From ebd510ef5e577d248024466407515edb96b834b6 Mon Sep 17 00:00:00 2001
From: Nico Weber <thakis@chromium.org>
Date: Fri, 21 Aug 2020 21:41:43 -0400
Subject: [PATCH] LibJS: Allow conversion from Symbol to String via explicit
 String() call

https://tc39.es/ecma262/#sec-string-constructor-string-value has an
explicit special case for Symbols allowing this:

    If NewTarget is undefined and Type(value) is Symbol,
    return SymbolDescriptiveString(value).
---
 Libraries/LibJS/Runtime/StringConstructor.cpp               | 2 ++
 .../Tests/builtins/Symbol/Symbol.prototype.toString.js      | 6 ++++--
 2 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/Libraries/LibJS/Runtime/StringConstructor.cpp b/Libraries/LibJS/Runtime/StringConstructor.cpp
index 7ab381e257..1edc7a141f 100644
--- a/Libraries/LibJS/Runtime/StringConstructor.cpp
+++ b/Libraries/LibJS/Runtime/StringConstructor.cpp
@@ -59,6 +59,8 @@ Value StringConstructor::call(Interpreter& interpreter)
 {
     if (!interpreter.argument_count())
         return js_string(interpreter, "");
+    if (interpreter.argument(0).is_symbol())
+        return js_string(interpreter, interpreter.argument(0).as_symbol().to_string());
     auto* string = interpreter.argument(0).to_primitive_string(interpreter);
     if (interpreter.exception())
         return {};
diff --git a/Libraries/LibJS/Tests/builtins/Symbol/Symbol.prototype.toString.js b/Libraries/LibJS/Tests/builtins/Symbol/Symbol.prototype.toString.js
index 734b7a2191..4a95fe2397 100644
--- a/Libraries/LibJS/Tests/builtins/Symbol/Symbol.prototype.toString.js
+++ b/Libraries/LibJS/Tests/builtins/Symbol/Symbol.prototype.toString.js
@@ -1,10 +1,12 @@
 describe("correct behavior", () => {
     test("basic functionality", () => {
         const s1 = Symbol("baz");
-        // const s2 = Symbol.for("qux");
+        const s2 = Symbol.for("qux");
 
+        // Explicit conversions to string are fine, but implicit toString via concatenation throws.
         expect(s1.toString()).toBe("Symbol(baz)");
-        // expect(s2.toString()).toBe("Symbol(qux)");
+        expect(String(s1)).toBe("Symbol(baz)");
+        expect(s2.toString()).toBe("Symbol(qux)");
     });
 });