ryanmcdermott / esish

Recursive descent parser written in Rust for an ECMAScript inspired language.

ESish

Recursive descent parser written in Rust for an ECMAScript inspired language.

Example

Crate usage

use esish::{Parser, Tokenizer};

let program = r#"
    class Fib {
        function calc(num) {
            if (num <= 1) {
                return 1;
            }

            return this.calc(num - 1) + this.calc(num - 2);
        }
    }

    let fib = new Fib();
    fib.calc(42);
"#
.to_string();

let tokenizer = Tokenizer::new(program);
let mut parser = Parser::new(tokenizer);
let parse_tree = parser.parse();
let mut actual_ast = serde_json::to_string_pretty(&parse_tree).unwrap();

println!("AST:\n {}", actual_ast);

Output

{
  "Program": {
    "body": [
      {
        "ClassDeclaration": {
          "id": {
            "name": "Fib"
          },
          "body": {
            "body": [
              {
                "FunctionDeclaration": {
                  "name": {
                    "name": "calc"
                  },
                  "params": [
                    {
                      "name": "num"
                    }
                  ],
                  "body": {
                    "body": [
                      {
                        "IfStatement": {
                          "test": {
                            "BinaryExpression": {
                              "left": {
                                "Identifier": {
                                  "name": "num"
                                }
                              },
                              "right": {
                                "Literal": {
                                  "NumericLiteral": {
                                    "value": 1
                                  }
                                }
                              },
                              "operator": "OperatorRelational"
                            }
                          },
                          "consequent": {
                            "BlockStatement": {
                              "body": [
                                {
                                  "ReturnStatement": {
                                    "argument": {
                                      "Literal": {
                                        "NumericLiteral": {
                                          "value": 1
                                        }
                                      }
                                    }
                                  }
                                }
                              ]
                            }
                          },
                          "alternate": null
                        }
                      },
                      {
                        "ReturnStatement": {
                          "argument": {
                            "BinaryExpression": {
                              "left": {
                                "CallExpression": {
                                  "callee": {
                                    "MemberExpression": {
                                      "object": {
                                        "ThisExpression": {}
                                      },
                                      "computed": false,
                                      "property": {
                                        "Identifier": {
                                          "name": "calc"
                                        }
                                      }
                                    }
                                  },
                                  "arguments": [
                                    {
                                      "BinaryExpression": {
                                        "left": {
                                          "Identifier": {
                                            "name": "num"
                                          }
                                        },
                                        "right": {
                                          "Literal": {
                                            "NumericLiteral": {
                                              "value": 1
                                            }
                                          }
                                        },
                                        "operator": "OperatorAdd"
                                      }
                                    }
                                  ]
                                }
                              },
                              "right": {
                                "CallExpression": {
                                  "callee": {
                                    "MemberExpression": {
                                      "object": {
                                        "ThisExpression": {}
                                      },
                                      "computed": false,
                                      "property": {
                                        "Identifier": {
                                          "name": "calc"
                                        }
                                      }
                                    }
                                  },
                                  "arguments": [
                                    {
                                      "BinaryExpression": {
                                        "left": {
                                          "Identifier": {
                                            "name": "num"
                                          }
                                        },
                                        "right": {
                                          "Literal": {
                                            "NumericLiteral": {
                                              "value": 2
                                            }
                                          }
                                        },
                                        "operator": "OperatorAdd"
                                      }
                                    }
                                  ]
                                }
                              },
                              "operator": "OperatorAdd"
                            }
                          }
                        }
                      }
                    ]
                  }
                }
              }
            ]
          },
          "super_class": null
        }
      },
      {
        "VariableStatement": {
          "declarations": [
            {
              "id": {
                "name": "fib"
              },
              "init": {
                "NewExpression": {
                  "callee": {
                    "Identifier": {
                      "name": "Fib"
                    }
                  },
                  "arguments": []
                }
              }
            }
          ]
        }
      },
      {
        "ExpressionStatement": {
          "expression": {
            "CallExpression": {
              "callee": {
                "MemberExpression": {
                  "object": {
                    "Identifier": {
                      "name": "fib"
                    }
                  },
                  "computed": false,
                  "property": {
                    "Identifier": {
                      "name": "calc"
                    }
                  }
                }
              },
              "arguments": [
                {
                  "Literal": {
                    "NumericLiteral": {
                      "value": 42
                    }
                  }
                }
              ]
            }
          }
        }
      }
    ]
  }
}