-bash: command substitution: line XX: syntax error: unexpected end of file

Question

Why does the following code give me the error in the title?

_say_hey()
{
    echo "hey"
}
echo "$(_say_hey())"

Answer 1

When calling a function, call it like an ordinary command (leave off the brackets):

echo "$(_say_hey)"

Note that the echo here is redundant; you could just write _say_hey on a line by itself for the same effect.