diff --git a/test/js/samples/debug-empty/expected-bundle.js b/test/js/samples/debug-empty/expected-bundle.js
new file mode 100644
index 0000000000..ba3b1dda59
--- /dev/null
+++ b/test/js/samples/debug-empty/expected-bundle.js
@@ -0,0 +1,200 @@
+function noop() {}
+
+function assign(tar, src) {
+	for (var k in src) tar[k] = src[k];
+	return tar;
+}
+
+function append(target, node) {
+	target.appendChild(node);
+}
+
+function insert(target, node, anchor) {
+	target.insertBefore(node, anchor);
+}
+
+function detachNode(node) {
+	node.parentNode.removeChild(node);
+}
+
+function createElement(name) {
+	return document.createElement(name);
+}
+
+function createText(data) {
+	return document.createTextNode(data);
+}
+
+function setData(text, data) {
+	text.data = '' + data;
+}
+
+function blankObject() {
+	return Object.create(null);
+}
+
+function destroy(detach) {
+	this.destroy = noop;
+	this.fire('destroy');
+	this.set = noop;
+
+	this._fragment.d(detach !== false);
+	this._fragment = null;
+	this._state = {};
+}
+
+function _differs(a, b) {
+	return a != a ? b == b : a !== b || ((a && typeof a === 'object') || typeof a === 'function');
+}
+
+function fire(eventName, data) {
+	var handlers =
+		eventName in this._handlers && this._handlers[eventName].slice();
+	if (!handlers) return;
+
+	for (var i = 0; i < handlers.length; i += 1) {
+		var handler = handlers[i];
+
+		if (!handler.__calling) {
+			try {
+				handler.__calling = true;
+				handler.call(this, data);
+			} finally {
+				handler.__calling = false;
+			}
+		}
+	}
+}
+
+function get() {
+	return this._state;
+}
+
+function init(component, options) {
+	component._handlers = blankObject();
+	component._bind = options._bind;
+
+	component.options = options;
+	component.root = options.root || component;
+	component.store = options.store || component.root.store;
+}
+
+function on(eventName, handler) {
+	var handlers = this._handlers[eventName] || (this._handlers[eventName] = []);
+	handlers.push(handler);
+
+	return {
+		cancel: function() {
+			var index = handlers.indexOf(handler);
+			if (~index) handlers.splice(index, 1);
+		}
+	};
+}
+
+function set(newState) {
+	this._set(assign({}, newState));
+	if (this.root._lock) return;
+	this.root._lock = true;
+	callAll(this.root._beforecreate);
+	callAll(this.root._oncreate);
+	callAll(this.root._aftercreate);
+	this.root._lock = false;
+}
+
+function _set(newState) {
+	var oldState = this._state,
+		changed = {},
+		dirty = false;
+
+	for (var key in newState) {
+		if (this._differs(newState[key], oldState[key])) changed[key] = dirty = true;
+	}
+	if (!dirty) return;
+
+	this._state = assign(assign({}, oldState), newState);
+	this._recompute(changed, this._state);
+	if (this._bind) this._bind(changed, this._state);
+
+	if (this._fragment) {
+		this.fire("state", { changed: changed, current: this._state, previous: oldState });
+		this._fragment.p(changed, this._state);
+		this.fire("update", { changed: changed, current: this._state, previous: oldState });
+	}
+}
+
+function callAll(fns) {
+	while (fns && fns.length) fns.shift()();
+}
+
+function _mount(target, anchor) {
+	this._fragment[this._fragment.i ? 'i' : 'm'](target, anchor || null);
+}
+
+var proto = {
+	destroy,
+	get,
+	fire,
+	on,
+	set,
+	_recompute: noop,
+	_set,
+	_mount,
+	_differs
+};
+
+/* generated by Svelte vX.Y.Z */
+
+function create_main_fragment(component, ctx) {
+	var h1, text, text_1, text_2, text_3;
+
+	return {
+		c() {
+			h1 = createElement("h1");
+			text = createText("Hello ");
+			text_1 = createText(ctx.name);
+			text_2 = createText("!");
+			text_3 = createText("\n");
+			debugger;
+		},
+
+		m(target, anchor) {
+			insert(target, h1, anchor);
+			append(h1, text);
+			append(h1, text_1);
+			append(h1, text_2);
+			insert(target, text_3, anchor);
+		},
+
+		p(changed, ctx) {
+			if (changed.name) {
+				setData(text_1, ctx.name);
+			}
+
+			debugger;
+		},
+
+		d(detach) {
+			if (detach) {
+				detachNode(h1);
+				detachNode(text_3);
+			}
+		}
+	};
+}
+
+function SvelteComponent(options) {
+	init(this, options);
+	this._state = assign({}, options.data);
+	this._intro = true;
+
+	this._fragment = create_main_fragment(this, this._state);
+
+	if (options.target) {
+		this._fragment.c();
+		this._mount(options.target, options.anchor);
+	}
+}
+
+assign(SvelteComponent.prototype, proto);
+
+export default SvelteComponent;
diff --git a/test/js/samples/debug-empty/expected.js b/test/js/samples/debug-empty/expected.js
new file mode 100644
index 0000000000..592f3a7a2b
--- /dev/null
+++ b/test/js/samples/debug-empty/expected.js
@@ -0,0 +1,56 @@
+/* generated by Svelte vX.Y.Z */
+import { append, assign, createElement, createText, detachNode, init, insert, proto, setData } from "svelte/shared.js";
+
+function create_main_fragment(component, ctx) {
+	var h1, text, text_1, text_2, text_3;
+
+	return {
+		c() {
+			h1 = createElement("h1");
+			text = createText("Hello ");
+			text_1 = createText(ctx.name);
+			text_2 = createText("!");
+			text_3 = createText("\n");
+			debugger;
+		},
+
+		m(target, anchor) {
+			insert(target, h1, anchor);
+			append(h1, text);
+			append(h1, text_1);
+			append(h1, text_2);
+			insert(target, text_3, anchor);
+		},
+
+		p(changed, ctx) {
+			if (changed.name) {
+				setData(text_1, ctx.name);
+			}
+
+			debugger;
+		},
+
+		d(detach) {
+			if (detach) {
+				detachNode(h1);
+				detachNode(text_3);
+			}
+		}
+	};
+}
+
+function SvelteComponent(options) {
+	init(this, options);
+	this._state = assign({}, options.data);
+	this._intro = true;
+
+	this._fragment = create_main_fragment(this, this._state);
+
+	if (options.target) {
+		this._fragment.c();
+		this._mount(options.target, options.anchor);
+	}
+}
+
+assign(SvelteComponent.prototype, proto);
+export default SvelteComponent;
\ No newline at end of file
diff --git a/test/js/samples/debug-empty/input.html b/test/js/samples/debug-empty/input.html
new file mode 100644
index 0000000000..11da4f6d15
--- /dev/null
+++ b/test/js/samples/debug-empty/input.html
@@ -0,0 +1,2 @@
+<h1>Hello {name}!</h1>
+{@debug}
\ No newline at end of file
diff --git a/test/js/samples/debug-foo-bar-baz-things/expected-bundle.js b/test/js/samples/debug-foo-bar-baz-things/expected-bundle.js
new file mode 100644
index 0000000000..e6796c685f
--- /dev/null
+++ b/test/js/samples/debug-foo-bar-baz-things/expected-bundle.js
@@ -0,0 +1,290 @@
+function noop() {}
+
+function assign(tar, src) {
+	for (var k in src) tar[k] = src[k];
+	return tar;
+}
+
+function append(target, node) {
+	target.appendChild(node);
+}
+
+function insert(target, node, anchor) {
+	target.insertBefore(node, anchor);
+}
+
+function detachNode(node) {
+	node.parentNode.removeChild(node);
+}
+
+function destroyEach(iterations, detach) {
+	for (var i = 0; i < iterations.length; i += 1) {
+		if (iterations[i]) iterations[i].d(detach);
+	}
+}
+
+function createElement(name) {
+	return document.createElement(name);
+}
+
+function createText(data) {
+	return document.createTextNode(data);
+}
+
+function setData(text, data) {
+	text.data = '' + data;
+}
+
+function blankObject() {
+	return Object.create(null);
+}
+
+function destroy(detach) {
+	this.destroy = noop;
+	this.fire('destroy');
+	this.set = noop;
+
+	this._fragment.d(detach !== false);
+	this._fragment = null;
+	this._state = {};
+}
+
+function _differs(a, b) {
+	return a != a ? b == b : a !== b || ((a && typeof a === 'object') || typeof a === 'function');
+}
+
+function fire(eventName, data) {
+	var handlers =
+		eventName in this._handlers && this._handlers[eventName].slice();
+	if (!handlers) return;
+
+	for (var i = 0; i < handlers.length; i += 1) {
+		var handler = handlers[i];
+
+		if (!handler.__calling) {
+			try {
+				handler.__calling = true;
+				handler.call(this, data);
+			} finally {
+				handler.__calling = false;
+			}
+		}
+	}
+}
+
+function get() {
+	return this._state;
+}
+
+function init(component, options) {
+	component._handlers = blankObject();
+	component._bind = options._bind;
+
+	component.options = options;
+	component.root = options.root || component;
+	component.store = options.store || component.root.store;
+}
+
+function on(eventName, handler) {
+	var handlers = this._handlers[eventName] || (this._handlers[eventName] = []);
+	handlers.push(handler);
+
+	return {
+		cancel: function() {
+			var index = handlers.indexOf(handler);
+			if (~index) handlers.splice(index, 1);
+		}
+	};
+}
+
+function set(newState) {
+	this._set(assign({}, newState));
+	if (this.root._lock) return;
+	this.root._lock = true;
+	callAll(this.root._beforecreate);
+	callAll(this.root._oncreate);
+	callAll(this.root._aftercreate);
+	this.root._lock = false;
+}
+
+function _set(newState) {
+	var oldState = this._state,
+		changed = {},
+		dirty = false;
+
+	for (var key in newState) {
+		if (this._differs(newState[key], oldState[key])) changed[key] = dirty = true;
+	}
+	if (!dirty) return;
+
+	this._state = assign(assign({}, oldState), newState);
+	this._recompute(changed, this._state);
+	if (this._bind) this._bind(changed, this._state);
+
+	if (this._fragment) {
+		this.fire("state", { changed: changed, current: this._state, previous: oldState });
+		this._fragment.p(changed, this._state);
+		this.fire("update", { changed: changed, current: this._state, previous: oldState });
+	}
+}
+
+function callAll(fns) {
+	while (fns && fns.length) fns.shift()();
+}
+
+function _mount(target, anchor) {
+	this._fragment[this._fragment.i ? 'i' : 'm'](target, anchor || null);
+}
+
+var proto = {
+	destroy,
+	get,
+	fire,
+	on,
+	set,
+	_recompute: noop,
+	_set,
+	_mount,
+	_differs
+};
+
+/* generated by Svelte vX.Y.Z */
+
+function create_main_fragment(component, ctx) {
+	var text, p, text_1, text_2;
+
+	var each_value = ctx.things;
+
+	var each_blocks = [];
+
+	for (var i = 0; i < each_value.length; i += 1) {
+		each_blocks[i] = create_each_block(component, get_each_context(ctx, each_value, i));
+	}
+
+	return {
+		c() {
+			for (var i = 0; i < each_blocks.length; i += 1) {
+				each_blocks[i].c();
+			}
+
+			text = createText("\n\n");
+			p = createElement("p");
+			text_1 = createText("foo: ");
+			text_2 = createText(ctx.foo);
+		},
+
+		m(target, anchor) {
+			for (var i = 0; i < each_blocks.length; i += 1) {
+				each_blocks[i].m(target, anchor);
+			}
+
+			insert(target, text, anchor);
+			insert(target, p, anchor);
+			append(p, text_1);
+			append(p, text_2);
+		},
+
+		p(changed, ctx) {
+			if (changed.things) {
+				each_value = ctx.things;
+
+				for (var i = 0; i < each_value.length; i += 1) {
+					const child_ctx = get_each_context(ctx, each_value, i);
+
+					if (each_blocks[i]) {
+						each_blocks[i].p(changed, child_ctx);
+					} else {
+						each_blocks[i] = create_each_block(component, child_ctx);
+						each_blocks[i].c();
+						each_blocks[i].m(text.parentNode, text);
+					}
+				}
+
+				for (; i < each_blocks.length; i += 1) {
+					each_blocks[i].d(1);
+				}
+				each_blocks.length = each_value.length;
+			}
+
+			if (changed.foo) {
+				setData(text_2, ctx.foo);
+			}
+		},
+
+		d(detach) {
+			destroyEach(each_blocks, detach);
+
+			if (detach) {
+				detachNode(text);
+				detachNode(p);
+			}
+		}
+	};
+}
+
+// (1:0) {#each things as thing}
+function create_each_block(component, ctx) {
+	var span, text_value = ctx.thing.name, text, text_1;
+
+	return {
+		c() {
+			span = createElement("span");
+			text = createText(text_value);
+			text_1 = createText("\n\t");
+
+			const { foo, bar, baz } = ctx;
+			console.log({ foo, bar, baz });
+			debugger;
+		},
+
+		m(target, anchor) {
+			insert(target, span, anchor);
+			append(span, text);
+			insert(target, text_1, anchor);
+		},
+
+		p(changed, ctx) {
+			if ((changed.things) && text_value !== (text_value = ctx.thing.name)) {
+				setData(text, text_value);
+			}
+
+			if (changed.foo || changed.bar || changed.baz) {
+				const { foo, bar, baz } = ctx;
+				console.log({ foo, bar, baz });
+				debugger;
+			}
+		},
+
+		d(detach) {
+			if (detach) {
+				detachNode(span);
+				detachNode(text_1);
+			}
+		}
+	};
+}
+
+function get_each_context(ctx, list, i) {
+	const child_ctx = Object.create(ctx);
+	child_ctx.thing = list[i];
+	child_ctx.each_value = list;
+	child_ctx.thing_index = i;
+	return child_ctx;
+}
+
+function SvelteComponent(options) {
+	init(this, options);
+	this._state = assign({}, options.data);
+	this._intro = true;
+
+	this._fragment = create_main_fragment(this, this._state);
+
+	if (options.target) {
+		this._fragment.c();
+		this._mount(options.target, options.anchor);
+	}
+}
+
+assign(SvelteComponent.prototype, proto);
+
+export default SvelteComponent;
diff --git a/test/js/samples/debug-foo-bar-baz-things/expected.js b/test/js/samples/debug-foo-bar-baz-things/expected.js
new file mode 100644
index 0000000000..1406c3b927
--- /dev/null
+++ b/test/js/samples/debug-foo-bar-baz-things/expected.js
@@ -0,0 +1,140 @@
+/* generated by Svelte vX.Y.Z */
+import { append, assign, createElement, createText, destroyEach, detachNode, init, insert, proto, setData } from "svelte/shared.js";
+
+function create_main_fragment(component, ctx) {
+	var text, p, text_1, text_2;
+
+	var each_value = ctx.things;
+
+	var each_blocks = [];
+
+	for (var i = 0; i < each_value.length; i += 1) {
+		each_blocks[i] = create_each_block(component, get_each_context(ctx, each_value, i));
+	}
+
+	return {
+		c() {
+			for (var i = 0; i < each_blocks.length; i += 1) {
+				each_blocks[i].c();
+			}
+
+			text = createText("\n\n");
+			p = createElement("p");
+			text_1 = createText("foo: ");
+			text_2 = createText(ctx.foo);
+		},
+
+		m(target, anchor) {
+			for (var i = 0; i < each_blocks.length; i += 1) {
+				each_blocks[i].m(target, anchor);
+			}
+
+			insert(target, text, anchor);
+			insert(target, p, anchor);
+			append(p, text_1);
+			append(p, text_2);
+		},
+
+		p(changed, ctx) {
+			if (changed.things) {
+				each_value = ctx.things;
+
+				for (var i = 0; i < each_value.length; i += 1) {
+					const child_ctx = get_each_context(ctx, each_value, i);
+
+					if (each_blocks[i]) {
+						each_blocks[i].p(changed, child_ctx);
+					} else {
+						each_blocks[i] = create_each_block(component, child_ctx);
+						each_blocks[i].c();
+						each_blocks[i].m(text.parentNode, text);
+					}
+				}
+
+				for (; i < each_blocks.length; i += 1) {
+					each_blocks[i].d(1);
+				}
+				each_blocks.length = each_value.length;
+			}
+
+			if (changed.foo) {
+				setData(text_2, ctx.foo);
+			}
+		},
+
+		d(detach) {
+			destroyEach(each_blocks, detach);
+
+			if (detach) {
+				detachNode(text);
+				detachNode(p);
+			}
+		}
+	};
+}
+
+// (1:0) {#each things as thing}
+function create_each_block(component, ctx) {
+	var span, text_value = ctx.thing.name, text, text_1;
+
+	return {
+		c() {
+			span = createElement("span");
+			text = createText(text_value);
+			text_1 = createText("\n\t");
+
+			const { foo, bar, baz, thing } = ctx;
+			console.log({ foo, bar, baz, thing });
+			debugger;
+		},
+
+		m(target, anchor) {
+			insert(target, span, anchor);
+			append(span, text);
+			insert(target, text_1, anchor);
+		},
+
+		p(changed, ctx) {
+			if ((changed.things) && text_value !== (text_value = ctx.thing.name)) {
+				setData(text, text_value);
+			}
+
+			if (changed.foo || changed.bar || changed.baz || changed.things) {
+				const { foo, bar, baz, thing } = ctx;
+				console.log({ foo, bar, baz, thing });
+				debugger;
+			}
+		},
+
+		d(detach) {
+			if (detach) {
+				detachNode(span);
+				detachNode(text_1);
+			}
+		}
+	};
+}
+
+function get_each_context(ctx, list, i) {
+	const child_ctx = Object.create(ctx);
+	child_ctx.thing = list[i];
+	child_ctx.each_value = list;
+	child_ctx.thing_index = i;
+	return child_ctx;
+}
+
+function SvelteComponent(options) {
+	init(this, options);
+	this._state = assign({}, options.data);
+	this._intro = true;
+
+	this._fragment = create_main_fragment(this, this._state);
+
+	if (options.target) {
+		this._fragment.c();
+		this._mount(options.target, options.anchor);
+	}
+}
+
+assign(SvelteComponent.prototype, proto);
+export default SvelteComponent;
\ No newline at end of file
diff --git a/test/js/samples/debug-foo-bar-baz-things/input.html b/test/js/samples/debug-foo-bar-baz-things/input.html
new file mode 100644
index 0000000000..6fa8611415
--- /dev/null
+++ b/test/js/samples/debug-foo-bar-baz-things/input.html
@@ -0,0 +1,6 @@
+{#each things as thing}
+	<span>{thing.name}</span>
+	{@debug foo, bar, baz, thing}
+{/each}
+
+<p>foo: {foo}</p>
\ No newline at end of file
diff --git a/test/validator/samples/debug-invalid/errors.json b/test/validator/samples/debug-invalid/errors.json
new file mode 100644
index 0000000000..1dc4507a39
--- /dev/null
+++ b/test/validator/samples/debug-invalid/errors.json
@@ -0,0 +1,15 @@
+[{
+	"code": "invalid-debug",
+	"message": "{@debug ...} arguments must be identifers, not arbitrary expressions",
+	"start": {
+		"line": 2,
+		"column": 9,
+		"character": 13
+	},
+	"end": {
+		"line": 2,
+		"column": 14,
+		"character": 18
+	},
+	"pos": 13
+}]
\ No newline at end of file
diff --git a/test/validator/samples/debug-invalid/input.html b/test/validator/samples/debug-invalid/input.html
new file mode 100644
index 0000000000..5c89e7049d
--- /dev/null
+++ b/test/validator/samples/debug-invalid/input.html
@@ -0,0 +1,4 @@
+<p>
+	{@debug a + b}
+	{a + b}
+</p>
\ No newline at end of file