ArrayList.ToArray(type) throws exception for enum type in Blazor WebAssembly

[jjzhang12]

Is there an existing issue for this?

• I have searched the existing issues

Describe the bug

Code snippet:

ArrayList list = new ArrayList();
list.Add(Day.Monday);
var array = list.ToArray(typeof(Day));

public enum Day { Monday, Tuesday }

This is working fine in .net 6 desktop. But in Blazor WebAssembly, it throws exception System.InvalidCastException: At least one element in the source array could not be cast down to the destination array type.

list.ToArray() without type is fine. But we are using type which is loaded in runtime, so the type is required.

Expected Behavior

Array created without exception

Steps To Reproduce

https://github.com/jjzhang12/WasmToArrayIssue.git

I added above code snippet to index page and you can observe the exception.

Also the .net console app is working fine.

Exceptions (if any)

System.InvalidCastException: At least one element in the source array could not be cast down to the destination array type.

.NET Version

6.0.101

Anything else?

No response

I couldn't figure out the best area label to add to this issue. If you have write-permissions please help me learn by adding exactly one area label.

Tagging subscribers to 'arch-wasm': @lewing
See info in area-owners.md if you want to be subscribed.

Issue Details

---

Is there an existing issue for this?

• I have searched the existing issues

Describe the bug

Code snippet:

ArrayList list = new ArrayList();
list.Add(Day.Monday);
var array = list.ToArray(typeof(Day));

public enum Day { Monday, Tuesday }

This is working fine in .net 6 desktop. But in Blazor WebAssembly, it throws exception System.InvalidCastException: At least one element in the source array could not be cast down to the destination array type.

list.ToArray() without type is fine. But we are using type which is loaded in runtime, so the type is required.

Expected Behavior

Array created without exception

Steps To Reproduce

https://github.com/jjzhang12/WasmToArrayIssue.git

I added above code snippet to index page and you can observe the exception.

Also the .net console app is working fine.

Exceptions (if any)

System.InvalidCastException: At least one element in the source array could not be cast down to the destination array type.

.NET Version

6.0.101

Anything else?

No response

Author:	jjzhang12
Assignees:	-
Labels:	arch-wasm, untriaged
Milestone:	-

Tagging subscribers to this area: @BrzVlad
See info in area-owners.md if you want to be subscribed.

Issue Details

---

Is there an existing issue for this?

• I have searched the existing issues

Describe the bug

Code snippet:

ArrayList list = new ArrayList();
list.Add(Day.Monday);
var array = list.ToArray(typeof(Day));

public enum Day { Monday, Tuesday }

This is working fine in .net 6 desktop. But in Blazor WebAssembly, it throws exception System.InvalidCastException: At least one element in the source array could not be cast down to the destination array type.

list.ToArray() without type is fine. But we are using type which is loaded in runtime, so the type is required.

Expected Behavior

Array created without exception

Steps To Reproduce

https://github.com/jjzhang12/WasmToArrayIssue.git

I added above code snippet to index page and you can observe the exception.

Also the .net console app is working fine.

Exceptions (if any)

System.InvalidCastException: At least one element in the source array could not be cast down to the destination array type.

.NET Version

6.0.101

Anything else?

No response

Author:	jjzhang12
Assignees:	-
Labels:	arch-wasm, untriaged, area-Codegen-Interpreter-mono
Milestone:	-

[lewing]

cc @vargaz

[lewing]

System.InvalidCastException: InvalidCast_DownCastArrayElement
dotnet.js:13    at System.Array.CopySlow(Array sourceArray, Int32 sourceIndex, Array destinationArray, Int32 destinationIndex, Int32 length, Boolean reliable) in /Users/lewing/Source/backup/runtime/src/mono/System.Private.CoreLib/src/System/Array.Mono.cs:line 203
dotnet.js:13    at System.Array.Copy(Array sourceArray, Int32 sourceIndex, Array destinationArray, Int32 destinationIndex, Int32 length, Boolean reliable) in /Users/lewing/Source/backup/runtime/src/mono/System.Private.CoreLib/src/System/Array.Mono.cs:line 147
dotnet.js:13    at System.Array.Copy(Array sourceArray, Int32 sourceIndex, Array destinationArray, Int32 destinationIndex, Int32 length) in /Users/lewing/Source/backup/runtime/src/mono/System.Private.CoreLib/src/System/Array.Mono.cs:line 121
dotnet.js:13    at System.Array.Copy(Array sourceArray, Array destinationArray, Int32 length) in /Users/lewing/Source/backup/runtime/src/mono/System.Private.CoreLib/src/System/Array.Mono.cs:line 115
dotnet.js:13    at System.Collections.ArrayList.ToArray(Type type) in /Users/lewing/Source/backup/runtime/src/libraries/System.Private.CoreLib/src/System/Collections/ArrayList.cs:line 727

[lambdageek]

It's hitting this check added by mono/mono#15585

runtime/src/mono/System.Private.CoreLib/src/System/Array.Mono.cs

Lines 202 to 203 in 9eb9051

	if (!src_type.IsValueType && dst_is_enum)
	throw new InvalidCastException(SR.InvalidCast_DownCastArrayElement);

which doesn't look right to me (it's comparing src_type which is the array element type which doesn't change each time through the loop. I think it actually wants srcval.GetType())

Repro with:

var list = new System.Collections.ArrayList();
list.Add(Day.Monday);
Console.WriteLine ($"First elt is a {list[0].GetType()}");
var array = list.ToArray(typeof(Day));

foreach (var x in array)
    Console.WriteLine ($"{x}");;


public enum Day { Monday, Tuesday }

<Project Sdk="Microsoft.NET.Sdk">
  <PropertyGroup>
    <OutputType>Exe</OutputType>
    <TargetFramework>net6.0</TargetFramework>
    <ImplicitUsings>enable</ImplicitUsings>
    <Nullable>enable</Nullable>
  </PropertyGroup>
  <PropertyGroup>
    <RuntimeIdentifier>linux-x64</RuntimeIdentifier>
    <UseMonoRuntime>true</UseMonoRuntime>
    <SelfContained>true</SelfContained>
  </PropertyGroup>
</Project>

Issue happens with both the JIT and the interpreter (as expected)