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Document sentinel type in langref

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Jonathan Marler 2019-12-07 12:16:05 -07:00 committed by Andrew Kelley
parent 7699b5b997
commit 4cb4148b35
1 changed files with 20 additions and 0 deletions
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doc/langref.html.in
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@ -8363,6 +8363,7 @@ pub const TypeInfo = union(TypeId) {
alignment: comptime_int, alignment: comptime_int,
child: type, child: type,
is_allowzero: bool, is_allowzero: bool,
sentinel: var,
pub const Size = enum { pub const Size = enum {
One, One,
@ -8375,6 +8376,7 @@ pub const TypeInfo = union(TypeId) {
pub const Array = struct { pub const Array = struct {
len: comptime_int, len: comptime_int,
child: type, child: type,
sentinel: var,
}; };
pub const ContainerLayout = enum { pub const ContainerLayout = enum {
@ -8505,6 +8507,24 @@ pub const TypeInfo = union(TypeId) {
{#link|error sets|Error Set Type#}, the fields are guaranteed to be in the same {#link|error sets|Error Set Type#}, the fields are guaranteed to be in the same
order as declared. For declarations, the order is unspecified. order as declared. For declarations, the order is unspecified.
</p> </p>
<p>
Note that the {#syntax#}sentinel{#endsyntax#} field in {#syntax#}TypeInfo.Pointer{#endsyntax#}
and {#syntax#}TypeInfo.Array{#endsyntax#} is of type {#syntax#}var{#endsyntax#} rather
than {#syntax#}?child{#endsyntax#}. {#syntax#}TypeInfo.Pointer{#endsyntax#}
and {#syntax#}TypeInfo.Array{#endsyntax#} can be constructed with any comptime value for the
{#syntax#}sentinel{#endsyntax#} field. However, the {#syntax#}@Type{#endsyntax#} builtin will
only accept the TypeInfo struct if the sentinel value is implicitly convertible to
{#syntax#}child{#endsyntax#}. Furthermore, any {#syntax#}TypeInfo.Pointer{#endsyntax#}
or {#syntax#}TypeInfo.Array{#endsyntax#} retreived from {#syntax#}@typeInfo{#endsyntax#} will
guarantee that {#syntax#}@typeOf(sentinel){#endsyntax#} is equal to
{#syntax#}?child{#endsyntax#}. For example, {#syntax#}@typeOf(sentinel){#endsyntax#} for a
{#syntax#}TypeInfo.Pointer{#endsyntax#} constructed with
{#syntax#}TypeInfo.Pointer { ... .sentinel = 0; ... }{#endsyntax#} would be
{#syntax#}comptime_int{#endsyntax#} rather than {#syntax#}?u8{#endsyntax#}. However, if you
passed that {#syntax#}TypeInfo.Pointer{#endsyntax#} struct to
{#syntax#}@typeInfo(@Type(myPointerInfo)){#endsyntax#} then {#syntax#}@typeOf(sentinel){#endsyntax#}
would be {#syntax#}?u8{#endsyntax#}.
</p>
{#header_close#} {#header_close#}
{#header_open|@typeName#} {#header_open|@typeName#}