Make explicit the assumption that targetFileName is checked before ever calling printDep

include/asm/main.hpp

@@ -8,6 +8,8 @@
 #include <stdio.h>
 #include <string>
 
+#include "helpers.hpp" // assume
+
 enum MissingInclude {
 	INC_ERROR,    // A missing included file is an error that halts assembly
 	GEN_EXIT,     // A missing included file is assumed to be generated; exit normally
@@ -36,6 +38,7 @@ struct Options {
 
 	void printDep(std::string const &depName) {
 		if (dependFile) {
+			assume(targetFileName.has_value());
 			fprintf(dependFile, "%s: %s\n", targetFileName->c_str(), depName.c_str());
 		}
 	}