Fix FSharpMemberOrFunctionOrValue.IsConstructor property for ctor definition (#3972)

* fix FSharpMemberOrFunctionOrValue.IsConstructor property for ctor definition

* add a test

Author: vasily-kirichenko

src/fsharp/symbols/Symbols.fs

@@ -1796,6 +1796,7 @@ and FSharpMemberOrFunctionOrValue(cenv, d:FSharpMemberOrValData, item) =
     member x.IsConstructor =
         match d with
         | C _ -> true
+        | V v -> v.IsConstructor
         | _ -> false
 
     member x.Data = d

tests/service/EditorTests.fs

@@ -715,6 +715,37 @@ type Class1() =
           ("member .cctor", (10, 5, 10, 11))
           ("Test", (1, 0, 1, 0))|]
 
+[<Test>]
+let ``IsConstructor property should return true for constructors`` () = 
+    let input = 
+      """
+type T(x: int) =
+    new() = T(0)
+let x: T()
+"""
+    let file = "/home/user/Test.fsx"
+    let _, typeCheckResults = parseAndCheckScript(file, input) 
+    typeCheckResults.GetAllUsesOfAllSymbolsInFile()
+    |> Async.RunSynchronously
+    |> Array.map (fun su -> 
+        let r = su.RangeAlternate
+        let isConstructor =
+            match su.Symbol with
+            | :? FSharpMemberOrFunctionOrValue as f -> f.IsConstructor
+            | _ -> false
+        su.Symbol.ToString(), (r.StartLine, r.StartColumn, r.EndLine, r.EndColumn), isConstructor)
+    |> Array.distinct
+    |> shouldEqual 
+        [|("T", (2, 5, 2, 6), false)
+          ("int", (2, 10, 2, 13), false)
+          ("val x", (2, 7, 2, 8), false)
+          ("member .ctor", (2, 5, 2, 6), true)
+          ("member .ctor", (3, 4, 3, 7), true)
+          ("member .ctor", (3, 12, 3, 13), true)
+          ("T", (4, 7, 4, 8), false)
+          ("val x", (4, 4, 4, 5), false)
+          ("Test", (1, 0, 1, 0), false)|]
+
 //-------------------------------------------------------------------------------