Update frontend.h

Author: ntrel

compiler/src/dmd/frontend.h

@@ -2595,6 +2595,7 @@ class CallExp final : public UnaExp
     bool inDebugStatement;
     bool ignoreAttributes;
     bool isUfcsRewrite;
+    bool fromOpAssignment;
     VarDeclaration* vthis2;
     Expression* loweredFrom;
     static CallExp* create(Loc loc, Expression* e, Array<Expression* >* exps);