error if component has transition (fixes #791)

src/validate/html/validateElement.ts

@@ -116,6 +116,10 @@ export default function validateElement(validator: Validator, node: Node, refs:
 		} else if (attribute.type === 'EventHandler') {
 			validateEventHandler(validator, attribute, refCallees);
 		} else if (attribute.type === 'Transition') {
+			if (isComponent) {
+				validator.error(`Transitions can only be applied to DOM elements, not components`, attribute.start);
+			}
+
 			const bidi = attribute.intro && attribute.outro;
 
 			if (hasTransition) {

test/validator/samples/transition-on-component/errors.json

@@ -0,0 +1,8 @@
+[{
+	"message": "Transitions can only be applied to DOM elements, not components",
+	"loc": {
+		"line": 1,
+		"column": 8
+	},
+	"pos": 8
+}]

test/validator/samples/transition-on-component/input.html

@@ -0,0 +1,15 @@
+<Widget in:foo/>
+
+<script>
+	import Widget from './Widget.html';
+
+	export default {
+		components: {
+			Widget
+		},
+
+		transitions: {
+			foo() {}
+		}
+	};
+</script>