prevent possibility of conflicts with __file

src/compile/Compiler.ts

@@ -118,6 +118,7 @@ export default class Compiler {
 	usesRefs: boolean;
 
 	file: string;
+	fileVar: string;
 	locate: (c: number) => { line: number, column: number };
 
 	stylesheet: Stylesheet;
@@ -182,6 +183,8 @@ export default class Compiler {
 		this.aliases = new Map();
 		this.usedNames = new Set();
 
+		this.fileVar = options.dev && this.getUniqueName('file');
+
 		this.computations = [];
 		this.templateProperties = {};
 

src/compile/dom/index.ts

@@ -101,7 +101,7 @@ export default function dom(
 	}
 
 	if (compiler.options.dev) {
-		builder.addLine(`const __file = ${JSON.stringify(compiler.file)};`);
+		builder.addLine(`const ${compiler.fileVar} = ${JSON.stringify(compiler.file)};`);
 	}
 
 	const css = compiler.stylesheet.render(options.filename, !compiler.customElement);

src/compile/nodes/Element.ts

@@ -399,7 +399,7 @@ export default class Element extends Node {
 		if (this.compiler.options.dev) {
 			const loc = this.compiler.locate(this.start);
 			block.builders.hydrate.addLine(
-				`@addLoc(${this.var}, __file, ${loc.line}, ${loc.column}, ${this.start});`
+				`@addLoc(${this.var}, ${this.compiler.fileVar}, ${loc.line}, ${loc.column}, ${this.start});`
 			);
 		}
 	}

test/cli/samples/dev/expected/Main.js

@@ -1,6 +1,6 @@
 /* src/Main.html generated by Svelte vx.y.z */
 
-const __file = "src/Main.html";
+const file = "src/Main.html";
 
 function create_main_fragment(component, ctx) {
 	var p, text;
@@ -9,7 +9,7 @@ function create_main_fragment(component, ctx) {
 		c: function create() {
 			p = createElement("p");
 			text = createText("Hello world!");
-			addLoc(p, __file, 0, 0, 0);
+			addLoc(p, file, 0, 0, 0);
 		},
 
 		m: function mount(target, anchor) {

test/js/samples/dev-warning-missing-data-computed/expected-bundle.js

@@ -165,7 +165,7 @@ function bar({ foo }) {
 	return foo * 2;
 }
 
-const __file = undefined;
+const file = undefined;
 
 function create_main_fragment(component, ctx) {
 	var p, text_value = ctx.Math.max(0, ctx.foo), text, text_1, text_2;
@@ -176,7 +176,7 @@ function create_main_fragment(component, ctx) {
 			text = createText(text_value);
 			text_1 = createText("\n\t");
 			text_2 = createText(ctx.bar);
-			addLoc(p, __file, 0, 0, 0);
+			addLoc(p, file, 0, 0, 0);
 		},
 
 		m: function mount(target, anchor) {

test/js/samples/dev-warning-missing-data-computed/expected.js

@@ -5,7 +5,7 @@ function bar({ foo }) {
 	return foo * 2;
 }
 
-const __file = undefined;
+const file = undefined;
 
 function create_main_fragment(component, ctx) {
 	var p, text_value = ctx.Math.max(0, ctx.foo), text, text_1, text_2;
@@ -16,7 +16,7 @@ function create_main_fragment(component, ctx) {
 			text = createText(text_value);
 			text_1 = createText("\n\t");
 			text_2 = createText(ctx.bar);
-			addLoc(p, __file, 0, 0, 0);
+			addLoc(p, file, 0, 0, 0);
 		},
 
 		m: function mount(target, anchor) {