jq handles "$-arguments" in function definitions as implicit "as" statements,
whereas gojq does not. This introduces a source of potential inconsistency.

Consider for example:

def prod: .[0] * .[1];
def prodEqual($p): prod == $p;

This works as expected in both jq and gojq.

However, if prodEq were defined as:

def prodEq($prod): prod == $prod;

then we would see the discrepancy, as jq implicitly expands
the definition of prodEq to

def prodEq($prod): prod as $prod | prod == $prod;

Because of shadowing, in jq, prodEq would therefore always returns true!

For example:

[1,1] | prodEq(0) #=> true using jq
[1,1] | prodEq(0) #=> false using gojq