Performs an implicit conversion between types following the language rules for implicit conversion; if an implicit conversion is otherwise allowed by the language in the given context, this function performs such an implicit conversion.
Synopsis
Declared in <absl/base/casts.h>
template<typename To>
constexpr
To
implicit_cast(To to)
requires !type_traits_internal::IsView<std::enable_if_t<
!std::is_reference_v<To>, std::remove_cv_t<To>>>::value;Description
Example:
// If the context allows implicit conversion: From from; To to = from;
// Such code can be replaced by: implicit_cast<To>(from);
An implicit_cast() may also be used to annotate numeric type conversions that, although safe, may produce compiler warnings (such as long to int). Additionally, an implicit_cast() is also useful within return statements to indicate a specific implicit conversion is being undertaken.
Example:
return implicit_cast<double>(size_in_bytes) / capacity_;
Annotating code with implicit_cast() allows you to explicitly select particular overloads and template instantiations, while providing a safer cast than reinterpret_cast() or static_cast().
Additionally, an implicit_cast() can be used to allow upcasting within a type hierarchy where incorrect use of static_cast() could accidentally allow downcasting.
Finally, an implicit_cast() can be used to perform implicit conversions from unrelated types that otherwise couldn't be implicitly cast directly; C++ will normally only implicitly cast "one step" in such conversions.
That is, if C is a type which can be implicitly converted to B, with B being a type that can be implicitly converted to A, an implicit_cast() can be used to convert C to B (which the compiler can then implicitly convert to A using language rules).
Example:
// Assume an object C is convertible to B, which is implicitly convertible // to A A a = implicit_cast<B>©;
Such implicit cast chaining may be useful within template logic. This overload participates in overload resolution when To is not a view type and not a reference type.
Return Value
The value of to, converted to To.
Parameters
Name |
Description |
to |
The value to convert to |
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