AttributeTargets.Method can be targeted in a constructor incorrectly

[edgarfgp]

AttributeTargets.Method can be targeted in a constructor incorrectly.

Repro steps

open System
[<AttributeUsage(AttributeTargets.Method)>]
type CustomMethodAttribute() =
    inherit Attribute()

type Class [<CustomMethod>] () = class end

type Struct [<CustomMethod>] (x: int) = struct end

Expected behavior
Should not compile and Error 842 "This attribute is not valid for use on this language element" should be reported.

Actual behavior
Compiles

Provide a description of the actual behaviour observed.

Known workarounds

Provide a description of any known workarounds.

Related information

Provide any related information (optional):

• Operating system
• .NET Runtime kind (.NET Core, .NET Framework, Mono)
• Editing Tools (e.g. Visual Studio Version, Visual Studio)

[edgarfgp]

I would like to fix this after Im done with #13526 to make easy for reviewers