grep problem with -io, v 2.5.1

[Brian Craft]

This looks fishy to me, with grep 2.5.1:

porky 32 /home/bcboy> echo foo | grep -io foo
foo
porky 33 /home/bcboy> echo foo | grep -io Foo
porky 34 /home/bcboy> echo foo | grep -i Foo
foo
porky 35 /home/bcboy> echo foo | grep -o Foo
porky 36 /home/bcboy> echo foo | grep -io Foo
porky 37 /home/bcboy> echo Foo | grep -io Foo
porky 38 /home/bcboy> echo Foo | grep -io foo
foo


32 is ok
33 looks wrong. Case is not ignored.
34 is ok and verifies the match with -i when -o is not used.
35 is ok
36 repeats 33, still wrong
37 looks wrong. That should be a match with or without -i
38 is ok

It looks like the match in pseudocode reads something like

  if (lowercase(target) == pattern) output(lowercase(target))

while it should be (as I understand the docs)

  if (lowercase(target) == lowercase(pattern)) ouput(target)

b.c.