Create an id lib function for memory or storage variables

[MerlinEgalite]

          Updating the test suite to use `toId` would have been a small change & small improvement. This refactoring looks great as is.

Originally posted by @Rubilmax in #134 (review)

The id helper function cannot be used for storage or memory variable.

Aave did the same in their libraries.

[Rubilmax]

Anything that gives integrators (including us in our test suite) the ability to mimick the behavior of the id function on Market storage/memory structs is fine for me. I have no requirement on the naming or location of it (a priori).

[QGarchery]

I agree that this is something that should be provided, and we could batch similar requests:

• extsload getter & accrued interests (see refactor(interests): expose accrued interests and fee #138)
• supply balances and borrow balances, as it is done in the tests here at the moment
• maybe things referenced in Store a list of the markets created #143

[MathisGD]

• supply balances and borrow balances, as it is done in the tests here at the moment

at the moment there is no consensus on this one (#3)

[MathisGD]

By the way, have we thought about asking for the market in memory directly in Blue ?

[MathisGD]

By the way, have we thought about asking for the market in memory directly in Blue ?

I just gave it a try, it seems to not increase the gas cost so maybe we are better of doing this

[Rubilmax]

I just gave it a try, it seems to not increase the gas cost so maybe we are better of doing this

This highlights that it's mostly a syntax thing, so I'm ok with this. (I understand that under specific conditions, calldata & memory wouldn't be equivalent in gas cost, but here it is - most likely because of optimization at compilation).

This answers where we'd store an id function that converts a memory Market struct into its id. But it doesn't solve the issue for the storage Market structs: we either need another function, or another library.

Note that overloading the id function in the same library, so we can use it both on memory, calldata and/or storage Market struct, doesn't work. Using both functions wouldn't compile for example (solidity 0.20.0). I believe the first defined function takes precedence over the second.

[MerlinEgalite]

Note that there is a more notable difference between calldata and memory on L2s that we must check as well

[MathisGD]

This answers where we'd store an id function that converts a memory Market struct into its id. But it doesn't solve the issue for the storage Market structs: we either need another function, or another library.

Indeed. And same for calldata actually. But storage and calldata can easily be stored in memory. This is a bit annoying to write dead code.. but not a huge deal neither.