-to-ty-list (flattens :field NAMES TYPE to
    a flat list of N types), go-extend-with-params (folds extend-field
    over a param-group list), go-repeat-ty.

Coverage tests:
  func empty() {}                                          → ok
  func add(x, y int) int { return x + y }                  → ok
  func bad() int { return "hi" }                           → typed error
  func sig(x int) int                                      → signature-only binds
  func sumsq(x, y int) int { return x*x + y*y }            → params visible
  func two() int { var x int = 1; var y int = 2;           → nested decl
                   return x + y }
  func g() int { var x int; x = 5; return x }              → assign verified

types 47/47, total 352/352.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

plans/go-on-sx.md

@@ -234,8 +234,11 @@ Progress-log line → push `origin/loops/go`.
       the extended context or a `:type-error`. Untyped synthesized types
       get their default-type (`untyped-int → int`, `untyped-float →
       float64`, etc.) when bound in inferred-type decls.
-- [ ] Function declaration: extend ctx with params via `:field` group,
-      check body, verify return-list types match signature.
+- [x] Function declaration: extends ctx with each `:field` param group,
+      checks block body (decls thread through, returns verify against
+      signature, assignments verify RHS assignable to LHS). The function
+      itself is bound in the body's ctx so recursion will work once
+      call-checking lands. Signature-only (no body) just binds.
 - [ ] Call type-checking (synth callee, check args against param types,
       synth result).
 - [ ] Composite type element checking (slice / map / chan).
@@ -243,7 +246,7 @@ Progress-log line → push `origin/loops/go`.
 - [ ] Short variable declaration `:=` (synth RHS into LHS bindings).
 - Defer: generics (Phase 7), full conversion rules, type assertions,
   type switches.
-- **Acceptance:** types/ suite at 60+ tests. Current: 40/40. Chisel note
+- **Acceptance:** types/ suite at 60+ tests. Current: 47/47. Chisel note
   `shapes-static-types-bidirectional` — sister-plan design diary is the
   cross-language record.
 
@@ -544,6 +547,19 @@ Minimal repro: see `lib/go/lex.sx#gl-oct-digit?` and `#gl-match-op`.
 
 _Newest first. Append one dated entry per commit._
 
+- 2026-05-27 — Phase 3 cont.: function-declaration checking +
+  statement-level dispatch. `go-check-func-decl` binds the function in
+  the outer ctx (so the body can see itself), extends the body's ctx
+  with each `:field` param group via `go-ctx-extend-field` (the
+  binding-group shape's third consumer in the type checker — now
+  five total across parser+typer combined), then runs `go-check-block`
+  through every statement. `go-check-stmt` dispatches on `:return`,
+  `:assign`, `:var-decl`/`:const-decl`/`:short-decl`/`:type-decl`,
+  `:block`, falling back to `go-synth` for expression statements.
+  Return-list and assign-pair count mismatches are typed errors. +7
+  tests, types 47/47, total 352/352. `[nothing]` — pure Go-side
+  composition; the kit-relevant insights are already in the sister-
+  plan diary.
 - 2026-05-27 — Phase 3 cont.: declaration checking — `var`/`const`/`type`
   + short-decl `:=`. `go-check-decl` returns the extended context (or a
   `:type-error`). New helpers: `go-default-type` (untyped-int → int,