progess default field

[ringabout]

inspired by https://github.com/nim-lang/Nim/pull/12378

default fields for object

• [x] result
• [x] object variant

the addition compared to https://github.com/nim-lang/Nim/pull/12378

• [x] var
• [x] omit type for default fields
• [x] default(Type)
• [x] new(ref)
• [x] nested object definition
• [x] array
• [x] an object of array etc. in the definition of the object
• [x] threadvar
• [x] noinit
• [x] range
• [x] fieldVisible issue
• [x] tuple
• [ ] distinct
• [ ] newFinalize
• [ ] seq(var, result, setLen)
• [ ] docs
• [x] tests

notes for me only

abstractInst vs {tyGenericInst, tyAlias, tySink}

[ringabout]

It is quite complex...

[ringabout]

It seems that now I need to add a flag to handle fieldVisible issue...

[ringabout]

As a bonus, range defined in the object seem to work now(namely DateTime can be used as an object attribute) ignoring the field visible issue.

[ringabout]

succeeded by https://github.com/nim-lang/Nim/pull/20220