[v3,2/2] extend.texi: Add documentation for all missing built-in traits [PR87343]

diff --git a/gcc/doc/extend.texi b/gcc/doc/extend.texi
index 1c61682b102..2c8199fb1ab 100644
--- a/gcc/doc/extend.texi
+++ b/gcc/doc/extend.texi
@@ -29489,6 +29489,12 @@  compile-time determination of
 various characteristics of a type (or of a
 pair of types).
 
+
+@subsection Expression-yielding Type Traits
+
+These built-in traits yield an expression of type @code{bool}
+or @code{size_t}.
+
 @defbuiltin{bool __has_nothrow_assign (@var{type})}
 If @var{type} is @code{const}-qualified or is a reference type then
 the trait is @code{false}.  Otherwise if @code{__has_trivial_assign (type)}
@@ -29555,6 +29561,15 @@  Requires: @var{type} shall be a complete type, (possibly cv-qualified)
 @code{void}, or an array of unknown bound.
 @enddefbuiltin
 
+@defbuiltin{bool __has_unique_object_representations (@var{type})}
+If @code{__is_trivially_copyable (type)} is @code{true} and @var{type}
+has no padding bits, meaning that any two objects of @var{type} with
+the same value will have identical object representations, then
+the trait is @code{true}, else it is @code{false}.
+Requires: @var{type} shall be a complete type, (possibly cv-qualified)
+@code{void}, or an array of unknown bound.
+@enddefbuiltin
+
 @defbuiltin{bool __has_virtual_destructor (@var{type})}
 If @var{type} is a class type with a virtual destructor
 ([class.dtor]) then the trait is @code{true}, else it is @code{false}.
@@ -29580,6 +29595,23 @@  If @var{type} is an aggregate type ([dcl.init.aggr]) the trait is
 Requires: If @var{type} is a class type, it shall be a complete type.
 @enddefbuiltin
 
+@anchor{__is_array}
+@defbuiltin{bool __is_array (@var{type})}
+If @var{type} is an array type ([dcl.array]) the trait is @code{true},
+else it is @code{false}.
+See also: @ref{__is_bounded_array}.
+@enddefbuiltin
+
+@anchor{__is_assignable}
+@defbuiltin{bool __is_assignable (@var{type1}, @var{type2})}
+If @var{type1} is a class type that has an assignment operator
+accepting @var{type2}, or if @var{type2} can be implicitly converted to
+a type that @var{type1} can accept on assignment, then the trait is
+@code{true}, else it is @code{false}.
+Requires: If @var{type1} is a class type, it shall be a complete type.
+See also: @ref{__is_nothrow_assignable}, @ref{__is_trivially_assignable}.
+@enddefbuiltin
+
 @defbuiltin{bool __is_base_of (@var{base_type}, @var{derived_type})}
 If @var{base_type} is a base class of @var{derived_type}
 ([class.derived]) then the trait is @code{true}, otherwise it is @code{false}.
@@ -29592,11 +29624,37 @@  type (disregarding cv-qualifiers), @var{derived_type} shall be a complete
 type.  A diagnostic is produced if this requirement is not met.
 @enddefbuiltin
 
+@anchor{__is_bounded_array}
+@defbuiltin{bool __is_bounded_array (@var{type})}
+If @var{type} is an array type of known bound ([dcl.array])
+the trait is @code{true}, else it is @code{false}.
+See also: @ref{__is_array}.
+@enddefbuiltin
+
 @defbuiltin{bool __is_class (@var{type})}
 If @var{type} is a cv-qualified class type, and not a union type
 ([basic.compound]) the trait is @code{true}, else it is @code{false}.
 @enddefbuiltin
 
+@anchor{__is_constructible}
+@defbuiltin{bool __is_constructible (@var{type}, @var{arg_types}...)}
+If @var{type} is an object or reference type that can be constructed with
+arguments of types @var{arg_types}..., then the trait is @code{true},
+else it is @code{false}.
+Requires: If @var{type} or @var{arg_types}... is a class type, it shall be
+a complete type.
+See also: @ref{__is_nothrow_constructible}, @ref{__is_trivially_constructible}.
+@enddefbuiltin
+
+@anchor{__is_convertible}
+@defbuiltin{bool __is_convertible (@var{from_type}, @var{to_type})}
+If @var{from_type} can be implicitly converted to @var{to_type} then the
+trait is @code{true}, else it is @code{false}.
+Requires: If @var{from_type} or @var{to_type} is a class type, it shall be
+a complete type.
+See also: @ref{__is_nothrow_convertible}.
+@enddefbuiltin
+
 @c FIXME Commented out for GCC 13, discuss user interface for GCC 14.
 @c @defbuiltin{bool __is_deducible (@var{template}, @var{type})}
 @c If template arguments for @code{template} can be deduced from
@@ -29614,9 +29672,11 @@  has no base classes @var{base_type} for which
 Requires: If @var{type} is a non-union class type, it shall be a complete type.
 @enddefbuiltin
 
+@anchor{__is_enum}
 @defbuiltin{bool __is_enum (@var{type})}
 If @var{type} is a cv enumeration type ([basic.compound]) the trait is
 @code{true}, else it is @code{false}.
+See also: @ref{__is_scoped_enum}.
 @enddefbuiltin
 
 @defbuiltin{bool __is_final (@var{type})}
@@ -29625,6 +29685,18 @@  is @code{true}, else it is @code{false}.
 Requires: If @var{type} is a class type, it shall be a complete type.
 @enddefbuiltin
 
+@defbuiltin{bool __is_function (@var{type})}
+If @var{type} is a function type ([dcl.fct]) the trait is @code{true},
+else it is @code{false}.
+@enddefbuiltin
+
+@defbuiltin{bool __is_layout_compatible (@var{type1}, @var{type2})}
+If @var{type1} and @var{type2} are layout-compatible ([basic.types]) then
+the trait is @code{true}, else it is @code{false}.
+Requires: @var{type1} and @var{type2} shall be complete types, (possibly
+cv-qualified) @code{void}, or arrays of unknown bound.
+@enddefbuiltin
+
 @defbuiltin{bool __is_literal_type (@var{type})}
 If @var{type} is a literal type ([basic.types]) the trait is
 @code{true}, else it is @code{false}.
@@ -29632,6 +29704,72 @@  Requires: @var{type} shall be a complete type, (possibly cv-qualified)
 @code{void}, or an array of unknown bound.
 @enddefbuiltin
 
+@anchor{__is_member_function_pointer}
+@defbuiltin{bool __is_member_function_pointer (@var{type})}
+If @var{type} is a pointer to member function type ([dcl.mptr]) the trait is
+@code{true}, else it is @code{false}.
+See also: @ref{__is_member_object_pointer}, @ref{__is_member_pointer}.
+@enddefbuiltin
+
+@anchor{__is_member_object_pointer}
+@defbuiltin{bool __is_member_object_pointer (@var{type})}
+If @var{type} is a pointer to member object type ([dcl.mptr]) the trait is
+@code{true}, else it is @code{false}.
+See also: @ref{__is_member_function_pointer}, @ref{__is_member_pointer}.
+@enddefbuiltin
+
+@anchor{__is_member_pointer}
+@defbuiltin{bool __is_member_pointer (@var{type})}
+If @var{type} is a pointer to member type ([dcl.mptr]) the trait is
+@code{true}, else it is @code{false}.
+See also: @ref{__is_member_function_pointer}, @ref{__is_member_object_pointer}.
+@enddefbuiltin
+
+@anchor{__is_nothrow_assignable}
+@defbuiltin{bool __is_nothrow_assignable (@var{type1}, @var{type2})}
+If @code{__is_assignable (type1, type2)} is @code{true} and the assignment
+operation does not throw an exception then the trait is @code{true}, else
+it is @code{false}.
+Requires: If @var{type1} or @var{type2} is a class type, it shall be a
+complete type.
+See also: @ref{__is_assignable}, @ref{__is_trivially_assignable}.
+@enddefbuiltin
+
+@anchor{__is_nothrow_constructible}
+@defbuiltin{bool __is_nothrow_constructible (@var{type}, @var{arg_types}...)}
+If @code{__is_constructible (type, arg_types...)} is @code{true} and the
+construction does not throw an exception then the trait is @code{true},
+else it is @code{false}.
+Requires: If @var{type} or @var{arg_types}... is a class type, it shall be
+a complete type.
+See also: @ref{__is_constructible}, @ref{__is_trivially_constructible}.
+@enddefbuiltin
+
+@anchor{__is_nothrow_convertible}
+@defbuiltin{bool __is_nothrow_convertible (@var{from_type}, @var{to_type})}
+If @code{__is_convertible (from_type, to_type)} is @code{true} and the
+conversion does not throw an exception then the trait is @code{true},
+else it is @code{false}.
+Requires: If @var{from_type} or @var{to_type} is a class type, it shall be
+a complete type.
+See also: @ref{__is_convertible}.
+@enddefbuiltin
+
+@defbuiltin{bool __is_object (@var{type})}
+If @var{type} is an object type ([basic.types]) the trait is
+@code{true}, else it is @code{false}.
+@enddefbuiltin
+
+@defbuiltin{bool __is_pointer_interconvertible_base_of (@var{base_type}, @var{derived_type})}
+If @var{base_type} and @var{derived_type} are pointer-interconvertible
+([conv.ptr]) and @var{base_type} is a base class of @var{derived_type}
+([class.derived]) then the trait is @code{true}, else it is @code{false}.
+Requires: if @code{__is_class (base_type)} and @code{__is_class (derived_type)}
+are @code{true} and @var{base_type} and @var{derived_type} are not the same
+type (disregarding cv-qualifiers), @var{derived_type} shall be a complete
+type.  A diagnostic is produced if this requirement is not met.
+@enddefbuiltin
+
 @defbuiltin{bool __is_pod (@var{type})}
 If @var{type} is a cv POD type ([basic.types]) then the trait is @code{true},
 else it is @code{false}.
@@ -29645,6 +29783,23 @@  is @code{true}, else it is @code{false}.
 Requires: If @var{type} is a non-union class type, it shall be a complete type.
 @enddefbuiltin
 
+@defbuiltin{bool __is_reference (@var{type})}
+If @var{type} is a reference type ([dcl.ref]) the trait is @code{true},
+else it is @code{false}.
+@enddefbuiltin
+
+@defbuiltin{bool __is_same (@var{type1}, @var{type2})}
+A binary type trait: @code{true} whenever the @var{type1} and
+@var{type2} refer to the same type.
+@enddefbuiltin
+
+@anchor{__is_scoped_enum}
+@defbuiltin{bool __is_scoped_enum (@var{type})}
+If @var{type} is a scoped enumeration type ([dcl.enum]) the trait is
+@code{true}, else it is @code{false}.
+See also: @ref{__is_enum}.
+@enddefbuiltin
+
 @defbuiltin{bool __is_standard_layout (@var{type})}
 If @var{type} is a standard-layout type ([basic.types]) the trait is
 @code{true}, else it is @code{false}.
@@ -29652,11 +29807,45 @@  Requires: @var{type} shall be a complete type, an array of complete types,
 or (possibly cv-qualified) @code{void}.
 @enddefbuiltin
 
+@anchor{__is_trivial}
 @defbuiltin{bool __is_trivial (@var{type})}
 If @var{type} is a trivial type ([basic.types]) the trait is
 @code{true}, else it is @code{false}.
 Requires: @var{type} shall be a complete type, an array of complete types,
 or (possibly cv-qualified) @code{void}.
+See also: @ref{__is_trivially_assignable}, @ref{__is_trivially_constructible},
+@ref{__is_trivially_copyable}.
+@enddefbuiltin
+
+@anchor{__is_trivially_assignable}
+@defbuiltin{bool __is_trivially_assignable (@var{type1}, @var{type2})}
+If @code{__is_assignable (type1, type2)} is @code{true} and
+@code{__is_trivial (type1)} is @code{true} then the trait is @code{true},
+else it is @code{false}.
+Requires: If @var{type1} or @var{type2} is a class type, it shall be a
+complete type.
+See also: @ref{__is_trivial}, @ref{__is_assignable},
+@ref{__is_nothrow_assignable}.
+@enddefbuiltin
+
+@anchor{__is_trivially_constructible}
+@defbuiltin{bool __is_trivially_constructible (@var{type}, @var{arg_types}...)}
+If @code{__is_constructible (type, arg_types...)} is @code{true} and
+@code{__is_trivial (type)} is @code{true} then the trait is @code{true},
+else it is @code{false}.
+Requires: If @var{type} or @var{arg_types}... is a class type, it shall be
+a complete type.
+See also: @ref{__is_trivial}, @ref{__is_constructible},
+@ref{__is_nothrow_constructible}.
+@enddefbuiltin
+
+@anchor{__is_trivially_copyable}
+@defbuiltin{bool __is_trivially_copyable (@var{type})}
+If @var{type} is a trivially copyable type ([basic.types]) the trait is
+@code{true}, else it is @code{false}.
+Requires: @var{type} shall be a complete type, an array of complete types,
+or (possibly cv-qualified) @code{void}.
+See also: @ref{__is_trivial}.
 @enddefbuiltin
 
 @defbuiltin{bool __is_union (@var{type})}
@@ -29664,12 +29853,93 @@  If @var{type} is a cv union type ([basic.compound]) the trait is
 @code{true}, else it is @code{false}.
 @enddefbuiltin
 
+@anchor{__reference_constructs_from_temporary}
+@defbuiltin{bool __reference_constructs_from_temporary (@var{type1}, @var{type2})}
+If @var{type1} is a reference type and a value of type @var{type2} can be
+bound to @var{type1} in direct-initialization, such that a temporary object
+would be bound to the reference, then the trait is @code{true},
+else it is @code{false}.
+Requires: If @var{type1} or @var{type2} is a class type, it shall be
+a complete type.
+See also: @ref{__reference_converts_from_temporary}
+@enddefbuiltin
+
+@anchor{__reference_converts_from_temporary}
+@defbuiltin{bool __reference_converts_from_temporary (@var{type1}, @var{type2})}
+If @var{type1} is a reference type and a value of type @var{type2} can be
+bound to @var{type1} in copy-initialization, such that a temporary object
+would be bound to the reference, then the trait is @code{true},
+else it is @code{false}.
+Requires: If @var{type1} or @var{type2} is a class type, it shall be
+a complete type.
+See also: @ref{__reference_constructs_from_temporary}
+@enddefbuiltin
+
 @defbuiltin{bool __underlying_type (@var{type})}
 The underlying type of @var{type}.
 Requires: @var{type} shall be an enumeration type ([dcl.enum]).
 @enddefbuiltin
 
 
+@subsection Type-yielding Type Traits
+
+These built-in traits yield a type.
+
+@anchor{__bases}
+@defbuiltin{@var{types}... __bases (@var{type})}
+If @var{type} is a class type ([class.derived]) then the trait is a
+typelist of the base classes of @var{type}, else it is an empty typelist.
+See also: @ref{__direct_bases}.
+@enddefbuiltin
+
+@anchor{__direct_bases}
+@defbuiltin{@var{types}... __direct_bases (@var{type})}
+If @var{type} is a class type ([class.derived]) then the trait is a
+typelist of the direct base classes of @var{type}, else it is an empty
+typelist.
+See also: @ref{__bases}.
+@enddefbuiltin
+
+@anchor{__remove_cv}
+@defbuiltin{@var{type} __remove_cv (@var{cv_type})}
+If @var{cv_type} is a cv-qualified type ([basic.type.qualifier]), then the
+trait is the type @var{type} of @var{cv_type} with its top-level cv-qualifiers
+removed, else it is @var{cv_type}.
+See also: @ref{__remove_cvref}
+@enddefbuiltin
+
+@anchor{__remove_cvref}
+@defbuiltin{@var{type} __remove_cvref (@var{cvref_type})}
+If @var{cvref_type} is a cv-qualified ([basic.type.qualifier]) or reference
+type ([dcl.ref]), then the trait is the type @var{type} of
+@var{cvref_type} with its top-level cv-qualifiers and reference removed,
+else it is @var{cvref_type}.
+See also: @ref{__remove_cv}, @ref{__remove_reference}.
+@enddefbuiltin
+
+@defbuiltin{@var{type} __remove_pointer (@var{ptr_type})}
+If @var{ptr_type} is a pointer type ([dcl.ptr]), then the trait is the
+@var{type} pointed to by @var{ptr_type}, else it is @var{ptr_type}.
+@enddefbuiltin
+
+@anchor{__remove_reference}
+@defbuiltin{@var{type} __remove_reference (@var{ref_type})}
+If @var{ref_type} is a reference type ([dcl.ref]), then the trait is the
+@var{type} referred to by @var{ref_type}, else it is @var{ref_type}.
+See also: @ref{__remove_cvref}
+@enddefbuiltin
+
+@defbuiltin{@var{type} __type_pack_element (int @var{index}, @var{types}...)}
+If 0 < @var{index} < sizeof...(@var{types}), then the trait is the
+@var{index}-th type in the pack @var{types}..., else it emits an error.
+@enddefbuiltin
+
+@defbuiltin{@var{type} __underlying_type (@var{enum_type})}
+If @var{enum_type} is a complete enumeration type ([dcl.enum]), then
+the trait is the underlying type of @var{enum_type}, else it emits an error.
+@enddefbuiltin
+
+
 @node C++ Concepts
 @section C++ Concepts
 
@@ -29708,15 +29978,6 @@  Introduces constraints on template arguments or requirements for a member
 function of a class template.
 @end table
 
-The front end also exposes a number of internal mechanism that can be used
-to simplify the writing of type traits. Note that some of these traits are
-likely to be removed in the future.
-
-@defbuiltin{bool __is_same (@var{type1}, @var{type2})}
-A binary type trait: @code{true} whenever the @var{type1} and
-@var{type2} refer to the same type.
-@enddefbuiltin
-
 
 @node Deprecated Features
 @section Deprecated Features