Remove isAppTy (#9282) (#9293)

Co-authored-by: Steffen Forkmann <steffen.forkmann@msu-solutions.de>

Author: dotnet-bot

src/fsharp/infos.fs

@@ -41,13 +41,18 @@ let CanImportILType scoref amap m ilty =
 
 /// Indicates if an F# type is the type associated with an F# exception declaration
 let isExnDeclTy g ty =
-    isAppTy g ty && (tcrefOfAppTy g ty).IsExceptionDecl
+    match tryTcrefOfAppTy g ty with
+    | ValueSome tcref -> tcref.IsExceptionDecl
+    | _ -> false
 
 /// Get the base type of a type, taking into account type instantiations. Return None if the
 /// type has no base type.
 let GetSuperTypeOfType g amap m ty =
 #if !NO_EXTENSIONTYPING
-    let ty = (if isAppTy g ty && (tcrefOfAppTy g ty).IsProvided then stripTyEqns g ty else stripTyEqnsAndMeasureEqns g ty)
+    let ty =
+        match tryTcrefOfAppTy g ty with
+        | ValueSome tcref when tcref.IsProvided -> stripTyEqns g ty 
+        | _ -> stripTyEqnsAndMeasureEqns g ty
 #else
     let ty = stripTyEqnsAndMeasureEqns g ty
 #endif
@@ -107,10 +112,11 @@ let rec GetImmediateInterfacesOfType skipUnref g amap m ty =
                 [ match tcref.TypeReprInfo with
                   | TMeasureableRepr reprTy ->
                        for ity in GetImmediateInterfacesOfType skipUnref g amap m reprTy do
-                          if isAppTy g ity then
-                              let itcref = tcrefOfAppTy g ity
+                          match tryTcrefOfAppTy g ity with
+                          | ValueNone -> ()
+                          | ValueSome itcref ->
                               if not (tyconRefEq g itcref g.system_GenericIComparable_tcref) &&
-                                 not (tyconRefEq g itcref g.system_GenericIEquatable_tcref)  then
+                                 not (tyconRefEq g itcref g.system_GenericIEquatable_tcref) then
                                    yield ity
                   | _ -> ()
                   yield mkAppTy g.system_GenericIComparable_tcref [ty]
@@ -157,7 +163,10 @@ type AllowMultiIntfInstantiations = Yes | No
 let private FoldHierarchyOfTypeAux followInterfaces allowMultiIntfInst skipUnref visitor g amap m ty acc =
     let rec loop ndeep ty ((visitedTycon, visited: TyconRefMultiMap<_>, acc) as state) =
 
-        let seenThisTycon = isAppTy g ty && Set.contains (tcrefOfAppTy g ty).Stamp visitedTycon
+        let seenThisTycon = 
+            match tryTcrefOfAppTy g ty with
+            | ValueSome tcref -> Set.contains tcref.Stamp visitedTycon
+            | _ -> false
 
         // Do not visit the same type twice. Could only be doing this if we've seen this tycon
         if seenThisTycon && List.exists (typeEquiv g ty) (visited.Find (tcrefOfAppTy g ty)) then state else
@@ -166,11 +175,11 @@ let private FoldHierarchyOfTypeAux followInterfaces allowMultiIntfInst skipUnref
         if seenThisTycon && allowMultiIntfInst = AllowMultiIntfInstantiations.No then state else
 
         let state =
-            if isAppTy g ty then
-                let tcref = tcrefOfAppTy g ty
+            match tryTcrefOfAppTy g ty with
+            | ValueSome tcref ->
                 let visitedTycon = Set.add tcref.Stamp visitedTycon
                 visitedTycon, visited.Add (tcref, ty), acc
-            else
+            | _ ->
                 state
 
         if ndeep > 100 then (errorR(Error((FSComp.SR.recursiveClassHierarchy (showType ty)), m)); (visitedTycon, visited, acc)) else
@@ -257,14 +266,18 @@ let AllInterfacesOfType g amap m allowMultiIntfInst ty =
 
 /// Check if two types have the same nominal head type
 let HaveSameHeadType g ty1 ty2 =
-    isAppTy g ty1 && isAppTy g ty2 &&
-    tyconRefEq g (tcrefOfAppTy g ty1) (tcrefOfAppTy g ty2)
+    match tryTcrefOfAppTy g ty1 with
+    | ValueSome tcref1 ->
+        match tryTcrefOfAppTy g ty2 with
+        | ValueSome tcref2 -> tyconRefEq g tcref1 tcref2
+        | _ -> false
+    | _ -> false
 
 /// Check if a type has a particular head type
 let HasHeadType g tcref ty2 =
-        isAppTy g ty2 &&
-        tyconRefEq g tcref (tcrefOfAppTy g ty2)
-
+    match tryTcrefOfAppTy g ty2 with
+    | ValueSome tcref2 -> tyconRefEq g tcref tcref2
+    | ValueNone -> false
 
 /// Check if a type exists somewhere in the hierarchy which has the same head type as the given type (note, the given type need not have a head type at all)
 let ExistsSameHeadTypeInHierarchy g amap m typeToSearchFrom typeToLookFor =