while(!?T catch {}) |payload| {}: Type resolution bug for |*payload|

[rened]

Zig Version

0.10.0-dev.4197+9a2f17f9f

Steps to Reproduce

Put the following in test.zig and run zig test test.zig:

const std = @import("std");

pub fn Reader(comptime T: type) type {
    return struct {
        buf: std.ArrayList(u8) = undefined,
        const Self = @This();

        pub fn init(allocator: std.mem.Allocator) Self {
            return Self{
                .buf = std.ArrayList(u8).init(allocator),
            };
        }

        pub fn next(self: *Self) !?T {
            if (self.buf.items.len >= 4) {
                var stream = std.io.fixedBufferStream(self.buf.items);
                var len: u32 = try stream.reader().readIntLittle(u32);
                if (self.buf.items.len >= len + 4) {
                    return @as(usize, 1);
                } else return null;
            } else return null;
        }
    };
}

test "iterator" {
    const allocator = std.testing.allocator_instance.allocator();
    var reader = Reader(usize).init(allocator);
    while (reader.next() catch label: {
        break :label null;
    }) |*x| { // fails, |x| works
        _ = x;
    }
}

Expected Behavior

The test should pass.

Actual Behavior

It fails for stage2 with

test.zig:29:26: error: incompatible types: '*const ?usize' and '*const @TypeOf(null)'
    while (reader.next() catch label: {
           ~~~~~~~~~~~~~~^~~~~

It passes for zig test test.zig -fstage1 and also for 0.8x and 0.9.x.

It also passes for stage2 when omitting the pointer to the payload. It seems that the type resolution looks at the loop payload type instead of the type used in the while condition.

[Vexu]

Related to #11969, #11812, etc.

[BratishkaErik]

Can reproduce for 0.11.0-dev.4403+e84cda0eb:

test.zig:29:26: error: incompatible types: '*const ?usize' and '*const @TypeOf(null)'
    while (reader.next() catch label: {
           ~~~~~~~~~~~~~~^~~~~
test.zig:29:26: note: type '*const ?usize' here
test.zig:29:39: note: type '*const @TypeOf(null)' here
    while (reader.next() catch label: {
                               ~~~~~~~^