dotnet-install.sh fails when dot-sourced from the command line

[JayBazuzi]

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• [ ] This issue is blocking
• [ ] This issue is causing unreasonable pain

On a Mac running ZSH:

> . dotnet-install.sh   
(eval):1: FUNCNAME[0]: parameter not set
(eval):1: FUNCNAME[0]: parameter not set

and then my shell closes, ouch!