Correct generation of operator +.

Author: MaxSagebaum

source/reflect.h

@@ -4250,8 +4250,8 @@ auto autodiff(meta::type_declaration& t) -> void
                             CPP2_UFCS(error)(m, "temporary alpha limitation: the addition's right-hand side '" + cpp2::to_string(rhs) + "' must be a parameter or return name");
                         }
 
-                        line1 += "" + cpp2::to_string(lhs) + " * " + cpp2::to_string(rhs) + "_d + " + cpp2::to_string(rhs) + " * " + cpp2::to_string(lhs) + "_d;";
-                        line2 += "" + cpp2::to_string(cpp2::move(lhs)) + " * " + cpp2::to_string(cpp2::move(rhs)) + ";";
+                        line1 += "" + cpp2::to_string(lhs) + "_d + " + cpp2::to_string(rhs) + "_d;";
+                        line2 += "" + cpp2::to_string(cpp2::move(lhs)) + " + " + cpp2::to_string(cpp2::move(rhs)) + ";";
 
                         diff += cpp2::move(line1) + cpp2::move(line2);
 

source/reflect.h2

@@ -2205,8 +2205,8 @@ autodiff: (inout t: meta::type_declaration) =
                             m.error( "temporary alpha limitation: the addition's right-hand side '(rhs)$' must be a parameter or return name");
                         }
 
-                        line1 += "(lhs)$ * (rhs)$_d + (rhs)$ * (lhs)$_d;";
-                        line2 += "(lhs)$ * (rhs)$;";
+                        line1 += "(lhs)$_d + (rhs)$_d;";
+                        line2 += "(lhs)$ + (rhs)$;";
 
                         diff += line1 + line2;