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std.meta: remove isTag (#15584)

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This is not used by Zig itself anywhere and not using the function is more idiomatic.
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Meghan 2023-07-10 11:35:36 -07:00 committed by GitHub
parent cd0594e4a6
commit 3d5751b579
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1 changed files with 1 additions and 47 deletions
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lib/std/meta.zig
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@ -16,53 +16,7 @@ test {
pub const tagName = @compileError("deprecated; use @tagName or @errorName directly");
/// Given an enum or tagged union, returns true if the comptime-supplied
/// string matches the name of the tag value. This match process should
/// be, at runtime, O(1) in the number of tags available to the enum or
/// union, and it should also be O(1) in the length of the comptime tag
/// names.
pub fn isTag(tagged_value: anytype, comptime tag_name: []const u8) bool {
const T = @TypeOf(tagged_value);
const type_info = @typeInfo(T);
const type_name = @typeName(T);
// select the Enum type out of the type (in the case of the tagged union, extract it)
const E = if (.Enum == type_info) T else if (.Union == type_info) (type_info.Union.tag_type orelse {
@compileError("attempted to use isTag on the untagged union " ++ type_name);
}) else {
@compileError("attempted to use isTag on a value of type (" ++ type_name ++ ") that isn't an enum or a union.");
};
return tagged_value == @field(E, tag_name);
}
test "std.meta.isTag for Enums" {
const EnumType = enum { a, b };
var a_type: EnumType = .a;
var b_type: EnumType = .b;
try testing.expect(isTag(a_type, "a"));
try testing.expect(!isTag(a_type, "b"));
try testing.expect(isTag(b_type, "b"));
try testing.expect(!isTag(b_type, "a"));
}
test "std.meta.isTag for Tagged Unions" {
const TaggedUnionEnum = enum { int, flt };
const TaggedUnionType = union(TaggedUnionEnum) {
int: i64,
flt: f64,
};
var int = TaggedUnionType{ .int = 1234 };
var flt = TaggedUnionType{ .flt = 12.34 };
try testing.expect(isTag(int, "int"));
try testing.expect(!isTag(int, "flt"));
try testing.expect(isTag(flt, "flt"));
try testing.expect(!isTag(flt, "int"));
}
pub const isTag = @compileError("deprecated; use 'tagged_value == @field(E, tag_name)' directly");
/// Returns the variant of an enum type, `T`, which is named `str`, or `null` if no such variant exists.
pub fn stringToEnum(comptime T: type, str: []const u8) ?T {