feat(slang): modifiers

[hedgar2017]

Lowers modifiers in the Slang frontend: modifier definitions, invocation regions evaluating their arguments, the placeholder, and Slang's answer for which modifier an entry runs when the compiled contract dispatches it.

[github-actions]

Coverage Summary

Crate	Line Coverage	Function Coverage
solx	🟢 83.6%	🔴 20.0%
solx-benchmark-converter	🔴 0.0%	🔴 0.0%
solx-codegen-evm	🟡 55.9%	🔴 48.4%
solx-compiler-downloader	🔴 0.0%	🔴 0.0%
solx-core	🔴 46.9%	🟡 53.9%
solx-dev	🔴 3.2%	🔴 4.2%
solx-mlir	🟡 50.7%	🔴 46.3%
solx-slang	🔴 22.3%	🔴 30.1%
solx-solc-test-adapter	🔴 1.7%	🔴 2.1%
solx-standard-json	🔴 40.7%	🔴 44.6%
solx-tester	🔴 36.6%	🔴 34.6%
solx-utils	🔴 32.2%	🔴 36.7%
Total	🔴 12.8%	🔴 15.9%

Codecov Report | HTML Report | Workflow Run

[ggiraldez]

Left some suggestions for code readability, but looks good to me as far as Slang lowering goes.

[abinavpp]

LGTM. Could add to a lit test: a modifier with two _;, a modifier invocation whose argument is an expression rather than a bare identifier, and a modifier on a function returning two values.

[hedgar2017]

LGTM. Could add to a lit test: a modifier with two _;, a modifier invocation whose argument is an expression rather than a bare identifier, and a modifier on a function returning two values.

Thanks, added!