Jit: Long method Jit time for ImmutableList.Enumerator.Dispose

[benaadams]

JitTime 
(msec)	ILSize	NativeSize
17.4        74         163	

Method
System.Collections.Immutable.ImmutableList1+Enumerator[System.Collections.Generic.KeyValuePair2[System.__Canon,System.__Canon]].Dispose()

BG    Module
JIT   System.Collections.Immutable.dll

Corefx issue https://github.com/dotnet/corefx/issues/23125
MsBuild issue dotnet/msbuild#2419

/cc @davkean

[benaadams]

Method for reference

https://github.com/dotnet/corefx/blob/1fe52f7ff4e29462f75da9ae1c35d9789ad13709/src/System.Collections.Immutable/src/System/Collections/Immutable/ImmutableList_1.Enumerator.cs#L150-L162

public void Dispose()
{
    _root = null;
    _current = null;
    Stack<RefAsValueType<Node>> stack;
    if (_stack != null && _stack.TryUse(ref this, out stack))
    {
        stack.ClearFastWhenEmpty();
        s_EnumeratingStacks.TryAdd(this, _stack);
    }
    
    _stack = null;
}

[RussKeldorph]

@AndyAyersMS Not clear this is actionable at this point, but assigning since you started looking. Feel free to un-assign or close if there is nothing to do.

[AndyAyersMS]

Yeah, probably not actionable. So am going to close.