The best way to write IDE helper tool

[Basile B.]

On Thursday, 20 December 2018 at 18:21:55 UTC, Andre Pany wrote:
> On Thursday, 20 December 2018 at 14:17:11 UTC, unDEFER wrote:
>> Hello!
>> I know there is IDE tools like DCD, but I don't like it 
>> because it hasn't UCFS-suggestions.
>> So I have written my own patches to DMD to decide this 
>> problem. The patches adds the "-interp" option to compiler. In 
>> this mode the compiler is interrupted after semantic3 stage 
>> and displays the next prompt:
>>
>> [...]
>
> Without knowing the details I assume dcd is using libdparse and 
> here some features are missing.
> If we could add the missing features to libdparse, dcd and also 
> other tools would immediately profit (dscanner, dfrmt,...)
>
> Kind regards
> Andre

Unfortunately he's right about dparse. Dparse and dsymbols are 
really far from being able to give correct UFCS suggestions 
because

1. it does not do the semantic of expressions and statements

   This basically means that CTFE is not possible (mixin, static 
if) because before
   intepreting the expressions they must be analyzed but most 
importantly this means
   that the return type of auto functions cant be infered (it 
relies on the type of
   the expression wrapped in a return statement).

2. it does not instantiate templates

   AST copy and patch parameter with instances.

So for now any attempt to implement UFCS suggestions will work to 
a very limited extant when trying to be type-correct. Some rules 
could be applied such as "if the type of the first parameter is 
not known then presume that by default it will work" but then the 
suggestions will be mostly wrong.

If someone wants to give a try there's been an attempt from 
Soulaimane last year:
https://github.com/SSoulaimane/dcd/commit/dc666817139e6fc135a6d02dc4dc63406aeca439