simplify and fix some broadcasts

 * fixes https://scratch.mit.edu/projects/304369304
   and other projects where broadcast IDs are inconsistent
 * remove lookupBroadcast, addBroadcast, broadcastReferences
 * sb3: broadcast names used instead of IDs

phosphorus/core.ts

@@ -960,12 +960,6 @@ namespace P.core {
       this.drawChildren(renderer, skip);
     }
 
-    /**
-     * Determines the internal ID for a broadcast.
-     * @param name The name of the broadcast. It's what you see in the Scratch editor.
-     */
-    abstract lookupBroadcast(name: string): string;
-
     // Implement rotatedBounds() to return something.
     rotatedBounds() {
       return {

phosphorus/runtime.ts

@@ -490,7 +490,7 @@ namespace P.runtime {
   }
 
   var broadcast = function(name) {
-    return runtime.trigger('whenIReceive', self.lookupBroadcast(name));
+    return runtime.trigger('whenIReceive', name);
   };
 
   var running = function(bases) {
@@ -546,7 +546,7 @@ namespace P.runtime {
       this.onError = this.onError.bind(this);
     }
 
-    startThread(sprite: core.Base, base) {
+    startThread(sprite: core.Base, base: Fn) {
       const thread = new Thread(sprite, base, base, [{
         args: [],
         stack: [{}],
@@ -567,8 +567,8 @@ namespace P.runtime {
     /**
      * Triggers an event for a single sprite.
      */
-    triggerFor(sprite: P.core.Base, event: string, arg?: any): Thread[] {
-      let threads;
+    triggerFor(sprite: P.core.Base, event: string, arg?: any): Fn[] {
+      let threads: Fn[];
       switch (event) {
         case 'whenClicked': threads = sprite.listeners.whenClicked; break;
         case 'whenCloned': threads = sprite.listeners.whenCloned; break;
@@ -578,6 +578,7 @@ namespace P.runtime {
         case 'whenBackdropChanges': threads = sprite.listeners.whenBackdropChanges['' + arg]; break;
         case 'whenIReceive':
           arg = '' + arg;
+          // TODO: remove toLowerCase() check?
           threads = sprite.listeners.whenIReceive[arg] || sprite.listeners.whenIReceive[arg.toLowerCase()];
           break;
         default: throw new Error('Unknown trigger event: ' + event);
@@ -594,7 +595,7 @@ namespace P.runtime {
      * Triggers an event on all sprites.
      */
     trigger(event: string, arg?: any) {
-      let threads: Thread[] = [];
+      let threads: Fn[] = [];
       for (let i = this.stage.children.length; i--;) {
         threads = threads.concat(this.triggerFor(this.stage.children[i], event, arg));
       }

phosphorus/sb2.ts

@@ -344,11 +344,6 @@ namespace P.sb2 {
     private defaultWatcherX = 10;
     private defaultWatcherY = 10;
 
-    lookupBroadcast(name: string) {
-      // Scratch 2 uses names as IDs.
-      return name;
-    }
-
     lookupVariable(name: string) {
       return this.vars[name];
     }

phosphorus/sb3.ts

@@ -114,20 +114,9 @@ namespace P.sb3 {
   // Implements a Scratch 3 Stage.
   // Adds Scratch 3 specific things such as broadcastReferences
   export class Scratch3Stage extends P.core.Stage {
-    private broadcastReferences: ObjectMap<string> = {};
     public variableNames: ObjectMap<string> = {};
     public sb3data: SB3Target;
 
-    addBroadcast(name: string, id: string) {
-      this.broadcastReferences[name] = id;
-    }
-
-    lookupBroadcast(name: string) {
-      // Use the mapped ID or fall back to the name.
-      // Usually the name is the unique ID, but occasionally it is not.
-      return this.broadcastReferences[name] || name;
-    }
-
     lookupVariable(name: string) {
       return this.vars[this.variableNames[name]];
     }
@@ -700,11 +689,7 @@ namespace P.sb3 {
       target.sb3data = data;
 
       if (target.isStage) {
-        const stage = target as Scratch3Stage;
-        for (const id of Object.keys(data.broadcasts)) {
-          const name = data.broadcasts[id];
-          stage.addBroadcast(name, id);
-        }
+
       } else {
         const sprite = target as Scratch3Sprite;
         sprite.scratchX = data.x;
@@ -1024,11 +1009,11 @@ namespace P.sb3.compiler {
       currentTarget.listeners.whenBackdropChanges[backdrop].push(f);
     },
     event_whenbroadcastreceived(block, f) {
-      const optionId = block.fields.BROADCAST_OPTION[1];
-      if (!currentTarget.listeners.whenIReceive[optionId]) {
-        currentTarget.listeners.whenIReceive[optionId] = [];
+      const name = block.fields.BROADCAST_OPTION[0];
+      if (!currentTarget.listeners.whenIReceive[name]) {
+        currentTarget.listeners.whenIReceive[name] = [];
       }
-      currentTarget.listeners.whenIReceive[optionId].push(f);
+      currentTarget.listeners.whenIReceive[name].push(f);
     },
 
     // Control
@@ -1810,7 +1795,7 @@ namespace P.sb3.compiler {
       const condition = block.inputs.CONDITION;
       const substack = block.inputs.SUBSTACK;
       const id = label();
-      source += 'if (!' + compileExpression(condition) + ') {\n';
+      source += 'if (!' + compileExpression(condition, 'boolean') + ') {\n';
       compileSubstack(substack);
       queue(id);
       source += '}\n';
@@ -2404,8 +2389,8 @@ namespace P.sb3.compiler {
         return listReference(constant[2]);
 
       case PrimitiveTypes.BROADCAST:
-        // Similar to variable references.
-        return compileExpression(constant[2]);
+        // [type, name, id]
+        return compileExpression(constant[1]);
 
       case PrimitiveTypes.COLOR_PICKER:
         // Colors are stored as strings like "#123ABC", so we must do some conversions to use them as numbers.