MissingMethodException after changing method signature on hot reload

[isadorasophia]

Description

When trying to rename methods with hot reload on .NET 7, I consistently get a MissingMethodException when changing the methods signatures.

Reproduction Steps

1. Debug the following app with .NET 7:

static void Main(string[] args)
{
    Debugger.Break();
    Foo(23);
}

static int Foo(int something)
{
    Console.WriteLine(something);
    return 0;
}

2. F5 and break.
3. Modify Foo with:

static int Foo(int something, bool aValue = false)
{
    Console.WriteLine(something);
    return 0;
}

4. Successfully apply changes and F5

Expected behavior

Successfully execute the modified Foo method.

Actual behavior

MissingMethodException gets thrown:

Regression?

No response

Known Workarounds

No response

Configuration

No response

Other information

No response

[isadorasophia]

Similar to #65442 (on Roslyn)

[mikelle-rogers]

I tried reproducing this with .NET 7 in Visual Studio, without checking "Do not use top-level statements". In order to get the Debugger.Break to stop the process, I had to remove the main function. After changing Foo, and continuing, the following popup resulted:

[mikelle-rogers]

I then tried reproducing this with .NET 7 in Visual Studio and checked the box next to "Do not use top-level statements" and the issue reproduced.

[ghost]

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Issue Details

---

Description

When trying to rename methods with hot reload on .NET 7, I consistently get a MissingMethodException when changing the methods signatures.

Reproduction Steps

1. Debug the following app with .NET 7:

static void Main(string[] args)
{
    Debugger.Break();
    Foo(23);
}

static int Foo(int something)
{
    Console.WriteLine(something);
    return 0;
}

2. F5 and break.
3. Modify Foo with:

static int Foo(int something, bool aValue = false)
{
    Console.WriteLine(something);
    return 0;
}

4. Successfully apply changes and F5

Expected behavior

Successfully execute the modified Foo method.

Actual behavior

MissingMethodException gets thrown:

Regression?

No response

Known Workarounds

No response

Configuration

No response

Other information

No response

Author:	isadorasophia
Assignees:	-
Labels:	area-Diagnostics-coreclr, untriaged
Milestone:	-

[AaronRobinsonMSFT]

@isadorasophia I've not debugged this, but this might be an issue with the default value in the signature. What if you update both the callsite and the method?

@tmat Are default values supported in EnC in general?

[tmat]

/cc @davidwengier

The reason for MethodMissingException is that Main is not recompiled because it does not have any changes, so it calls the old version of Foo, which now throws because it has been "deleted".

This behavior is currently expected. Issue dotnet/roslyn#59264 tracks improving this by emitting a call to the newer version of Foo into the body of its old version instead of MethodMissingException throw.

[tmat]

Closing this issue as dup of dotnet/roslyn#65442.