From d6a29d58155ff67c8ee50da1d49f567a1542326f Mon Sep 17 00:00:00 2001
From: Mangel Maxime <me@mangelmaxime.fr>
Date: Mon, 26 Oct 2026 21:25:31 +0100
Subject: [PATCH] fix(python/beam/rust): implicit DateTime to DateTimeOffset

---
 src/Fable.Transforms/Beam/Replacements.fs   |  3 +++
 src/Fable.Transforms/Python/Replacements.fs |  3 +++
 src/Fable.Transforms/Rust/Replacements.fs   |  1 +
 tests/Beam/DateTimeOffsetTests.fs           | 13 +++++++++++++
 tests/Python/TestDateTimeOffset.fs          | 13 +++++++++++++
 tests/Rust/tests/src/DateTimeOffsetTests.fs | 13 +++++++++++++
 6 files changed, 46 insertions(+)

diff --git a/src/Fable.Transforms/Beam/Replacements.fs b/src/Fable.Transforms/Beam/Replacements.fs
index 4b3df7f340..22d086f994 100644
--- a/src/Fable.Transforms/Beam/Replacements.fs
+++ b/src/Fable.Transforms/Beam/Replacements.fs
@@ -5036,6 +5036,9 @@ let private dateTimeOffsets
     (args: Expr list)
     =
     match info.CompiledName with
+    | "op_Implicit" ->
+        Helper.LibCall(com, "fable_date_offset", "from_date", t, args @ [ makeIntConst 0 ], ?loc = r)
+        |> Some
     | ".ctor" ->
         match args with
         | [] -> Helper.LibCall(com, "fable_date_offset", "min_value", t, [], ?loc = r) |> Some
diff --git a/src/Fable.Transforms/Python/Replacements.fs b/src/Fable.Transforms/Python/Replacements.fs
index 248e3266ef..3c8095f08f 100644
--- a/src/Fable.Transforms/Python/Replacements.fs
+++ b/src/Fable.Transforms/Python/Replacements.fs
@@ -3191,6 +3191,9 @@ let dates (com: ICompiler) (ctx: Context) r t (i: CallInfo) (thisArg: Expr optio
             "DateOffset"
 
     match i.CompiledName with
+    | "op_Implicit" ->
+        Helper.LibCall(com, "DateOffset", "fromDate", t, args, i.SignatureArgTypes, ?loc = r)
+        |> Some
     | ".ctor" ->
         match args with
         | [] -> Helper.LibCall(com, moduleName, "minValue", t, [], [], ?loc = r) |> Some
diff --git a/src/Fable.Transforms/Rust/Replacements.fs b/src/Fable.Transforms/Rust/Replacements.fs
index 91add9cd16..f02f077db3 100644
--- a/src/Fable.Transforms/Rust/Replacements.fs
+++ b/src/Fable.Transforms/Rust/Replacements.fs
@@ -2652,6 +2652,7 @@ let dateTimeOffsets (com: ICompiler) (ctx: Context) r t (i: CallInfo) (thisArg:
             _offset ] -> "new_ymdhms_micro" |> Some
         | _ -> None
         |> Option.map (fun meth -> makeStaticMemberCall com r t i "DateTimeOffset" meth args)
+    | "op_Implicit", _ -> makeStaticMemberCall com r t i "DateTimeOffset" "new_datetime" args |> Some
     | ("Compare" | "CompareTo" | "Equals" | "GetHashCode"), thisArg -> valueTypes com ctx r t i thisArg args
     | "Add", Some c ->
         Operation(Binary(BinaryOperator.BinaryPlus, c, args.Head), Tags.empty, t, r)
diff --git a/tests/Beam/DateTimeOffsetTests.fs b/tests/Beam/DateTimeOffsetTests.fs
index 64eb006b15..e791c81ca9 100644
--- a/tests/Beam/DateTimeOffsetTests.fs
+++ b/tests/Beam/DateTimeOffsetTests.fs
@@ -518,3 +518,16 @@ let ``test DateTimeOffset constructor from DateOnly and TimeOnly works`` () =
     dt.Minute |> equal dt_exp.Minute
     dt.Second |> equal dt_exp.Second
     dt.Millisecond |> equal dt_exp.Millisecond
+
+[<Fact>]
+let ``test Implicit conversion from DateTime preserves value`` () =
+    let d = DateTime(2024, 1, 15, 13, 23, 30, DateTimeKind.Utc)
+    let dto: DateTimeOffset = d
+    dto |> equal (DateTimeOffset(d))
+    dto.Offset |> equal TimeSpan.Zero
+    dto.Year |> equal 2024
+    dto.Month |> equal 1
+    dto.Day |> equal 15
+    dto.Hour |> equal 13
+    dto.Minute |> equal 23
+    dto.Second |> equal 30
diff --git a/tests/Python/TestDateTimeOffset.fs b/tests/Python/TestDateTimeOffset.fs
index c4ea6ac15c..af806354cc 100644
--- a/tests/Python/TestDateTimeOffset.fs
+++ b/tests/Python/TestDateTimeOffset.fs
@@ -569,3 +569,16 @@ let ``test DateTimeOffset constructor from DateOnly and TimeOnly works`` () =
     dt.Minute |> equal dt_exp.Minute
     dt.Second |> equal dt_exp.Second
     dt.Millisecond |> equal dt_exp.Millisecond
+
+[<Fact>]
+let ``test Implicit conversion from DateTime preserves value`` () =
+    let d = DateTime(2024, 1, 15, 13, 23, 30, DateTimeKind.Utc)
+    let dto: DateTimeOffset = d
+    dto |> equal (DateTimeOffset(d))
+    dto.Offset |> equal TimeSpan.Zero
+    dto.UtcDateTime.Year |> equal 2024
+    dto.UtcDateTime.Month |> equal 1
+    dto.UtcDateTime.Day |> equal 15
+    dto.UtcDateTime.Hour |> equal 13
+    dto.UtcDateTime.Minute |> equal 23
+    dto.UtcDateTime.Second |> equal 30
diff --git a/tests/Rust/tests/src/DateTimeOffsetTests.fs b/tests/Rust/tests/src/DateTimeOffsetTests.fs
index e0f13dd684..d95c8c5b67 100644
--- a/tests/Rust/tests/src/DateTimeOffsetTests.fs
+++ b/tests/Rust/tests/src/DateTimeOffsetTests.fs
@@ -1031,3 +1031,16 @@ let ``-10s offset throws exception`` () =
     let source = DateTimeOffset(2007, 9, 1, 14, 30, 0, TimeSpan.Zero)
     (fun () -> source.ToOffset(TimeSpan(0, 0, -10)))
     |> throwsErrorContaining "Offset must be specified in whole minutes"
+
+[<Fact>]
+let ``Implicit conversion from DateTime preserves value`` () =
+    let d = DateTime(2024, 1, 15, 13, 23, 30, DateTimeKind.Utc)
+    let dto: DateTimeOffset = d
+    dto |> equal (DateTimeOffset(d))
+    dto.Offset |> equal TimeSpan.Zero
+    dto.Year |> equal 2024
+    dto.Month |> equal 1
+    dto.Day |> equal 15
+    dto.Hour |> equal 13
+    dto.Minute |> equal 23
+    dto.Second |> equal 30