Prevent changing meaning of std in desugared expressions

[sbarzowski]

Some constructs are desugared to functions from std. The problem is that if the user wraps them in their own definition of std they can change the meaning of core language constructs (probably just break them) which will be extremely confusing.

We can have special alias for std, unavailable for the user, for example $td.

[sparkprime]

This is also a bug in the C++ version I think?

[sparkprime]

Short answer is "yes":

$ jsonnet -e '1 == 1'
true

$ jsonnet -e 'local std2 = std; local std = std2 { primitiveEquals(a, b):: false }; 1 == 1'
false

[netomi]

shouldn't std be just a reserved keyword which can not be used to create a local?

[CertainLach]

In jrsonnet, I have fixed this by not desugaring and instead implementing the comparison/mod (formatting) operator directly.
https://github.com/CertainLach/jrsonnet/blob/master/crates/jrsonnet-evaluator/src/evaluate/operator.rs#L141

In sjsonnet they have implemented the same approach.
https://github.com/databricks/sjsonnet/blob/master/sjsonnet/src/sjsonnet/Evaluator.scala#L363

(This caused some problems: in jrsonnet, stdlib is not special, but the separate library, same as any user can write when using jrsonnet as a library, so formatting/comparison are implemented in core language, and not in the stdlib. I don't think this applies to cpp-jsonnet/go-jsonnet, though.)
https://github.com/CertainLach/jrsonnet/blob/master/crates/jrsonnet-stdlib/src/lib.rs