• This note in [class.temporary]/(6.8) :

An explicit type conversion ([expr.type.conv], [expr.cast]) is interpreted as a sequence of elementary casts, covered above.

• [dcl.attr.nodiscard]/(3.2):

an explicit type conversion ([expr.type.conv], [expr.static.cast], [expr.cast]) that constructs an object through a constructor declared nodiscard in a reachable declaration, or that initializes an object of a nodiscard type.

• [class.conv]/1:

Type conversions of class objects can be specified by constructors and by conversion functions. These conversions are called user-defined conversions and are used for implicit type conversions ([conv]), for initialization ([dcl.init]), and for explicit type conversions ([expr.type.conv], [expr.cast], [expr.static.cast]).

• [class.abstract]/3:

[Note: An abstract class type cannot be used as a parameter or return type of a function being defined ([dcl.fct]) or called ([expr.call]), except as specified in [dcl.type.simple]. Further, an abstract class type cannot be used as the type of an explicit type conversion ([expr.static.cast], [expr.reinterpret.cast], [expr.const.cast]), because the resulting prvalue would be of abstract class type ([basic.lval]). However, pointers and references to abstract class types can appear in such contexts. — end note]

• [over.over]/(1.6):

an explicit type conversion ([expr.type.conv], [expr.static.cast], [expr.cast]), or