From 7f8a53efef78c973c58b9d046836a099ec057893 Mon Sep 17 00:00:00 2001
From: Chet Husk <chusk3@gmail.com>
Date: Wed, 30 Dec 2020 13:00:18 -0600
Subject: [PATCH 1/2] stub out test

---
 .../FSharp.Compiler.ComponentTests.fsproj     |  1 +
 .../Language/AttributeCheckingTests.fs        | 28 +++++++++++++++++++
 2 files changed, 29 insertions(+)
 create mode 100644 tests/FSharp.Compiler.ComponentTests/Language/AttributeCheckingTests.fs

diff --git a/tests/FSharp.Compiler.ComponentTests/FSharp.Compiler.ComponentTests.fsproj b/tests/FSharp.Compiler.ComponentTests/FSharp.Compiler.ComponentTests.fsproj
index 62254811bc5..08a1e44e639 100644
--- a/tests/FSharp.Compiler.ComponentTests/FSharp.Compiler.ComponentTests.fsproj
+++ b/tests/FSharp.Compiler.ComponentTests/FSharp.Compiler.ComponentTests.fsproj
@@ -43,6 +43,7 @@
     <Compile Include="ErrorMessages\WrongSyntaxInForLoop.fs" />
     <Compile Include="ErrorMessages\ConfusingTypeName.fs" />
     <Compile Include="Language\RegressionTests.fs" />
+    <Compile Include="Language\AttributeCheckingTests.fs" />
     <Compile Include="Language\XmlComments.fs" />
     <Compile Include="Language\CompilerDirectiveTests.fs" />
     <Compile Include="Language\CodeQuotationTests.fs" />
diff --git a/tests/FSharp.Compiler.ComponentTests/Language/AttributeCheckingTests.fs b/tests/FSharp.Compiler.ComponentTests/Language/AttributeCheckingTests.fs
new file mode 100644
index 00000000000..78c189bb952
--- /dev/null
+++ b/tests/FSharp.Compiler.ComponentTests/Language/AttributeCheckingTests.fs
@@ -0,0 +1,28 @@
+// Copyright (c) Microsoft Corporation.  All Rights Reserved.  See License.txt in the project root for license information.
+
+namespace FSharp.Compiler.ComponentTests.AttributeChecking
+
+open Xunit
+open FSharp.Test.Utilities.Compiler
+
+[<TestFixture>]
+module AttributeCheckingTests =
+
+        [<Fact>]
+    let ``attributes check inherited AllowMultiple`` () =
+        Fsx"""
+open System
+
+[<AttributeUsage(AttributeTargets.Class, AllowMultiple = true, Inherited = true)>]
+type HttpMethodAttribute() = inherit Attribute()
+type HttpGetAttribute() = inherit HttpMethodAttribute()
+
+[<HttpGet; HttpGet>] // this shouldn't error like 
+[<HttpMethod; HttpMethod>] // this doesn't
+type C() =
+    member _.M() = ()
+        """
+         |> ignoreWarnings
+         |> compile
+         |> shouldSucceed
+        
\ No newline at end of file

From fa9b97933fd9793bdf12628adf684860ac6dd8a0 Mon Sep 17 00:00:00 2001
From: Chet Husk <chusk3@gmail.com>
Date: Sun, 3 Jan 2021 20:45:50 -0600
Subject: [PATCH 2/2] extend attributeusage-checking logic to walk the entire
 parent tree

---
 src/fsharp/TypedTreeOps.fs                          | 13 +++++++++++--
 .../Language/AttributeCheckingTests.fs              |  5 ++---
 2 files changed, 13 insertions(+), 5 deletions(-)

diff --git a/src/fsharp/TypedTreeOps.fs b/src/fsharp/TypedTreeOps.fs
index 4311ad55b6c..6c25a422685 100644
--- a/src/fsharp/TypedTreeOps.fs
+++ b/src/fsharp/TypedTreeOps.fs
@@ -3013,6 +3013,11 @@ let superOfTycon (g: TcGlobals) (tycon: Tycon) =
     | None -> g.obj_ty 
     | Some ty -> ty 
 
+/// walk a TyconRef's inheritance tree, yielding any parent types as an array
+let supersOfTyconRef (tcref: TyconRef) =
+    Array.unfold (fun (tcref: TyconRef) -> match tcref.TypeContents.tcaug_super with Some (TType_app(sup, _)) -> Some(sup, sup) | _ -> None) tcref
+
+
 //----------------------------------------------------------------------------
 // Detect attributes
 //----------------------------------------------------------------------------
@@ -3119,12 +3124,16 @@ let TryFindTyconRefBoolAttribute g m attribSpec tcref =
                    | ([ Some ((:? bool as v) : obj) ], _) -> Some v 
                    | _ -> None)
 
+/// Try to find the resolved attributeusage for an type by walking its inheritance tree and picking the correct attribute usage value
 let TryFindAttributeUsageAttribute g m tcref =
-    TryBindTyconRefAttribute g m g.attrib_AttributeUsageAttribute tcref 
+    [| yield tcref
+       yield! supersOfTyconRef tcref |]
+    |> Array.tryPick (fun tcref ->
+        TryBindTyconRefAttribute g m g.attrib_AttributeUsageAttribute tcref
                 (fun (_, named) -> named |> List.tryPick (function ("AllowMultiple", _, _, ILAttribElem.Bool res) -> Some res | _ -> None))
                 (fun (Attrib(_, _, _, named, _, _, _)) -> named |> List.tryPick (function AttribNamedArg("AllowMultiple", _, _, AttribBoolArg res ) -> Some res | _ -> None))
                 (fun (_, named) -> named |> List.tryPick (function ("AllowMultiple", Some ((:? bool as res) : obj)) -> Some res | _ -> None))
-
+    )
 
 /// Try to find a specific attribute on a type definition, where the attribute accepts a string argument.
 ///
diff --git a/tests/FSharp.Compiler.ComponentTests/Language/AttributeCheckingTests.fs b/tests/FSharp.Compiler.ComponentTests/Language/AttributeCheckingTests.fs
index 78c189bb952..503ad0312bc 100644
--- a/tests/FSharp.Compiler.ComponentTests/Language/AttributeCheckingTests.fs
+++ b/tests/FSharp.Compiler.ComponentTests/Language/AttributeCheckingTests.fs
@@ -5,12 +5,11 @@ namespace FSharp.Compiler.ComponentTests.AttributeChecking
 open Xunit
 open FSharp.Test.Utilities.Compiler
 
-[<TestFixture>]
 module AttributeCheckingTests =
 
-        [<Fact>]
+    [<Fact>]
     let ``attributes check inherited AllowMultiple`` () =
-        Fsx"""
+        Fsx """
 open System
 
 [<AttributeUsage(AttributeTargets.Class, AllowMultiple = true, Inherited = true)>]