Unnamed repository; edit this file 'description' to name the repository.
Diffstat (limited to 'crates/span/src/ast_id.rs')
| -rw-r--r-- | crates/span/src/ast_id.rs | 249 |
1 files changed, 249 insertions, 0 deletions
diff --git a/crates/span/src/ast_id.rs b/crates/span/src/ast_id.rs new file mode 100644 index 0000000000..2d98aa81e5 --- /dev/null +++ b/crates/span/src/ast_id.rs @@ -0,0 +1,249 @@ +//! `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::{BuildHasher, BuildHasherDefault, Hash, Hasher}, + marker::PhantomData, +}; + +use la_arena::{Arena, Idx, RawIdx}; +use rustc_hash::FxHasher; +use syntax::{ast, AstNode, AstPtr, SyntaxNode, SyntaxNodePtr}; + +/// See crates\hir-expand\src\ast_id_map.rs +/// This is a type erased FileAstId. +pub type ErasedFileAstId = la_arena::Idx<syntax::SyntaxNodePtr>; + +/// `AstId` points to an AST node in a specific file. +pub struct FileAstId<N: AstIdNode> { + raw: ErasedFileAstId, + covariant: PhantomData<fn() -> N>, +} + +impl<N: AstIdNode> Clone for FileAstId<N> { + fn clone(&self) -> FileAstId<N> { + *self + } +} +impl<N: AstIdNode> Copy for FileAstId<N> {} + +impl<N: AstIdNode> PartialEq for FileAstId<N> { + fn eq(&self, other: &Self) -> bool { + self.raw == other.raw + } +} +impl<N: AstIdNode> Eq for FileAstId<N> {} +impl<N: AstIdNode> Hash for FileAstId<N> { + fn hash<H: Hasher>(&self, hasher: &mut H) { + self.raw.hash(hasher); + } +} + +impl<N: AstIdNode> 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: AstIdNode> FileAstId<N> { + // Can't make this a From implementation because of coherence + pub fn upcast<M: AstIdNode>(self) -> FileAstId<M> + where + N: Into<M>, + { + FileAstId { raw: self.raw, covariant: PhantomData } + } + + pub fn erase(self) -> ErasedFileAstId { + self.raw + } +} + +pub trait AstIdNode: AstNode {} +macro_rules! register_ast_id_node { + (impl AstIdNode for $($ident:ident),+ ) => { + $( + impl AstIdNode for ast::$ident {} + )+ + fn should_alloc_id(kind: syntax::SyntaxKind) -> bool { + $( + ast::$ident::can_cast(kind) + )||+ + } + }; +} +register_ast_id_node! { + impl AstIdNode for + Item, + Adt, + Enum, + Struct, + Union, + Const, + ExternBlock, + ExternCrate, + Fn, + Impl, + Macro, + MacroDef, + MacroRules, + MacroCall, + Module, + Static, + Trait, + TraitAlias, + TypeAlias, + Use, + AssocItem, BlockExpr, Variant, RecordField, TupleField, ConstArg, Param, SelfParam +} + +/// Maps items' `SyntaxNode`s to `ErasedFileAstId`s and back. +#[derive(Default)] +pub struct AstIdMap { + /// Maps stable id to unstable ptr. + arena: Arena<SyntaxNodePtr>, + /// Reverse: map ptr to id. + map: hashbrown::HashMap<Idx<SyntaxNodePtr>, (), ()>, +} + +impl fmt::Debug for AstIdMap { + fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { + f.debug_struct("AstIdMap").field("arena", &self.arena).finish() + } +} + +impl PartialEq for AstIdMap { + fn eq(&self, other: &Self) -> bool { + self.arena == other.arena + } +} +impl Eq for AstIdMap {} + +impl AstIdMap { + pub fn from_source(node: &SyntaxNode) -> AstIdMap { + assert!(node.parent().is_none()); + let mut res = AstIdMap::default(); + + // make sure to allocate the root node + if !should_alloc_id(node.kind()) { + res.alloc(node); + } + // 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| { + if should_alloc_id(it.kind()) { + res.alloc(&it); + TreeOrder::BreadthFirst + } else { + TreeOrder::DepthFirst + } + }); + res.map = hashbrown::HashMap::with_capacity_and_hasher(res.arena.len(), ()); + for (idx, ptr) in res.arena.iter() { + let hash = hash_ptr(ptr); + match res.map.raw_entry_mut().from_hash(hash, |idx2| *idx2 == idx) { + hashbrown::hash_map::RawEntryMut::Occupied(_) => unreachable!(), + hashbrown::hash_map::RawEntryMut::Vacant(entry) => { + entry.insert_with_hasher(hash, idx, (), |&idx| hash_ptr(&res.arena[idx])); + } + } + } + res.arena.shrink_to_fit(); + res + } + + /// The [`AstId`] of the root node + pub fn root(&self) -> SyntaxNodePtr { + self.arena[Idx::from_raw(RawIdx::from_u32(0))] + } + + pub fn ast_id<N: AstIdNode>(&self, item: &N) -> FileAstId<N> { + let raw = self.erased_ast_id(item.syntax()); + FileAstId { raw, covariant: PhantomData } + } + + pub fn ast_id_for_ptr<N: AstIdNode>(&self, ptr: AstPtr<N>) -> FileAstId<N> { + let ptr = ptr.syntax_node_ptr(); + let hash = hash_ptr(&ptr); + match self.map.raw_entry().from_hash(hash, |&idx| self.arena[idx] == ptr) { + Some((&raw, &())) => FileAstId { raw, covariant: PhantomData }, + None => panic!( + "Can't find {:?} in AstIdMap:\n{:?}", + ptr, + self.arena.iter().map(|(_id, i)| i).collect::<Vec<_>>(), + ), + } + } + + pub fn get<N: AstIdNode>(&self, id: FileAstId<N>) -> AstPtr<N> { + AstPtr::try_from_raw(self.arena[id.raw]).unwrap() + } + + pub fn get_erased(&self, id: ErasedFileAstId) -> SyntaxNodePtr { + self.arena[id] + } + + fn erased_ast_id(&self, item: &SyntaxNode) -> ErasedFileAstId { + let ptr = SyntaxNodePtr::new(item); + let hash = hash_ptr(&ptr); + match self.map.raw_entry().from_hash(hash, |&idx| self.arena[idx] == ptr) { + Some((&idx, &())) => idx, + None => panic!( + "Can't find {:?} in AstIdMap:\n{:?}", + item, + self.arena.iter().map(|(_id, i)| i).collect::<Vec<_>>(), + ), + } + } + + fn alloc(&mut self, item: &SyntaxNode) -> ErasedFileAstId { + self.arena.alloc(SyntaxNodePtr::new(item)) + } +} + +fn hash_ptr(ptr: &SyntaxNodePtr) -> u64 { + BuildHasherDefault::<FxHasher>::default().hash_one(ptr) +} + +#[derive(Copy, Clone, PartialEq, Eq)] +enum TreeOrder { + BreadthFirst, + DepthFirst, +} + +/// 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 [`TreeOrder::BreadthFirst`] are visited breadth-first, all the other nodes are explored +/// [`TreeOrder::DepthFirst`]. +/// +/// 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) -> TreeOrder) { + 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()) == TreeOrder::BreadthFirst { + next_layer.extend(node.children()); + preorder.skip_subtree(); + } + } + syntax::WalkEvent::Leave(_) => {} + } + } + }); + std::mem::swap(&mut curr_layer, &mut next_layer); + } +} |