bug#60464: 29.0.60; Regression - pcomplete-arg fails with argument 'last

[Gregory Heytings]

> If you don't use Eshell, maybe you use Shell? Pcomplete issues should 
> also occur there.

They don't, or at least the specific issue of this bug doesn't, AFAICS. 
The pcomplete-parse-arguments-function in Shell is 
shell--parse-pcomplete-arguments, which only splits the command line into 
its whitespace-separated elements.  IOW, that function only returns 
strings.  The problem with Eshell, in which the 
pcomplete-parse-arguments-function is eshell-complete-parse-arguments, is 
that it returns non-strings.