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std.mem.eql: make comparisons for zero-sized and non-sized types work

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The `if (@sizeOf(T) == 0) return true;` check simply doesn't work for a number
of cases so that is removed and changed into `@sizeOf(T) != 0` and then
used in the `eqlBytes` check chain to make comparing `enum{}`s possible.

The rest special-cases for comptime-only types and undefined to make
those comparisons possible as well.

Fixes #19929
This commit is contained in:
Andrew Kelley 2024-11-22 15:10:34 -08:00
parent 73dcd19140
commit a3342cea18
1 changed files with 32 additions and 1 deletions
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33
lib/std/mem.zig
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@ -656,7 +656,18 @@ const eqlBytes_allowed = switch (builtin.zig_backend) {
/// Compares two slices and returns whether they are equal.
pub fn eql(comptime T: type, a: []const T, b: []const T) bool {
if (@sizeOf(T) == 0) return true;
switch (@typeInfo(T)) {
.Type, .ComptimeInt, .ComptimeFloat => {
if (a.len != b.len) return false;
inline for (a, b) |a_elem, b_elem| {
if (a_elem != b_elem) return false;
}
return true;
},
.Null, .Undefined => return a.len == b.len,
else => {},
}
if (@sizeOf(T) == 0) return a.len == b.len;
if (!@inComptime() and std.meta.hasUniqueRepresentation(T) and eqlBytes_allowed) return eqlBytes(sliceAsBytes(a), sliceAsBytes(b));
if (a.len != b.len) return false;
@ -3296,6 +3307,26 @@ test eql {
try testing.expect(eql(u8, "abcd", "abcd"));
try testing.expect(!eql(u8, "abcdef", "abZdef"));
try testing.expect(!eql(u8, "abcdefg", "abcdef"));
try testing.expect(eql(type, &.{ bool, f32 }, &.{ bool, f32 }));
try testing.expect(!eql(type, &.{ bool, f32 }, &.{ f32, bool }));
try testing.expect(!eql(type, &.{ bool, f32 }, &.{bool}));
try testing.expect(eql(comptime_int, &.{ 1, 2, 3 }, &.{ 1, 2, 3 }));
try testing.expect(!eql(comptime_int, &.{ 1, 2, 3 }, &.{ 3, 2, 1 }));
try testing.expect(!eql(comptime_int, &.{1}, &.{ 1, 2 }));
try testing.expect(eql(@TypeOf(undefined), &.{ undefined, undefined }, &.{ undefined, undefined }));
try testing.expect(!eql(@TypeOf(undefined), &.{undefined}, &.{ undefined, undefined }));
try testing.expect(eql(enum {}, &.{ undefined, undefined }, &.{ undefined, undefined }));
try testing.expect(!eql(enum {}, &.{undefined}, &.{ undefined, undefined }));
try testing.expect(eql(void, &.{ {}, {} }, &.{ {}, {} }));
try testing.expect(!eql(void, &.{{}}, &.{ {}, {} }));
try testing.expect(eql(@TypeOf(null), &.{ null, null }, &.{ null, null }));
try testing.expect(!eql(@TypeOf(null), &.{null}, &.{ null, null }));
}
fn moreReadIntTests() !void {