From 014fb592260e472f69f98525c2da3e1b91c7616e Mon Sep 17 00:00:00 2001
From: Alfonso Garcia-Caro <alfonso.garcia-caro@outlook.com>
Date: Mon, 1 Nov 2021 15:31:00 +0900
Subject: [PATCH] Fix #2564: op_Implicit overloads

---
 src/Fable.Transforms/OverloadSuffix.fs |  3 +++
 tests/Main/CustomOperatorsTests.fs     | 18 +++++++++++++++++-
 2 files changed, 20 insertions(+), 1 deletion(-)

diff --git a/src/Fable.Transforms/OverloadSuffix.fs b/src/Fable.Transforms/OverloadSuffix.fs
index cb2991588e..7721e2bc59 100644
--- a/src/Fable.Transforms/OverloadSuffix.fs
+++ b/src/Fable.Transforms/OverloadSuffix.fs
@@ -150,6 +150,9 @@ let getHash (entity: FSharpEntity) (m: FSharpMemberOrFunctionOrValue) =
     if m.CurriedParameterGroups.Count <> 1 then ""
     else
         let paramTypes = m.CurriedParameterGroups.[0] |> Seq.map (fun p -> p.Type) |> Seq.toList
+        let paramTypes =
+            if m.CompiledName = "op_Implicit" then paramTypes @ [m.ReturnParameter.Type]
+            else paramTypes
         if hasEmptyOverloadSuffix paramTypes then ""
         else
             // Generics can have different names in signature
diff --git a/tests/Main/CustomOperatorsTests.fs b/tests/Main/CustomOperatorsTests.fs
index 2c2e554b2f..c0ebcb5305 100644
--- a/tests/Main/CustomOperatorsTests.fs
+++ b/tests/Main/CustomOperatorsTests.fs
@@ -88,15 +88,31 @@ type ToLength = ToLength with
 
 let inline toLen x : string = (Unchecked.defaultof<ToLength> &. x) D1 D2 D3
 
+type MyType =
+    { Field : int}
+    static member op_Implicit(s: MyType):int = s.Field + 2
+    static member op_Implicit(s: MyType):string = $"Field is %i{s.Field}"
+
+#nowarn "3391"
+
 let operatorsForOverloads = [
     testCase "first overload" <| fun () ->
         toLen 1<px>
         |> equal "1px"
+
     testCase "second overload" <| fun () ->
         toLen 1<em>
         |> equal "1em"
+
+    testCase "op_Implicit can be overloaded" <| fun () ->
+        let takeInt(x: int) = x
+        let takeString(x: string) = x
+        let x = { MyType.Field = 5 }
+        // TODO Remove MyType.op_Implicit with F# 6
+        takeInt(MyType.op_Implicit x) |> equal 7
+        takeString(MyType.op_Implicit x) |> equal "Field is 5"
 ]
 
 let tests =
-  testList "Miscellaneous"
+  testList "Custom operators"
     (typeOperators @ moduleOperators @ operatorsAsFunctions @ operatorsForOverloads)