I still do not fully understand sets

[Stefan_Salewski]

    const
      AlphaNum: set[char] = {'a' .. 'z', 'A' .. 'Z', '0' .. '9'}
      MathOp = {'+', '-', '*', '/'} # set[char]
      
      ANMO = AlphaNum + MathOp # union
    
    var x: char = 's'
    echo x in AlphaNum
    echo x in MathOp
    
    type
      CharRange = set['a' .. 'f']
    
    # var y: CharRange = {'x'} #invalid
    
    var y: CharRange = {'b', 'd'}
    echo 'c' in y
    
    type
      ChessPos = set[0'i8 .. 63'i8]
    
    var baseLine: ChessPos = {1.int8}
    var p: int8
    echo p in baseLine
    
    type
      H = set[0 .. 63]
    
    var h: H = H({1})
    
    echo typeof({1})
    echo typeof({-1})
    echo typeof({1'i8})
    
    
    Run

Sets of char are easy. But sets of numbers are more difficult.

The operations with the ChessPos type are OK. But with

type
    H = set[0 .. 63]

var h: H = H({1})

I do not get the assignment to var h working. Nothing of following code seems 
to compile:

var h: H = {1} var h: H = H({1}) var h: H = {1'i8} var h: H = {1'}

And

echo typeof({-1})

is

set[range 0..65535(int)]

which is also a bit strange.