Trait Tree

pub trait Tree: Debug + AsAny {
    // Provided method
    fn declare_keywords(declare: impl FnMut(&'static str, Self))
       where Self: Sized { ... }
}

A type that represents a parse tree.

There are many types that implement Tree. It would be inconvenient to define an enum that can contain any of them. Instead, we use dyn Tree. You can use the methods of dyn Tree to match its actual type:

use welly_parser::{Tree};

// Invent a new kind of `Tree`.
#[derive(Debug)]
struct Fruit(&'static str);
impl Tree for Fruit {}

// An example `Fruit` wrapped as a `dyn Tree`.
let tree: Box<dyn Tree> = Box::new(Fruit("Apple"));

// Test whether `tree` is a `Fruit`.
let is_fruit: bool = tree.is::<Fruit>();
println!("{}", is_fruit);

// Borrow the `Fruit`.
let borrowed_fruit: Option<&Fruit> = tree.downcast_ref::<Fruit>();
println!("{}", borrowed_fruit.expect("Not a Fruit").0);

// Move the `Fruit`.
let owned_fruit: Result<Box<Fruit>, Box<dyn Tree>> = tree.downcast::<Fruit>();
println!("{}", owned_fruit.expect("Not a Fruit").0);

Provided Methods

fn declare_keywords(declare: impl FnMut(&'static str, Self))

where Self: Sized,

declare() all the keywords whose parse trees are Selfs.

The default implementation declares no keywords.

Implementations

impl dyn Tree

pub fn is<T: Tree>(&self) -> bool

Returns true if the actual type of self is T.

pub fn downcast_ref<T: Tree>(&self) -> Option<&T>

Returns Some if the actual type of self is T.

pub fn downcast<T: Tree>(self: Box<Self>) -> Result<Box<T>, Box<Self>>

Returns Ok if the actual type of self is T.

Trait Implementations

impl<T: Tree + PartialEq> PartialEq<T> for dyn Tree

fn eq(&self, other: &T) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

Implementations on Foreign Types

impl Tree for char

impl Tree for ()

Implementors

impl Tree for Expr

impl Tree for welly_parser::expr::Keyword

impl Tree for AssignOp

impl Tree for welly_parser::stmt::Keyword

impl Tree for Stmt

impl Tree for Brace

impl Tree for Round

impl Tree for Square

impl Tree for Operator

impl Tree for CharacterLiteral

impl Tree for Comment

impl Tree for StringLiteral

impl Tree for EndOfFile

impl Tree for Alphanumeric

impl Tree for Symbol

impl Tree for Whitespace