Add u16string literals

Fixes error C2022: '55357': too big for character

or similar errors

Author: aminya

test/native/encoding-conversion-test.cc

@@ -67,7 +67,7 @@ TEST_CASE("EncodingConversion::decode - four-byte UTF-16 characters") {
 
   u16string string;
   conversion->decode(string, input.data(), input.size());
-  REQUIRE(string == u"ab" "\xd83d" "\xde01" "cd");
+  REQUIRE(string == u"ab" u"\xd83d"  u"\xde01" u"cd");
 }
 
 TEST_CASE("EncodingConversion::encode - basic") {
@@ -93,7 +93,7 @@ TEST_CASE("EncodingConversion::encode - basic") {
 
 TEST_CASE("EncodingConversion::encode - four-byte UTF-16 characters") {
   auto conversion = transcoding_to("UTF-8");
-  u16string string = u"ab" "\xd83d" "\xde01" "cd";  // 'ab😁cd'
+  u16string string = u"ab" u"\xd83d" u"\xde01" u"cd";  // 'ab😁cd'
 
   vector<char> output(10);
   size_t bytes_encoded = 0, start = 0;
@@ -116,7 +116,7 @@ TEST_CASE("EncodingConversion::encode - four-byte UTF-16 characters") {
 
 TEST_CASE("EncodingConversion::encode - invalid characters in the middle of the string") {
   auto conversion = transcoding_to("UTF-8");
-  u16string string = u"abc" "\xD800" "def";
+  u16string string = u"abc" u"\xD800" u"def";
 
   vector<char> output(10);
   size_t bytes_encoded = 0, start = 0;
@@ -136,7 +136,7 @@ TEST_CASE("EncodingConversion::encode - invalid characters in the middle of the
 
 TEST_CASE("EncodingConversion::encode - invalid characters at the end of the string") {
   auto conversion = transcoding_to("UTF-8");
-  u16string string = u"abc" "\xD800";
+  u16string string = u"abc" u"\xD800";
 
   vector<char> output(10);
   size_t bytes_encoded = 0, start = 0;

test/native/text-buffer-test.cc

@@ -467,7 +467,7 @@ TEST_CASE("TextBuffer::find_words_with_subsequence_in_range") {
 }
 
 TEST_CASE("TextBuffer::has_astral") {
-  REQUIRE(TextBuffer{u"ab" "\xd83d" "\xde01" "cd"}.has_astral());
+  REQUIRE(TextBuffer{u"ab" u"\xd83d" u"\xde01" u"cd"}.has_astral());
   REQUIRE(!TextBuffer{u"abcd"}.has_astral());
 }