From e759f26a987b06cac187c469a07c920776c6d41d Mon Sep 17 00:00:00 2001
From: Giannis Ntovas <ntovas.gi@gmail.com>
Date: Mon, 10 Oct 2022 22:02:33 +0300
Subject: [PATCH 1/2] Infer string type when using nameof pattern #13377

---
 src/Compiler/Checking/CheckPatterns.fs        |  2 +-
 .../Language/NameofTests.fs                   | 23 +++++++++++++++++++
 2 files changed, 24 insertions(+), 1 deletion(-)

diff --git a/src/Compiler/Checking/CheckPatterns.fs b/src/Compiler/Checking/CheckPatterns.fs
index 2767cca37de..112a6af6077 100644
--- a/src/Compiler/Checking/CheckPatterns.fs
+++ b/src/Compiler/Checking/CheckPatterns.fs
@@ -555,7 +555,7 @@ and TcPatLongIdentNewDef warnOnUpperForId warnOnUpper (cenv: cenv) env ad valRep
     | [arg]
         when g.langVersion.SupportsFeature LanguageFeature.NameOf && IsNameOf cenv env ad m id ->
         match TcNameOfExpr cenv env tpenv (ConvSynPatToSynExpr arg) with
-        | Expr.Const(c, m, _) -> (fun _ -> TPat_const (c, m)), patEnv
+        | Expr.Const(c, m, _) -> TcConstPat warnOnUpper cenv env vFlags patEnv ty (SynConst.String(c.ToString(), SynStringKind.Regular, m)) m
         | _ -> failwith "Impossible: TcNameOfExpr must return an Expr.Const"
 
     | _ ->
diff --git a/tests/FSharp.Compiler.ComponentTests/Language/NameofTests.fs b/tests/FSharp.Compiler.ComponentTests/Language/NameofTests.fs
index 3c338e02203..ad08df068b0 100644
--- a/tests/FSharp.Compiler.ComponentTests/Language/NameofTests.fs
+++ b/tests/FSharp.Compiler.ComponentTests/Language/NameofTests.fs
@@ -60,3 +60,26 @@ if actual <> expected then failwith $"Expected nameof({{expected}}) to be '{{exp
         |> withLangVersion50
         |> compileAndRun
         |> shouldSucceed
+
+    [<Fact>]
+    let ``nameof() in a pattern should return the correct type`` () =    
+        let source = $"""
+open Microsoft.FSharp.Reflection
+let f x = match x with nameof x -> true | _ -> false
+
+let expected = "System.String -> System.Boolean"
+let elms s = if FSharpType.IsFunction s then
+               let domain, range = FSharpType.GetFunctionElements s
+               $"{{domain}} -> {{range}}"
+             else
+               ""
+let fType = f.GetType()
+let actual = elms fType
+if actual <> expected then failwith $"Expected type to be '{{expected}}', but got '{{actual}}'"
+        """
+        Fsx source
+        |> asExe
+        |> withLangVersion50
+        |> ignoreWarnings
+        |> compileAndRun
+        |> shouldSucceed

From 7d0bf1e10450ec52c678868fc1dd9f93e980554f Mon Sep 17 00:00:00 2001
From: Tomas Grosup <tomasgrosup@microsoft.com>
Date: Thu, 3 Nov 2022 16:31:20 +0100
Subject: [PATCH 2/2] Fix nameof pattern matching

Fixing nameof pattern matching by avoiding .ToString(), which is a debug-oriented representation that adds double quotes to the string.

Which then meant a difference between string itself and then one being matched.

Also adding a case to the component tests suite to cover for this.
---
 src/Compiler/Checking/CheckPatterns.fs        |  4 +-
 .../Language/NameofTests.fs                   | 46 +++++++++++++++++++
 2 files changed, 48 insertions(+), 2 deletions(-)

diff --git a/src/Compiler/Checking/CheckPatterns.fs b/src/Compiler/Checking/CheckPatterns.fs
index 112a6af6077..88998544d52 100644
--- a/src/Compiler/Checking/CheckPatterns.fs
+++ b/src/Compiler/Checking/CheckPatterns.fs
@@ -555,8 +555,8 @@ and TcPatLongIdentNewDef warnOnUpperForId warnOnUpper (cenv: cenv) env ad valRep
     | [arg]
         when g.langVersion.SupportsFeature LanguageFeature.NameOf && IsNameOf cenv env ad m id ->
         match TcNameOfExpr cenv env tpenv (ConvSynPatToSynExpr arg) with
-        | Expr.Const(c, m, _) -> TcConstPat warnOnUpper cenv env vFlags patEnv ty (SynConst.String(c.ToString(), SynStringKind.Regular, m)) m
-        | _ -> failwith "Impossible: TcNameOfExpr must return an Expr.Const"
+        | Expr.Const(Const.String s, m, _) -> TcConstPat warnOnUpper cenv env vFlags patEnv ty (SynConst.String(s, SynStringKind.Regular, m)) m
+        | _ -> failwith "Impossible: TcNameOfExpr must return an Expr.Const of type string"
 
     | _ ->
         let _, acc = TcArgPats warnOnUpper cenv env vFlags patEnv args
diff --git a/tests/FSharp.Compiler.ComponentTests/Language/NameofTests.fs b/tests/FSharp.Compiler.ComponentTests/Language/NameofTests.fs
index ad08df068b0..27e7ca95bec 100644
--- a/tests/FSharp.Compiler.ComponentTests/Language/NameofTests.fs
+++ b/tests/FSharp.Compiler.ComponentTests/Language/NameofTests.fs
@@ -83,3 +83,49 @@ if actual <> expected then failwith $"Expected type to be '{{expected}}', but go
         |> ignoreWarnings
         |> compileAndRun
         |> shouldSucceed
+
+
+    [<Fact>]
+    let ``nameof works for pattern matching of DU case names`` () =  
+        let source = """
+/// Simplified version of EventStore's API
+type RecordedEvent = { EventType: string; Data: string }
+
+/// My concrete type:
+type MyEvent =
+    | A of string
+    | B of string
+
+let deserialize (e: RecordedEvent) : MyEvent =
+    printfn "EventType is '%s'" e.EventType
+    printfn "Nameof A is '%s'" (nameof A)
+    printfn "Nameof B is '%s'" (nameof B)
+    match e.EventType with
+    | nameof A -> A e.Data
+    | nameof B -> B e.Data
+    | t -> failwithf "Invalid EventType: '%s'" t
+
+let getData event =
+    match event with
+    | A amsg -> amsg
+    | B bmsg -> bmsg
+
+let re1 = { EventType = nameof A; Data = "hello" }
+let re2 = { EventType = nameof B; Data = "world" }
+
+let a = deserialize re1
+let b = deserialize re2
+
+if not((getData a) = re1.Data) then
+    failwith $"Record1 mismatch;; {getData a} <> {re1.Data}"
+
+if not((getData b) = re2.Data) then
+    failwith $"Record1 mismatch;; {getData b} <> {re2.Data}"
+        """
+        Fsx source
+        |> asExe
+        |> withLangVersionPreview
+        |> ignoreWarnings
+        |> compileAndRun
+        |> shouldSucceed
+