Enforce attribute targets on let values

[edgarfgp]

Fixes#8547

• Normal let bindings
• Recursive let bindings
• More testing
• LangVersion flag

[vzarytovskii]

LangVersion flag ?

Yes, at the very least. However, just language version will not be good enought for people who will all of the sudden have this issue when upgrading SDKs.

I.e. it won't explain why do the have it now and how do they rollback to previous behaviour.

[edgarfgp]

LangVersion flag ?

Yes, at the very least. However, just language version will not be good enought for people who will all of the sudden have this issue when upgrading SDKs.

I.e. it won't explain why do the have it now and how do they rollback to previous behaviour.

Hum, a new error number and message it is the way to go here

[edgarfgp]

Findings:

• The __useResumableCode is a let-bound value but has the Attribute MethodImpl(MethodImplOptions.NoInlining) which should only be used with (AttributeTargets.Method | AttributeTargets.Constructor)

[AttributeUsage(AttributeTargets.Method|AttributeTargets.Constructor,Inherited=false)]sealedpublicclassMethodImplAttribute:Attribute{

[<MethodImpl(MethodImplOptions.NoInlining)>]let__useResumableCode<'T>:bool =false

Questions:

• Should enforce the AttributeTargets.Method to __useResumableCode and update the resumable.fs
• Make an exception for `MethodImpl(MethodImplOptions.NoInlining) to be used in let values.

cc @vzarytovskii

[vzarytovskii]

MethodImpl is something we don't control, right? I don't think we should hack attribute checking in compiler.

And __useResumableCode is not a value, it's a type function and compiler intrinsic at the same time.

What codegen does it currently result in?

[vzarytovskii]

So, I think whatever rules we enforce now for functions (AttributeTargets.Method, I suppose?), should also be enforced for type functions.

[edgarfgp]

And __useResumableCode is not a value, it's a type function and compiler intrinsic at the same time.

This makes more sense now . Thanks

[edgarfgp]

[<AttributeUsage(AttributeTargets.Method,AllowMultiple=false)>][<Sealed>]typeTailCallAttribute()=inherit System.Attribute()[<TailCall>]letsomeX=23

With this PR will also enforce that you can not use [<TailCall>] cc @dawedawe

[edgarfgp]

Better now :)