[core:text/regex] Follow up to fix #6323 and add test case. As was said in the issue discussion I had suspicion that there may be a sibling bug in .Assert_Non_Word_Boundary implementation and I was able to confirm that with re.findall(rB", ") python code. Odin implementation outputed an empty string wherase python gave "'". That is the same bug related to incorrect logic on string ends. This commit makes implementation of those 2 instructions cleaner and adds a test case.

core/text/regex/virtual_machine/virtual_machine.odin

@@ -204,15 +204,8 @@ add_thread :: proc(vm: ^Machine, saved: ^[2 * common.MAX_CAPTURE_GROUPS]int, pc:
 		case .Assert_Word_Boundary:
 			sp := vm.string_pointer+vm.current_rune_size
 
-			left_is_wc := false
-			if sp > 0 {
-				left_is_wc = is_word_class(vm.current_rune)
-			}
-
-			right_is_wc := false
-			if sp < len(vm.memory) {
-				right_is_wc = is_word_class(vm.next_rune)
-			}
+			left_is_wc := sp > 0 && is_word_class(vm.current_rune)
+			right_is_wc := sp < len(vm.memory) && is_word_class(vm.next_rune)
 
 			if left_is_wc != right_is_wc {
 				pc += size_of(Opcode)
@@ -221,14 +214,13 @@ add_thread :: proc(vm: ^Machine, saved: ^[2 * common.MAX_CAPTURE_GROUPS]int, pc:
 
 		case .Assert_Non_Word_Boundary:
 			sp := vm.string_pointer+vm.current_rune_size
-			if sp != 0 && sp != len(vm.memory) {
-				last_rune_is_wc := is_word_class(vm.current_rune)
-				this_rune_is_wc := is_word_class(vm.next_rune)
 
-				if last_rune_is_wc && this_rune_is_wc || !last_rune_is_wc && !this_rune_is_wc {
-					pc += size_of(Opcode)
-					continue
-				}
+			left_is_wc := sp > 0 && is_word_class(vm.current_rune)
+			right_is_wc := sp < len(vm.memory) && is_word_class(vm.next_rune)
+
+			if left_is_wc == right_is_wc {
+				pc += size_of(Opcode)
+				continue
 			}
 
 		case .Wait_For_Byte:

tests/core/text/regex/test_core_text_regex.odin

@@ -564,6 +564,10 @@ test_non_word_boundaries :: proc(t: ^testing.T) {
 		EXPR :: `.+\B`
 		check_expression(t, EXPR, "abc", "ab")
 	}
+	{
+		EXPR :: `\B'`
+		check_expression(t, EXPR, "'", "'")
+	}
 }
 
 @test