This is a type and shape analyzer based on an extension to Constant Propagation with Conditional Branches (PDF) for a very small Ruby subset. It is primarily documented in this Rails at Scale blog post.

It is just for show alongside the blog post and does not accept contributions.

cargo build --release

cargo run --release

The main function generates two big torture test programs pseudo-randomly and then analyzes them. Then it parses a third program from source and analyzes it. It prints some stats and the parsed IR to standard out.

cargo test

It's a pain to write IR test cases by hand, so we wrote a little simplified Ruby-esque parser. Unlike many other parsers, it does not go to an AST but instead straight to the SSA IR.

 let sample_program = " class Point  attr_accessor :x  attr_accessor :y  def initialize(x, y)  @x = x  @y = y  end end  def main()  p = Point.new(3, 4)  return p.x + p.y end "; let lexer = Lexer::new(sample_program); let mut parser = Parser::from_lexer(lexer); parser.parse_program(); let prog = parser.prog; let result = sctp(&prog);

That lets us write test cases in a form similar to the above without actually hand-writing a class data structure definition, two functions, a binary add, etc. We can still write asserts on the generated data structures and their discovered types without doing everything by hand.