fix: error when comparing arrays containing function elements

[He-Pin]

Motivation

Array equality silently returned true when comparing arrays containing function elements that shared the same scope binding reference. The (x eq y) reference-equality shortcut and the array equality loop's shared-reference optimization bypassed the "cannot test equality of functions" error that go-jsonnet raises. Additionally, equal() had no top-level check for Val.Func operands, so function comparisons in any context silently returned false instead of raising an error.

Modification

• Guarded the (x eq y) shortcut in equal() to exclude Val.Func, so same-reference functions fall through to an explicit Val.Func case that errors
• Added Val.Func case in equal() that errors when both sides are functions, returns false for func-vs-non-func
• Fixed the array equality loop: shared Eval references now force the value and check for Val.Func before skipping

The top-level Val.Func case in equal() handles function detection at any nesting depth through recursion — no explicit checks needed in array/object comparison loops.

Result

[f, 1] == [f, 1] and f == f now correctly error with "cannot test equality of functions", matching go-jsonnet, jsonnet-cpp, and jrsonnet behavior. All nested cases ([f] == [g], {a: f} == {a: g}, [[f]] == [[g]]) also work correctly through equal() recursion.

Expression	go-jsonnet v0.22.0	sjsonnet (before)	sjsonnet (after)
local f = function(x) x; f == f	ERROR	ERROR	ERROR
local f = function(x) x; [f, 1] == [f, 1]	ERROR	true (bug)	ERROR
local f = function() 3; local g = function() 4; [f] == [g]	ERROR	false (bug)	ERROR
local f = function() 3; local g = function() 4; {a: f} == {a: g}	ERROR	false (bug)	ERROR
local f = function(x) x; f == 42	false	false	false
[1, 2, 3] == [1, 2, 3]	true	true	true
[f] == [1]	false	false	false
{a: f} == {a: 1}	false	false	false

References

• go-jsonnet function equality check in builtins.go

[He-Pin]

@stephenamar-db This is ready too.