progess default field

[ringabout]

inspired by #12378

default fields for object

• result
• object variant

the addition compared to #12378

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

[Araq]

There is a better way, query sym.ast and see if it contains a value and not nkEmpty.

[ringabout]

This flag is to solve field visible problem.

  Default* = object
    poi: int = 12
    clc: Clean
    se*: range[0'i32 .. high(int32)]

poi is not a public object attribute. For a object construct in other modules, I need to distinguish default construct from manual construct.

Default() should pass while Default(poi: 15) should raise. And The ast of Default isn't empty.

[Araq]

I don't understand your remark. What does it mean "it should raise"?

[ringabout]

The flag is used to indicate that this field has been used as the default object construction so that the semConstr won't issues an error for private fields.

For example, I have a a.nim module which has a Default object with private fields.

# a.nim
type
  Default* = object
    id: int = 1

Now I imports it in the b.nim module. var x: Default will be transformed into var x: Default = Default(id: 1). id is a private field, we need to use .ast != nil or
a new flag to let the compiler allow this.

# b.nim
import a

var x: Default

However .ast != nil doesn't work in the case that users use the id field wrongly. Even if id is a private field, users can still use it in the other modules, which causes confusion.

# b.nim
import a

var x = Default(id: 10)

Using .ast != nil cannot distinguish the two cases.

[ringabout]

succeeded by #20220