How can we make it easier to experiment with the compiler?

[Iain Buclaw]

On Tuesday, 25 May 2021 at 00:03:56 UTC, Walter Bright wrote:
> On 5/24/2021 2:01 PM, Max Haughton wrote:
>> Where do you start?
>
> At the first function you notice that has poor/missing/wrong 
> documentation.
>
> Like this one I just did:
>
> https://github.com/dlang/dmd/pull/12570

Another place you can make a big impact with zero change in 
language behavior is this:

```
Error: none of the overloads of size are callable using a const 
object, candidates are:
        dmd.mtype.Type.size()
        dmd.mtype.Type.size(ref const(Loc) loc)
Error: mutable method dmd.mtype.TypeVector.elementType is not 
callable using a const object
        Consider adding const or inout here
Error: mutable method dmd.mtype.TypeVector.isscalar is not 
callable using a const object
        Consider adding const or inout here
Error: mutable method dmd.mtype.TypeVector.isintegral is not 
callable using a const object
        Consider adding const or inout here
Error: mutable method dmd.mtype.TypeVector.isfloating is not 
callable using a const object
        Consider adding const or inout here
```

Which is but a small portion of the monster error that occurs 
when you use `const` instead of `auto` for any AST `Type` or 
`Dsymbol`.