Error message that explicitly disallows static abstract members in classes.

docs/release-notes/.FSharp.Compiler.Service/8.0.400.md

@@ -1,5 +1,6 @@
 ### Fixed
 
+* Static abstract method on classes no longer yields internal error. ([Issue #17044](https://github.com/dotnet/fsharp/issues/17044), [PR #17055](https://github.com/dotnet/fsharp/pull/17055))
 * Disallow calling abstract methods directly on interfaces. ([Issue #14012](https://github.com/dotnet/fsharp/issues/14012), [Issue #16299](https://github.com/dotnet/fsharp/issues/16299), [PR #17021](https://github.com/dotnet/fsharp/pull/17021))
 * Various parenthesization API fixes. ([PR #16977](https://github.com/dotnet/fsharp/pull/16977)) 
 * Fix bug in optimization of for-loops over integral ranges with steps and units of measure. ([Issue #17025](https://github.com/dotnet/fsharp/issues/17025), [PR #17040](https://github.com/dotnet/fsharp/pull/17040), [PR #17048](https://github.com/dotnet/fsharp/pull/17048))

src/Compiler/Checking/CheckDeclarations.fs

@@ -3608,6 +3608,20 @@ module EstablishTypeDefinitionCores =
                             elif not (isClassTy g ty) then 
                                 errorR(Error(FSComp.SR.tcCannotInheritFromInterfaceType(), m)))
 
+                        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 kind = 
                             match kind with 
                               | SynTypeDefnKind.Struct -> 
@@ -3632,6 +3646,9 @@ module EstablishTypeDefinitionCores =
                                   noCLIMutableAttributeCheck()
                                   structLayoutAttributeCheck(not isIncrClass)
                                   allowNullLiteralAttributeCheck()
+                                  for slot in abstractSlots do
+                                      if not slot.IsInstanceMember then
+                                          errorR(Error(FSComp.SR.chkStaticAbstractMembersOnClasses(), slot.Range))
                                   TFSharpClass
                               | SynTypeDefnKind.Delegate (ty, arity) -> 
                                   noCLIMutableAttributeCheck()
@@ -3666,21 +3683,7 @@ module EstablishTypeDefinitionCores =
                                 | (_, m, baseIdOpt) :: _ -> 
                                     match baseIdOpt with 
                                     | None -> Some(ident("base", m)) 
-                                    | Some id -> Some id
-
-                        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 ]
+                                    | Some id -> Some id                            
 
                         let baseValOpt = MakeAndPublishBaseVal cenv envinner baseIdOpt (superOfTycon g tycon)
                         let safeInitInfo = ComputeInstanceSafeInitInfo cenv envinner thisTyconRef.Range thisTy
@@ -4453,7 +4456,7 @@ module TcDeclarations =
 
             let slotsigs = members |> List.choose (function  SynMemberDefn.AbstractSlot (slotSig = x; flags = y) -> Some(x, y) | _ -> None)
 
-            let members,_vals_Inherits_Abstractslots = SplitAutoProps members
+            let members, _vals_Inherits_Abstractslots = SplitAutoProps members
 
             let isConcrete = 
                 members |> List.exists (function 

src/Compiler/FSComp.txt

@@ -1746,4 +1746,5 @@ featureReuseSameFieldsInStructUnions,"Share underlying fields in a [<Struct>] di
 3863,parsExpectingField,"Expecting record field"
 3864,tooManyMethodsInDotNetTypeWritingAssembly,"The type '%s' has too many methods. Found: '%d', maximum: '%d'"
 3865,parsOnlySimplePatternsAreAllowedInConstructors,"Only simple patterns are allowed in primary constructors"
-3866,chkStaticAbstractInterfaceMembers,"A static abstract non-virtual interface member should only be called via type parameter (for example: 'T.%s)."
+3866,chkStaticAbstractInterfaceMembers,"A static abstract non-virtual interface member should only be called via type parameter (for example: 'T.%s)."
+3867,chkStaticAbstractMembersOnClasses,"Classes cannot contain static abstract members."

tests/FSharp.Compiler.ComponentTests/Conformance/Types/TypeConstraints/IWSAMsAndSRTPs/IWSAMsAndSRTPsTests.fs

@@ -1241,4 +1241,31 @@ printf "%A" res"""
             (Error 3866, Line 12, Col 82, Line 12, Col 126, "A static abstract non-virtual interface member should only be called via type parameter (for example: 'T.op_Addition).")
             (Error 3866, Line 13, Col 82, Line 13, Col 126, "A static abstract non-virtual interface member should only be called via type parameter (for example: 'T.op_Addition).")
             (Error 3866, Line 15, Col 82, Line 15, Col 129, "A static abstract non-virtual interface member should only be called via type parameter (for example: 'T.Parse).")
-        ]
+        ]
+
+    [<FactForNETCOREAPP>]
+    let ``Error message that explicitly disallows static abstract methods in abstract classes.`` () =
+        Fsx """
+[<AbstractClass>]
+type A () =
+    static abstract M : unit -> unit
+        """
+        |> withOptions [ "--nowarn:3536" ; "--nowarn:3535" ]
+        |> typecheck
+        |> shouldFail
+        |> withDiagnostics [
+            (Error 3867, Line 4, Col 21, Line 4, Col 22, "Classes cannot contain static abstract members.")
+        ]
+
+    [<FactForNETCOREAPP>]
+    let ``Error message that explicitly disallows static abstract methods in classes.`` () =
+        Fsx """
+type A () =
+    static abstract M : unit -> unit
+        """
+        |> withOptions [ "--nowarn:3536" ; "--nowarn:3535" ]
+        |> typecheck
+        |> shouldFail
+        |> withDiagnostics [
+            (Error 3867, Line 3, Col 21, Line 3, Col 22, "Classes cannot contain static abstract members.")
+        ]