diff --git a/packages/core/src/warning.ts b/packages/core/src/warning.ts
new file mode 100644
index 00000000..80f9ad31
--- /dev/null
+++ b/packages/core/src/warning.ts
@@ -0,0 +1,20 @@
+import { MountedComponent, ComponentType } from './component'
+
+let currentComponent: MountedComponent | null = null
+let currentComponentDefinition: ComponentType | null = null
+
+export function setCurrentComponent(c: MountedComponent) {
+  currentComponent = c
+}
+
+export function unsetCurrentComponent() {
+  currentComponent = null
+}
+
+export function setCurrentComponentDefinition(d: ComponentType) {
+  currentComponentDefinition = d
+}
+
+export function unsetCurrentComponentDefinition() {
+  currentComponentDefinition = null
+}