Change unknown prop dev warning to look at readable props as well

src/compiler/compile/render_dom/index.ts

@@ -365,11 +365,11 @@ export default function dom(
 		});
 
 		let unknown_props_check;
-		if (component.compile_options.dev && !component.var_lookup.has('$$props') && writable_props.length) {
+		if (component.compile_options.dev && !component.var_lookup.has('$$props') && props.length) {
 			unknown_props_check = b`
-				const writable_props = [${writable_props.map(prop => x`'${prop.export_name}'`)}];
+				const props = [${props.map(prop => x`'${prop.export_name}'`)}];
 				@_Object.keys($$props).forEach(key => {
-					if (!~writable_props.indexOf(key) && key.slice(0, 2) !== '$$') @_console.warn(\`<${component.tag}> was created with unknown prop '\${key}'\`);
+					if (!~props.indexOf(key) && key.slice(0, 2) !== '$$') @_console.warn(\`<${component.tag}> was created with unknown prop '\${key}'\`);
 				});
 			`;
 		}

test/runtime/samples/dev-warning-unknown-props-uses-readable/Foo.svelte

@@ -0,0 +1,5 @@
+<script>
+	export const foo = undefined;
+</script>
+
+<div>{foo}</div>

test/runtime/samples/dev-warning-unknown-props-uses-readable/_config.js

@@ -0,0 +1,7 @@
+export default {
+	compileOptions: {
+		dev: true
+	},
+
+	warnings: []
+};

test/runtime/samples/dev-warning-unknown-props-uses-readable/main.svelte

@@ -0,0 +1,5 @@
+<script>
+	import Foo from './Foo.svelte';
+</script>
+
+<Foo foo="sho"/>