1 files changed, 33 insertions, 0 deletions
diff --git a/js/src/jit-test/tests/basic/bug920484.js b/js/src/jit-test/tests/basic/bug920484.js
new file mode 100644
index 000000000..0c9e4c9ac
--- /dev/null
+++ b/js/src/jit-test/tests/basic/bug920484.js
@@ -0,0 +1,33 @@
+load(libdir + "asserts.js");
+
+// Add an invalid "localeMatcher" option to Object.prototype, the exact value does not matter,
+// any value except "best fit" or "lookup" is okay.
+Object.prototype.localeMatcher = "invalid matcher option";
+
+// The Intl API may not be available in the testing environment. Note that |hasOwnProperty("Intl")|
+// initializes the Intl API if present, so this if-statement needs to appear after "localeMatcher"
+// was added to Object.prototype.
+if (this.hasOwnProperty("Intl")) {
+    // Intl prototypes are properly initialized despite changed Object.prototype.
+    Intl.Collator.prototype.compare("a", "b");
+    Intl.NumberFormat.prototype.format(10);
+    Intl.DateTimeFormat.prototype.format(new Date);
+
+    // Intl constructors no longer work properly, because "localeMatcher" defaults to the invalid
+    // value from Object.prototype. Except for Intl.DateTimeFormat, cf. ECMA-402 ToDateTimeOptions.
+    assertThrowsInstanceOf(() => new Intl.Collator(), RangeError);
+    assertThrowsInstanceOf(() => new Intl.NumberFormat(), RangeError);
+    new Intl.DateTimeFormat().format(new Date);
+
+    // If an explicit "localeMatcher" option is given, the default from Object.prototype is ignored.
+    new Intl.Collator(void 0, {localeMatcher: "lookup"}).compare("a", "b");
+    new Intl.NumberFormat(void 0, {localeMatcher: "lookup"}).format(10);
+    new Intl.DateTimeFormat(void 0, {localeMatcher: "lookup"}).format(new Date);
+
+    delete Object.prototype.localeMatcher;
+
+    // After removing the default option from Object.prototype, everything works again as expected.
+    new Intl.Collator().compare("a", "b");
+    new Intl.NumberFormat().format(10);
+    new Intl.DateTimeFormat().format(new Date);
+}