Add tests for Intl.DateTimeFormat conflicting options (#3033)

Relates to tc39/proposal-temporal#1590

test/intl402/DateTimeFormat/constructor-options-style-conflict.js

@@ -0,0 +1,44 @@
+// Copyright 2021 Kate Miháliková. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-initializedatetimeformat
+description: >
+    Conflicting properties of dateStyle/timeStyle must be rejected with a TypeError for the options argument to the DateTimeFormat constructor.
+info: |
+    InitializeDateTimeFormat ( dateTimeFormat, locales, options )
+
+    ...
+    36. If dateStyle is not undefined or timeStyle is not undefined, then
+      a. For each row in Table 4, except the header row, do
+        i. Let prop be the name given in the Property column of the row.
+        ii. Let p be opt.[[<prop>]].
+        iii. If p is not undefined, then
+          1. Throw a TypeError exception.
+---*/
+
+
+// Table 4 - Property column + example value from Values column
+const conflictingOptions = [
+ [ "weekday", "short" ],
+ [ "era", "short" ],
+ [ "year", "numeric" ],
+ [ "month", "numeric" ],
+ [ "day", "numeric" ],
+ [ "dayPeriod", "short" ],
+ [ "hour", "numeric" ],
+ [ "minute", "numeric" ],
+ [ "second", "numeric" ],
+ [ "fractionalSecondDigits", 3 ],
+ [ "timeZoneName", "short" ],
+];
+
+for (const [ option, value ] of conflictingOptions) {
+  assert.throws(TypeError, function() {
+    new Intl.DateTimeFormat("en", { [option]: value, dateStyle: "short" });
+  }, `new Intl.DateTimeFormat("en", { ${option}: "${value}",  dateStyle: "short" }) throws TypeError`);
+
+  assert.throws(TypeError, function() {
+    new Intl.DateTimeFormat("en", { [option]: value, timeStyle: "short" });
+  }, `new Intl.DateTimeFormat("en", { ${option}: "${value}",  timeStyle: "short" }) throws TypeError`);
+}