Simple compiler in Rust

Simple rust compiler with a backend targeting WebAssembly.

Overview

• scanner: Converts source code into tokens.
• syntax: Contains language constructs.
• parser: Builds an abstract syntax tree (AST) from tokens.
• typecheck: Ensures type correctness of the AST.
• codegen: Generates WebAssembly code from on the AST.

Libraries used

• wasm-tools (by Bytecode Alliance)
  • wasm-encoder for code generation.
  • wasmi for the interpreter.
  • helper functions.
• pretty_assertions (for colored test diffs)

Commands

• Compile and run a .lg file:

cargo run -- filename.lg

• Run all the tests (nocapture is used for scanner test):

cargo test -- --nocapture

Basics

• Every programs must have a main entry point function, returning an int.
• Numeric types are 32-bit integers, booleans are compiled as 0 or 1.
• Types: int and bool.
• let and = body are defined by the next underneath line, at least one line break.
• Everything except functions are expressions.

Example

• Returns 3 if is_null is true, otherwise returns 3:

int main()
    let is_null = true
    let var = (foo(is_null, 5*2, 0-10) + 1) * 2
    var = var + 2 / 2
    var
end

int foo(bool null, int res1, int res2)
    if null then
        0
    else
        let boolean = if fee() then res1 else res2 end
        boolean
    end
end

bool fee()
    (1 < 2 & 4-2 > 3) == false & true 
end