Anonymous (unlabeled) block expressions when there is no ambiguity

[gpanders]

Consider the following snippet:

const dir = blk: {                                                                                    
    if (std.os.getenv("FOO_DIR")) |dir| {                                                          
        break :blk try std.mem.dupe(allocator, u8, dir);                                              
    } else if (std.os.getenv("XDG_DATA_HOME")) |xdg_data_home| {                                      
        break :blk try std.fs.path.join(allocator, &[_][]const u8{ xdg_data_home, "foo" });           
    } else if (std.os.getenv("HOME")) |home| {                                                        
        break :blk try std.fs.path.join(allocator, &[_][]const u8{ home, ".local", "share", "foo" }); 
    } else {                                                                                          
        return error.NoFooDirFound;                              
    }                                                                                                 
};                                                                                                    
defer allocator.free(dir);         

In this case, there is no ambiguity in the meaning of break within the block, since there is no parent loop. The repeated blk: and :blk labels add code noise; would it be possible to allow for anonymous/unlabeled blocks when there is no ambiguity? Example:

var y = someFunction();
const x = {
    if (y >= 0) {
        break y * y;
    else {
        break 0;
    }
};

(I realize there are better ways to do the above, it's merely a contrived example).

In cases where there is ambiguity (e.g. in a while or for loop), the labels would still need to be explicitly defined.

[Vexu]

Duplicate of #2990