refactor: extremely cheap ass error reports

app/astride/sandbox.js

@@ -699,7 +699,7 @@ export default class Sandbox {
         stack: [],
       };
     }
-    let result = this.executeSync(this.ast, 0);
+    const result = this.executeSync(this.ast, 0);
     const stepResult = {async: false, done: false, value: undefined};
     switch (result.yield) {
       case YIELD_PROMISE: {

app/util/script.js

@@ -24,13 +24,14 @@ export const cache = new LRUCache({
 
 export default class Script {
 
-  constructor(sandbox) {
+  constructor(sandbox, code) {
+    this.code = code;
     this.sandbox = sandbox;
     this.promise = null;
   }
 
   clone() {
-    return new this.constructor(this.sandbox.clone());
+    return new this.constructor(this.sandbox.clone(), this.code);
   }
 
   get context() {
@@ -76,6 +77,7 @@ export default class Script {
     }
     return new this(
       new Sandbox(await cache.get(code), this.createContext(context)),
+      code,
     );
   }
 
@@ -102,7 +104,19 @@ export default class Script {
     }
     while (true) {
       this.sandbox.context.elapsed = elapsed;
-      const {async, done, value} = this.sandbox.step();
+      let async, done, value;
+      try {
+        ({async, done, value} = this.sandbox.step());
+      }
+      catch (error) {
+        const node = this.sandbox.$$execution.stack.pop();
+        console.warn('Script ran into a problem at', this.code.slice(node.start, node.end));
+        console.warn(error);
+        if (resolve) {
+          resolve();
+        }
+        return;
+      }
       if (async) {
         this.promise = value;
         value