erlang: -module/M:F cross-module calls (+10 tests)

lib/erlang/runtime.sx

@@ -742,3 +742,75 @@
     (er-proc-set! target :exit-result nil)
     (er-proc-set! target :continuation nil)
     (er-propagate-exit! target reason)))
+
+;; ── module registry ─────────────────────────────────────────────
+;; Global mutable dict from module name -> module env (which itself
+;; binds each function name to a fun value capturing the same env, so
+;; sibling functions can call each other recursively).
+(define er-modules (list {}))
+(define er-modules-get (fn () (nth er-modules 0)))
+(define er-modules-reset! (fn () (set-nth! er-modules 0 {})))
+
+;; Load an Erlang module declaration. Source must start with
+;; `-module(Name).` and contain function definitions. Functions
+;; sharing a name (different arities) get their clauses concatenated
+;; into a single fun value — `er-apply-fun-clauses` already filters
+;; by arity, so multi-arity dispatch falls out for free.
+(define
+  erlang-load-module
+  (fn
+    (src)
+    (let
+      ((module-ast (er-parse-module src)))
+      (let
+        ((mod-name (get module-ast :name))
+          (functions (get module-ast :functions))
+          (mod-env (er-env-new))
+          (by-name {}))
+        (for-each
+          (fn
+            (i)
+            (let
+              ((f (nth functions i)))
+              (let
+                ((name (get f :name)) (clauses (get f :clauses)))
+                (if
+                  (dict-has? by-name name)
+                  (let
+                    ((existing (get by-name name)))
+                    (for-each
+                      (fn (j) (append! existing (nth clauses j)))
+                      (range 0 (len clauses))))
+                  (let
+                    ((init (list)))
+                    (for-each
+                      (fn (j) (append! init (nth clauses j)))
+                      (range 0 (len clauses)))
+                    (dict-set! by-name name init))))))
+          (range 0 (len functions)))
+        (for-each
+          (fn
+            (k)
+            (let
+              ((all-clauses (get by-name k)))
+              (er-env-bind! mod-env k (er-mk-fun all-clauses mod-env))))
+          (keys by-name))
+        (dict-set! (er-modules-get) mod-name mod-env)
+        (er-mk-atom mod-name)))))
+
+(define
+  er-apply-user-module
+  (fn
+    (mod name vs)
+    (let
+      ((mod-env (get (er-modules-get) mod)))
+      (if
+        (not (dict-has? mod-env name))
+        (raise
+          (er-mk-error-marker
+            (er-mk-tuple
+              (list
+                (er-mk-atom "undef")
+                (er-mk-atom mod)
+                (er-mk-atom name)))))
+        (er-apply-fun (get mod-env name) vs)))))