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std.enums: add tagName()

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This is safe alternative to `@tagName()` for non-exhaustive enums that
doesn't panic when given an enum value that has no tag.
This commit is contained in:
Travis Staloch 2023-05-02 16:10:59 -07:00 committed by Veikka Tuominen
parent 37f56a4259
commit 5d1e69389c
1 changed files with 16 additions and 0 deletions
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16
lib/std/enums.zig
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@ -48,6 +48,22 @@ pub fn values(comptime E: type) []const E {
return comptime valuesFromFields(E, @typeInfo(E).Enum.fields);
}
/// A safe alternative to @tagName() for non-exhaustive enums that doesn't
/// panic when `e` has no tagged value.
/// Returns the tag name for `e` or null if no tag exists.
pub fn tagName(comptime E: type, e: E) ?[]const u8 {
return inline for (@typeInfo(E).Enum.fields) |f| {
if (@enumToInt(e) == f.value) break f.name;
} else null;
}
test tagName {
const E = enum(u8) { a, b, _ };
try testing.expect(tagName(E, .a) != null);
try testing.expectEqualStrings("a", tagName(E, .a).?);
try testing.expect(tagName(E, @intToEnum(E, 42)) == null);
}
/// Determines the length of a direct-mapped enum array, indexed by
/// @intCast(usize, @enumToInt(enum_value)).
/// If the enum is non-exhaustive, the resulting length will only be enough