Affected subclause: [depr.meta.types]
Remove deprecated type traits.
The traits had unreliable or awkward interfaces.
trait provided no way to detect which subset of constructors and member
functions of a type were declared constexpr.
trait had a surprising syntax that did not directly support function types.
It has been superseded by the invoke_result
Effect on original feature:
A valid C++ 2017 program that relies on the is_literal_type
type traits, on the is_literal_type_v
or on the result_of_t
alias template may fail to compile.