AstGen doesn't pass type to switch prong

[Vexu]

test {
    var a: u32 = 0;
    var b: [2]u32 = undefined;
    b[0] = @as(u32, switch (a) {
        1 => 1,
        else => 0,
    });
}

a.zig:29:21: error: value with comptime only type 'comptime_int' depends on runtime control flow
    b[0] = @as(u32, switch (a) {
                    ^
a.zig:29:29: note: runtime control flow here
    b[0] = @as(u32, switch (a) {
                            ^

Related #11135