Add code generation for bbml

hkmc2/shared/src/main/scala/hkmc2/semantics/Elaborator.scala

@@ -170,9 +170,15 @@ extends Importer:
           N
       case N =>
         N
-    case S(_: TopLevelSymbol) => ctx.get(nme.name).flatMap(_.symbol) match
-      case S(sym: FieldSymbol) => S(sym)
-      case _ => N
+    case S(_: TopLevelSymbol) =>
+      def rec(ctx: Ctx): Opt[Ctx] = // * To avoid shadowing if users write `globalThis.somefield`
+        if ctx.getOuter.filter(_.isInstanceOf[TopLevelSymbol]).nonEmpty then S(ctx)
+        else ctx.parent match
+          case S(p) => rec(p)
+          case N => N
+      rec(ctx).flatMap(_.get(nme.name)).flatMap(_.symbol) match
+        case S(sym: FieldSymbol) => S(sym)
+        case _ => N
     case _ => N
 
   def cls(tree: Tree, inAppPrefix: Bool): Ctxl[Term] = trace[Term](s"Elab class ${tree.showDbg}", r => s"~> $r"):

hkmc2/shared/src/test/mlscript-compile/Predef.mjs

@@ -133,7 +133,7 @@ const Predef$class = class Predef {
       tmp7 = tmp6 + expected;
       tmp8 = tmp7 + " arguments but got ";
       tmp9 = tmp8 + got;
-      throw globalThis.Error(tmp9);
+      throw globalThis.Error(tmp9) ?? null;
     } else {
       return null;
     }

hkmc2/shared/src/test/mlscript-compile/Str.mjs

@@ -6,7 +6,7 @@ const Str$class = class Str {
     return a + b;
   } 
   string(value) {
-    return globalThis.String(value);
+    return globalThis.String(value) ?? null;
   }
   toString() { return "Str"; }
 }; const Str = new Str$class;

hkmc2/shared/src/test/mlscript/codegen/Getters.mls

@@ -25,6 +25,49 @@ this.t
 //│ = 42
 
 
+:sjs
+module T with
+  fun t() = 1
+  val a = globalThis.t
+  val b = this.t
+//│ JS:
+//│ const T$class = class T {
+//│   constructor() {
+//│     let selRes, tmp, tmp1, selRes1, tmp2;
+//│     selRes = globalThis.t;
+//│     if (selRes === undefined) {
+//│       throw new globalThis.Error("Access to required field 't' yielded 'undefined'");
+//│     } else {
+//│       tmp = selRes;
+//│     }
+//│     tmp1 = tmp();
+//│     this.a = tmp1;
+//│     selRes1 = this.t;
+//│     if (selRes1 === undefined) {
+//│       throw new globalThis.Error("Access to required field 't' yielded 'undefined'");
+//│     } else {
+//│       tmp2 = selRes1;
+//│     }
+//│     this.b = tmp2;
+//│   }
+//│   t(...args) {
+//│     globalThis.Predef.checkArgs("t", 0, true, args.length);
+//│     return 1;
+//│   }
+//│   toString() { return "T"; }
+//│ };
+//│ this.T = new T$class;
+//│ this.T.class = T$class;
+//│ null
+
+
+T.a
+//│ = 42
+
+T.b
+//│ = [Function: t]
+
+
 :sjs
 module M with
   fun t = 0