Motivated by What does the expression std::string {} = "..." mean?;
Does the left hand side of the std::string {} = "hi"; induce temporary materialization and if it does, which of the mentioned scenarios below does it fall within?
Temporary materialization occurs in the following situations:
- 1- when binding a reference to a prvalue;
- 2- when performing a member access on a class prvalue;
- 3- when performing an array-to-pointer conversion or subscripting on an array prvalue;
- 4- when initializing an object of type std::initializer_list from a braced-init-list;
- 5- when typeid is applied to a prvalue
- 6- when sizeof is applied to a prvalue
- 7- when a prvalue appears as a discarded-value expression.
I would expect that std::string {} induces temporary materialization since we create an object that is temporary, but couldn't find which scenario would fit here.
The expression is transformed (after overload resolution) to std::string{}.operator=("hi") by [over.match.oper]/2, at which point temporary materialization applies per the second point in the list. (In standardese, [expr.ref]/2 says that . expects its first operand to be a glvalue, and [basic.lval]/7 applies the temporary materialization conversion whenever a prvalue appears in such a context.)