About term "type-id"

In C++, a "type-id" refers to the type specifier used to define a variable or object.

• The Type-id specifies the type of the object being created with new.
• It can be a built-in type (like int, double, etc.) or a user-defined type (class or struct).
• It can also be a placeholder type specifier, such as auto or decltype(auto).

For example, when we talk about the "type-id of a new expression," we're specifically referring to the type specifier used in the allocation of memory for a new object using the new keyword.

1. New Expression:

   • In C++, the new operator is used to dynamically allocate memory for an object or array.
   • Syntax: new Type-id or new Type-id [size] for array allocation.

2. Type-id of a New Expression:

   • When we say "type-id of a new expression," we're referring to the Type-id used in the new expression.
   • This Type-id specifies the type of the object being allocated in memory.
   • For example:
     • new int allocates memory for an int.
     • new MyClass allocates memory for an object of type MyClass.
     • new auto or new decltype(expr) deduces the type from the initializer expression expr.