Parser: recover on unfinished abstract members

docs/release-notes/.FSharp.Compiler.Service/11.0.100.md

@@ -125,6 +125,7 @@
 * Fix FSI pretty printing to distinguish anonymous records (`{| ... |}`) from nominal records (`{ ... }`). ([Issue #6116](https://github.com/dotnet/fsharp/issues/6116), [PR #19919](https://github.com/dotnet/fsharp/pull/19919))
 * Fix dot-completion after indexed expressions (`a.[0].Data.`, `a[0].Data.`, `[1;2].Length.`) returning unrelated global completions instead of expression-typings members. ([Issue #4966](https://github.com/dotnet/fsharp/issues/4966), [PR #19934](https://github.com/dotnet/fsharp/pull/19934))
 * Quotations of `match s with "" -> _` no longer leak the `s <> null && s.Length = 0` lowering; the empty-string optimization moved from pattern-match compilation to the optimizer so quoted expressions keep `op_Equality(s, "")`. ([Issue #19873](https://github.com/dotnet/fsharp/issues/19873))
+* Parser: recover on unfinished abstract members ([PR #20070](https://github.com/dotnet/fsharp/pull/20070))
 
 ### Added
 

src/Compiler/Checking/CheckDeclarations.fs

@@ -3723,17 +3723,16 @@ module EstablishTypeDefinitionCores =
 
                         let abstractSlots = 
                             [ for synValSig, memberFlags in slotsigs do 
-
-                                  let (SynValSig(range=m)) = synValSig
-
-                                  CheckMemberFlags None NewSlotsOK OverridesOK memberFlags m
-
-                                  let slots = fst (TcAndPublishValSpec (cenv, envinner, containerInfo, ModuleOrMemberBinding, Some memberFlags, tpenv, synValSig))
-                                  // Multiple slots may be returned, e.g. for 
-                                  //    abstract P: int with get, set
-
-                                  for slot in slots do 
-                                      yield mkLocalValRef slot ]
+                                  let (SynValSig(ident = (SynIdent(id, _)); range = m)) = synValSig
+                                  if id.idText <> "" then
+                                      CheckMemberFlags None NewSlotsOK OverridesOK memberFlags m
+
+                                      let slots = fst (TcAndPublishValSpec (cenv, envinner, containerInfo, ModuleOrMemberBinding, Some memberFlags, tpenv, synValSig))
+                                      // Multiple slots may be returned, e.g. for 
+                                      //    abstract P: int with get, set
+
+                                      for slot in slots do 
+                                          yield mkLocalValRef slot ]
 
                         let kind = 
                             match kind with 

src/Compiler/SyntaxTree/ParseHelpers.fs

@@ -1136,3 +1136,65 @@ let mkLetBangExpression
             Trivia = { InKeyword = mIn }
             IsFromSource = true // User-written let!/use! bindings
         }
+
+let mkAbstractMember
+    parseState
+    attrs
+    (accessBeforeKeyword: SynAccess option)
+    memberFlags
+    (accessBeforeId: SynAccess option)
+    mInline
+    id
+    typeParams
+    typeWithConstraints
+    accessors
+    =
+    if Option.isSome accessBeforeKeyword then
+        errorR (Error(FSComp.SR.parsVisibilityDeclarationsShouldComePriorToIdentifier (), rhs parseState 2))
+
+    let (ty: SynType), arity = typeWithConstraints
+
+    let isInline, doc, explicitValTyparDecls =
+        Option.isSome mInline, grabXmlDoc (parseState, attrs, 1), typeParams
+
+    let mWith, (getSet, getSetRangeOpt: GetSetKeywords option, getterAccess, setterAccess) =
+        accessors
+
+    let getSetAdjuster arity =
+        match arity, getSet with
+        | SynValInfo([], _), SynMemberKind.Member -> SynMemberKind.PropertyGet
+        | _ -> getSet
+
+    let mWhole =
+        let m = rhs parseState 1
+
+        match getSetRangeOpt with
+        | None -> unionRanges m ty.Range
+        | Some gs -> unionRanges m gs.Range
+        |> unionRangeWithXmlDoc doc
+
+    [ accessBeforeKeyword; accessBeforeId; getterAccess; setterAccess ]
+    |> List.iter (function
+        | None -> ()
+        | Some access -> errorR (Error(FSComp.SR.parsAccessibilityModsIllegalForAbstract (), access.Range)))
+
+    let mkFlags, leadingKeyword = memberFlags
+
+    let trivia =
+        {
+            LeadingKeyword = leadingKeyword
+            InlineKeyword = mInline
+            WithKeyword = mWith
+            EqualsRange = None
+        }
+
+    let vis2 = SynValSigAccess.Single None
+
+    let valSpfn =
+        SynValSig(attrs, id, explicitValTyparDecls, ty, arity, isInline, false, doc, vis2, None, mWhole, trivia)
+
+    let trivia: SynMemberDefnAbstractSlotTrivia = { GetSetKeywords = getSetRangeOpt }
+
+    [
+        SynMemberDefn.AbstractSlot(valSpfn, mkFlags (getSetAdjuster arity), mWhole, trivia)
+    ]

src/Compiler/SyntaxTree/ParseHelpers.fsi

@@ -285,3 +285,16 @@ val mkSynField:
         SynField
 
 val leadingKeywordIsAbstract: SynLeadingKeyword -> bool
+
+val mkAbstractMember:
+    parseState: IParseState ->
+    attrs: SynAttributeList list ->
+    accessBeforeKeyword: SynAccess option ->
+    abstractMemberFlags: (SynMemberKind -> SynMemberFlags) * SynLeadingKeyword ->
+        accessBeforeId: SynAccess option ->
+        mInline: range option ->
+        id: SynIdent ->
+        typeParams: SynValTyparDecls ->
+        typeWithConstraints: SynType * SynValInfo ->
+            accessors: range option * (SynMemberKind * GetSetKeywords option * SynAccess option * SynAccess option) ->
+                SynMemberDefn list

src/Compiler/pars.fsy

@@ -2058,27 +2058,33 @@ classDefnMember:
        [ SynMemberDefn.Interface(ty, None, None, rhs2 parseState 1 3) ] }
 
   | opt_attributes opt_access abstractMemberFlags opt_access opt_inline nameop opt_explicitValTyparDecls COLON topTypeWithTypeConstraints classMemberSpfnGetSet opt_ODECLEND
-     { if Option.isSome $2 then errorR(Error(FSComp.SR.parsVisibilityDeclarationsShouldComePriorToIdentifier(), rhs parseState 2))
-       let ty, arity = $9
-       let isInline, doc, id, explicitValTyparDecls = (Option.isSome $5), grabXmlDoc(parseState, $1, 1), $6, $7
-       let mWith, (getSet, getSetRangeOpt, getterAccess, setterAccess) = $10
-       let getSetAdjuster arity = match arity, getSet with SynValInfo([], _), SynMemberKind.Member -> SynMemberKind.PropertyGet | _ -> getSet
-       let mWhole =
-           let m = rhs parseState 1
-           match getSetRangeOpt with
-           | None -> unionRanges m ty.Range
-           | Some gs -> unionRanges m gs.Range
-           |> unionRangeWithXmlDoc doc
-
-       [ $2; $4; getterAccess; setterAccess ]
-       |> List.iter (function None -> () | Some access -> errorR(Error(FSComp.SR.parsAccessibilityModsIllegalForAbstract(), access.Range)))
-
-       let mkFlags, leadingKeyword = $3
-       let trivia = { LeadingKeyword = leadingKeyword; InlineKeyword = $5; WithKeyword = mWith; EqualsRange = None }
-       let vis2 = SynValSigAccess.Single(None)
-       let valSpfn = SynValSig($1, id, explicitValTyparDecls, ty, arity, isInline, false, doc, vis2, None, mWhole, trivia)
-       let trivia: SynMemberDefnAbstractSlotTrivia = { GetSetKeywords = getSetRangeOpt }
-       [ SynMemberDefn.AbstractSlot(valSpfn, mkFlags (getSetAdjuster arity), mWhole, trivia) ] }
+     { mkAbstractMember parseState $1 $2 $3 $4 $5 $6 $7 $9 $10 }
+
+  | opt_attributes opt_access abstractMemberFlags opt_access opt_inline nameop opt_explicitValTyparDecls COLON recover opt_ODECLEND
+     { let id = $6
+       let typeWithConstraints = SynType.FromParseError(id.Range.EndRange), SynValInfo([], SynInfo.unnamedRetVal)
+       let accessors = None, (SynMemberKind.Member, None, None, None)
+       mkAbstractMember parseState $1 $2 $3 $4 $5 id $7 typeWithConstraints accessors }
+
+  | opt_attributes opt_access abstractMemberFlags opt_access opt_inline nameop opt_explicitValTyparDecls recover opt_ODECLEND
+     { let id = $6
+       let typeWithConstraints = SynType.FromParseError(id.Range.EndRange), SynValInfo([], SynInfo.unnamedRetVal)
+       let accessors = None, (SynMemberKind.Member, None, None, None)
+       mkAbstractMember parseState $1 $2 $3 $4 $5 id $7 typeWithConstraints accessors }
+
+  | opt_attributes opt_access abstractMemberFlags opt_access opt_inline recover opt_ODECLEND
+     { let mBeforeId =
+           match $2 with
+           | Some access -> access.Range
+           | _ ->
+               let _, leadingKeyword = $3
+               leadingKeyword.Range
+
+       let id = SynIdent(mkSynId mBeforeId.EndRange "", None)
+       let typeParams = SynValTyparDecls(None, true)
+       let typeWithConstraints = SynType.FromParseError(id.Range.EndRange), SynValInfo([], SynInfo.unnamedRetVal)
+       let accessors = None, (SynMemberKind.Member, None, None, None)
+       mkAbstractMember parseState $1 $2 $3 $4 $5 id typeParams typeWithConstraints accessors }
 
   | opt_attributes opt_access inheritsDefn
      { if not (isNil $1) then errorR(Error(FSComp.SR.parsAttributesIllegalOnInherit(), rhs parseState 1))

tests/service/data/SyntaxTree/Member/Abstract - Method 01.fs

@@ -0,0 +1,6 @@
+module Module
+
+type T =
+    abstract M: unit -> unit
+
+()

tests/service/data/SyntaxTree/Member/Abstract - Method 01.fs.bsl

@@ -0,0 +1,47 @@
+ImplFile
+  (ParsedImplFileInput
+     ("/root/Member/Abstract - Method 01.fs", false, QualifiedNameOfFile Module,
+      [],
+      [SynModuleOrNamespace
+         ([Module], false, NamedModule,
+          [Types
+             ([SynTypeDefn
+                 (SynComponentInfo
+                    ([], None, [], [T],
+                     PreXmlDoc ((3,0), FSharp.Compiler.Xml.XmlDocCollector),
+                     false, None, (3,5--3,6)),
+                  ObjectModel
+                    (Unspecified,
+                     [AbstractSlot
+                        (SynValSig
+                           ([], SynIdent (M, None),
+                            SynValTyparDecls (None, true),
+                            Fun
+                              (LongIdent (SynLongIdent ([unit], [], [None])),
+                               LongIdent (SynLongIdent ([unit], [], [None])),
+                               (4,16--4,28), { ArrowRange = (4,21--4,23) }),
+                            SynValInfo
+                              ([[SynArgInfo ([], false, None)]],
+                               SynArgInfo ([], false, None)), false, false,
+                            PreXmlDoc ((4,4), FSharp.Compiler.Xml.XmlDocCollector),
+                            Single None, None, (4,4--4,28),
+                            { LeadingKeyword = Abstract (4,4--4,12)
+                              InlineKeyword = None
+                              WithKeyword = None
+                              EqualsRange = None }),
+                         { IsInstance = true
+                           IsDispatchSlot = true
+                           IsOverrideOrExplicitImpl = false
+                           IsFinal = false
+                           GetterOrSetterIsCompilerGenerated = false
+                           MemberKind = Member }, (4,4--4,28),
+                         { GetSetKeywords = None })], (4,4--4,28)), [], None,
+                  (3,5--4,28), { LeadingKeyword = Type (3,0--3,4)
+                                 EqualsRange = Some (3,7--3,8)
+                                 WithKeyword = None })], (3,0--4,28));
+           Expr (Const (Unit, (6,0--6,2)), (6,0--6,2))],
+          PreXmlDoc ((1,0), FSharp.Compiler.Xml.XmlDocCollector), [], None,
+          (1,0--6,2), { LeadingKeyword = Module (1,0--1,6) })], (true, true),
+      { ConditionalDirectives = []
+        WarnDirectives = []
+        CodeComments = [] }, set []))

tests/service/data/SyntaxTree/Member/Abstract - Method 02.fs

@@ -0,0 +1,6 @@
+module Module
+
+type T =
+    abstract M: unit ->
+
+()

tests/service/data/SyntaxTree/Member/Abstract - Method 02.fs.bsl

@@ -0,0 +1,49 @@
+ImplFile
+  (ParsedImplFileInput
+     ("/root/Member/Abstract - Method 02.fs", false, QualifiedNameOfFile Module,
+      [],
+      [SynModuleOrNamespace
+         ([Module], false, NamedModule,
+          [Types
+             ([SynTypeDefn
+                 (SynComponentInfo
+                    ([], None, [], [T],
+                     PreXmlDoc ((3,0), FSharp.Compiler.Xml.XmlDocCollector),
+                     false, None, (3,5--3,6)),
+                  ObjectModel
+                    (Unspecified,
+                     [AbstractSlot
+                        (SynValSig
+                           ([], SynIdent (M, None),
+                            SynValTyparDecls (None, true),
+                            Fun
+                              (LongIdent (SynLongIdent ([unit], [], [None])),
+                               FromParseError (4,23--4,23), (4,16--6,1),
+                               { ArrowRange = (4,21--4,23) }),
+                            SynValInfo
+                              ([[SynArgInfo ([], false, None)]],
+                               SynArgInfo ([], false, None)), false, false,
+                            PreXmlDoc ((4,4), FSharp.Compiler.Xml.XmlDocCollector),
+                            Single None, None, (4,4--6,1),
+                            { LeadingKeyword = Abstract (4,4--4,12)
+                              InlineKeyword = None
+                              WithKeyword = None
+                              EqualsRange = None }),
+                         { IsInstance = true
+                           IsDispatchSlot = true
+                           IsOverrideOrExplicitImpl = false
+                           IsFinal = false
+                           GetterOrSetterIsCompilerGenerated = false
+                           MemberKind = Member }, (4,4--6,1),
+                         { GetSetKeywords = None })], (4,4--6,1)), [], None,
+                  (3,5--6,1), { LeadingKeyword = Type (3,0--3,4)
+                                EqualsRange = Some (3,7--3,8)
+                                WithKeyword = None })], (3,0--6,1));
+           Expr (Const (Unit, (6,0--6,2)), (6,0--6,2))],
+          PreXmlDoc ((1,0), FSharp.Compiler.Xml.XmlDocCollector), [], None,
+          (1,0--6,2), { LeadingKeyword = Module (1,0--1,6) })], (true, true),
+      { ConditionalDirectives = []
+        WarnDirectives = []
+        CodeComments = [] }, set []))
+
+(6,0)-(6,1) parse error Incomplete structured construct at or before this point in member definition

tests/service/data/SyntaxTree/Member/Abstract - Property 06.fs

@@ -0,0 +1,6 @@
+module Module
+
+type T =
+    abstract P:
+
+()

tests/service/data/SyntaxTree/Member/Abstract - Property 06.fs.bsl

@@ -0,0 +1,45 @@
+ImplFile
+  (ParsedImplFileInput
+     ("/root/Member/Abstract - Property 06.fs", false,
+      QualifiedNameOfFile Module, [],
+      [SynModuleOrNamespace
+         ([Module], false, NamedModule,
+          [Types
+             ([SynTypeDefn
+                 (SynComponentInfo
+                    ([], None, [], [T],
+                     PreXmlDoc ((3,0), FSharp.Compiler.Xml.XmlDocCollector),
+                     false, None, (3,5--3,6)),
+                  ObjectModel
+                    (Unspecified,
+                     [AbstractSlot
+                        (SynValSig
+                           ([], SynIdent (P, None),
+                            SynValTyparDecls (None, true),
+                            FromParseError (4,14--4,14),
+                            SynValInfo ([], SynArgInfo ([], false, None)), false,
+                            false,
+                            PreXmlDoc ((4,4), FSharp.Compiler.Xml.XmlDocCollector),
+                            Single None, None, (4,4--4,14),
+                            { LeadingKeyword = Abstract (4,4--4,12)
+                              InlineKeyword = None
+                              WithKeyword = None
+                              EqualsRange = None }),
+                         { IsInstance = true
+                           IsDispatchSlot = true
+                           IsOverrideOrExplicitImpl = false
+                           IsFinal = false
+                           GetterOrSetterIsCompilerGenerated = false
+                           MemberKind = PropertyGet }, (4,4--4,14),
+                         { GetSetKeywords = None })], (4,4--4,14)), [], None,
+                  (3,5--4,14), { LeadingKeyword = Type (3,0--3,4)
+                                 EqualsRange = Some (3,7--3,8)
+                                 WithKeyword = None })], (3,0--4,14));
+           Expr (Const (Unit, (6,0--6,2)), (6,0--6,2))],
+          PreXmlDoc ((1,0), FSharp.Compiler.Xml.XmlDocCollector), [], None,
+          (1,0--6,2), { LeadingKeyword = Module (1,0--1,6) })], (true, true),
+      { ConditionalDirectives = []
+        WarnDirectives = []
+        CodeComments = [] }, set []))
+
+(6,0)-(6,1) parse error Incomplete structured construct at or before this point in member definition

tests/service/data/SyntaxTree/Member/Abstract - Property 07.fs

@@ -0,0 +1,6 @@
+module Module
+
+type T =
+    abstract P
+
+()

tests/service/data/SyntaxTree/Member/Abstract - Property 07.fs.bsl

@@ -0,0 +1,45 @@
+ImplFile
+  (ParsedImplFileInput
+     ("/root/Member/Abstract - Property 07.fs", false,
+      QualifiedNameOfFile Module, [],
+      [SynModuleOrNamespace
+         ([Module], false, NamedModule,
+          [Types
+             ([SynTypeDefn
+                 (SynComponentInfo
+                    ([], None, [], [T],
+                     PreXmlDoc ((3,0), FSharp.Compiler.Xml.XmlDocCollector),
+                     false, None, (3,5--3,6)),
+                  ObjectModel
+                    (Unspecified,
+                     [AbstractSlot
+                        (SynValSig
+                           ([], SynIdent (P, None),
+                            SynValTyparDecls (None, true),
+                            FromParseError (4,14--4,14),
+                            SynValInfo ([], SynArgInfo ([], false, None)), false,
+                            false,
+                            PreXmlDoc ((4,4), FSharp.Compiler.Xml.XmlDocCollector),
+                            Single None, None, (4,4--4,14),
+                            { LeadingKeyword = Abstract (4,4--4,12)
+                              InlineKeyword = None
+                              WithKeyword = None
+                              EqualsRange = None }),
+                         { IsInstance = true
+                           IsDispatchSlot = true
+                           IsOverrideOrExplicitImpl = false
+                           IsFinal = false
+                           GetterOrSetterIsCompilerGenerated = false
+                           MemberKind = PropertyGet }, (4,4--4,14),
+                         { GetSetKeywords = None })], (4,4--4,14)), [], None,
+                  (3,5--4,14), { LeadingKeyword = Type (3,0--3,4)
+                                 EqualsRange = Some (3,7--3,8)
+                                 WithKeyword = None })], (3,0--4,14));
+           Expr (Const (Unit, (6,0--6,2)), (6,0--6,2))],
+          PreXmlDoc ((1,0), FSharp.Compiler.Xml.XmlDocCollector), [], None,
+          (1,0--6,2), { LeadingKeyword = Module (1,0--1,6) })], (true, true),
+      { ConditionalDirectives = []
+        WarnDirectives = []
+        CodeComments = [] }, set []))
+
+(6,0)-(6,1) parse error Incomplete structured construct at or before this point in member definition. Expected ':' or other token.

tests/service/data/SyntaxTree/Member/Abstract - Property 08.fs

@@ -0,0 +1,6 @@
+module Module
+
+type T =
+    abstract
+
+()