Replace FALLTHROUGH macro by C++17 [[fallthrough]]

This attribute is now part of the standard we target so we no longer
need compiler-specific hacks.

Also enables -Wimplicit-fallthrough for Clang now that we can properly
support it. It's already on by default for GCC's -Wextra.

Fixes new warnings raised by Clang's -Wimplicit-fallthrough.

1 files changed, 1 insertions, 0 deletions

diff --git a/core/ustring.cpp b/core/ustring.cpp
index c4543b89da..1d4d9c2dfd 100644
--- a/core/ustring.cpp
+++ b/core/ustring.cpp
@@ -2169,6 +2169,7 @@ int64_t String::to_int(const CharType *p_str, int p_len) {
 				} else {
 					break;
 				}
+				[[fallthrough]];
 			}
 			case READING_INT: {