perf(python): back int64 arrays with typed storage

src/Fable.Transforms/Python/Replacements.fs

@@ -30,15 +30,13 @@ let (|TypedArrayCompatible|_|) (com: Compiler) (arrayKind: ArrayKind) t =
         | UInt32 -> ValueSome "UInt32ArrayCons"
         | Float32 -> ValueSome "Float32ArrayCons"
         | Float64 -> ValueSome "Float64ArrayCons"
-        // Don't use typed array for int64 until we remove our int64 polyfill
-        // and use JS BigInt to represent int64
-        //        | Int64 -> Some "BigInt64ArrayCons"
-        //        | UInt64 -> Some "BigUint64ArrayCons"
+        // Unlike JavaScript, which has no typed array for int64 while it polyfills the
+        // type, Python backs these with `Vec<i64>`/`Vec<u64>` in the Rust core.
+        | Int64 -> ValueSome "Int64ArrayCons"
+        | UInt64 -> ValueSome "UInt64ArrayCons"
         | Int128
         | UInt128
         | Float16
-        | Int64
-        | UInt64
         | BigInt
         | Decimal
         | NativeInt

tests/Python/TestArray.fs

@@ -1461,3 +1461,36 @@ let ``test Array.randomSampleBy works`` () =
     Array.distinct sample |> Array.length |> equal 3
     throwsAnyError (fun () -> Array.randomSampleBy (fun () -> 1.0) 1 [|1; 2|] |> ignore)
     throwsAnyError (fun () -> Array.randomSampleBy (fun () -> -0.1) 1 [|1; 2|] |> ignore)
+
+[<Fact>]
+let ``test Int64 arrays roundtrip through their backing storage`` () =
+    let xs = [| 1L; -2L; 3L |]
+    Array.map (fun x -> x * 2L) xs |> equal [| 2L; -4L; 6L |]
+    Array.filter (fun x -> x > 0L) xs |> equal [| 1L; 3L |]
+    Array.append xs xs |> equal [| 1L; -2L; 3L; 1L; -2L; 3L |]
+    Array.rev xs |> equal [| 3L; -2L; 1L |]
+    Array.sort xs |> equal [| -2L; 1L; 3L |]
+    Array.sum xs |> equal 2L
+    Array.contains -2L xs |> equal true
+    Array.item 1 xs |> equal -2L
+    Array.map id xs = xs |> equal true
+
+[<Fact>]
+let ``test Int64 array values are not truncated`` () =
+    let xs = [| System.Int64.MinValue; 0L; System.Int64.MaxValue |]
+    Array.max xs |> equal System.Int64.MaxValue
+    Array.min xs |> equal System.Int64.MinValue
+    Array.sort xs |> equal [| System.Int64.MinValue; 0L; System.Int64.MaxValue |]
+    Array.rev (Array.rev xs) = xs |> equal true
+    Array.init 3 int64 |> equal [| 0L; 1L; 2L |]
+    Array.zeroCreate<int64> 2 |> equal [| 0L; 0L |]
+
+[<Fact>]
+let ``test UInt64 arrays roundtrip through their backing storage`` () =
+    let xs = [| 1UL; 2UL; System.UInt64.MaxValue |]
+    Array.map id xs |> equal xs
+    Array.filter (fun x -> x > 1UL) xs |> equal [| 2UL; System.UInt64.MaxValue |]
+    Array.max xs |> equal System.UInt64.MaxValue
+    Array.sort xs |> equal [| 1UL; 2UL; System.UInt64.MaxValue |]
+    Array.contains System.UInt64.MaxValue xs |> equal true
+    Array.zeroCreate<uint64> 2 |> equal [| 0UL; 0UL |]