Access modifier is lost in `extern` declaration

[auduchinok]

Issue created from fantomas-online

Code

[<DllImport("kernel32.dll")>]
extern UIntPtr private GetProcessHeap()

Result

[<DllImport("kernel32.dll")>]
extern UIntPtr GetProcessHeap()

The code is taken from Lib.fs.

[nojaf]

The AST I get for this is:

ParsedInput.ImplFile
  (ParsedImplFileInput
     ("tmp.fsx", true, QualifiedNameOfFile Tmp$fsx, [], [],
      [SynModuleOrNamespace
         ([Tmp], false, AnonModule,
          [SynModuleDecl.Let
             (false,
              [Binding
                 (None, NormalBinding, false, false,
                  [{ Attributes =
                                 [{ TypeName =
                                              LongIdentWithDots
                                                ([DllImport], [])
                                    ArgExpr =
                                             SynExpr.Paren
                                               (SynExpr.Const
                                                  (SynConst.String
                                                     ("kernel32.dll",
                                                      tmp.fsx (1,12--1,26) IsSynthetic=false),
                                                   tmp.fsx (1,12--1,26) IsSynthetic=false),
                                                tmp.fsx (1,11--1,12) IsSynthetic=false,
                                                Some
                                                  tmp.fsx (1,26--1,27) IsSynthetic=false,
                                                tmp.fsx (1,11--1,27) IsSynthetic=false)
                                    Target = None
                                    AppliesToGetterAndSetter = false
                                    Range =
                                           tmp.fsx (1,2--1,11) IsSynthetic=false }]
                     Range = tmp.fsx (1,0--1,29) IsSynthetic=false }],
                  PreXmlDoc ((2,6), FSharp.Compiler.XmlDoc+XmlDocCollector),
                  SynValData
                    (None, SynValInfo ([[]], SynArgInfo ([], false, None)), None),
                  SynPat.LongIdent
                    (LongIdentWithDots ([GetProcessHeap], []), None,
                     Some (SynValTyparDecls ([], false, [])),
                     Pats
                       [SynPat.Tuple
                          (false, [], tmp.fsx (2,37--2,38) IsSynthetic=false)],
                     None, tmp.fsx (2,15--2,22) IsSynthetic=false),
                  Some
                    (SynBindingReturnInfo
                       (SynType.App
                          (SynType.LongIdent (LongIdentWithDots ([UIntPtr], [])),
                           None, [], [], None, false,
                           tmp.fsx (2,7--2,14) IsSynthetic=false),
                        tmp.fsx (2,7--2,14) IsSynthetic=false, [])),
                  SynExpr.Typed
                    (SynExpr.App
                       (NonAtomic, false, SynExpr.Ident failwith,
                        SynExpr.Const
                          (SynConst.String
                             ("extern was not given a DllImport attribute",
                              tmp.fsx (2,38--2,39) IsSynthetic=false),
                           tmp.fsx (2,38--2,39) IsSynthetic=false),
                        tmp.fsx (2,0--2,39) IsSynthetic=false),
                     SynType.App
                       (SynType.LongIdent (LongIdentWithDots ([UIntPtr], [])),
                        None, [], [], None, false,
                        tmp.fsx (2,7--2,14) IsSynthetic=false),
                     tmp.fsx (2,0--2,39) IsSynthetic=false),
                  tmp.fsx (2,0--2,39) IsSynthetic=false,
                  NoDebugPointAtInvisibleBinding)],
              tmp.fsx (2,0--2,39) IsSynthetic=false)], PreXmlDocEmpty, [], None,
          tmp.fsx (1,0--2,39) IsSynthetic=false)], (true, true)))

The access modifier should be the first item of SynBinding but it is not present.

Binding
                 (None, NormalBinding, false, false,

Am I missing something here or is this a bug in the compiler?

[auduchinok]

Yes, it seems the access modifier is always ignored here: https://github.com/dotnet/fsharp/blob/05b0569a7d6acefd21ad31bce49f780d961db651/src/fsharp/pars.fsy#L2634

[dawedawe]

@auduchinok @nojaf I think, this can be closed. Current fantomas/fsharp keeps the access modifier.

[nojaf]

I tend to close issues that we can no longer reproduce with the latest version by adding a PR with a regression test.
Just so we ensure it stays fixed.