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