[webkit-changes] [WebKit/WebKit] 3c0f2f: Use std::void_t in HasLegacyDecoder, HasModernDecoder

[Žan Doberšek]

  Branch: refs/heads/main
  Home:   https://github.com/WebKit/WebKit
  Commit: 3c0f2fdb4126f5bf8adba030e6718fcbc0dc3e23
      https://github.com/WebKit/WebKit/commit/3c0f2fdb4126f5bf8adba030e6718fcbc0dc3e23
  Author: Žan Doberšek <zdobersek at igalia.com>
  Date:   2023-01-11 (Wed, 11 Jan 2023)

  Changed paths:
    M Source/WTF/wtf/ArgumentCoder.h
    M Source/WebKit/Platform/IPC/Decoder.h

  Log Message:
  -----------
  Use std::void_t in HasLegacyDecoder, HasModernDecoder
https://bugs.webkit.org/show_bug.cgi?id=250275

Reviewed by Fujii Hironori.

The HasLegacyDecoder and HasModernDecoder templates used to detect presence of
either decoding method on a given type's decoding-implementation class are
simplified.

The base templates inherit from std::false_type and gain the third template
parameter that defaults to void. In corresponding partial specializations that
inherit from std::true_type, that third template argument is then specified
as std::void_t instantiation with the type of the desired decoding method.
When the desired method is present, the std::true_type-based partial
specialization will be selected. When not present, the std::false_type-based
base template will be used.

Templated HasLegacyDecoderV and HasModernDecoderV constexpr booleans are
removed as they're only used in one place.

* Source/WTF/wtf/ArgumentCoder.h:
(IPC::ArgumentCoder::decode):
(IPC::Detail::TestLegacyDecoder): Deleted.
(IPC::Detail::TestModernDecoder): Deleted.
* Source/WebKit/Platform/IPC/Decoder.h:

Canonical link: https://commits.webkit.org/258778@main