[Feature]: Optional type declarations

[steinhh]

Description

Optional type declarations/assertions could greatly improve code completion features

Why it Matters

Declaring variable types can improve code completion for properties/methods, which could have a big positive impact on user (programmer) experience and producetivity.

Suggested Behavior

I have not "concluded" on the syntax I would like to have, feel free to augment this suggestion

pro test, a, b, c, d
  ; idl-declare b : { my_struct }
  ; idl-declare c : string
  ; idl-declare d : { my_class }
  d = my_func() ; idl-declare {my_struct}  [ an implicit "idl-declare d : { my_struct }" ]

This should then cause code completion features to behave accordingly.

This could also be extended with shorthand for function signatures, e.g.,:

pro test, a, $ ; idl-declare { my_struct }
          b, $ : idl-declare { int }
          c : idl-declare { string }

(Here using my suggested hanging indent formatting, see issue #52)

Alternate Behavior

No response

[steinhh]

Hmm... I guess the regular documentation system will take care of pro/func parameters (haven't experimented with it), would it be possible to extend it to local variables as well?

[steinhh]

To clarify, it would be nice to be able to write e.g,

;+
; :Variables:
;   b: out, optional, my_struct2   ;; Or preferably drop the out/optional part!
;-
PRO test
  b = someones_library_function()
  print,"b: ", b.

and then have the b. trigger auto-completion for my_struct2.

[znorman-harris]

Sorry for the slow reply here, working through your other items first.

We definitely want to have some way to manually specify the type for variables in-line with your code. I was chatting a little bit with our IDL team lead about this after this was first reported. Ideally we would have some syntax similar to TypeScript or Python for in-line types. That would be a core IDL language feature to allow you to include the syntax in your code, so it is probably a longer term item.

In the short term, we may have some other solutions using comments.

Example, it would likely look something like one of these snippets:

;+ i am a comment you see with hover help for a variable
myVar = someMysteryFunction()

;+ i am a comment for hover help and i have a type as well
; idl-var-type: Number
myVar = anotherMysteryFunction()

; or, without a comment for hover help

; idl-var-type: FooClass
myVar = FooClassConstructor()

And, in a future state, I would hope to have syntax that looks like this:

foo: MyClass = unknownFunction()

Let me think about this a bit and I'll circle back to it after the holidays!

[steinhh]

A very good preliminary solution!