fix(runtime-core): respect render function from mixins

fix #1630

packages/runtime-core/src/component.ts

@@ -589,6 +589,7 @@ function finishComponentSetup(
       instance.render = Component.render as InternalRenderFunction
     }
   } else if (!instance.render) {
+    // could be set from setup()
     if (compile && Component.template && !Component.render) {
       if (__DEV__) {
         startMeasure(instance, `compile`)
@@ -604,25 +605,6 @@ function finishComponentSetup(
       ;(Component.render as InternalRenderFunction)._rc = true
     }
 
-    if (__DEV__ && !Component.render) {
-      /* istanbul ignore if */
-      if (!compile && Component.template) {
-        warn(
-          `Component provided template option but ` +
-            `runtime compilation is not supported in this build of Vue.` +
-            (__ESM_BUNDLER__
-              ? ` Configure your bundler to alias "vue" to "vue/dist/vue.esm-bundler.js".`
-              : __ESM_BROWSER__
-                ? ` Use "vue.esm-browser.js" instead.`
-                : __GLOBAL__
-                  ? ` Use "vue.global.js" instead.`
-                  : ``) /* should not happen */
-        )
-      } else {
-        warn(`Component is missing template or render function.`)
-      }
-    }
-
     instance.render = (Component.render || NOOP) as InternalRenderFunction
 
     // for runtime-compiled render functions using `with` blocks, the render
@@ -642,6 +624,26 @@ function finishComponentSetup(
     applyOptions(instance, Component)
     currentInstance = null
   }
+
+  // warn missing template/render
+  if (__DEV__ && !Component.render && instance.render === NOOP) {
+    /* istanbul ignore if */
+    if (!compile && Component.template) {
+      warn(
+        `Component provided template option but ` +
+          `runtime compilation is not supported in this build of Vue.` +
+          (__ESM_BUNDLER__
+            ? ` Configure your bundler to alias "vue" to "vue/dist/vue.esm-bundler.js".`
+            : __ESM_BROWSER__
+              ? ` Use "vue.esm-browser.js" instead.`
+              : __GLOBAL__
+                ? ` Use "vue.global.js" instead.`
+                : ``) /* should not happen */
+      )
+    } else {
+      warn(`Component is missing template or render function.`)
+    }
+  }
 }
 
 const attrHandlers: ProxyHandler<Data> = {