Possible bug for nested curly brace expansion

[Trond Endrestøl]

$ bash --version
GNU bash, version 5.2.37(0)-release (amd64-portbld-freebsd14.1)
Copyright (C) 2022 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later 
<http://gnu.org/licenses/gpl.html>

This is free software; you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.

$ echo devel/llvm{1{1,2,3,4,5,6,7,8,9},2{0}}
devel/llvm11 devel/llvm12 devel/llvm13 devel/llvm14 devel/llvm15 devel/llvm16 
devel/llvm17 devel/llvm18 devel/llvm19 devel/llvm2{0}

$ echo devel/llvm{1{1,2,3,4,5,6,7,8,9},2{0,1}}
devel/llvm11 devel/llvm12 devel/llvm13 devel/llvm14 devel/llvm15 devel/llvm16 
devel/llvm17 devel/llvm18 devel/llvm19 devel/llvm20 devel/llvm21

I didn't expect the curly braces at the end of the first example. It 
should produce devel/llvm20 in my opinion. Everything is fine as long 
as the number of elements are > 1.

csh(1) in FreeBSD gives the expected expansion for both examples:

$ echo devel/llvm{1{1,2,3,4,5,6,7,8,9},2{0}}
devel/llvm11 devel/llvm12 devel/llvm13 devel/llvm14 devel/llvm15 devel/llvm16 
devel/llvm17 devel/llvm18 devel/llvm19 devel/llvm20

$ echo devel/llvm{1{1,2,3,4,5,6,7,8,9},2{0,1}}
devel/llvm11 devel/llvm12 devel/llvm13 devel/llvm14 devel/llvm15 devel/llvm16 
devel/llvm17 devel/llvm18 devel/llvm19 devel/llvm20 devel/llvm21

-- 
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Trond Endrestøl                   |       Trond.Endrestol@ximalas.info
Member of ACM, NAS, NUUG          |       FreeBSD 14.2-S & Alpine 2.26