Soroban counter.sol example

[salaheldinsoliman]

This PR aims to make Solang support a simple counter.sol example on Soroban, where a storage variable is instatiated, modified and retrieved. The counter contract is only limited to uint64 data types, and only supports instance soroban storage.

This can be considered a "skeleton" for supporting more data and storage types, as well as more host function invokations.

• Support Soroban storage function calls put_contract_data, get_contract_data and has_contract_data
• Implement a wrapper init for storage_initializer
• Implement wrappers for public functions
• Insert decoding/encoding instructions into the wrapper functions
• Soroban doesn't have function return codes. This needs to be handled all over emit
• Add integration tests and MockVm tests

[seanyoung]

Looks great

[seanyoung]

I was wondering if this should be enforced in sema; for Soroban, we could simply give an error diagnostic if a function returns anything else but an int64.

[salaheldinsoliman]

What is reffered to here is the wasm functions, not Solidity functions. That is, if a Solidity function returns nothing, the wasm function returns an i64 value to be XDR decoded as Void.

[seanyoung]

Right, the comment could with explaining that

[LucasSte]

Should this function be doing nothing?

[salaheldinsoliman]

When there is a runtime error, an overflow maybe, a call to this function is made. The ideal scenario is to make a call to Soroban's host function responsible for logging, but since this is out of scope for this PR, I left it out.

A //TODO might be better here

[codecov]

Codecov Report

Attention: Patch coverage is 92.87671% with 26 lines in your changes missing coverage. Please review.

Project coverage is 88.58%. Comparing base (08dbe49) to head (1a8cb27).

Files	Patch %	Lines
src/linker/soroban_wasm.rs	80.00%	9 Missing ⚠️
src/emit/soroban/mod.rs	93.00%	7 Missing ⚠️
src/emit/instructions.rs	89.13%	5 Missing ⚠️
src/emit/soroban/target.rs	93.02%	3 Missing ⚠️
src/codegen/dispatch/soroban.rs	98.23%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1645      +/-   ##
==========================================
+ Coverage   88.51%   88.58%   +0.07%     
==========================================
  Files         163      164       +1     
  Lines       72869    73152     +283     
==========================================
+ Hits        64497    64802     +305     
+ Misses       8372     8350      -22     

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