2_allocators.md

Allocators (questions only, no code needed)

Is the following code safe? If not, why and how would you fix it? (You do not have to write the fixed code).

use bumpalo::Bump;

pub type TokenVec<'s> = Vec<Token, &'s Bump>;

// We want the [`Lexer`] to own the allocator because this is an internal
// design that should not be exposed to the users.
#[repr(C)]
pub struct Lexer<'s> {
    model: LexerModel<'s>,
    allocator: Bump,
}

impl<'s> Lexer<'s> {
    pub fn new(input: &'s str) -> Self {
        let capacity = input.len() / AVERAGE_TOKEN_LEN;
        let allocator = Bump::with_capacity(capacity);
        let allocator_ref: &Bump = unsafe { &*(&allocator as *const Bump) };
        let model = LexerModel::new(allocator_ref, &input);
        Self { allocator, model }
    }
}

pub struct LexerModel<'s> {
    pub input: &'s str,
    pub iterator: std::str::CharIndices<'s>,
    pub output: TokenVec<'s>,
    pub state: ModelState
}

impl<'s> LexerModel<'s> {
    pub fn new(allocator_ref: &'s Bump, input: &'s str) -> Self {
        let iterator = input.char_indices();
        let output = Vec::new_in(allocator_ref);
        let state = Default::default();
        Self {input, iterator, output, state}
    }
}