erlang: verify hot-reload call dispatch semantics (+6 eval tests)

lib/erlang/tests/eval.sx

@@ -1252,6 +1252,63 @@
 (er-eval-test "code:is_loaded badarg"
   (nm (ev "try code:is_loaded(123) catch error:badarg -> ok end")) "ok")
 
+
+;; ── Phase 7: hot-reload call dispatch semantics ──────────────────
+;; Cross-module M:F() calls always hit the CURRENT version;
+;; local F() calls inside a module body resolve through the env
+;; the function closed over (i.e. the version it was loaded with).
+
+(er-modules-reset!)
+
+;; M:F always hits current
+(er-eval-test "cross-mod after reload v2"
+  (ev "code:load_binary(hr1, \"hr1\", \"-module(hr1). f() -> 1.\"),
+       code:load_binary(hr1, \"hr1\", \"-module(hr1). f() -> 2.\"),
+       hr1:f()")
+  2)
+
+;; Local call inside reloaded module body resolves via fresh mod-env
+;; (a() does a local b(); b() got upgraded too)
+(er-eval-test "local call inside reloaded module body"
+  (ev "code:load_binary(hr2, \"hr2\", \"-module(hr2). a() -> b(). b() -> 1.\"),
+       code:load_binary(hr2, \"hr2\", \"-module(hr2). a() -> b(). b() -> 99.\"),
+       hr2:a()")
+  99)
+
+;; Fun captured BEFORE reload, with local-call body, keeps v1 semantics
+(er-eval-test "captured fun keeps closed-over env (local call)"
+  (ev "code:load_binary(hr3, \"hr3\", \"-module(hr3). get_fn() -> fun () -> b() end. b() -> 1.\"),
+       Fn = hr3:get_fn(),
+       code:load_binary(hr3, \"hr3\", \"-module(hr3). get_fn() -> fun () -> b() end. b() -> 99.\"),
+       Fn()")
+  1)
+
+;; Fun captured BEFORE reload, with CROSS-mod body, sees v2's current
+(er-eval-test "captured fun follows cross-mod to current"
+  (ev "code:load_binary(hr4, \"hr4\", \"-module(hr4). get_xref() -> fun () -> hr4:b() end. b() -> 1.\"),
+       Fn = hr4:get_xref(),
+       code:load_binary(hr4, \"hr4\", \"-module(hr4). get_xref() -> fun () -> hr4:b() end. b() -> 99.\"),
+       Fn()")
+  99)
+
+;; Two captured funs from two different vintages
+(er-eval-test "two funs from two vintages stay independent"
+  (ev "code:load_binary(hr5, \"hr5\", \"-module(hr5). gf() -> fun () -> v() end. v() -> 10.\"),
+       F1 = hr5:gf(),
+       code:load_binary(hr5, \"hr5\", \"-module(hr5). gf() -> fun () -> v() end. v() -> 20.\"),
+       F2 = hr5:gf(),
+       F1() + F2()")
+  30)
+
+;; Version slot bumps correctly when a captured fun stays alive
+(er-eval-test "version bumps despite captured funs"
+  (ev "code:load_binary(hr6, \"hr6\", \"-module(hr6). gf() -> fun () -> v() end. v() -> 1.\"),
+       _Pinned = hr6:gf(),
+       code:load_binary(hr6, \"hr6\", \"-module(hr6). gf() -> fun () -> v() end. v() -> 2.\"),
+       code:load_binary(hr6, \"hr6\", \"-module(hr6). gf() -> fun () -> v() end. v() -> 3.\"),
+       hr6:v()")
+  3)
+
 (define
   er-eval-test-summary
   (str "eval " er-eval-test-pass "/" er-eval-test-count))