disallow `slot` as a prop name in inline components (#2019)

src/compile/nodes/InlineComponent.ts

@@ -42,6 +42,13 @@ export default class InlineComponent extends Node {
 					});
 
 				case 'Attribute':
+					if (node.name === 'slot') {
+						component.error(node, {
+							code: `invalid-prop`,
+							message: `'slot' is reserved for future use in named slots`
+						});
+					}
+					// fallthrough
 				case 'Spread':
 					this.attributes.push(new Attribute(component, this, scope, node));
 					break;

test/validator/samples/prop-slot/errors.json

@@ -0,0 +1,15 @@
+[{
+	"code": "invalid-prop",
+	"message": "'slot' is reserved for future use in named slots",
+	"start": {
+		"line": 5,
+		"column": 8,
+		"character": 65
+	},
+	"end": {
+		"line": 5,
+		"column": 18,
+		"character": 75
+	},
+	"pos": 65
+}]

test/validator/samples/prop-slot/input.html

@@ -0,0 +1,5 @@
+<script>
+	import Widget from './Widget.html';
+</script>
+
+<Widget slot='foo'/>