arithmetic syntax error loop after declaration of exported integer variable

[D630]

I get an infinite error loop in B, and I suppose that's not because of 
my settings.

# A

bash$ unset -v foo; declare -i foo; foo='bar bar'
bash: bar bar: syntax error in expression (error token is "bar")

# B

bash$ unset -v foo; foo='bar bar' declare -x -i foo
[...]