e0/src/parser.lalrpop

use crate::ast::*;

grammar;

pub Program: Vec<Decl> = Decl* => <>;

Decl: Decl = {
  Func => Decl::Func(<>),
};

Func: Func = {
  "fn" <name:Ident> "(" ")" "->" <return_ty:Type> "{" <stmts:Stmt*> "}" =>
    Func { name, return_ty, stmts },
};

Stmt: Stmt = {
  "let" <name:Ident> ":" <ty:Type> "=" <expr:Expr> ";" =>
    Stmt::Let(name, ty, expr),
  "return" <expr:Expr?> ";" => Stmt::Return(expr),
};

Expr: Expr = {
  Expr1 => <>,
};

Expr1: Expr = {
  r"[0-9]+" => Expr::Int(<>.parse::<i64>().unwrap()),
  Ident => Expr::Var(<>),
  "(" <expr:Expr> ")" => expr,
};

Type: Type = {
  "int" => Type::Int,
};

Ident: String = r"([A-Za-z][A-Za-z0-9_]*)|(_[A-Za-z0-9_]+)" => <>.to_string();