Add support for "collapse to definition" (#2810)

* add support for "collapse to definition"

* separate match cases with a blank line

vsintegration/src/FSharp.Editor/Structure/BlockStructureService.fs

@@ -66,6 +66,56 @@ module internal BlockStructure =
         | Scope.Comment
         | Scope.XmlDocComment -> BlockTypes.Comment
 
+    let isAutoCollapsible = function
+        | Scope.New
+        | Scope.Attribute
+        | Scope.Member
+        | Scope.LetOrUse
+        | Scope.EnumCase
+        | Scope.UnionCase
+        | Scope.SpecialFunc
+        | Scope.HashDirective
+        | Scope.Comment
+        | Scope.Open
+        | Scope.XmlDocComment -> true
+
+        | Scope.Namespace
+        | Scope.Module
+        | Scope.Record
+        | Scope.Interface
+        | Scope.TypeExtension
+        | Scope.RecordDefn
+        | Scope.CompExpr
+        | Scope.ObjExpr
+        | Scope.UnionDefn
+        | Scope.Type
+        | Scope.RecordField
+        | Scope.Match
+        | Scope.MatchClause
+        | Scope.MatchLambda
+        | Scope.ThenInIfThenElse
+        | Scope.ElseInIfThenElse
+        | Scope.TryWith
+        | Scope.TryInTryWith
+        | Scope.WithInTryWith
+        | Scope.TryFinally
+        | Scope.TryInTryFinally
+        | Scope.FinallyInTryFinally
+        | Scope.IfThenElse
+        | Scope.Tuple
+        | Scope.ArrayOrList
+        | Scope.CompExprInternal
+        | Scope.Quote
+        | Scope.Lambda
+        | Scope.LetOrUseBang
+        | Scope.Val
+        | Scope.YieldOrReturn
+        | Scope.YieldOrReturnBang
+        | Scope.TryWith
+        | Scope.Do
+        | Scope.While
+        | Scope.For -> false
+
     let createBlockSpans (sourceText:SourceText) (parsedInput:Ast.ParsedInput) =
         let linetext = sourceText.Lines |> Seq.map (fun x -> x.ToString()) |> Seq.toArray
         
@@ -84,7 +134,7 @@ module internal BlockStructure =
                     | Some span -> sourceText.GetSubText(span).ToString()+"..."
                     | None -> "..."
 
-                Some <| (BlockSpan(scopeToBlockType scopeRange.Scope, true, textSpan,hintSpan,bannerText):BlockSpan)
+                Some (BlockSpan(scopeToBlockType scopeRange.Scope, true, textSpan, hintSpan, bannerText, autoCollapse = isAutoCollapsible scopeRange.Scope))
             | _, _ -> None
         )