# How many fixing revisions added null checks? AddedNullCheck: output sum of int; p: Project = input; isfixing := false; count := 0; # map of file names to the last revision of that file files: map[string] of ChangedFile; visit(p, visitor { before node: Revision -> isfixing = isfixingrevision(node.log); before node: ChangedFile -> { # if this is a fixing revision and # there was a previous version of the file if (isfixing && haskey(files, node.name)) { # count how many null checks were previously in the file count = 0; visit(getast(files[node.name])); last := count; # count how many null checks are currently in the file count = 0; visit(getast(node)); # if there are more null checks, output if (count > last) AddedNullCheck << 1; } if (node.change == ChangeKind.DELETED) remove(files, node.name); else files[node.name] = node; stop; } before node: Statement -> # increase the counter if there is an IF statement # where the boolean condition is of the form: # null == expr OR expr == null OR null != expr OR expr != null if (node.kind == StatementKind.IF) visit(node.expression, visitor { before node: Expression -> if (node.kind == ExpressionKind.EQ || node.kind == ExpressionKind.NEQ) exists (i: int; isliteral(node.expressions[i], "null")) count++; }); });

AddedNullCheck[] = 149347