Implement prism -> sorbet conversion for multi-statement programs

[egiurleo]

Sorbet constructs slightly different ASTs depending on whether a program contains one statement or more than one statements. Correctly parsing programs with more than one statement will make it easier to benchmark this project.

Motivation

Sorbet constructs slightly different ASTs depending on whether a program contains one statement or more than one statements. Correctly parsing programs with more than one statement will make it easier to benchmark this project.

Test plan

Added automated tests for parsing a multi-statement program.

[egiurleo]

I'd love some advice on the implementation here -- I decided to handle all the statement logic in the program node case because Sorbet doesn't have a representation of statement nodes, it just stores them as a NodeVec (vector of nodes) in the body of a Begin node, which is the sorbet equivalent of program.

Probably not a huge deal because this is still a prototype but I'm trying to learn how to do things in C++ 😅

[KaanOzkan]

I think this is fine if you think adding a node will require too many changes.

My C++ comment would be to iterate using a range instead:
for (auto node : stmts->body.nodes) {}. It's cleaner and prevents range bugs. This version calls the copy constructor for node creation which may be inefficient and typed differently depending on what you need it for.

[egiurleo]

It's really good to know you can do that in C++! I actually can't iterate over a pm_node_list this way because it doesn't implement the begin function (I get the error Invalid range expression of type 'struct pm_node **'; no viable 'begin' function available). I can look into adding that to the Prism API, but for now I think this is the only way to iterate.

[KaanOzkan]

I think this is fine if you think adding a node will require too many changes.

My C++ comment would be to iterate using a range instead:
for (auto node : stmts->body.nodes) {}. It's cleaner and prevents range bugs. This version calls the copy constructor for node creation which may be inefficient and typed differently depending on what you need it for.

[amomchilov]

You can simplify this code a bit by wraping this raw C pointer and size into a C++ std::span. It's like a vector in that it'll let you use C++-style foreach loops, but it doesn't copy/own/free the buffer.

Suggested change

	pm_program_node *programNode = reinterpret_cast<pm_program_node *>(node);
	pm_statements_node *stmts = programNode->statements;
	auto size = stmts->body.size;
	pm_program_node *programNode = reinterpret_cast<pm_program_node *>(node);
	pm_statements_node *stmts = programNode->statements;
	std::span<pm_node_t *> nodes(stmts->body.nodes, stmts->body.size);

Then you can:

if (nodes.size() == 1) {
    return convertPrismToSorbet(nodes[0], parser, gs);
}

for (auto node : nodes) {
    unique_ptr<parser::Node> convertedStmt = convertPrismToSorbet(node, parser, gs);
    sorbetStmts.emplace_back(std::move(convertedStmt));
}

[egiurleo]

Aw man, we're actually using C++17, which doesn't implement span 😭

[amomchilov]

That would be a real bummer, but luckily, we have absl::span, which is already used a fair bit throughout the codebase! 🥳

#34