C# protected property can be assigned in a F# inherit constructor call

docs/release-notes/.FSharp.Compiler.Service/9.0.100.md

@@ -3,6 +3,7 @@
 * Compiler hangs when compiling inline recursive invocation ([Issue #17376](https://github.com/dotnet/fsharp/issues/17376), [PR #17394](https://github.com/dotnet/fsharp/pull/17394))
 * Fix reporting IsFromComputationExpression only for CE builder type constructors and let bindings. ([PR #17375](https://github.com/dotnet/fsharp/pull/17375))
 * Optimize simple mappings in comprehensions when the body of the mapping has `let`-bindings and/or sequential expressions before a single yield. ([PR #17419](https://github.com/dotnet/fsharp/pull/17419))
+* C# protected property can be assigned in F# inherit constructor call. ([Issue #13299](https://github.com/dotnet/fsharp/issues/13299), [PR #17391](https://github.com/dotnet/fsharp/pull/17391))
 
 ### Added
 

src/Compiler/Checking/MethodCalls.fs

@@ -1237,7 +1237,8 @@ let MethInfoChecks g amap isInstance tyargsOpt objArgs ad m (minfo: MethInfo)  =
                 AccessibleFrom(paths, None) 
         | _ -> ad
 
-    if not (IsTypeAndMethInfoAccessible amap m adOriginal ad minfo) then 
+    let isProtectedSetter = minfo.IsProtectedAccessibility && minfo.LogicalName.StartsWithOrdinal("set_")
+    if not (IsTypeAndMethInfoAccessible amap m adOriginal ad minfo) && not isProtectedSetter then 
       error (Error (FSComp.SR.tcMethodNotAccessible(minfo.LogicalName), m))
 
     if isAnyTupleTy g minfo.ApparentEnclosingType && not minfo.IsExtensionMember &&

src/Compiler/TypedTree/TypedTree.fs

@@ -90,7 +90,7 @@ type ValBaseOrThisInfo =
     /// Indicates a normal value
     | NormalVal  
 
-    /// Indicates the 'this' value specified in a memberm e.g. 'x' in 'member x.M() = 1'
+    /// Indicates the 'this' value specified in a member e.g. 'x' in 'member x.M() = 1'
     | MemberThisVal 
 
 /// Flags on values

tests/FSharp.Compiler.ComponentTests/Conformance/BasicGrammarElements/AccessibilityAnnotations/Basic/Basic.fs

@@ -188,3 +188,42 @@ module AccessibilityAnnotations_Basic =
         compilation
         |> verifyCompileAndRun
         |> shouldSucceed
+
+    [<Fact>]
+    let ``C# protected property can be assigned in a F# inherit constructor call`` () =
+
+        let csharp =
+            CSharp
+                """
+namespace Consumer
+{
+    public class Foo
+    {
+        protected string Value { get; set; } = "";
+    }
+}
+"""
+            |> withName "CSLib"
+
+        let fsharp =
+            FSharp
+                """
+module Hello
+open Consumer
+
+type Bar() =
+    inherit Foo(Value = "Works")
+
+type Bar2() as this =
+    inherit Foo()
+    do this.Value <- "Works"
+
+{ new Foo(Value = "OK") with member x.ToString() = "OK" } |> ignore
+"""
+            |> withLangVersion80
+            |> withName "FSLib"
+            |> withReferences [ csharp ]
+
+        fsharp
+        |> compile
+        |> shouldSucceed