LibJS: Replace Vector<u16> usage in PrimitiveString wth Utf16String

This commit does not go out of its way to reduce copying of the string
data yet, but is a minimum set of changes to compile LibJS after making
PrimitiveString hold a Utf16String.

Userland/Libraries/LibJS/Runtime/AbstractOperations.cpp

@@ -29,6 +29,7 @@
 #include <LibJS/Runtime/PropertyName.h>
 #include <LibJS/Runtime/ProxyObject.h>
 #include <LibJS/Runtime/Reference.h>
+#include <LibJS/Runtime/Utf16String.h>
 
 namespace JS {
 
@@ -576,7 +577,7 @@ String get_substitution(GlobalObject& global_object, Utf16View const& matched, U
     auto replace_string = replacement.to_utf16_string(global_object);
     if (vm.exception())
         return {};
-    Utf16View replace_view { replace_string };
+    auto replace_view = replace_string.view();
 
     StringBuilder result;
 

Userland/Libraries/LibJS/Runtime/PrimitiveString.cpp

@@ -17,7 +17,7 @@ PrimitiveString::PrimitiveString(String string)
 {
 }
 
-PrimitiveString::PrimitiveString(Vector<u16> string)
+PrimitiveString::PrimitiveString(Utf16String string)
     : m_utf16_string(move(string))
     , m_has_utf16_string(true)
 {
@@ -30,16 +30,16 @@ PrimitiveString::~PrimitiveString()
 String const& PrimitiveString::string() const
 {
     if (!m_has_utf8_string) {
-        m_utf8_string = utf16_string_view().to_utf8(Utf16View::AllowInvalidCodeUnits::Yes);
+        m_utf8_string = m_utf16_string.to_utf8();
         m_has_utf8_string = true;
     }
     return m_utf8_string;
 }
 
-Vector<u16> const& PrimitiveString::utf16_string() const
+Utf16String const& PrimitiveString::utf16_string() const
 {
     if (!m_has_utf16_string) {
-        m_utf16_string = AK::utf8_to_utf16(m_utf8_string);
+        m_utf16_string = Utf16String(m_utf8_string);
         m_has_utf16_string = true;
     }
     return m_utf16_string;
@@ -47,24 +47,12 @@ Vector<u16> const& PrimitiveString::utf16_string() const
 
 Utf16View PrimitiveString::utf16_string_view() const
 {
-    return Utf16View { utf16_string() };
+    return utf16_string().view();
 }
 
 PrimitiveString* js_string(Heap& heap, Utf16View const& view)
 {
-    if (view.is_empty())
-        return &heap.vm().empty_string();
-
-    if (view.length_in_code_units() == 1) {
-        u16 code_unit = view.code_unit_at(0);
-        if (is_ascii(code_unit))
-            return &heap.vm().single_ascii_character_string(static_cast<u8>(code_unit));
-    }
-
-    Vector<u16> string;
-    string.ensure_capacity(view.length_in_code_units());
-    string.append(view.data(), view.length_in_code_units());
-    return js_string(heap, move(string));
+    return js_string(heap, Utf16String(view));
 }
 
 PrimitiveString* js_string(VM& vm, Utf16View const& view)
@@ -72,13 +60,13 @@ PrimitiveString* js_string(VM& vm, Utf16View const& view)
     return js_string(vm.heap(), view);
 }
 
-PrimitiveString* js_string(Heap& heap, Vector<u16> string)
+PrimitiveString* js_string(Heap& heap, Utf16String string)
 {
     if (string.is_empty())
         return &heap.vm().empty_string();
 
-    if (string.size() == 1) {
-        u16 code_unit = string.at(0);
+    if (string.length_in_code_units() == 1) {
+        u16 code_unit = string.code_unit_at(0);
         if (is_ascii(code_unit))
             return &heap.vm().single_ascii_character_string(static_cast<u8>(code_unit));
     }
@@ -86,7 +74,7 @@ PrimitiveString* js_string(Heap& heap, Vector<u16> string)
     return heap.allocate_without_global_object<PrimitiveString>(move(string));
 }
 
-PrimitiveString* js_string(VM& vm, Vector<u16> string)
+PrimitiveString* js_string(VM& vm, Utf16String string)
 {
     return js_string(vm.heap(), move(string));
 }

Userland/Libraries/LibJS/Runtime/PrimitiveString.h

@@ -7,15 +7,15 @@
 #pragma once
 
 #include <AK/String.h>
-#include <AK/Vector.h>
 #include <LibJS/Heap/Cell.h>
+#include <LibJS/Runtime/Utf16String.h>
 
 namespace JS {
 
 class PrimitiveString final : public Cell {
 public:
     explicit PrimitiveString(String);
-    explicit PrimitiveString(Vector<u16>);
+    explicit PrimitiveString(Utf16String);
     virtual ~PrimitiveString();
 
     PrimitiveString(PrimitiveString const&) = delete;
@@ -23,7 +23,7 @@ public:
 
     String const& string() const;
 
-    Vector<u16> const& utf16_string() const;
+    Utf16String const& utf16_string() const;
     Utf16View utf16_string_view() const;
 
 private:
@@ -32,15 +32,15 @@ private:
     mutable String m_utf8_string;
     mutable bool m_has_utf8_string { false };
 
-    mutable Vector<u16> m_utf16_string;
+    mutable Utf16String m_utf16_string;
     mutable bool m_has_utf16_string { false };
 };
 
 PrimitiveString* js_string(Heap&, Utf16View const&);
 PrimitiveString* js_string(VM&, Utf16View const&);
 
-PrimitiveString* js_string(Heap&, Vector<u16>);
-PrimitiveString* js_string(VM&, Vector<u16>);
+PrimitiveString* js_string(Heap&, Utf16String);
+PrimitiveString* js_string(VM&, Utf16String);
 
 PrimitiveString* js_string(Heap&, String);
 PrimitiveString* js_string(VM&, String);

Userland/Libraries/LibJS/Runtime/RegExpPrototype.cpp

@@ -18,6 +18,7 @@
 #include <LibJS/Runtime/RegExpPrototype.h>
 #include <LibJS/Runtime/RegExpStringIterator.h>
 #include <LibJS/Runtime/StringPrototype.h>
+#include <LibJS/Runtime/Utf16String.h>
 #include <LibJS/Token.h>
 
 namespace JS {
@@ -414,7 +415,7 @@ JS_DEFINE_NATIVE_FUNCTION(RegExpPrototype::exec)
     auto string = vm.argument(0).to_utf16_string(global_object);
     if (vm.exception())
         return {};
-    Utf16View string_view { string };
+    auto string_view = string.view();
 
     return regexp_builtin_exec(global_object, *regexp_object, string_view);
 }
@@ -429,7 +430,7 @@ JS_DEFINE_NATIVE_FUNCTION(RegExpPrototype::test)
     auto string = vm.argument(0).to_utf16_string(global_object);
     if (vm.exception())
         return {};
-    Utf16View string_view { string };
+    auto string_view = string.view();
 
     auto match = regexp_exec(global_object, *regexp_object, string_view);
     if (vm.exception())
@@ -472,7 +473,7 @@ JS_DEFINE_NATIVE_FUNCTION(RegExpPrototype::symbol_match)
     auto string = vm.argument(0).to_utf16_string(global_object);
     if (vm.exception())
         return {};
-    Utf16View string_view { string };
+    auto string_view = string.view();
 
     auto global_value = regexp_object->get(vm.names.global);
     if (vm.exception())
@@ -597,7 +598,7 @@ JS_DEFINE_NATIVE_FUNCTION(RegExpPrototype::symbol_replace)
     auto string = string_value.to_utf16_string(global_object);
     if (vm.exception())
         return {};
-    Utf16View string_view { string };
+    auto string_view = string.view();
 
     if (!replace_value.is_function()) {
         auto replace_string = replace_value.to_string(global_object);
@@ -672,7 +673,7 @@ JS_DEFINE_NATIVE_FUNCTION(RegExpPrototype::symbol_replace)
         auto matched = matched_value.to_utf16_string(global_object);
         if (vm.exception())
             return {};
-        Utf16View matched_view { matched };
+        auto matched_length = matched.length_in_code_units();
 
         auto position_value = result.get(vm.names.index);
         if (vm.exception())
@@ -711,7 +712,7 @@ JS_DEFINE_NATIVE_FUNCTION(RegExpPrototype::symbol_replace)
 
         if (replace_value.is_function()) {
             MarkedValueList replacer_args(vm.heap());
-            replacer_args.append(js_string(vm, matched_view));
+            replacer_args.append(js_string(vm, move(matched)));
             replacer_args.extend(move(captures));
             replacer_args.append(Value(position));
             replacer_args.append(js_string(vm, string_view));
@@ -734,7 +735,7 @@ JS_DEFINE_NATIVE_FUNCTION(RegExpPrototype::symbol_replace)
                     return {};
             }
 
-            replacement = get_substitution(global_object, matched_view, string_view, position, captures, named_captures_object, replace_value);
+            replacement = get_substitution(global_object, matched.view(), string_view, position, captures, named_captures_object, replace_value);
             if (vm.exception())
                 return {};
         }
@@ -748,7 +749,7 @@ JS_DEFINE_NATIVE_FUNCTION(RegExpPrototype::symbol_replace)
             builder.append(replacement);
 
             accumulated_result = builder.build();
-            next_source_position = position + matched_view.length_in_code_units();
+            next_source_position = position + matched_length;
         }
     }
 
@@ -774,7 +775,7 @@ JS_DEFINE_NATIVE_FUNCTION(RegExpPrototype::symbol_search)
     auto string = vm.argument(0).to_utf16_string(global_object);
     if (vm.exception())
         return {};
-    Utf16View string_view { string };
+    auto string_view = string.view();
 
     auto previous_last_index = regexp_object->get(vm.names.lastIndex);
     if (vm.exception())
@@ -822,7 +823,7 @@ JS_DEFINE_NATIVE_FUNCTION(RegExpPrototype::symbol_split)
     auto string = vm.argument(0).to_utf16_string(global_object);
     if (vm.exception())
         return {};
-    Utf16View string_view { string };
+    auto string_view = string.view();
 
     auto* constructor = species_constructor(global_object, *regexp_object, *global_object.regexp_constructor());
     if (vm.exception())

Userland/Libraries/LibJS/Runtime/RegExpStringIterator.cpp

@@ -10,12 +10,12 @@
 namespace JS {
 
 // 22.2.7.1 CreateRegExpStringIterator ( R, S, global, fullUnicode ), https://tc39.es/ecma262/#sec-createregexpstringiterator
-RegExpStringIterator* RegExpStringIterator::create(GlobalObject& global_object, Object& regexp_object, Vector<u16> string, bool global, bool unicode)
+RegExpStringIterator* RegExpStringIterator::create(GlobalObject& global_object, Object& regexp_object, Utf16String string, bool global, bool unicode)
 {
     return global_object.heap().allocate<RegExpStringIterator>(global_object, *global_object.regexp_string_iterator_prototype(), regexp_object, move(string), global, unicode);
 }
 
-RegExpStringIterator::RegExpStringIterator(Object& prototype, Object& regexp_object, Vector<u16> string, bool global, bool unicode)
+RegExpStringIterator::RegExpStringIterator(Object& prototype, Object& regexp_object, Utf16String string, bool global, bool unicode)
     : Object(prototype)
     , m_regexp_object(regexp_object)
     , m_string(move(string))

Userland/Libraries/LibJS/Runtime/RegExpStringIterator.h

@@ -8,6 +8,7 @@
 
 #include <AK/Utf16View.h>
 #include <LibJS/Runtime/Object.h>
+#include <LibJS/Runtime/Utf16String.h>
 
 namespace JS {
 
@@ -15,13 +16,13 @@ class RegExpStringIterator final : public Object {
     JS_OBJECT(RegExpStringIterator, Object);
 
 public:
-    static RegExpStringIterator* create(GlobalObject&, Object& regexp_object, Vector<u16> string, bool global, bool unicode);
+    static RegExpStringIterator* create(GlobalObject&, Object& regexp_object, Utf16String string, bool global, bool unicode);
 
-    explicit RegExpStringIterator(Object& prototype, Object& regexp_object, Vector<u16> string, bool global, bool unicode);
+    explicit RegExpStringIterator(Object& prototype, Object& regexp_object, Utf16String string, bool global, bool unicode);
     virtual ~RegExpStringIterator() override = default;
 
     Object& regexp_object() { return m_regexp_object; }
-    Utf16View string() const { return Utf16View { m_string }; }
+    Utf16View string() const { return m_string.view(); }
     bool global() const { return m_global; }
     bool unicode() const { return m_unicode; }
 
@@ -32,7 +33,7 @@ private:
     virtual void visit_edges(Cell::Visitor&) override;
 
     Object& m_regexp_object;
-    Vector<u16> m_string;
+    Utf16String m_string;
     bool m_global { false };
     bool m_unicode { false };
     bool m_done { false };

Userland/Libraries/LibJS/Runtime/RegExpStringIteratorPrototype.cpp

@@ -9,6 +9,7 @@
 #include <LibJS/Runtime/RegExpPrototype.h>
 #include <LibJS/Runtime/RegExpStringIterator.h>
 #include <LibJS/Runtime/RegExpStringIteratorPrototype.h>
+#include <LibJS/Runtime/Utf16String.h>
 
 namespace JS {
 

Userland/Libraries/LibJS/Runtime/StringConstructor.cpp

@@ -13,6 +13,7 @@
 #include <LibJS/Runtime/GlobalObject.h>
 #include <LibJS/Runtime/StringConstructor.h>
 #include <LibJS/Runtime/StringObject.h>
+#include <LibJS/Runtime/Utf16String.h>
 
 namespace JS {
 
@@ -135,7 +136,7 @@ JS_DEFINE_NATIVE_FUNCTION(StringConstructor::from_char_code)
         string.append(code_unit);
     }
 
-    return js_string(vm, move(string));
+    return js_string(vm, Utf16String(move(string)));
 }
 
 // 22.1.2.2 String.fromCodePoint ( ...codePoints ), https://tc39.es/ecma262/#sec-string.fromcodepoint
@@ -161,7 +162,7 @@ JS_DEFINE_NATIVE_FUNCTION(StringConstructor::from_code_point)
         AK::code_point_to_utf16(string, static_cast<u32>(code_point));
     }
 
-    return js_string(vm, move(string));
+    return js_string(vm, Utf16String(move(string)));
 }
 
 }

Userland/Libraries/LibJS/Runtime/StringPrototype.cpp

@@ -19,6 +19,7 @@
 #include <LibJS/Runtime/StringIterator.h>
 #include <LibJS/Runtime/StringObject.h>
 #include <LibJS/Runtime/StringPrototype.h>
+#include <LibJS/Runtime/Utf16String.h>
 #include <LibJS/Runtime/Value.h>
 #include <LibUnicode/CharacterTypes.h>
 #include <string.h>
@@ -33,7 +34,7 @@ static Optional<String> ak_string_from(VM& vm, GlobalObject& global_object)
     return this_value.to_string(global_object);
 }
 
-static Vector<u16> utf16_string_from(VM& vm, GlobalObject& global_object)
+static Utf16String utf16_string_from(VM& vm, GlobalObject& global_object)
 {
     auto this_value = require_object_coercible(global_object, vm.this_value(global_object));
     if (vm.exception())
@@ -186,7 +187,7 @@ JS_DEFINE_NATIVE_FUNCTION(StringPrototype::char_at)
     if (vm.exception())
         return {};
 
-    Utf16View utf16_string_view { string };
+    auto utf16_string_view = string.view();
     if (position < 0 || position >= utf16_string_view.length_in_code_units())
         return js_string(vm, String::empty());
 
@@ -203,7 +204,7 @@ JS_DEFINE_NATIVE_FUNCTION(StringPrototype::char_code_at)
     if (vm.exception())
         return {};
 
-    Utf16View utf16_string_view { string };
+    auto utf16_string_view = string.view();
     if (position < 0 || position >= utf16_string_view.length_in_code_units())
         return js_nan();
 
@@ -220,7 +221,7 @@ JS_DEFINE_NATIVE_FUNCTION(StringPrototype::code_point_at)
     if (vm.exception())
         return {};
 
-    Utf16View utf16_string_view { string };
+    auto utf16_string_view = string.view();
     if (position < 0 || position >= utf16_string_view.length_in_code_units())
         return js_undefined();
 
@@ -283,10 +284,10 @@ JS_DEFINE_NATIVE_FUNCTION(StringPrototype::starts_with)
     if (vm.exception())
         return {};
 
-    Utf16View utf16_string_view { string };
+    auto utf16_string_view = string.view();
     auto string_length = utf16_string_view.length_in_code_units();
 
-    Utf16View utf16_search_view { search_string };
+    auto utf16_search_view = search_string.view();
     auto search_length = utf16_search_view.length_in_code_units();
 
     size_t start = 0;
@@ -329,10 +330,10 @@ JS_DEFINE_NATIVE_FUNCTION(StringPrototype::ends_with)
     if (vm.exception())
         return {};
 
-    Utf16View utf16_string_view { string };
+    auto utf16_string_view = string.view();
     auto string_length = utf16_string_view.length_in_code_units();
 
-    Utf16View utf16_search_view { search_string };
+    auto utf16_search_view = search_string.view();
     auto search_length = utf16_search_view.length_in_code_units();
 
     size_t end = string_length;
@@ -365,8 +366,8 @@ JS_DEFINE_NATIVE_FUNCTION(StringPrototype::index_of)
     if (vm.exception())
         return {};
 
-    Utf16View utf16_string_view { string };
-    Utf16View utf16_search_view { search_string };
+    auto utf16_string_view = string.view();
+    auto utf16_search_view = search_string.view();
 
     size_t start = 0;
     if (vm.argument_count() > 1) {
@@ -448,15 +449,14 @@ static Value pad_string(GlobalObject& global_object, String const& string, PadPl
 {
     auto& vm = global_object.vm();
 
-    auto utf16_string = AK::utf8_to_utf16(string);
-    Utf16View utf16_string_view { utf16_string };
-    auto string_length = utf16_string_view.length_in_code_units();
+    Utf16String utf16_string(string);
+    auto string_length = utf16_string.length_in_code_units();
 
     auto max_length = vm.argument(0).to_length(global_object);
     if (vm.exception())
         return {};
     if (max_length <= string_length)
-        return js_string(vm, utf16_string_view);
+        return js_string(vm, move(utf16_string));
 
     String fill_string = " ";
     if (!vm.argument(1).is_undefined()) {
@@ -464,11 +464,11 @@ static Value pad_string(GlobalObject& global_object, String const& string, PadPl
         if (vm.exception())
             return {};
         if (fill_string.is_empty())
-            return js_string(vm, utf16_string_view);
+            return js_string(vm, move(utf16_string));
     }
 
-    auto utf16_fill_string = AK::utf8_to_utf16(fill_string);
-    Utf16View utf16_fill_view { utf16_fill_string };
+    Utf16String utf16_fill_string(fill_string);
+    auto utf16_fill_view = utf16_fill_string.view();
     auto fill_code_units = utf16_fill_view.length_in_code_units();
     auto fill_length = max_length - string_length;
 
@@ -558,7 +558,7 @@ JS_DEFINE_NATIVE_FUNCTION(StringPrototype::substring)
     if (vm.exception())
         return {};
 
-    Utf16View utf16_string_view { string };
+    auto utf16_string_view = string.view();
     auto string_length = static_cast<double>(utf16_string_view.length_in_code_units());
 
     auto start = vm.argument(0).to_integer_or_infinity(global_object);
@@ -588,7 +588,7 @@ JS_DEFINE_NATIVE_FUNCTION(StringPrototype::substr)
     if (vm.exception())
         return {};
 
-    Utf16View utf16_string_view { string };
+    auto utf16_string_view = string.view();
     auto size = utf16_string_view.length_in_code_units();
 
     auto int_start = vm.argument(0).to_integer_or_infinity(global_object);
@@ -637,8 +637,8 @@ JS_DEFINE_NATIVE_FUNCTION(StringPrototype::includes)
     if (vm.exception())
         return {};
 
-    Utf16View utf16_string_view { string };
-    Utf16View utf16_search_view { search_string };
+    auto utf16_string_view = string.view();
+    auto utf16_search_view = search_string.view();
 
     size_t start = 0;
     if (!vm.argument(1).is_undefined()) {
@@ -659,7 +659,7 @@ JS_DEFINE_NATIVE_FUNCTION(StringPrototype::slice)
     if (vm.exception())
         return {};
 
-    Utf16View utf16_string_view { string };
+    auto utf16_string_view = string.view();
     auto string_length = static_cast<double>(utf16_string_view.length_in_code_units());
 
     auto int_start = vm.argument(0).to_integer_or_infinity(global_object);
@@ -730,10 +730,10 @@ JS_DEFINE_NATIVE_FUNCTION(StringPrototype::split)
     if (limit == 0)
         return array;
 
-    Utf16View utf16_string_view { string };
+    auto utf16_string_view = string.view();
     auto string_length = utf16_string_view.length_in_code_units();
 
-    Utf16View utf16_separator_view { separator };
+    auto utf16_separator_view = separator.view();
     auto separator_length = utf16_separator_view.length_in_code_units();
 
     if (separator_argument.is_undefined()) {
@@ -782,10 +782,10 @@ JS_DEFINE_NATIVE_FUNCTION(StringPrototype::last_index_of)
     if (vm.exception())
         return {};
 
-    Utf16View utf16_string_view { string };
+    auto utf16_string_view = string.view();
     auto string_length = utf16_string_view.length_in_code_units();
 
-    Utf16View utf16_search_view { search_string };
+    auto utf16_search_view = search_string.view();
     auto search_length = utf16_search_view.length_in_code_units();
 
     auto position = vm.argument(1).to_number(global_object);
@@ -822,7 +822,7 @@ JS_DEFINE_NATIVE_FUNCTION(StringPrototype::at)
     if (vm.exception())
         return {};
 
-    Utf16View utf16_string_view { string };
+    auto utf16_string_view = string.view();
     auto length = utf16_string_view.length_in_code_units();
 
     auto relative_index = vm.argument(0).to_integer_or_infinity(global_object);
@@ -873,7 +873,7 @@ JS_DEFINE_NATIVE_FUNCTION(StringPrototype::match)
     auto string = this_object.to_utf16_string(global_object);
     if (vm.exception())
         return {};
-    Utf16View utf16_string_view { string };
+    auto utf16_string_view = string.view();
 
     auto rx = regexp_create(global_object, regexp, js_undefined());
     if (!rx)
@@ -916,7 +916,7 @@ JS_DEFINE_NATIVE_FUNCTION(StringPrototype::match_all)
     auto string = this_object.to_utf16_string(global_object);
     if (vm.exception())
         return {};
-    Utf16View utf16_string_view { string };
+    auto utf16_string_view = string.view();
 
     auto rx = regexp_create(global_object, regexp, js_string(vm, "g"));
     if (!rx)
@@ -951,13 +951,13 @@ JS_DEFINE_NATIVE_FUNCTION(StringPrototype::replace)
         auto replace_string = replace_value.to_utf16_string(global_object);
         if (vm.exception())
             return {};
-        replace_value = js_string(vm, Utf16View { replace_string });
+        replace_value = js_string(vm, move(replace_string));
         if (vm.exception())
             return {};
     }
 
-    Utf16View utf16_string_view { string };
-    Utf16View utf16_search_view { search_string };
+    auto utf16_string_view = string.view();
+    auto utf16_search_view = search_string.view();
 
     Optional<size_t> position = string_index_of(utf16_string_view, utf16_search_view, 0);
     if (!position.has_value())
@@ -1042,15 +1042,15 @@ JS_DEFINE_NATIVE_FUNCTION(StringPrototype::replace_all)
         auto replace_string = replace_value.to_utf16_string(global_object);
         if (vm.exception())
             return {};
-        replace_value = js_string(vm, Utf16View { replace_string });
+        replace_value = js_string(vm, move(replace_string));
         if (vm.exception())
             return {};
     }
 
-    Utf16View utf16_string_view { string };
+    auto utf16_string_view = string.view();
     auto string_length = utf16_string_view.length_in_code_units();
 
-    Utf16View utf16_search_view { search_string };
+    auto utf16_search_view = search_string.view();
     auto search_length = utf16_search_view.length_in_code_units();
 
     Vector<size_t> match_positions;
@@ -1114,7 +1114,7 @@ JS_DEFINE_NATIVE_FUNCTION(StringPrototype::search)
     auto string = this_object.to_utf16_string(global_object);
     if (vm.exception())
         return {};
-    Utf16View utf16_string_view { string };
+    auto utf16_string_view = string.view();
 
     auto rx = regexp_create(global_object, regexp, js_undefined());
     if (!rx)

Userland/Libraries/LibJS/Runtime/Value.cpp

@@ -8,7 +8,6 @@
 #include <AK/AllOf.h>
 #include <AK/String.h>
 #include <AK/StringBuilder.h>
-#include <AK/Utf16View.h>
 #include <AK/Utf8View.h>
 #include <LibCrypto/BigInt/SignedBigInteger.h>
 #include <LibCrypto/NumberTheory/ModularFunctions.h>
@@ -363,7 +362,7 @@ String Value::to_string(GlobalObject& global_object, bool legacy_null_to_empty_s
     }
 }
 
-Vector<u16> Value::to_utf16_string(GlobalObject& global_object) const
+Utf16String Value::to_utf16_string(GlobalObject& global_object) const
 {
     if (m_type == Type::String)
         return m_value.as_string->utf16_string();
@@ -372,7 +371,7 @@ Vector<u16> Value::to_utf16_string(GlobalObject& global_object) const
     if (global_object.vm().exception())
         return {};
 
-    return AK::utf8_to_utf16(utf8_string);
+    return Utf16String(utf8_string);
 }
 
 // 7.1.2 ToBoolean ( argument ), https://tc39.es/ecma262/#sec-toboolean

Userland/Libraries/LibJS/Runtime/Value.h

@@ -18,6 +18,7 @@
 #include <LibJS/Forward.h>
 #include <LibJS/Runtime/BigInt.h>
 #include <LibJS/Runtime/PrimitiveString.h>
+#include <LibJS/Runtime/Utf16String.h>
 #include <math.h>
 
 // 2 ** 53 - 1
@@ -246,7 +247,7 @@ public:
     u64 encoded() const { return m_value.encoded; }
 
     String to_string(GlobalObject&, bool legacy_null_to_empty_string = false) const;
-    Vector<u16> to_utf16_string(GlobalObject&) const;
+    Utf16String to_utf16_string(GlobalObject&) const;
     PrimitiveString* to_primitive_string(GlobalObject&);
     Value to_primitive(GlobalObject&, PreferredType preferred_type = PreferredType::Default) const;
     Object* to_object(GlobalObject&) const;