Fix finding references to interface methods

src/Compiler/Service/ItemKey.fs

@@ -306,6 +306,21 @@ and [<Sealed>] ItemKeyStoreBuilder() =
             | ParentNone -> writeChar '%'
             | Parent eref -> writeEntityRef eref
 
+    let writeValue (vref: ValRef) =
+        if vref.IsPropertyGetterMethod || vref.IsPropertySetterMethod then
+            writeString ItemKeyTags.itemProperty
+            writeString vref.PropertyName
+
+            match vref.IsOverrideOrExplicitImpl, vref.MemberInfo with
+            | true, Some { ImplementedSlotSigs = slotSig :: _ } -> slotSig.DeclaringType |> writeType false
+            | _ ->
+
+                match vref.TryDeclaringEntity with
+                | ParentRef.Parent parent -> writeEntityRef parent
+                | _ -> ()
+        else
+            writeValRef vref
+
     let writeActivePatternCase (apInfo: ActivePatternInfo) index =
         writeString ItemKeyTags.itemActivePattern
 
@@ -327,16 +342,7 @@ and [<Sealed>] ItemKeyStoreBuilder() =
         let preCount = b.Count
 
         match item with
-        | Item.Value vref ->
-            if vref.IsPropertyGetterMethod || vref.IsPropertySetterMethod then
-                writeString ItemKeyTags.itemProperty
-                writeString vref.PropertyName
-
-                match vref.TryDeclaringEntity with
-                | ParentRef.Parent parent -> writeEntityRef parent
-                | _ -> ()
-            else
-                writeValRef vref
+        | Item.Value vref -> writeValue vref
 
         | Item.UnionCase (info, _) ->
             writeString ItemKeyTags.typeUnionCase
@@ -408,7 +414,7 @@ and [<Sealed>] ItemKeyStoreBuilder() =
         | Item.CtorGroup (_, [ info ]) ->
             match info with
             | FSMeth (_, ty, vref, _) when vref.IsConstructor -> writeType true ty
-            | FSMeth (_, _, vref, _) -> writeValRef vref
+            | FSMeth (_, _, vref, _) -> writeValue vref
             | ILMeth (_, info, _) ->
                 info.ILMethodRef.ArgTypes |> List.iter writeILType
                 writeILType info.ILMethodRef.ReturnType

tests/FSharp.Compiler.ComponentTests/FSharpChecker/FindReferences.fs

@@ -476,4 +476,76 @@ match 2 with | Even -> () | Odd -> ()
                 "FileFirst.fs", 2, 39, 43
                 //"FileFirst.fsi", 4, 6, 10 <-- this should also be found
             ])
-        }
+        }
+
+
+module Interfaces =
+
+    [<Fact>]
+    let ``We find all references to interface methods`` () =
+
+        let source = """
+type IInterface1 =
+    abstract member Method1 : int
+
+type IInterface2 =
+    abstract member Method2 : int
+
+type internal SomeType() =
+
+    interface IInterface1 with
+        member _.Method1 =
+            42
+
+    interface IInterface2 with
+        member this.Method2 =
+            (this :> IInterface1).Method1
+        """
+
+        SyntheticProject.Create( { sourceFile "Program" [] with Source = source } ).Workflow {
+            placeCursor "Program" "Method1"
+            findAllReferences (expectToFind [
+                "FileProgram.fs", 4, 20, 27
+                "FileProgram.fs", 12, 17, 24
+                "FileProgram.fs", 17, 12, 41 // Not sure why we get the whole range here, but it seems to work fine.
+            ])
+        }
+
+    [<Fact>]
+    let ``We find all references to interface methods starting from implementation`` () =
+
+        let source1 = """
+type IInterface1 =
+    abstract member Method1 : int
+
+type IInterface2 =
+    abstract member Method2 : int
+        """
+
+        let source2 = """
+open ModuleFirst
+
+type internal SomeType() =
+
+    interface IInterface1 with
+        member _.Method1 =
+            42
+
+    interface IInterface2 with
+        member this.Method2 =
+            (this :> IInterface1).Method1
+        """
+
+        SyntheticProject.Create(
+            { sourceFile "First" [] with Source = source1 },
+            { sourceFile "Second" [] with Source = source2 }
+        ).Workflow {
+            placeCursor "Second" "Method1"
+            findAllReferences (expectToFind [
+                "FileFirst.fs", 4, 20, 27
+                "FileSecond.fs", 8, 17, 24
+                "FileSecond.fs", 13, 12, 41 // Not sure why we get the whole range here, but it seems to work fine.
+            ])
+        }
+
+