Support ldelem.u8, ldelem.u opcode aliases (#18081)

docs/release-notes/.FSharp.Compiler.Service/9.0.200.md

@@ -13,6 +13,7 @@
 * Fix missing nullness warning in case of method resolution multiple candidates ([PR #17917](https://github.com/dotnet/fsharp/pull/17918))
 * Fix failure to use bound values in `when` clauses of `try-with` in `seq` expressions ([PR #17990](https://github.com/dotnet/fsharp/pull/17990))
 * Fix locals allocating for the special `copyOfStruct` defensive copy ([PR #18025](https://github.com/dotnet/fsharp/pull/18025))
+* Fix lowering of computed array expressions when the expression consists of a simple mapping from a `uint64` or `unativeint` array. [PR #18081](https://github.com/dotnet/fsharp/pull/18081)
 
 ### Added
 

src/Compiler/AbstractIL/ilwrite.fs

@@ -2026,11 +2026,11 @@ module Codebuf =
         | I_ldelem dt ->
             emitInstrCode codebuf
               (match dt with
-              | DT_I -> i_ldelem_i
+              | DT_I | DT_U -> i_ldelem_i
               | DT_I1 -> i_ldelem_i1
               | DT_I2 -> i_ldelem_i2
               | DT_I4 -> i_ldelem_i4
-              | DT_I8 -> i_ldelem_i8
+              | DT_I8 | DT_U8 -> i_ldelem_i8
               | DT_U1 -> i_ldelem_u1
               | DT_U2 -> i_ldelem_u2
               | DT_U4 -> i_ldelem_u4

tests/FSharp.Compiler.ComponentTests/EmittedIL/ComputedCollections/ForXInArray_ToArray.fs

@@ -35,3 +35,18 @@ let ``for Failure _ | _ in ...`` () = [|for Failure _ | _ in [||] do 0|]
 let ``for true | false in ...`` () = [|for true | false in [||] do 0|]
 let ``for true | _ in ...`` () = [|for true | _ in [||] do 0|]
 let ``for _ | true in ...`` () = [|for _ | true in [||] do 0|]
+
+// https://github.com/dotnet/fsharp/issues/18066
+let ``[|for x in sbyteArray -> x|]`` (xs : sbyte array) = [|for x in xs -> x|]
+let ``[|for x in byteArray -> x|]`` (xs : byte array) = [|for x in xs -> x|]
+let ``[|for x in int16Array -> x|]`` (xs : int16 array) = [|for x in xs -> x|]
+let ``[|for x in uint16Array -> x|]`` (xs : uint16 array) = [|for x in xs -> x|]
+let ``[|for x in charArray -> x|]`` (xs : char array) = [|for x in xs -> x|]
+let ``[|for x in intArray -> x|]`` (xs : int array) = [|for x in xs -> x|]
+let ``[|for x in uintArray -> x|]`` (xs : uint array) = [|for x in xs -> x|]
+let ``[|for x in int64Array -> x|]`` (xs : int64 array) = [|for x in xs -> x|]
+let ``[|for x in uint64Array -> x|]`` (xs : uint64 array) = [|for x in xs -> x|]
+let ``[|for x in nativeintArray -> x|]`` (xs : nativeint array) = [|for x in xs -> x|]
+let ``[|for x in unativeintArray -> x|]`` (xs : unativeint array) = [|for x in xs -> x|]
+let ``[|for x in floatArray -> x|]`` (xs : float array) = [|for x in xs -> x|]
+let ``[|for x in float32Array -> x|]`` (xs : float32 array) = [|for x in xs -> x|]