try 1

src/compiler/compile/Component.ts

@@ -63,6 +63,8 @@ export default class Component {
 
 	imports: ImportDeclaration[] = [];
 
+	function_args: Set<string> = new Set();
+
 	hoistable_nodes: Set<Node> = new Set();
 	node_for_declaration: Map<string, Node> = new Map();
 	partly_hoisted: Array<(Node | Node[])> = [];
@@ -699,7 +701,7 @@ export default class Component {
 
 		const component = this;
 		const { content } = script;
-		const { instance_scope, instance_scope_map: map } = this;
+		const { function_args, instance_scope, instance_scope_map: map } = this;
 
 		let scope = instance_scope;
 
@@ -716,6 +718,14 @@ export default class Component {
 					scope = map.get(node);
 				}
 
+				if (node.type === 'CallExpression') {
+					node.arguments.forEach(arg => {
+						if (arg.type == 'Identifier') {
+							function_args.add(arg.name);
+						}
+					})
+				}
+
 				if (node.type === 'ImportDeclaration') {
 					component.extract_imports(node);
 					// TODO: to use actual remove
@@ -1054,6 +1064,7 @@ export default class Component {
 			const instance_scope = this.instance_scope;
 			let scope = this.instance_scope;
 			const map = this.instance_scope_map;
+			const function_args = this.function_args;
 
 			let hoistable = true;
 
@@ -1072,7 +1083,9 @@ export default class Component {
 						const { name } = flatten_reference(node);
 						const owner = scope.find_owner(name);
 						
-						if (injected_reactive_declaration_vars.has(name)) {
+						if (function_args.has(name)) {
+							hoistable = false;
+						} else if (injected_reactive_declaration_vars.has(name)) {
 							hoistable = false;
 						} else if (name[0] === '$' && !owner) {
 							hoistable = false;

test/js/samples/action-custom-event-handler/expected.js

@@ -21,10 +21,10 @@ function create_fragment(ctx) {
 		},
 		m(target, anchor) {
 			insert(target, button, anchor);
-			foo_action = foo.call(null, button, /*foo_function*/ ctx[1]) || ({});
+			foo_action = foo.call(null, button, /*foo_function*/ ctx[2]) || ({});
 		},
 		p(ctx, [dirty]) {
-			if (is_function(foo_action.update) && dirty & /*bar*/ 1) foo_action.update.call(null, /*foo_function*/ ctx[1]);
+			if (is_function(foo_action.update) && dirty & /*bar*/ 1) foo_action.update.call(null, /*foo_function*/ ctx[2]);
 		},
 		i: noop,
 		o: noop,
@@ -35,23 +35,24 @@ function create_fragment(ctx) {
 	};
 }
 
-function handleFoo(bar) {
-	console.log(bar);
-}
-
 function foo(node, callback) {
 	
 }
 
 function instance($$self, $$props, $$invalidate) {
 	let { bar } = $$props;
+
+	function handleFoo(bar) {
+		console.log(bar);
+	}
+
 	const foo_function = () => handleFoo(bar);
 
 	$$self.$set = $$props => {
 		if ("bar" in $$props) $$invalidate(0, bar = $$props.bar);
 	};
 
-	return [bar, foo_function];
+	return [bar, handleFoo, foo_function];
 }
 
 class Component extends SvelteComponent {

test/js/samples/action/expected.js

@@ -23,7 +23,7 @@ function create_fragment(ctx) {
 		},
 		m(target, anchor) {
 			insert(target, a, anchor);
-			link_action = link.call(null, a) || ({});
+			link_action = /*link*/ ctx[0].call(null, a) || ({});
 		},
 		p: noop,
 		i: noop,
@@ -35,6 +35,7 @@ function create_fragment(ctx) {
 	};
 }
 
+function instance($$self) {
 	function link(node) {
 		function onClick(event) {
 			event.preventDefault();
@@ -50,10 +51,13 @@ function link(node) {
 		};
 	}
 
+	return [link];
+}
+
 class Component extends SvelteComponent {
 	constructor(options) {
 		super();
-		init(this, options, null, create_fragment, safe_not_equal, {});
+		init(this, options, instance, create_fragment, safe_not_equal, {});
 	}
 }
 

test/js/samples/hoisted-function/expected.js

@@ -0,0 +1,50 @@
+/* generated by Svelte vX.Y.Z */
+import {
+	SvelteComponent,
+	detach,
+	element,
+	init,
+	insert,
+	noop,
+	safe_not_equal
+} from "svelte/internal";
+
+import { bar } from "./utils.js";
+
+function create_fragment(ctx) {
+	let p;
+
+	return {
+		c() {
+			p = element("p");
+			p.textContent = `You'll be pleased to know the answer is ${/*foo*/ ctx[0]()}.`;
+		},
+		m(target, anchor) {
+			insert(target, p, anchor);
+		},
+		p: noop,
+		i: noop,
+		o: noop,
+		d(detaching) {
+			if (detaching) detach(p);
+		}
+	};
+}
+
+function instance($$self) {
+	function foo() {
+		return 42;
+	}
+
+	bar(foo);
+	return [foo];
+}
+
+class Component extends SvelteComponent {
+	constructor(options) {
+		super();
+		init(this, options, instance, create_fragment, safe_not_equal, {});
+	}
+}
+
+export default Component;

test/js/samples/hoisted-function/input.svelte

@@ -0,0 +1,11 @@
+<script>
+	import { bar } from './utils.js';
+			
+	function foo() {
+		return 42;
+	}
+	
+	bar(foo);
+</script>
+
+<p>You'll be pleased to know the answer is {foo()}.</p>

test/js/samples/hoisted-function/utils.js

@@ -0,0 +1,3 @@
+export function bar(fn) {
+	console.log(`I'm safe but you'd never know, ${fn}!`);
+}