Peer type resolution cannot handle nested branches with a nullable struct result

[ghost]

It appears that the peer type resolution is able to infer a nullable struct result in a simple one-level if or switch expression, but not a nested one.

However it does work if the result is a bool, i32, or []const u8.

pub fn main() void {
    const Thing = struct { n: i32 };
    var a = false;
    var b = false;

    // this works
    var result1: ?Thing =
        if (a)
            Thing { .n = 1 }
        else
            null;

    // this does not work
    var result2: ?Thing =
        if (a)
            Thing { .n = 0 }
        else if (b)
            Thing { .n = 1 }
        else
            null;
}

Semantic Analysis [705/709] /home/dbandstra/host/asdf.zig:20:13: error: expected type 'Thing', found '(null)'
            null;
            ^
/home/dbandstra/host/asdf.zig:2:19: note: Thing declared here
    const Thing = struct { n: i32 };
                  ^

Edit: it even fails if I do an explicit cast on the null in the last branch:

pub fn main() void {
    const Thing = struct { n: i32 };
    var a = false;
    var b = false;

    var result2: ?Thing =
        if (a)
            Thing { .n = 0 }
        else if (b)
            Thing { .n = 1 }
        else
            @as(?Thing, null);
}

Semantic Analysis [722/740] /home/dbandstra/host/asdf.zig:13:13: error: expected type 'Thing', found '?Thing'
            @as(?Thing, null);
            ^
/home/dbandstra/host/asdf.zig:2:19: note: Thing declared here
    const Thing = struct { n: i32 };
                  ^

To get it to work I need to cast the FIRST branch result, like @as(?Thing, Thing { .n = 0 }) .

Edit 2: actually, if I do that, I get runtime glitches.

pub fn main() void {
    const Thing = struct { n: i32 };
    var a = true;
    var b = false;

    var result2: ?Thing =
        if (a)
            @as(?Thing, Thing { .n = 0 })
        else if (b)
            Thing { .n = 1 }
        else
            null;

    if (result2) |r|
        @import("std").debug.warn("{}\n", r);
}

This program sometimes prints nothing, sometimes prints things like Thing{ .n = 1534746352 }.

edit: fixed typo

[ghost]

This is probably mislabeled, I think it's the result location type failing to carry into nested conditional expressions, not peer type resolution.