Question

So I’m getting type clashes in bison, of the form

warning: type clash on default action: <stmt> != <expr>

because I have a production like

%type <stmt> Stmt
%type <expr> Expr
...
Stmt : Expr    /* empty */
     | Otherstuff {do other stuff.....}
     ;

I was wondering if there was a way to get rid of these errors, because Expr is a subclass of Stmt (I’m using c++), but has extra functions so just putting in

%type <stmt> Stmt Expr

won’t work. Any ideas?

Answer 1

The easy way is:

Stmt : Expr         {$$ =  $1;} // This is the same as default action