Fixed taking native address of an immutable local value (#8618)

Author: TIHan

src/fsharp/TastOps.fs

@@ -6078,6 +6078,16 @@ let mkDerefAddrExpr mAddrGet expr mExpr exprTy =
 /// have intended effect (i.e. is a readonly pointer and/or a defensive copy).
 let rec mkExprAddrOfExprAux g mustTakeAddress useReadonlyForGenericArrayAddress mut expr addrExprVal m =
     if mustTakeAddress then 
+        let isNativePtr = 
+            match addrExprVal with
+            | Some vf -> valRefEq g vf g.addrof2_vref
+            | _ -> false
+
+        // If we are taking the native address using "&&" to get a nativeptr, disallow if it's readonly.
+        let checkTakeNativeAddress readonly =
+            if isNativePtr && readonly then
+                error(Error(FSComp.SR.tastValueMustBeMutable(), m))
+
         match expr with 
         // LVALUE of "*x" where "x" is byref is just the byref itself
         | Expr.Op (TOp.LValueOp (LByrefGet, vref), _, [], m) when MustTakeAddressOfByrefGet g vref || CanTakeAddressOfByrefGet g vref mut -> 
@@ -6090,6 +6100,7 @@ let rec mkExprAddrOfExprAux g mustTakeAddress useReadonlyForGenericArrayAddress
         | Expr.Val (vref, _, m) when MustTakeAddressOfVal g vref || CanTakeAddressOfImmutableVal g m vref mut ->
             let readonly = not (MustTakeAddressOfVal g vref)
             let writeonly = false
+            checkTakeNativeAddress readonly
             None, mkValAddr m readonly vref, readonly, writeonly
 
         // LVALUE of "e.f" where "f" is an instance F# field or record field. 
@@ -6134,15 +6145,11 @@ let rec mkExprAddrOfExprAux g mustTakeAddress useReadonlyForGenericArrayAddress
 
         // LVALUE of "e.[n]" where e is an array of structs 
         | Expr.App (Expr.Val (vf, _, _), _, [elemTy], [aexpr;nexpr], _) when (valRefEq g vf g.array_get_vref) -> 
-        
+      
             let readonly = false // array address is never forced to be readonly
             let writeonly = false
             let shape = ILArrayShape.SingleDimensional
             let ilInstrReadOnlyAnnotation = if isTyparTy g elemTy && useReadonlyForGenericArrayAddress then ReadonlyAddress else NormalAddress
-            let isNativePtr = 
-                match addrExprVal with
-                | Some vf -> valRefEq g vf g.addrof2_vref
-                | _ -> false
             None, mkArrayElemAddress g (readonly, ilInstrReadOnlyAnnotation, isNativePtr, shape, elemTy, [aexpr; nexpr], m), readonly, writeonly
 
         // LVALUE of "e.[n1, n2]", "e.[n1, n2, n3]", "e.[n1, n2, n3, n4]" where e is an array of structs 
@@ -6153,11 +6160,6 @@ let rec mkExprAddrOfExprAux g mustTakeAddress useReadonlyForGenericArrayAddress
             let writeonly = false
             let shape = ILArrayShape.FromRank args.Length
             let ilInstrReadOnlyAnnotation = if isTyparTy g elemTy && useReadonlyForGenericArrayAddress then ReadonlyAddress else NormalAddress
-            let isNativePtr = 
-                match addrExprVal with
-                | Some vf -> valRefEq g vf g.addrof2_vref
-                | _ -> false
-            
             None, mkArrayElemAddress g (readonly, ilInstrReadOnlyAnnotation, isNativePtr, shape, elemTy, (aexpr :: args), m), readonly, writeonly
 
         // LVALUE: "&meth(args)" where meth has a byref or inref return. Includes "&span.[idx]".