Add test for user data.

Also moved the VM parameter in the error callback to be first like it
is in other callbacks.

src/cli/vm.c

@@ -154,8 +154,8 @@ static void write(WrenVM* vm, const char* text)
   fflush(stdout);
 }
 
-static void reportError(WrenErrorType type,
-                        const char* module, int line, const char* message, WrenVM* vm)
+static void reportError(WrenVM* vm, WrenErrorType type,
+                        const char* module, int line, const char* message)
 {
   switch (type)
   {

src/include/wren.h

@@ -96,7 +96,8 @@ typedef enum
 // Each of those has the module and line where the method or function is
 // defined and [message] is the name of the method or function.
 typedef void (*WrenErrorFn)(
-    WrenErrorType type, const char* module, int line, const char* message, WrenVM* vm);
+    WrenVM* vm, WrenErrorType type, const char* module, int line,
+    const char* message);
 
 typedef struct
 {
@@ -207,7 +208,7 @@ typedef struct
   // If zero, defaults to 50.
   int heapGrowthPercent;
 
-  // User defined state data associated with the WrenVM.
+  // User-defined data associated with the VM.
   void* userData;
 
 } WrenConfiguration;

src/vm/wren_compiler.c

@@ -403,8 +403,8 @@ static void printError(Parser* parser, int line, const char* label,
   length += vsprintf(message + length, format, args);
   ASSERT(length < ERROR_MESSAGE_SIZE, "Error should not exceed buffer.");
   
-  parser->vm->config.errorFn(WREN_ERROR_COMPILE,
-                             parser->module->name->value, line, message, parser->vm);
+  parser->vm->config.errorFn(parser->vm, WREN_ERROR_COMPILE,
+                             parser->module->name->value, line, message);
 }
 
 // Outputs a compile or syntax error. This also marks the compilation as having

src/vm/wren_debug.c

@@ -10,13 +10,15 @@ void wrenDebugPrintStackTrace(WrenVM* vm)
   ObjFiber* fiber = vm->fiber;
   if (IS_STRING(fiber->error))
   {
-    vm->config.errorFn(WREN_ERROR_RUNTIME, NULL, -1, AS_CSTRING(fiber->error), vm);
+    vm->config.errorFn(vm, WREN_ERROR_RUNTIME,
+                       NULL, -1, AS_CSTRING(fiber->error));
   }
   else
   {
     // TODO: Print something a little useful here. Maybe the name of the error's
     // class?
-    vm->config.errorFn(WREN_ERROR_RUNTIME, NULL, -1, "[error object]", vm);
+    vm->config.errorFn(vm, WREN_ERROR_RUNTIME,
+                       NULL, -1, "[error object]");
   }
 
   for (int i = fiber->numFrames - 1; i >= 0; i--)
@@ -34,8 +36,9 @@ void wrenDebugPrintStackTrace(WrenVM* vm)
     
     // -1 because IP has advanced past the instruction that it just executed.
     int line = fn->debug->sourceLines.data[frame->ip - fn->code.data - 1];
-    vm->config.errorFn(WREN_ERROR_STACK_TRACE, fn->module->name->value, line,
-                       fn->debug->name, vm);
+    vm->config.errorFn(vm, WREN_ERROR_STACK_TRACE,
+                       fn->module->name->value, line,
+                       fn->debug->name);
   }
 }