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dust/dust-lang/src/scope.rs

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//! Scope, a type that represents the locality of a variable.
use std::{
cmp::Ordering,
fmt::{self, Display, Formatter},
};
use serde::{Deserialize, Serialize};
/// Variable locality, as defined by its depth and block index.
///
/// The `block index` is a unique identifier for a block within a chunk. It is used to differentiate
/// between blocks that are not nested together but have the same depth, i.e. sibling scopes. If the
/// `block_index` is 0, then the scope is the root scope of the chunk. The `block_index` is always 0
/// when the `depth` is 0. See [Chunk::begin_scope][] and [Chunk::end_scope][] to see how scopes are
/// incremented and decremented.
#[derive(Debug, Clone, Copy, Default, Eq, PartialEq, PartialOrd, Ord, Serialize, Deserialize)]
pub struct Scope {
/// Level of block nesting.
pub depth: u8,
/// Index of the block in the chunk.
pub block_index: u8,
}
impl Scope {
pub fn new(depth: u8, block_index: u8) -> Self {
Self { depth, block_index }
}
pub fn contains(&self, other: &Self) -> bool {
match self.depth.cmp(&other.depth) {
Ordering::Less => false,
Ordering::Greater => self.block_index >= other.block_index,
Ordering::Equal => self.block_index == other.block_index,
}
}
pub fn begin(&mut self, block_index: u8) {
self.depth += 1;
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self.block_index = block_index;
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}
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pub fn end(&mut self, block_index: u8) {
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self.depth -= 1;
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self.block_index = block_index;
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}
}
impl Display for Scope {
fn fmt(&self, f: &mut Formatter) -> fmt::Result {
write!(f, "({}, {})", self.depth, self.block_index)
}
}