@enumFromInt(@truncate(x)) should work

[wooster0]

Zig Version

0.13.0-dev.351+64ef45eb0

Steps to Reproduce and Observed Behavior

This could also be seen as a proposal.

const X = enum(u1) {
    a = 0,
    b = 1,
};

test {
    var y: u64 = 239823;
    const x: X = @enumFromInt(@truncate(y));
    _ = x;
}

When I want to convert an integer to an enum and @enumFromInt knows the enum because of the : X type annotation, it can know the result type of the @truncate by looking at the tag type I specified for the X enum.

Currently this happens:

x.zig:8:31: error: @truncate must have a known result type
    const x: X = @enumFromInt(@truncate(y));
                              ^~~~~~~~~~~~
x.zig:8:31: note: use @as to provide explicit result type

Similar to #18218

Expected Behavior

For the code above to compile.

[rohlem]

Currently @enumFromInt is stated (only in the section about non-exhaustive enums) to include a hidden @intCast.
An optional extension proposal could be to remove this hidden assertion,
meaning @enumFromInt(x) would be safer and status-quo would instead be written as @enumFromInt(@intCast(x)).

[mlugg]

Right now, this could only work if the change suggested by @rohlem above were implemented. Note that status quo behavior was implemented in (IIRC) 0.9.0; before then, @enumFromInt did not perform an implicit @intCast. I think it's definitely worth revisiting this with the new casting syntax in place.

[mlugg]

This proposal is now equivalent to #22712; closing as duplicate for that reason.