Implement explicit type conversion

[joshcarp]

I have implemented var.(<type>) conversions on my fork.

// vars
a := 1
b := a.(any)
c := b.(num)
d := a.(string) // fails
a:any
a = 1
a = "b"
print (typeof a) // prints underlying type, not `any`. Consistent with current behaviour

// Maps
{a: true b: false}.({}any)
{a: true b: false}.({}any).({}bool)
{a: true b: false}.({}string) // fails
{a: true b: "false"}.({}bool) // fails

// Arrays
print [1 2 3].([]any).([]num).([]any).([]num)
x:[]any
x = [[1 2 3]]
print x
assertEqual "[]any" (typeof x)
x[0] = [7 8 9]
print "x:" x
x[0] = [7 8 9].([]string)
print "x:" x
assert false
[7 8 9].([]string) // fails

[joshcarp]

Honestly i think this would be one of the biggest improvements to the language in its current form. Type conversions always trip me up and it isn't getting any more familiar

[juliaogris]

Yeah - I also noticed some friction in this space playing with your huaman eval examples - could you please post a couple of examples where in specific you are missing this feature, @joshcarp ?

[joshcarp]

The main one was with asserts. An empty type is always instantiated as an any slice/map so

a := [1 2 3] // returned from whatever function
a = a[0:0] // empty num slice
print (typeof []) (typeof a) // []any []num

So this basically happens every time you need to:

• Assign an empty list
• Assign an empty map

[juliaogris]

The need for it also popped up here:
https://github.com/juliaogris/humaneval-evy/blob/main/manual_conversion/136.evy#L26