148 lines
4.6 KiB
Rust
148 lines
4.6 KiB
Rust
//! `AstIdMap` allows to create stable IDs for "large" syntax nodes like items
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//! and macro calls.
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//!
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//! Specifically, it enumerates all items in a file and uses position of a an
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//! item as an ID. That way, id's don't change unless the set of items itself
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//! changes.
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use std::{
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any::type_name,
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fmt,
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hash::{Hash, Hasher},
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marker::PhantomData,
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};
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use la_arena::{Arena, Idx};
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use profile::Count;
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use syntax::{ast, match_ast, AstNode, AstPtr, SyntaxNode, SyntaxNodePtr};
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/// `AstId` points to an AST node in a specific file.
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pub struct FileAstId<N: AstNode> {
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raw: ErasedFileAstId,
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_ty: PhantomData<fn() -> N>,
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}
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impl<N: AstNode> Clone for FileAstId<N> {
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fn clone(&self) -> FileAstId<N> {
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*self
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}
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}
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impl<N: AstNode> Copy for FileAstId<N> {}
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impl<N: AstNode> PartialEq for FileAstId<N> {
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fn eq(&self, other: &Self) -> bool {
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self.raw == other.raw
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}
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}
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impl<N: AstNode> Eq for FileAstId<N> {}
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impl<N: AstNode> Hash for FileAstId<N> {
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fn hash<H: Hasher>(&self, hasher: &mut H) {
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self.raw.hash(hasher);
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}
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}
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impl<N: AstNode> fmt::Debug for FileAstId<N> {
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fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
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write!(f, "FileAstId::<{}>({})", type_name::<N>(), self.raw.into_raw())
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}
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}
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impl<N: AstNode> FileAstId<N> {
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// Can't make this a From implementation because of coherence
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pub fn upcast<M: AstNode>(self) -> FileAstId<M>
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where
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N: Into<M>,
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{
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FileAstId { raw: self.raw, _ty: PhantomData }
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}
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}
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type ErasedFileAstId = Idx<SyntaxNodePtr>;
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/// Maps items' `SyntaxNode`s to `ErasedFileAstId`s and back.
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#[derive(Debug, PartialEq, Eq, Default)]
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pub struct AstIdMap {
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arena: Arena<SyntaxNodePtr>,
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_c: Count<Self>,
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}
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impl AstIdMap {
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pub(crate) fn from_source(node: &SyntaxNode) -> AstIdMap {
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assert!(node.parent().is_none());
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let mut res = AstIdMap::default();
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// By walking the tree in breadth-first order we make sure that parents
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// get lower ids then children. That is, adding a new child does not
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// change parent's id. This means that, say, adding a new function to a
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// trait does not change ids of top-level items, which helps caching.
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bdfs(node, |it| {
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match_ast! {
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match it {
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ast::Item(module_item) => {
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res.alloc(module_item.syntax());
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true
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},
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ast::BlockExpr(block) => {
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res.alloc(block.syntax());
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true
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},
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_ => false,
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}
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}
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});
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res
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}
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pub fn ast_id<N: AstNode>(&self, item: &N) -> FileAstId<N> {
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let raw = self.erased_ast_id(item.syntax());
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FileAstId { raw, _ty: PhantomData }
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}
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fn erased_ast_id(&self, item: &SyntaxNode) -> ErasedFileAstId {
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let ptr = SyntaxNodePtr::new(item);
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match self.arena.iter().find(|(_id, i)| **i == ptr) {
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Some((it, _)) => it,
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None => panic!(
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"Can't find {:?} in AstIdMap:\n{:?}",
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item,
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self.arena.iter().map(|(_id, i)| i).collect::<Vec<_>>(),
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),
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}
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}
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pub fn get<N: AstNode>(&self, id: FileAstId<N>) -> AstPtr<N> {
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self.arena[id.raw].clone().cast::<N>().unwrap()
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}
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fn alloc(&mut self, item: &SyntaxNode) -> ErasedFileAstId {
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self.arena.alloc(SyntaxNodePtr::new(item))
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}
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}
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/// Walks the subtree in bdfs order, calling `f` for each node. What is bdfs
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/// order? It is a mix of breadth-first and depth first orders. Nodes for which
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/// `f` returns true are visited breadth-first, all the other nodes are explored
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/// depth-first.
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///
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/// In other words, the size of the bfs queue is bound by the number of "true"
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/// nodes.
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fn bdfs(node: &SyntaxNode, mut f: impl FnMut(SyntaxNode) -> bool) {
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let mut curr_layer = vec![node.clone()];
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let mut next_layer = vec![];
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while !curr_layer.is_empty() {
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curr_layer.drain(..).for_each(|node| {
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let mut preorder = node.preorder();
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while let Some(event) = preorder.next() {
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match event {
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syntax::WalkEvent::Enter(node) => {
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if f(node.clone()) {
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next_layer.extend(node.children());
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preorder.skip_subtree();
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}
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}
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syntax::WalkEvent::Leave(_) => {}
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}
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}
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});
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std::mem::swap(&mut curr_layer, &mut next_layer);
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}
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}
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