Incorrect codegen with multiple returns of a field of a Nullable or struct type

[sfoslund]

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Issue moved from dotnet/sdk#14535

• Please respond to @dale-personal.

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From @dale-personal on Friday, November 13, 2020 2:54:27 PM

Here is a repo which reproduces the issue:

https://github.com/dale-personal/net5-issue

The code in question functions as expected for a number of iterations, then starts producing unexpected results.

[sfoslund]

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Issue moved from dotnet/sdk#14535

• Please respond to @sfoslund.

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From @sfoslund on Wednesday, November 18, 2020 9:11:00 PM

@dale-personal can you please give more detail on what the unexpected results are?

[Dotnet-GitSync-Bot]

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[sfoslund]

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Issue moved from dotnet/sdk#14535

• Please respond to @dale-personal.

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From @dale-personal on Wednesday, November 18, 2020 9:25:14 PM

Sure, I've created a repo which reproduces the issue:
https://github.com/dale-personal/net5-issue/blob/main/test.cs

In the test provided, given enough loop iterations, the behavior of this line changes
if (_default != null && _default.Value.HasValue) return _default.Value.Value;

_default.Value.HasValue is false, while at the same time _default.Value.Value = "test"

[JulieLeeMSFT]

CC @briansull

[briansull]

Taking a look

[briansull]

I am testing a fix for this issue