Filter completions on abstract member type signature (dotnet#13090)

* Filter completions on abstract member type signature

Author: kerams

src/Compiler/Service/ServiceParseTreeWalk.fs

@@ -157,7 +157,7 @@ type SyntaxVisitorBase<'T>() =
         ignore (path, isRecursive, defaultTraverse, bindings, range)
         None
 
-    /// VisitType allows overriding behavior when visiting simple pats
+    /// VisitSimplePats allows overriding behavior when visiting simple pats
     abstract VisitSimplePats: path: SyntaxVisitorPath * synPats: SynSimplePat list -> 'T option
 
     default _.VisitSimplePats(path, synPats) =
@@ -813,8 +813,7 @@ module SyntaxTraversal =
 
                 match ty with
                 | SynType.App (typeName, _, typeArgs, _, _, _, _)
-                | SynType.LongIdentApp (typeName, _, _, typeArgs, _, _, _) ->
-                    [ yield typeName; yield! typeArgs ] |> List.tryPick (traverseSynType path)
+                | SynType.LongIdentApp (typeName, _, _, typeArgs, _, _, _) -> typeName :: typeArgs |> List.tryPick (traverseSynType path)
                 | SynType.Fun (argType = ty1; returnType = ty2) -> [ ty1; ty2 ] |> List.tryPick (traverseSynType path)
                 | SynType.MeasurePower (ty, _, _)
                 | SynType.HashConstraint (ty, _)
@@ -921,12 +920,12 @@ module SyntaxTraversal =
             | SynMemberDefn.AutoProperty (synExpr = synExpr) -> traverseSynExpr path synExpr
             | SynMemberDefn.LetBindings (synBindingList, isRecursive, _, range) ->
                 match visitor.VisitLetOrUse(path, isRecursive, traverseSynBinding path, synBindingList, range) with
-                | Some x -> Some x
                 | None ->
                     synBindingList
                     |> List.map (fun x -> dive x x.RangeOfBindingWithRhs (traverseSynBinding path))
                     |> pick m
-            | SynMemberDefn.AbstractSlot (_synValSig, _memberFlags, _range) -> None
+                | x -> x
+            | SynMemberDefn.AbstractSlot (SynValSig (synType = synType), _memberFlags, _range) -> traverseSynType path synType
             | SynMemberDefn.Interface (interfaceType = synType; members = synMemberDefnsOption) ->
                 match visitor.VisitInterfaceSynMemberDefnType(path, synType) with
                 | None ->

vsintegration/tests/UnitTests/CompletionProviderTests.fs

@@ -572,6 +572,14 @@ type T() =
 """
     VerifyNoCompletionList(fileContents, "member this.M(p:int, h")
 
+[<Test>]
+let ``Completion list on abstract member type signature contains modules and types but not keywords or functions`` =
+    let fileContents = """
+type Interface =
+    abstract member Eat: l
+"""
+    VerifyCompletionList(fileContents, "Eat: l", ["LanguagePrimitives"; "List" ], ["let"; "log"])
+
 [<Test>]
 let ``Provide completion on first function argument type hint``() =
     let fileContents = """