rust/src/librustc_ast/node_id.rs

use rustc_serialize::{Decoder, Encoder};
use rustc_span::ExpnId;
use std::fmt;

rustc_index::newtype_index! {
    pub struct NodeId {
        ENCODABLE = custom
        DEBUG_FORMAT = "NodeId({})"
    }
}

rustc_data_structures::define_id_collections!(NodeMap, NodeSet, NodeId);

/// `NodeId` used to represent the root of the crate.
pub const CRATE_NODE_ID: NodeId = NodeId::from_u32_const(0);

/// When parsing and doing expansions, we initially give all AST nodes this AST
/// node value. Then later, in the renumber pass, we renumber them to have
/// small, positive ids.
pub const DUMMY_NODE_ID: NodeId = NodeId::MAX;

impl NodeId {
    pub fn placeholder_from_expn_id(expn_id: ExpnId) -> Self {
        NodeId::from_u32(expn_id.as_u32())
    }

    pub fn placeholder_to_expn_id(self) -> ExpnId {
        ExpnId::from_u32(self.as_u32())
    }
}

impl fmt::Display for NodeId {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        fmt::Display::fmt(&self.as_u32(), f)
    }
}

impl rustc_serialize::UseSpecializedEncodable for NodeId {
    fn default_encode<S: Encoder>(&self, s: &mut S) -> Result<(), S::Error> {
        s.emit_u32(self.as_u32())
    }
}

impl rustc_serialize::UseSpecializedDecodable for NodeId {
    fn default_decode<D: Decoder>(d: &mut D) -> Result<NodeId, D::Error> {
        d.read_u32().map(NodeId::from_u32)
    }
}