LibJS: Start implementing Temporal.PlainDate

This commit adds the PlainDate object itself, its constructor and
prototype (currently empty), and several required abstract operations.

Userland/Libraries/LibJS/Runtime/Temporal/PlainDateConstructor.cpp

@@ -0,0 +1,96 @@
+/*
+ * Copyright (c) 2021, Idan Horowitz <idan.horowitz@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <AK/Checked.h>
+#include <LibJS/Runtime/GlobalObject.h>
+#include <LibJS/Runtime/Temporal/Calendar.h>
+#include <LibJS/Runtime/Temporal/PlainDate.h>
+#include <LibJS/Runtime/Temporal/PlainDateConstructor.h>
+
+namespace JS::Temporal {
+
+// 3.1 The Temporal.PlainDate Constructor, https://tc39.es/proposal-temporal/#sec-temporal-plaindate-constructor
+PlainDateConstructor::PlainDateConstructor(GlobalObject& global_object)
+    : NativeFunction(vm().names.PlainDate.as_string(), *global_object.function_prototype())
+{
+}
+
+void PlainDateConstructor::initialize(GlobalObject& global_object)
+{
+    NativeFunction::initialize(global_object);
+
+    auto& vm = this->vm();
+
+    // 3.2.1 Temporal.PlainDate.prototype, https://tc39.es/proposal-temporal/#sec-temporal-plaindate-prototype
+    define_direct_property(vm.names.prototype, global_object.temporal_plain_date_prototype(), 0);
+
+    define_direct_property(vm.names.length, Value(0), Attribute::Configurable);
+}
+
+// 3.1.1 Temporal.PlainDate ( isoYear, isoMonth, isoDay [ , calendarLike ] ), https://tc39.es/proposal-temporal/#sec-temporal.plaindate
+Value PlainDateConstructor::call()
+{
+    auto& vm = this->vm();
+
+    // 1. If NewTarget is undefined, throw a TypeError exception.
+    vm.throw_exception<TypeError>(global_object(), ErrorType::ConstructorWithoutNew, "Temporal.PlainDate");
+    return {};
+}
+
+// 3.1.1 Temporal.PlainDate ( isoYear, isoMonth, isoDay [ , calendarLike ] ), https://tc39.es/proposal-temporal/#sec-temporal.plaindate
+Value PlainDateConstructor::construct(FunctionObject& new_target)
+{
+    auto& vm = this->vm();
+    auto& global_object = this->global_object();
+
+    // 2. Let y be ? ToIntegerOrInfinity(isoYear).
+    auto y = vm.argument(0).to_integer_or_infinity(global_object);
+    if (vm.exception())
+        return {};
+    // 3. If y is +∞ or -∞, throw a RangeError exception.
+    if (Value(y).is_infinity()) {
+        vm.throw_exception<RangeError>(global_object, ErrorType::TemporalInvalidPlainDate);
+        return {};
+    }
+
+    // 4. Let m be ? ToIntegerOrInfinity(isoMonth).
+    auto m = vm.argument(1).to_integer_or_infinity(global_object);
+    if (vm.exception())
+        return {};
+    // 5. If m is +∞ or -∞, throw a RangeError exception.
+    if (Value(m).is_infinity()) {
+        vm.throw_exception<RangeError>(global_object, ErrorType::TemporalInvalidPlainDate);
+        return {};
+    }
+
+    // 6. Let d be ? ToIntegerOrInfinity(isoDay).
+    auto d = vm.argument(2).to_integer_or_infinity(global_object);
+    if (vm.exception())
+        return {};
+    // 7. If d is +∞ or -∞, throw a RangeError exception.
+    if (Value(d).is_infinity()) {
+        vm.throw_exception<RangeError>(global_object, ErrorType::TemporalInvalidPlainDate);
+        return {};
+    }
+
+    // 8. Let calendar be ? ToTemporalCalendarWithISODefault(calendarLike).
+    auto* calendar = to_temporal_calendar_with_iso_default(global_object, vm.argument(3));
+    if (vm.exception())
+        return {};
+
+    // IMPLEMENTATION DEFINED: This is an optimization that allows us to treat these doubles as normal integers from this point onwards.
+    // This does not change the exposed behaviour as the call to CreateTemporalDate will immediately check that these values are valid
+    // ISO values (for years: -273975 - 273975, for months: 1 - 12, for days: 1 - 31) all of which are subsets of this check.
+    if (!AK::is_within_range<i32>(y) || !AK::is_within_range<i32>(m) || !AK::is_within_range<i32>(d)) {
+        vm.throw_exception<RangeError>(global_object, ErrorType::TemporalInvalidPlainDate);
+        return {};
+    }
+
+    // 9. Return ? CreateTemporalDate(y, m, d, calendar, NewTarget).
+    return create_temporal_date(global_object, y, m, d, *calendar, &new_target);
+}
+
+}