SC1081

If true
Then
  echo "hello"
Fi

if true
then
  echo "hello"
fi

Shells are case sensitive and do not accept If or IF in place of lowercase if.

If you're aware of this and insist on naming a function WHILE, you can quote the name to prevent shellcheck from thinking you meant while. Or if you really want the names, add things like alias If=if IF=if to replace those keywords and ask shellcheck to ignore them.