Improve error reporting: report visibility issue between two assemblies

[smoothdeveloper]

What

Declare private or internal member in project A

namespace Foo

[<AutoOpen>]
module internal Utils =
    let normalizeArgName () = ()

Try to use private or internal member in project B

open Foo

module Bar =
    let foo = normalizeArgName ()

Why

It might be worth considering reporting visibility issue when private or internal members of referenced assemblies are used (sometimes due to faulty InternalsVisible assembly declaration)

How

The value 'Foo.Utils.normalizeArgName' is not accessible from this code location

(this is same as error FS1094, but with qualified name)

Note that if I put the qualified name in usage spot:

open Foo

module Bar =
    let foo = Foo.Utils.normalizeArgName ()

I get expected error message.

Related #1103

[forki]

I looked at this a bit,

Giving The value 'Foo.Utils.normalizeArgName' is not accessible from this code location seems hard from the error location.

But maybe we can change the The value or constructor 'normalizeArgName' is not defined to The value or constructor 'normalizeArgName' is not defined or not accessible from this code location. But then it would be displayed in all cases - even when it wasn't defined at all.

[smoothdeveloper]

@forki I think the option of changing the current error message is not best option.

I haven't checked what C# does but I believe it would also report visibility (seen this with similar use case tweaking InternalsVisible).

I think this is anyway low priority, just an opportunity to make error message greater.