Catch errors in the first try()

src/vm/wren_core.c

@@ -82,6 +82,12 @@ DEF_PRIMITIVE(fiber_abort)
 static bool runFiber(WrenVM* vm, ObjFiber* fiber, Value* args, bool isCall,
                      bool hasValue, const char* verb)
 {
+
+  if (!IS_NULL(fiber->error))
+  {
+    RETURN_ERROR_FMT("Cannot $ an aborted fiber.", verb);
+  }
+
   if (isCall)
   {
     if (fiber->caller != NULL) RETURN_ERROR("Fiber has already been called.");
@@ -95,11 +101,6 @@ static bool runFiber(WrenVM* vm, ObjFiber* fiber, Value* args, bool isCall,
     RETURN_ERROR_FMT("Cannot $ a finished fiber.", verb);
   }
 
-  if (!IS_NULL(fiber->error))
-  {
-    RETURN_ERROR_FMT("Cannot $ an aborted fiber.", verb);
-  }
-
   // When the calling fiber resumes, we'll store the result of the call in its
   // stack. If the call has two arguments (the fiber and the value), we only
   // need one slot for the result, so discard the other slot now.

src/vm/wren_vm.c

@@ -384,12 +384,19 @@ static void runtimeError(WrenVM* vm)
 {
   ASSERT(!IS_NULL(vm->fiber->error), "Should only call this after an error.");
 
-  // Unhook the caller since we will never resume and return to it.
-  ObjFiber* caller = vm->fiber->caller;
-  vm->fiber->caller = NULL;
+  ObjFiber* current = vm->fiber;
+  while (current->caller != NULL) {
+    if (current->callerIsTrying) {
+        break;
+    }
+    ObjFiber* temp = current;
+    current = temp->caller;
+    temp->caller = NULL;
+  }
+  ObjFiber* caller = current->caller;
 
   // If the caller ran this fiber using "try", give it the error.
-  if (vm->fiber->callerIsTrying)
+  if (current->callerIsTrying)
   {
     // Make the caller's try method return the error message.
     caller->stackTop[-1] = vm->fiber->error;

test/core/fiber/try.wren

@@ -8,3 +8,34 @@ System.print(fiber.try())
 // expect: before
 // expect: Bool does not implement 'unknownMethod'.
 System.print("after try") // expect: after try
+
+var fiber2 = Fiber.new {
+  var fiberInner = Fiber.new {
+    System.print("before")
+    true.unknownMethod
+    System.print("after")
+  }
+  fiberInner.call()
+}
+
+System.print(fiber2.try())
+// expect: before
+// expect: Bool does not implement 'unknownMethod'.
+System.print("after try") // expect: after try
+
+var fiber3 = Fiber.new {
+  var fiberInner = Fiber.new {
+    var fiberInnerInner = Fiber.new {
+      System.print("before")
+      true.unknownMethod
+      System.print("after")
+    }
+    fiberInnerInner.call()
+  }
+  fiberInner.call()
+}
+
+System.print(fiber3.try())
+// expect: before
+// expect: Bool does not implement 'unknownMethod'.
+System.print("after try") // expect: after try