Difference between error= and error=''

Question

In Bash is there a difference between these two variable definitions?

error=
error=''

Testing them on emptiness / being unset seems to suggest that they are equal but I still I would like to be sure.

Answer 1

Short answer: No, there are no differences at all. The quotes are stripped during parsing.

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From the Variable Assignment section of the POSIX reference:

In the shell command language, a word consisting of the following parts:

varname=value

and a few lines below you'll see:

If value is not specified, the variable shall be given a null value.

To check this (in Bash):

$ variable1=
$ variable2=''
$ declare -p variable{1,2}
declare -- variable1=""
declare -- variable2=""

they do look identical!