AK: Add support for AK::StringView literals with operator""sv

A new operator, operator""sv was added as of C++17 to support
string_view literals. This allows string_views to be constructed
from string literals and with no runtime cost to find the string
length.

See: https://en.cppreference.com/w/cpp/string/basic_string_view/operator%22%22sv

This change implements that functionality in AK::StringView.
We do have to suppress some warnings about implementing reserved
operators as we are essentially implementing STL functions in AK
as we have no STL :).

AK/StringView.h

@@ -213,4 +213,9 @@ struct Traits<StringView> : public GenericTraits<String> {
 
 }
 
+[[nodiscard]] ALWAYS_INLINE constexpr AK::StringView operator"" sv(const char* cstring, size_t length)
+{
+    return AK::StringView(cstring, length);
+}
+
 using AK::StringView;

AK/Tests/TestStringView.cpp

@@ -59,6 +59,15 @@ TEST_CASE(compare_views)
     EXPECT_EQ(view1, "foo");
 }
 
+TEST_CASE(string_view_literal_operator)
+{
+    StringView literal_view = "foo"sv;
+    String test_string = "foo";
+
+    EXPECT_EQ(literal_view.length(), test_string.length());
+    EXPECT_EQ(literal_view, test_string);
+}
+
 TEST_CASE(starts_with)
 {
     String test_string = "ABCDEF";

CMakeLists.txt

@@ -80,9 +80,9 @@ else()
 endif()
 
 if ("${CMAKE_CXX_COMPILER_ID}" STREQUAL "GNU")
-    add_compile_options(-fconcepts)
+    add_compile_options(-fconcepts -Wno-literal-suffix)
 elseif ("${CMAKE_CXX_COMPILER_ID}" STREQUAL "Clang")
-    add_compile_options(-Wno-overloaded-virtual)
+    add_compile_options(-Wno-overloaded-virtual -Wno-user-defined-literals)
 endif()
 
 if (ENABLE_ALL_THE_DEBUG_MACROS)

Meta/Lagom/CMakeLists.txt

@@ -9,7 +9,7 @@ endif()
 
 
 if ("${CMAKE_CXX_COMPILER_ID}" STREQUAL "Clang")
-    set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Wno-overloaded-virtual")
+    set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Wno-overloaded-virtual -Wno-user-defined-literals")
 
     if (ENABLE_ADDRESS_SANITIZER)
         add_definitions(-fsanitize=address -fno-omit-frame-pointer)