diff --git a/src/compile/nodes/DebugTag.ts b/src/compile/nodes/DebugTag.ts
index 11f8812398..5a273bdf71 100644
--- a/src/compile/nodes/DebugTag.ts
+++ b/src/compile/nodes/DebugTag.ts
@@ -7,10 +7,13 @@ import addToSet from '../../utils/addToSet';
 
 export default class DebugTag extends Node {
 	expressions: Expression[];
+	shouldSkip: boolean;
 
 	constructor(compiler, parent, scope, info) {
 		super(compiler, parent, scope, info);
 
+		this.shouldSkip = !compiler.options.dev;
+
 		this.expressions = info.identifiers.map(node => {
 			return new Expression(compiler, parent, scope, node);
 		});
@@ -21,6 +24,8 @@ export default class DebugTag extends Node {
 		parentNode: string,
 		parentNodes: string,
 	) {
+		if (this.shouldSkip) return;
+
 		// Debug all
 		if (this.expressions.length === 0) {
 			block.builders.create.addLine('debugger;');
diff --git a/test/js/samples/debug-empty/_config.js b/test/js/samples/debug-empty/_config.js
new file mode 100644
index 0000000000..b1f2518e8a
--- /dev/null
+++ b/test/js/samples/debug-empty/_config.js
@@ -0,0 +1,5 @@
+export default {
+	options: {
+		dev: true
+	}
+};
\ No newline at end of file
diff --git a/test/js/samples/debug-empty/expected-bundle.js b/test/js/samples/debug-empty/expected-bundle.js
index 93c50eed56..36f2b87a80 100644
--- a/test/js/samples/debug-empty/expected-bundle.js
+++ b/test/js/samples/debug-empty/expected-bundle.js
@@ -5,6 +5,12 @@ function assign(tar, src) {
 	return tar;
 }
 
+function addLoc(element, file, line, column, char) {
+	element.__svelte_meta = {
+		loc: { file, line, column, char }
+	};
+}
+
 function append(target, node) {
 	target.appendChild(node);
 }
@@ -43,6 +49,13 @@ function destroy(detach) {
 	this._state = {};
 }
 
+function destroyDev(detach) {
+	destroy.call(this, detach);
+	this.destroy = function() {
+		console.warn('Component was already destroyed');
+	};
+}
+
 function _differs(a, b) {
 	return a != a ? b == b : a !== b || ((a && typeof a === 'object') || typeof a === 'function');
 }
@@ -122,6 +135,17 @@ function _set(newState) {
 	}
 }
 
+function setDev(newState) {
+	if (typeof newState !== 'object') {
+		throw new Error(
+			this._debugName + '.set was called without an object of data key-values to update.'
+		);
+	}
+
+	this._checkReadOnly(newState);
+	set.call(this, newState);
+}
+
 function callAll(fns) {
 	while (fns && fns.length) fns.shift()();
 }
@@ -130,12 +154,12 @@ function _mount(target, anchor) {
 	this._fragment[this._fragment.i ? 'i' : 'm'](target, anchor || null);
 }
 
-var proto = {
-	destroy,
+var protoDev = {
+	destroy: destroyDev,
 	get,
 	fire,
 	on,
-	set,
+	set: setDev,
 	_recompute: noop,
 	_set,
 	_mount,
@@ -144,20 +168,23 @@ var proto = {
 
 /* generated by Svelte vX.Y.Z */
 
+const file = undefined;
+
 function create_main_fragment(component, ctx) {
 	var h1, text, text_1, text_2, text_3;
 
 	return {
-		c() {
+		c: function create() {
 			h1 = createElement("h1");
 			text = createText("Hello ");
 			text_1 = createText(ctx.name);
 			text_2 = createText("!");
 			text_3 = createText("\n");
 			debugger;
+			addLoc(h1, file, 0, 0, 0);
 		},
 
-		m(target, anchor) {
+		m: function mount(target, anchor) {
 			insert(target, h1, anchor);
 			append(h1, text);
 			append(h1, text_1);
@@ -165,7 +192,7 @@ function create_main_fragment(component, ctx) {
 			insert(target, text_3, anchor);
 		},
 
-		p(changed, ctx) {
+		p: function update(changed, ctx) {
 			if (changed.name) {
 				setData(text_1, ctx.name);
 			}
@@ -173,7 +200,7 @@ function create_main_fragment(component, ctx) {
 			debugger;
 		},
 
-		d(detach) {
+		d: function destroy$$1(detach) {
 			if (detach) {
 				detachNode(h1);
 				detachNode(text_3);
@@ -183,18 +210,25 @@ function create_main_fragment(component, ctx) {
 }
 
 function SvelteComponent(options) {
+	this._debugName = '<SvelteComponent>';
+	if (!options || (!options.target && !options.root)) throw new Error("'target' is a required option");
 	init(this, options);
 	this._state = assign({}, options.data);
+	if (!('name' in this._state)) console.warn("<SvelteComponent> was created without expected data property 'name'");
 	this._intro = true;
 
 	this._fragment = create_main_fragment(this, this._state);
 
 	if (options.target) {
+		if (options.hydrate) throw new Error("options.hydrate only works if the component was compiled with the `hydratable: true` option");
 		this._fragment.c();
 		this._mount(options.target, options.anchor);
 	}
 }
 
-assign(SvelteComponent.prototype, proto);
+assign(SvelteComponent.prototype, protoDev);
+
+SvelteComponent.prototype._checkReadOnly = function _checkReadOnly(newState) {
+};
 
-export default SvelteComponent;
\ No newline at end of file
+export default SvelteComponent;
diff --git a/test/js/samples/debug-empty/expected.js b/test/js/samples/debug-empty/expected.js
index 592f3a7a2b..9e0023fde2 100644
--- a/test/js/samples/debug-empty/expected.js
+++ b/test/js/samples/debug-empty/expected.js
@@ -1,20 +1,23 @@
 /* generated by Svelte vX.Y.Z */
-import { append, assign, createElement, createText, detachNode, init, insert, proto, setData } from "svelte/shared.js";
+import { addLoc, append, assign, createElement, createText, detachNode, init, insert, protoDev, setData } from "svelte/shared.js";
+
+const file = undefined;
 
 function create_main_fragment(component, ctx) {
 	var h1, text, text_1, text_2, text_3;
 
 	return {
-		c() {
+		c: function create() {
 			h1 = createElement("h1");
 			text = createText("Hello ");
 			text_1 = createText(ctx.name);
 			text_2 = createText("!");
 			text_3 = createText("\n");
 			debugger;
+			addLoc(h1, file, 0, 0, 0);
 		},
 
-		m(target, anchor) {
+		m: function mount(target, anchor) {
 			insert(target, h1, anchor);
 			append(h1, text);
 			append(h1, text_1);
@@ -22,7 +25,7 @@ function create_main_fragment(component, ctx) {
 			insert(target, text_3, anchor);
 		},
 
-		p(changed, ctx) {
+		p: function update(changed, ctx) {
 			if (changed.name) {
 				setData(text_1, ctx.name);
 			}
@@ -30,7 +33,7 @@ function create_main_fragment(component, ctx) {
 			debugger;
 		},
 
-		d(detach) {
+		d: function destroy(detach) {
 			if (detach) {
 				detachNode(h1);
 				detachNode(text_3);
@@ -40,17 +43,24 @@ function create_main_fragment(component, ctx) {
 }
 
 function SvelteComponent(options) {
+	this._debugName = '<SvelteComponent>';
+	if (!options || (!options.target && !options.root)) throw new Error("'target' is a required option");
 	init(this, options);
 	this._state = assign({}, options.data);
+	if (!('name' in this._state)) console.warn("<SvelteComponent> was created without expected data property 'name'");
 	this._intro = true;
 
 	this._fragment = create_main_fragment(this, this._state);
 
 	if (options.target) {
+		if (options.hydrate) throw new Error("options.hydrate only works if the component was compiled with the `hydratable: true` option");
 		this._fragment.c();
 		this._mount(options.target, options.anchor);
 	}
 }
 
-assign(SvelteComponent.prototype, proto);
+assign(SvelteComponent.prototype, protoDev);
+
+SvelteComponent.prototype._checkReadOnly = function _checkReadOnly(newState) {
+};
 export default SvelteComponent;
\ No newline at end of file
diff --git a/test/js/samples/debug-foo-bar-baz-things/_config.js b/test/js/samples/debug-foo-bar-baz-things/_config.js
new file mode 100644
index 0000000000..b1f2518e8a
--- /dev/null
+++ b/test/js/samples/debug-foo-bar-baz-things/_config.js
@@ -0,0 +1,5 @@
+export default {
+	options: {
+		dev: true
+	}
+};
\ 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
index 92431339d1..873b28aa2b 100644
--- a/test/js/samples/debug-foo-bar-baz-things/expected-bundle.js
+++ b/test/js/samples/debug-foo-bar-baz-things/expected-bundle.js
@@ -5,6 +5,12 @@ function assign(tar, src) {
 	return tar;
 }
 
+function addLoc(element, file, line, column, char) {
+	element.__svelte_meta = {
+		loc: { file, line, column, char }
+	};
+}
+
 function append(target, node) {
 	target.appendChild(node);
 }
@@ -49,6 +55,13 @@ function destroy(detach) {
 	this._state = {};
 }
 
+function destroyDev(detach) {
+	destroy.call(this, detach);
+	this.destroy = function() {
+		console.warn('Component was already destroyed');
+	};
+}
+
 function _differs(a, b) {
 	return a != a ? b == b : a !== b || ((a && typeof a === 'object') || typeof a === 'function');
 }
@@ -128,6 +141,17 @@ function _set(newState) {
 	}
 }
 
+function setDev(newState) {
+	if (typeof newState !== 'object') {
+		throw new Error(
+			this._debugName + '.set was called without an object of data key-values to update.'
+		);
+	}
+
+	this._checkReadOnly(newState);
+	set.call(this, newState);
+}
+
 function callAll(fns) {
 	while (fns && fns.length) fns.shift()();
 }
@@ -136,12 +160,12 @@ function _mount(target, anchor) {
 	this._fragment[this._fragment.i ? 'i' : 'm'](target, anchor || null);
 }
 
-var proto = {
-	destroy,
+var protoDev = {
+	destroy: destroyDev,
 	get,
 	fire,
 	on,
-	set,
+	set: setDev,
 	_recompute: noop,
 	_set,
 	_mount,
@@ -150,6 +174,8 @@ var proto = {
 
 /* generated by Svelte vX.Y.Z */
 
+const file = undefined;
+
 function create_main_fragment(component, ctx) {
 	var text, p, text_1, text_2;
 
@@ -162,7 +188,7 @@ function create_main_fragment(component, ctx) {
 	}
 
 	return {
-		c() {
+		c: function create() {
 			for (var i = 0; i < each_blocks.length; i += 1) {
 				each_blocks[i].c();
 			}
@@ -171,9 +197,10 @@ function create_main_fragment(component, ctx) {
 			p = createElement("p");
 			text_1 = createText("foo: ");
 			text_2 = createText(ctx.foo);
+			addLoc(p, file, 5, 0, 91);
 		},
 
-		m(target, anchor) {
+		m: function mount(target, anchor) {
 			for (var i = 0; i < each_blocks.length; i += 1) {
 				each_blocks[i].m(target, anchor);
 			}
@@ -184,7 +211,7 @@ function create_main_fragment(component, ctx) {
 			append(p, text_2);
 		},
 
-		p(changed, ctx) {
+		p: function update(changed, ctx) {
 			if (changed.things) {
 				each_value = ctx.things;
 
@@ -211,7 +238,7 @@ function create_main_fragment(component, ctx) {
 			}
 		},
 
-		d(detach) {
+		d: function destroy$$1(detach) {
 			destroyEach(each_blocks, detach);
 
 			if (detach) {
@@ -227,7 +254,7 @@ function create_each_block(component, ctx) {
 	var span, text_value = ctx.thing.name, text, text_1;
 
 	return {
-		c() {
+		c: function create() {
 			span = createElement("span");
 			text = createText(text_value);
 			text_1 = createText("\n\t");
@@ -235,15 +262,16 @@ function create_each_block(component, ctx) {
 			const { foo, bar, baz, thing } = ctx;
 			console.log({ foo, bar, baz, thing });
 			debugger;
+			addLoc(span, file, 1, 1, 25);
 		},
 
-		m(target, anchor) {
+		m: function mount(target, anchor) {
 			insert(target, span, anchor);
 			append(span, text);
 			insert(target, text_1, anchor);
 		},
 
-		p(changed, ctx) {
+		p: function update(changed, ctx) {
 			if ((changed.things) && text_value !== (text_value = ctx.thing.name)) {
 				setData(text, text_value);
 			}
@@ -255,7 +283,7 @@ function create_each_block(component, ctx) {
 			}
 		},
 
-		d(detach) {
+		d: function destroy$$1(detach) {
 			if (detach) {
 				detachNode(span);
 				detachNode(text_1);
@@ -273,18 +301,28 @@ function get_each_context(ctx, list, i) {
 }
 
 function SvelteComponent(options) {
+	this._debugName = '<SvelteComponent>';
+	if (!options || (!options.target && !options.root)) throw new Error("'target' is a required option");
 	init(this, options);
 	this._state = assign({}, options.data);
+	if (!('things' in this._state)) console.warn("<SvelteComponent> was created without expected data property 'things'");
+	if (!('foo' in this._state)) console.warn("<SvelteComponent> was created without expected data property 'foo'");
+	if (!('bar' in this._state)) console.warn("<SvelteComponent> was created without expected data property 'bar'");
+	if (!('baz' in this._state)) console.warn("<SvelteComponent> was created without expected data property 'baz'");
 	this._intro = true;
 
 	this._fragment = create_main_fragment(this, this._state);
 
 	if (options.target) {
+		if (options.hydrate) throw new Error("options.hydrate only works if the component was compiled with the `hydratable: true` option");
 		this._fragment.c();
 		this._mount(options.target, options.anchor);
 	}
 }
 
-assign(SvelteComponent.prototype, proto);
+assign(SvelteComponent.prototype, protoDev);
+
+SvelteComponent.prototype._checkReadOnly = function _checkReadOnly(newState) {
+};
 
-export default SvelteComponent;
\ No newline at end of file
+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
index 1406c3b927..eb8c70bac6 100644
--- a/test/js/samples/debug-foo-bar-baz-things/expected.js
+++ b/test/js/samples/debug-foo-bar-baz-things/expected.js
@@ -1,5 +1,7 @@
 /* generated by Svelte vX.Y.Z */
-import { append, assign, createElement, createText, destroyEach, detachNode, init, insert, proto, setData } from "svelte/shared.js";
+import { addLoc, append, assign, createElement, createText, destroyEach, detachNode, init, insert, protoDev, setData } from "svelte/shared.js";
+
+const file = undefined;
 
 function create_main_fragment(component, ctx) {
 	var text, p, text_1, text_2;
@@ -13,7 +15,7 @@ function create_main_fragment(component, ctx) {
 	}
 
 	return {
-		c() {
+		c: function create() {
 			for (var i = 0; i < each_blocks.length; i += 1) {
 				each_blocks[i].c();
 			}
@@ -22,9 +24,10 @@ function create_main_fragment(component, ctx) {
 			p = createElement("p");
 			text_1 = createText("foo: ");
 			text_2 = createText(ctx.foo);
+			addLoc(p, file, 5, 0, 91);
 		},
 
-		m(target, anchor) {
+		m: function mount(target, anchor) {
 			for (var i = 0; i < each_blocks.length; i += 1) {
 				each_blocks[i].m(target, anchor);
 			}
@@ -35,7 +38,7 @@ function create_main_fragment(component, ctx) {
 			append(p, text_2);
 		},
 
-		p(changed, ctx) {
+		p: function update(changed, ctx) {
 			if (changed.things) {
 				each_value = ctx.things;
 
@@ -62,7 +65,7 @@ function create_main_fragment(component, ctx) {
 			}
 		},
 
-		d(detach) {
+		d: function destroy(detach) {
 			destroyEach(each_blocks, detach);
 
 			if (detach) {
@@ -78,7 +81,7 @@ function create_each_block(component, ctx) {
 	var span, text_value = ctx.thing.name, text, text_1;
 
 	return {
-		c() {
+		c: function create() {
 			span = createElement("span");
 			text = createText(text_value);
 			text_1 = createText("\n\t");
@@ -86,15 +89,16 @@ function create_each_block(component, ctx) {
 			const { foo, bar, baz, thing } = ctx;
 			console.log({ foo, bar, baz, thing });
 			debugger;
+			addLoc(span, file, 1, 1, 25);
 		},
 
-		m(target, anchor) {
+		m: function mount(target, anchor) {
 			insert(target, span, anchor);
 			append(span, text);
 			insert(target, text_1, anchor);
 		},
 
-		p(changed, ctx) {
+		p: function update(changed, ctx) {
 			if ((changed.things) && text_value !== (text_value = ctx.thing.name)) {
 				setData(text, text_value);
 			}
@@ -106,7 +110,7 @@ function create_each_block(component, ctx) {
 			}
 		},
 
-		d(detach) {
+		d: function destroy(detach) {
 			if (detach) {
 				detachNode(span);
 				detachNode(text_1);
@@ -124,17 +128,27 @@ function get_each_context(ctx, list, i) {
 }
 
 function SvelteComponent(options) {
+	this._debugName = '<SvelteComponent>';
+	if (!options || (!options.target && !options.root)) throw new Error("'target' is a required option");
 	init(this, options);
 	this._state = assign({}, options.data);
+	if (!('things' in this._state)) console.warn("<SvelteComponent> was created without expected data property 'things'");
+	if (!('foo' in this._state)) console.warn("<SvelteComponent> was created without expected data property 'foo'");
+	if (!('bar' in this._state)) console.warn("<SvelteComponent> was created without expected data property 'bar'");
+	if (!('baz' in this._state)) console.warn("<SvelteComponent> was created without expected data property 'baz'");
 	this._intro = true;
 
 	this._fragment = create_main_fragment(this, this._state);
 
 	if (options.target) {
+		if (options.hydrate) throw new Error("options.hydrate only works if the component was compiled with the `hydratable: true` option");
 		this._fragment.c();
 		this._mount(options.target, options.anchor);
 	}
 }
 
-assign(SvelteComponent.prototype, proto);
+assign(SvelteComponent.prototype, protoDev);
+
+SvelteComponent.prototype._checkReadOnly = function _checkReadOnly(newState) {
+};
 export default SvelteComponent;
\ No newline at end of file
diff --git a/test/js/samples/debug-foo/_config.js b/test/js/samples/debug-foo/_config.js
new file mode 100644
index 0000000000..b1f2518e8a
--- /dev/null
+++ b/test/js/samples/debug-foo/_config.js
@@ -0,0 +1,5 @@
+export default {
+	options: {
+		dev: true
+	}
+};
\ No newline at end of file
diff --git a/test/js/samples/debug-foo/expected-bundle.js b/test/js/samples/debug-foo/expected-bundle.js
index 53d68c309f..d4fd9ffaec 100644
--- a/test/js/samples/debug-foo/expected-bundle.js
+++ b/test/js/samples/debug-foo/expected-bundle.js
@@ -5,6 +5,12 @@ function assign(tar, src) {
 	return tar;
 }
 
+function addLoc(element, file, line, column, char) {
+	element.__svelte_meta = {
+		loc: { file, line, column, char }
+	};
+}
+
 function append(target, node) {
 	target.appendChild(node);
 }
@@ -49,6 +55,13 @@ function destroy(detach) {
 	this._state = {};
 }
 
+function destroyDev(detach) {
+	destroy.call(this, detach);
+	this.destroy = function() {
+		console.warn('Component was already destroyed');
+	};
+}
+
 function _differs(a, b) {
 	return a != a ? b == b : a !== b || ((a && typeof a === 'object') || typeof a === 'function');
 }
@@ -128,6 +141,17 @@ function _set(newState) {
 	}
 }
 
+function setDev(newState) {
+	if (typeof newState !== 'object') {
+		throw new Error(
+			this._debugName + '.set was called without an object of data key-values to update.'
+		);
+	}
+
+	this._checkReadOnly(newState);
+	set.call(this, newState);
+}
+
 function callAll(fns) {
 	while (fns && fns.length) fns.shift()();
 }
@@ -136,12 +160,12 @@ function _mount(target, anchor) {
 	this._fragment[this._fragment.i ? 'i' : 'm'](target, anchor || null);
 }
 
-var proto = {
-	destroy,
+var protoDev = {
+	destroy: destroyDev,
 	get,
 	fire,
 	on,
-	set,
+	set: setDev,
 	_recompute: noop,
 	_set,
 	_mount,
@@ -150,6 +174,8 @@ var proto = {
 
 /* generated by Svelte vX.Y.Z */
 
+const file = undefined;
+
 function create_main_fragment(component, ctx) {
 	var text, p, text_1, text_2;
 
@@ -162,7 +188,7 @@ function create_main_fragment(component, ctx) {
 	}
 
 	return {
-		c() {
+		c: function create() {
 			for (var i = 0; i < each_blocks.length; i += 1) {
 				each_blocks[i].c();
 			}
@@ -171,9 +197,10 @@ function create_main_fragment(component, ctx) {
 			p = createElement("p");
 			text_1 = createText("foo: ");
 			text_2 = createText(ctx.foo);
+			addLoc(p, file, 5, 0, 74);
 		},
 
-		m(target, anchor) {
+		m: function mount(target, anchor) {
 			for (var i = 0; i < each_blocks.length; i += 1) {
 				each_blocks[i].m(target, anchor);
 			}
@@ -184,7 +211,7 @@ function create_main_fragment(component, ctx) {
 			append(p, text_2);
 		},
 
-		p(changed, ctx) {
+		p: function update(changed, ctx) {
 			if (changed.things) {
 				each_value = ctx.things;
 
@@ -211,7 +238,7 @@ function create_main_fragment(component, ctx) {
 			}
 		},
 
-		d(detach) {
+		d: function destroy$$1(detach) {
 			destroyEach(each_blocks, detach);
 
 			if (detach) {
@@ -227,7 +254,7 @@ function create_each_block(component, ctx) {
 	var span, text_value = ctx.thing.name, text, text_1;
 
 	return {
-		c() {
+		c: function create() {
 			span = createElement("span");
 			text = createText(text_value);
 			text_1 = createText("\n\t");
@@ -235,15 +262,16 @@ function create_each_block(component, ctx) {
 			const { foo } = ctx;
 			console.log({ foo });
 			debugger;
+			addLoc(span, file, 1, 1, 25);
 		},
 
-		m(target, anchor) {
+		m: function mount(target, anchor) {
 			insert(target, span, anchor);
 			append(span, text);
 			insert(target, text_1, anchor);
 		},
 
-		p(changed, ctx) {
+		p: function update(changed, ctx) {
 			if ((changed.things) && text_value !== (text_value = ctx.thing.name)) {
 				setData(text, text_value);
 			}
@@ -255,7 +283,7 @@ function create_each_block(component, ctx) {
 			}
 		},
 
-		d(detach) {
+		d: function destroy$$1(detach) {
 			if (detach) {
 				detachNode(span);
 				detachNode(text_1);
@@ -273,18 +301,26 @@ function get_each_context(ctx, list, i) {
 }
 
 function SvelteComponent(options) {
+	this._debugName = '<SvelteComponent>';
+	if (!options || (!options.target && !options.root)) throw new Error("'target' is a required option");
 	init(this, options);
 	this._state = assign({}, options.data);
+	if (!('things' in this._state)) console.warn("<SvelteComponent> was created without expected data property 'things'");
+	if (!('foo' in this._state)) console.warn("<SvelteComponent> was created without expected data property 'foo'");
 	this._intro = true;
 
 	this._fragment = create_main_fragment(this, this._state);
 
 	if (options.target) {
+		if (options.hydrate) throw new Error("options.hydrate only works if the component was compiled with the `hydratable: true` option");
 		this._fragment.c();
 		this._mount(options.target, options.anchor);
 	}
 }
 
-assign(SvelteComponent.prototype, proto);
+assign(SvelteComponent.prototype, protoDev);
+
+SvelteComponent.prototype._checkReadOnly = function _checkReadOnly(newState) {
+};
 
-export default SvelteComponent;
\ No newline at end of file
+export default SvelteComponent;
diff --git a/test/js/samples/debug-foo/expected.js b/test/js/samples/debug-foo/expected.js
index 4795565e59..214ec7486e 100644
--- a/test/js/samples/debug-foo/expected.js
+++ b/test/js/samples/debug-foo/expected.js
@@ -1,5 +1,7 @@
 /* generated by Svelte vX.Y.Z */
-import { append, assign, createElement, createText, destroyEach, detachNode, init, insert, proto, setData } from "svelte/shared.js";
+import { addLoc, append, assign, createElement, createText, destroyEach, detachNode, init, insert, protoDev, setData } from "svelte/shared.js";
+
+const file = undefined;
 
 function create_main_fragment(component, ctx) {
 	var text, p, text_1, text_2;
@@ -13,7 +15,7 @@ function create_main_fragment(component, ctx) {
 	}
 
 	return {
-		c() {
+		c: function create() {
 			for (var i = 0; i < each_blocks.length; i += 1) {
 				each_blocks[i].c();
 			}
@@ -22,9 +24,10 @@ function create_main_fragment(component, ctx) {
 			p = createElement("p");
 			text_1 = createText("foo: ");
 			text_2 = createText(ctx.foo);
+			addLoc(p, file, 5, 0, 74);
 		},
 
-		m(target, anchor) {
+		m: function mount(target, anchor) {
 			for (var i = 0; i < each_blocks.length; i += 1) {
 				each_blocks[i].m(target, anchor);
 			}
@@ -35,7 +38,7 @@ function create_main_fragment(component, ctx) {
 			append(p, text_2);
 		},
 
-		p(changed, ctx) {
+		p: function update(changed, ctx) {
 			if (changed.things) {
 				each_value = ctx.things;
 
@@ -62,7 +65,7 @@ function create_main_fragment(component, ctx) {
 			}
 		},
 
-		d(detach) {
+		d: function destroy(detach) {
 			destroyEach(each_blocks, detach);
 
 			if (detach) {
@@ -78,7 +81,7 @@ function create_each_block(component, ctx) {
 	var span, text_value = ctx.thing.name, text, text_1;
 
 	return {
-		c() {
+		c: function create() {
 			span = createElement("span");
 			text = createText(text_value);
 			text_1 = createText("\n\t");
@@ -86,15 +89,16 @@ function create_each_block(component, ctx) {
 			const { foo } = ctx;
 			console.log({ foo });
 			debugger;
+			addLoc(span, file, 1, 1, 25);
 		},
 
-		m(target, anchor) {
+		m: function mount(target, anchor) {
 			insert(target, span, anchor);
 			append(span, text);
 			insert(target, text_1, anchor);
 		},
 
-		p(changed, ctx) {
+		p: function update(changed, ctx) {
 			if ((changed.things) && text_value !== (text_value = ctx.thing.name)) {
 				setData(text, text_value);
 			}
@@ -106,7 +110,7 @@ function create_each_block(component, ctx) {
 			}
 		},
 
-		d(detach) {
+		d: function destroy(detach) {
 			if (detach) {
 				detachNode(span);
 				detachNode(text_1);
@@ -124,17 +128,25 @@ function get_each_context(ctx, list, i) {
 }
 
 function SvelteComponent(options) {
+	this._debugName = '<SvelteComponent>';
+	if (!options || (!options.target && !options.root)) throw new Error("'target' is a required option");
 	init(this, options);
 	this._state = assign({}, options.data);
+	if (!('things' in this._state)) console.warn("<SvelteComponent> was created without expected data property 'things'");
+	if (!('foo' in this._state)) console.warn("<SvelteComponent> was created without expected data property 'foo'");
 	this._intro = true;
 
 	this._fragment = create_main_fragment(this, this._state);
 
 	if (options.target) {
+		if (options.hydrate) throw new Error("options.hydrate only works if the component was compiled with the `hydratable: true` option");
 		this._fragment.c();
 		this._mount(options.target, options.anchor);
 	}
 }
 
-assign(SvelteComponent.prototype, proto);
+assign(SvelteComponent.prototype, protoDev);
+
+SvelteComponent.prototype._checkReadOnly = function _checkReadOnly(newState) {
+};
 export default SvelteComponent;
\ No newline at end of file