Added FAIL and FAIL_WITH_DEV_MESSAGE macros.

These macros allow to throw an wml_exception without any condition. This
can be used when a code path is reached that should be unreachable with
valid WML.

changelog

@@ -285,6 +285,7 @@ Version 1.11.0-svn:
    * Fixed: grids now recursively search for widgets by pointer.
    * Fixed: Wrong current side number after side turns (bug #19735)
      It also affected the lua field wesnoth.current.side
+   * Added: Fail macros FAIL and FAIL_WITH_DEV_MESSAGE.
 
 Version 1.10.0:
  * Campaigns:

src/wml_exception.cpp

@@ -41,8 +41,13 @@ void wml_exception(
 		, const std::string& dev_message)
 {
 	std::ostringstream sstr;
-	sstr << "Condition '" << cond << "' failed at "
-		<< file << ":" << line << " in function '" << function << "'.";
+	if(cond) {
+		sstr << "Condition '" << cond << "' failed at ";
+	} else {
+		sstr << "Unconditional failure at ";
+	}
+
+	sstr << file << ":" << line << " in function '" << function << "'.";
 
 	if(!dev_message.empty()) {
 		sstr << " Extra development information: " << dev_message;

src/wml_exception.hpp

@@ -66,6 +66,21 @@ class display;
 		}                                                                 \
 	} while(0)
 
+#define FAIL(message)                                                     \
+	do {                                                                  \
+		wml_exception(NULL, __FILE__, __LINE__, __func__, message);       \
+	} while(0)
+
+#define FAIL_WITH_DEV_MESSAGE(message, dev_message)                       \
+	do {                                                                  \
+		wml_exception(NULL                                                \
+				, __FILE__                                                \
+				, __LINE__                                                \
+				, __func__                                                \
+				, message                                                 \
+				, dev_message);                                           \
+	} while(0)
+
 /**
  *  Helper function, don't call this directly.
  *