The 'member' keyword gets deleted in 'abstract member' declarations

[vsinha]

Issue created from fantomas-online

Code

module Example

type Foo = 
    abstract member bar : int

Result

module Example

type Foo =
    abstract bar: int

Problem description

Member keyword is deleted.

This may be intentional, is that the case?

Extra information

• The formatted result breaks by code.
• The formatted result gives compiler warnings.
• I or my company would be willing to help fix this.

Options

Fantomas 4.0.0-beta-003

Default Fantomas configuration

[nojaf]

This is a bit historical I think. In short in case of implementation files, it will lead to the same compiled code.
From an AST point of view, these things are exactly the same construct.

Take for example:

module Example

type Foo = 
    abstract member bar : int

type Foo2 = 
    abstract member bar : int

ParsedInput.ImplFile
  (ParsedImplFileInput
     ("tmp.fsx", true, QualifiedNameOfFile Example$fsx, [], [],
      [SynModuleOrNamespace
         ([Example], false, NamedModule,
          [SynModuleDecl.Types
             ([TypeDefn
                 (ComponentInfo
                    ([], [], [], [Foo],
                     PreXmlDoc ((3,8), FSharp.Compiler.XmlDoc+XmlDocCollector),
                     false, None, tmp.fsx (3,5--3,8) IsSynthetic=false),
                  SynTypeDefnRepr.ObjectModel
                    (TyconUnspecified,
                     [SynMemberDefn.AbstractSlot
                        (ValSpfn
                           ([], bar, SynValTyparDecls ([], true, []),
                            SynType.LongIdent (LongIdentWithDots ([int], [])),
                            SynValInfo ([], SynArgInfo ([], false, None)), false,
                            false,
                            PreXmlDoc
                              ((4,19), FSharp.Compiler.XmlDoc+XmlDocCollector),
                            None, None, tmp.fsx (4,4--4,29) IsSynthetic=false),
                         { IsInstance = true
                           IsDispatchSlot = true
                           IsOverrideOrExplicitImpl = false
                           IsFinal = false
                           MemberKind = MemberKind.PropertyGet },
                         tmp.fsx (4,4--4,29) IsSynthetic=false)],
                     tmp.fsx (4,4--4,29) IsSynthetic=false), [],
                  tmp.fsx (3,5--4,29) IsSynthetic=false)],
              tmp.fsx (3,0--4,29) IsSynthetic=false);
           SynModuleDecl.Types
             ([TypeDefn
                 (ComponentInfo
                    ([], [], [], [Foo2],
                     PreXmlDoc ((6,9), FSharp.Compiler.XmlDoc+XmlDocCollector),
                     false, None, tmp.fsx (6,5--6,9) IsSynthetic=false),
                  SynTypeDefnRepr.ObjectModel
                    (TyconUnspecified,
                     [SynMemberDefn.AbstractSlot
                        (ValSpfn
                           ([], bar, SynValTyparDecls ([], true, []),
                            SynType.LongIdent (LongIdentWithDots ([int], [])),
                            SynValInfo ([], SynArgInfo ([], false, None)), false,
                            false,
                            PreXmlDoc
                              ((7,19), FSharp.Compiler.XmlDoc+XmlDocCollector),
                            None, None, tmp.fsx (7,4--7,29) IsSynthetic=false),
                         { IsInstance = true
                           IsDispatchSlot = true
                           IsOverrideOrExplicitImpl = false
                           IsFinal = false
                           MemberKind = MemberKind.PropertyGet },
                         tmp.fsx (7,4--7,29) IsSynthetic=false)],
                     tmp.fsx (7,4--7,29) IsSynthetic=false), [],
                  tmp.fsx (6,5--7,29) IsSynthetic=false)],
              tmp.fsx (6,0--7,29) IsSynthetic=false)],
          PreXmlDoc ((1,6), FSharp.Compiler.XmlDoc+XmlDocCollector), [], None,
          tmp.fsx (1,0--7,29) IsSynthetic=false)], (true, true)))

Notice that both SynMemberDefn.AbstractSlot are identical, so we don't have the information to make the correct call.

Now in case of signature files, this does matter (see #944) and there we have a workaround via the trivia information.

I guess the same trick can be applied here for SynMemberDefn_AbstractSlot.

[knocte]

it will lead to the same compiled code.

Then one could argue this is not a bug but a feature?