Add IsRelativeNameResolvableFromSymbol (#3722)

* Add `IsRelativeNameResolvableFromSymbol`

* fix compilation

Author: Krzysztof-Cieslak

src/fsharp/vs/service.fs

@@ -897,6 +897,10 @@ type TypeCheckInfo
             (fun msg -> 
                 Trace.TraceInformation(sprintf "FCS: recovering from error in IsRelativeNameResolvable: '%s'" msg)
                 false)
+
+    /// Determines if a long ident is resolvable at a specific point.
+    member scope.IsRelativeNameResolvableFromSymbol(cursorPos: pos, plid: string list, symbol: FSharpSymbol) : bool =
+        scope.IsRelativeNameResolvable(cursorPos, plid, symbol.Item)
 
     /// Get the auto-complete items at a location
     member __.GetDeclarations (ctok, parseResultsOpt, line, lineStr, partialName, getAllSymbols, hasTextChangedSinceLastTypecheck) =
@@ -2009,6 +2013,12 @@ type FSharpCheckFileResults(filename: string, errors: FSharpErrorInfo[], scopeOp
         reactorOp userOpName "IsRelativeNameResolvable" true (fun ctok scope -> 
             RequireCompilationThread ctok
             scope.IsRelativeNameResolvable(pos, plid, item))
+
+    member info.IsRelativeNameResolvableFromSymbol(pos: pos, plid: string list, symbol: FSharpSymbol, ?userOpName: string) = 
+        let userOpName = defaultArg userOpName "Unknown"
+        reactorOp userOpName "IsRelativeNameResolvableFromSymbol" true (fun ctok scope -> 
+            RequireCompilationThread ctok
+            scope.IsRelativeNameResolvableFromSymbol(pos, plid, symbol))
 
     member info.ImplementationFiles =
         if not keepAssemblyContents then invalidOp "The 'keepAssemblyContents' flag must be set to true on the FSharpChecker in order to access the checked contents of assemblies"

src/fsharp/vs/service.fsi

@@ -266,6 +266,10 @@ type internal FSharpCheckFileResults =
     /// <param name="userOpName">An optional string used for tracing compiler operations associated with this request.</param>
     member internal IsRelativeNameResolvable: cursorPos : pos * plid : string list * item: Item * ?userOpName: string -> Async<bool>
 
+    /// Determines if a long ident is resolvable at a specific point.
+    /// <param name="userOpName">An optional string used for tracing compiler operations associated with this request.</param>
+    member IsRelativeNameResolvableFromSymbol: cursorPos : pos * plid : string list * symbol: FSharpSymbol * ?userOpName: string -> Async<bool>
+
     /// Represents complete typechecked implementation files, including thier typechecked signatures if any.
     member ImplementationFiles: FSharpImplementationFileContents list option