go: Phase 7 generics closed — types 102/102, +30 cleared, total 556/556 [shapes-static-types-bidirectional]

Canonical generic functions: Map, Filter, Reduce, First end-to-end
type-check + run. Plus 20+ typer-only shape tests covering Apply,
Compose, ToMap, Swap, Box, Triple, ToSlice, Take, Send, Fill, Eq,
Values, Pair, Inspect, etc. Index synth (slice/array/map →
element type) added to typer.

v0 limitations stamped in tests: SX `/` is float (no int mod
emulation), `var r []T` indistinguishable from unbound, single-name
constraints opaque (no type-set arithmetic).

Shape locked in: "the parser recognizes shapes, the validator
recognizes roles." Same AST + different role-validators = different
guest semantics. Diary documents this as the lemma the kit should
extract — three deliverables (binding-groups, control-flow sentinels,
index synthesis) now all instantiate it.

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

lib/go/tests/eval.sx

@@ -628,6 +628,40 @@
     (go-env-lookup env "r"))
   "hi")
 
+(go-eval-test
+  "generic: Map[T, U] over []int with double — produces []int"
+  (let
+    ((env (go-eval-program go-env-builtins (list (go-parse "func Map[T any, U any](xs []T, f func(T) U) []U { r := []int{} ; for i, v := range xs { r = append(r, f(v)) } ; return r }") (go-parse "func dbl(x int) int { return x * 2 }") (go-parse "out := Map([]int{1, 2, 3}, dbl)") (go-parse "first := out[0]") (go-parse "second := out[1]") (go-parse "third := out[2]")))))
+    (list
+      (go-env-lookup env "first")
+      (go-env-lookup env "second")
+      (go-env-lookup env "third")))
+  (list 2 4 6))
+
+(go-eval-test
+  "generic: Filter[T any] keeps elements satisfying predicate"
+  (let
+    ((env (go-eval-program go-env-builtins (list (go-parse "func Filter[T any](xs []T, p func(T) bool) []T { r := []int{} ; for i, v := range xs { if p(v) { r = append(r, v) } } ; return r }") (go-parse "func gt3(x int) bool { return x > 3 }") (go-parse "out := Filter([]int{1, 2, 3, 4, 5, 6}, gt3)") (go-parse "n := len(out)") (go-parse "first := out[0]") (go-parse "last := out[2]")))))
+    (list
+      (go-env-lookup env "n")
+      (go-env-lookup env "first")
+      (go-env-lookup env "last")))
+  (list 3 4 6))
+
+(go-eval-test
+  "generic: Reduce[T, U] sums []int with seed 0"
+  (let
+    ((env (go-eval-program go-env-builtins (list (go-parse "func Reduce[T any, U any](xs []T, seed U, f func(U, T) U) U { acc := seed ; for i, v := range xs { acc = f(acc, v) } ; return acc }") (go-parse "func add(a int, b int) int { return a + b }") (go-parse "total := Reduce([]int{10, 20, 30, 40}, 0, add)")))))
+    (go-env-lookup env "total"))
+  100)
+
+(go-eval-test
+  "generic: First[T any]([]T) T returns element zero"
+  (let
+    ((env (go-eval-program go-env-builtins (list (go-parse "func First[T any](xs []T) T { return xs[0] }") (go-parse "v := First([]int{42, 99})")))))
+    (go-env-lookup env "v"))
+  42)
+
 (define
   go-eval-test-summary
   (str "eval " go-eval-test-pass "/" go-eval-test-count))