540 lines
19 KiB
Rust
540 lines
19 KiB
Rust
// Graph abstraction
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//
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// Copyright (C) 2014-2023 Ryan Specialty, LLC.
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//
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// This file is part of TAME.
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//
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// This program is free software: you can redistribute it and/or modify
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// it under the terms of the GNU General Public License as published by
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// the Free Software Foundation, either version 3 of the License, or
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// (at your option) any later version.
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//
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// This program is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU General Public License for more details.
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//
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// You should have received a copy of the GNU General Public License
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// along with this program. If not, see <http://www.gnu.org/licenses/>.
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//! Abstract semantic graph.
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//!
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//! 
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use self::object::{
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DynObjectRel, ObjectIndexRelTo, ObjectRelFrom, ObjectRelTy,
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ObjectRelatable, Root,
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};
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use super::{air::EnvScopeKind, AsgError, Object, ObjectIndex, ObjectKind};
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use crate::{
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diagnose::{panic::DiagnosticPanic, Annotate, AnnotatedSpan},
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f::Functor,
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global,
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parse::{util::SPair, Token},
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span::Span,
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sym::SymbolId,
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};
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use fxhash::FxHashMap;
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use petgraph::{
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graph::{DiGraph, Graph, NodeIndex},
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visit::EdgeRef,
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Direction,
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};
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use std::{fmt::Debug, result::Result};
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pub mod object;
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pub mod visit;
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pub mod xmli;
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use object::ObjectContainer;
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/// Datatype representing node and edge indexes.
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pub trait IndexType = petgraph::graph::IndexType;
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/// A [`Result`] with a hard-coded [`AsgError`] error type.
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///
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/// This is the result of every [`Asg`] operation that could potentially
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/// fail in error.
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pub type AsgResult<T> = Result<T, AsgError>;
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/// The [`ObjectRelTy`] (representing the [`ObjectKind`]) of the source and
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/// destination [`Node`]s respectively.
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///
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/// This small memory expense allows for bidirectional edge filtering
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/// and [`ObjectIndex`] [`ObjectKind`] resolution without an extra layer
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/// of indirection to look up the source/target [`Node`].
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///
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/// The edge may also optionally contain a [`Span`] that provides additional
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/// context in situations where the distinction between the span of the
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/// target object and the span of the _reference_ to that object is
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/// important.
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type AsgEdge = (ObjectRelTy, ObjectRelTy, Option<Span>);
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/// Each node of the graph.
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type Node = ObjectContainer;
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/// Index size for Graph nodes and edges.
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type Ix = global::ProgSymSize;
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/// An abstract semantic graph (ASG) of [objects](object).
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///
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/// This implementation is currently based on [`petgraph`].
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///
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/// Objects are never deleted from the graph,
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/// so [`ObjectIndex`]s will remain valid for the lifetime of the ASG.
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///
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/// For more information,
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/// see the [module-level documentation][self].
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pub struct Asg {
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/// Directed graph on which objects are stored.
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graph: DiGraph<Node, AsgEdge, Ix>,
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/// Environment cache of [`SymbolId`][crate::sym::SymbolId] to
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/// [`ObjectIndex`]es.
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///
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/// This maps a `(SymbolId, NodeIndex)` pair to a node on the graph for
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/// a given [`ObjectRelTy`].
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/// _This indexing is not automatic_;
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/// it must be explicitly performed using [`Self::index`].
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///
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/// This index serves as a shortcut for finding nodes on a graph,
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/// _but makes no claims about the structure of the graph_.
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///
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/// This allows for `O(1)` lookup of identifiers in the graph relative
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/// to a given node.
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/// Note that,
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/// while we store [`NodeIndex`] internally,
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/// the public API encapsulates it within an [`ObjectIndex`].
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index: FxHashMap<
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(ObjectRelTy, SymbolId, ObjectIndex<Object>),
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EnvScopeKind<ObjectIndex<Object>>,
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>,
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/// The root node used for reachability analysis and topological
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/// sorting.
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root_node: NodeIndex<Ix>,
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}
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impl Debug for Asg {
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/// Trimmed-down Asg [`Debug`] output.
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///
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/// This primarily hides the large `self.index` that takes up so much
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/// space in parser traces,
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/// but also hides irrelevant information.
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///
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/// The better option in the future may be to create a newtype for
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/// `index` if it sticks around in its current form,
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/// which in turn can encapsulate `self.empty_node`.
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fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
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f.debug_struct("Asg")
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.field("root_node", &self.root_node)
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.field("graph", &self.graph)
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.finish_non_exhaustive()
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}
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}
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impl Default for Asg {
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fn default() -> Self {
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Self::new()
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}
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}
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impl Asg {
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/// Create a new ASG.
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///
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/// See also [`with_capacity`](Asg::with_capacity).
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pub fn new() -> Self {
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// TODO: Determine a proper initial capacity.
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Self::with_capacity(0, 0)
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}
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/// Create an ASG with the provided initial capacity.
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///
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/// The value for `objects` will be used as the capacity for the nodes
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/// in the graph,
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/// as well as the initial index capacity.
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/// The value for `edges` may be more difficult to consider,
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/// since edges are used to represent various relationships between
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/// different types of objects,
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/// but it's safe to say that each object will have at least one
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/// edge to another object.
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pub fn with_capacity(objects: usize, edges: usize) -> Self {
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let mut graph = Graph::with_capacity(objects, edges);
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let index =
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FxHashMap::with_capacity_and_hasher(objects, Default::default());
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// Automatically add the root which will be used to determine what
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// identifiers ought to be retained by the final program.
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// This is not indexed and is not accessable by name.
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let root_node = graph.add_node(Object::Root(Root).into());
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Self {
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graph,
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index,
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root_node,
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}
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}
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/// Get the underlying Graph
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pub fn into_inner(self) -> DiGraph<Node, AsgEdge, Ix> {
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self.graph
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}
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/// Number of [`Object`]s on the graph.
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///
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/// This is equivalent to the number of nodes on the graph at the time
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/// of writing,
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/// but that may not always be the case.
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fn object_count(&self) -> usize {
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self.graph.node_count()
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}
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pub(super) fn try_index<
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O: ObjectRelatable,
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OS: ObjectIndexRelTo<O>,
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S: Into<SymbolId>,
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>(
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&mut self,
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imm_env: OS,
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name: S,
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eoi: EnvScopeKind<ObjectIndex<O>>,
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) -> Result<(), ObjectIndex<O>> {
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let sym = name.into();
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let prev = self.index.insert(
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(O::rel_ty(), sym, imm_env.widen()),
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eoi.map(ObjectIndex::widen),
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);
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match prev {
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None => Ok(()),
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Some(eoi) => Err(eoi.into_inner().must_narrow_into::<O>()),
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}
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}
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/// Index the provided symbol `name` as representing the
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/// [`ObjectIndex`] in the immediate environment `imm_env`.
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///
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/// An index does not require the existence of an edge,
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/// but an index may only be created if an edge `imm_env->oi` _could_
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/// be constructed.
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///
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/// This index permits `O(1)` object lookups.
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/// The term "immediate environment" is meant to convey that this index
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/// applies only to the provided `imm_env` node and does not
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/// propagate to any other objects that share this environment.
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///
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/// After an object is indexed it is not expected to be re-indexed
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/// to another node.
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/// Debug builds contain an assertion that will panic in this instance.
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pub(super) fn index<
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O: ObjectRelatable,
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OS: ObjectIndexRelTo<O>,
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S: Into<SymbolId>,
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>(
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&mut self,
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imm_env: OS,
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name: S,
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eoi: EnvScopeKind<ObjectIndex<O>>,
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) {
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let sym = name.into();
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let prev = self.try_index(imm_env, sym, eoi);
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// We should never overwrite indexes
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#[allow(unused_variables)] // used only for debug
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#[allow(unused_imports)]
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if let Err(prev_oi) = prev {
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use crate::fmt::{DisplayWrapper, TtQuote};
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crate::debug_diagnostic_panic!(
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vec![
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imm_env.widen().note("at this scope boundary"),
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prev_oi.note("previously indexed identifier was here"),
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eoi.internal_error(
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"this identifier has already been indexed at the above scope boundary"
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),
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eoi.help(
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"this is a bug in the system responsible for analyzing \
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identifier scope;"
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),
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eoi.help(
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" you can try to work around it by duplicating the definition of "
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),
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eoi.help(
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format!(
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" {} as a _new_ identifier with a different name.",
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TtQuote::wrap(sym),
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)
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),
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],
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"re-indexing of identifier at scope boundary",
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);
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}
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}
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/// Root object.
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///
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/// All [`Object`]s reachable from the root will be included in the
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/// compilation unit or linked executable.
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///
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/// The `witness` is used in the returned [`ObjectIndex`] and is
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/// intended for diagnostic purposes to highlight the source entity that
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/// triggered the request of the root.
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pub fn root<S: Into<Span>>(&self, witness: S) -> ObjectIndex<Root> {
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ObjectIndex::new(self.root_node, witness.into())
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}
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/// Create a new object on the graph.
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///
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/// The provided [`ObjectIndex`] will be augmented with the span
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/// of `obj`.
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pub(super) fn create<O: ObjectKind>(&mut self, obj: O) -> ObjectIndex<O> {
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let o = obj.into();
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let span = o.span();
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let node_id = self.graph.add_node(ObjectContainer::from(o.into()));
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ObjectIndex::new(node_id, span)
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}
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/// Add an edge from the [`Object`] represented by the
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/// [`ObjectIndex`] `from_oi` to the object represented by `to_oi`.
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///
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/// The edge may optionally contain a _contextual [`Span`]_,
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/// in cases where it is important to distinguish between the span
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/// associated with the target and the span associated with the
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/// _reference_ to the target.
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///
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/// For more information on how the ASG's ontology is enforced statically,
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/// see [`ObjectRelTo`](object::ObjectRelTo).
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fn add_edge<OB: ObjectKind + ObjectRelatable>(
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&mut self,
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from_oi: impl ObjectIndexRelTo<OB>,
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to_oi: ObjectIndex<OB>,
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ctx_span: Option<Span>,
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) {
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self.graph.add_edge(
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from_oi.widen().into(),
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to_oi.into(),
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(from_oi.src_rel_ty(), OB::rel_ty(), ctx_span),
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);
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}
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/// Retrieve an object from the graph by [`ObjectIndex`].
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///
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/// Since an [`ObjectIndex`] should only be produced by an [`Asg`],
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/// and since objects are never deleted from the graph,
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/// this should never fail so long as references are not shared
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/// between multiple graphs.
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/// It is nevertheless wrapped in an [`Option`] just in case.
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#[inline]
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pub fn get<O: ObjectKind>(&self, index: ObjectIndex<O>) -> Option<&O> {
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self.graph
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.node_weight(index.into())
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.map(ObjectContainer::get)
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}
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/// Attempt to map over an inner [`Object`] referenced by
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/// [`ObjectIndex`].
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///
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/// The type `O` is the expected type of the [`Object`],
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/// which should be known to the caller based on the provied
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/// [`ObjectIndex`].
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/// This method will attempt to narrow to that object type,
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/// panicing if there is a mismatch;
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/// see the [`object` module documentation](object) for more
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/// information and rationale on this behavior.
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///
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/// Panics
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/// ======
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/// This method chooses to simplify the API by choosing panics for
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/// situations that ought never to occur and represent significant bugs
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/// in the compiler.
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/// Those situations are:
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///
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/// 1. If the provided [`ObjectIndex`] references a node index that is
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/// not present on the graph;
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/// 2. If the node referenced by [`ObjectIndex`] exists but its container
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/// is empty because an object was taken but never returned; and
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/// 3. If an object cannot be narrowed (downcast) to type `O`,
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/// representing a type mismatch between what the caller thinks
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/// this object represents and what the object actually is.
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#[must_use = "returned ObjectIndex has a possibly-updated and more relevant span"]
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pub(super) fn try_map_obj<O: ObjectKind, E>(
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&mut self,
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index: ObjectIndex<O>,
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f: impl FnOnce(O) -> Result<O, (O, E)>,
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) -> Result<ObjectIndex<O>, E> {
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let obj_container =
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self.graph.node_weight_mut(index.into()).diagnostic_expect(
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|| diagnostic_node_missing_desc(index),
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"invalid ObjectIndex: data are missing from the ASG",
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);
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obj_container
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.try_replace_with(f)
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.map(|()| index.overwrite(obj_container.get::<Object>().span()))
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}
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/// Create an iterator over the [`ObjectIndex`]es of the outgoing edges
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/// of `oi`.
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///
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/// This is a generic method that simply returns an [`ObjectKind`] of
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/// [`Object`] for each [`ObjectIndex`];
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/// it is the responsibility of the caller to narrow the type to
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/// what is intended.
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/// This is sufficient in practice,
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/// since the graph cannot be constructed without adhering to the edge
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/// ontology defined by [`ObjectRelTo`](object::ObjectRelTo),
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/// but this API is not helpful for catching problems at
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/// compile-time.
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///
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/// The reason for providing a generic index to [`Object`] is that it
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/// allows the caller to determine how strict it wants to be with
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/// reading from the graph;
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/// for example,
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/// it may prefer to filter unwanted objects rather than panicing
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/// if they do not match a given [`ObjectKind`],
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/// depending on its ontology.
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fn edges<'a, O: ObjectKind + ObjectRelatable + 'a>(
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&'a self,
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oi: ObjectIndex<O>,
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) -> impl Iterator<Item = O::Rel> + 'a {
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self.edges_dyn(oi.widen()).map(move |dyn_rel| {
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let target_ty = dyn_rel.target_ty();
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dyn_rel.narrow_target::<O>().diagnostic_unwrap(|| {
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vec![
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oi.internal_error(format!(
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"encountered invalid outgoing edge type {:?}",
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target_ty,
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)),
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oi.help(
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"this means that Asg did not enforce edge invariants \
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during construction, which is a significant bug",
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),
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]
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})
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})
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}
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/// Create an iterator over the [`ObjectIndex`]es of the outgoing edges
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/// of `oi` in a dynamic context.
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///
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/// _This method should be used only when the types of objects cannot be
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/// statically known,_
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/// which is generally true only for code paths operating on
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/// significant portions of
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/// (or the entirety of)
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/// the graph without distinction.
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/// See [`Self::edges`] for more information.
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fn edges_dyn<'a>(
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&'a self,
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oi: ObjectIndex<Object>,
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) -> impl Iterator<Item = DynObjectRel> + 'a {
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self.graph.edges(oi.into()).map(move |edge| {
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let (src_ty, target_ty, ctx_span) = edge.weight();
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DynObjectRel::new(
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*src_ty,
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*target_ty,
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oi,
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ObjectIndex::<Object>::new(edge.target(), oi),
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*ctx_span,
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)
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})
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}
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/// Incoming edges to `oi` filtered by [`ObjectKind`] `OI`.
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///
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/// The rationale behind the filtering is that objects ought to focus
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/// primarily on what they _relate to_,
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/// which is what the ontology is designed around.
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/// If an object cares about what has an edge _to_ it,
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/// it should have good reason and a specific use case in mind.
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fn incoming_edges_filtered<'a, OI: ObjectKind + ObjectRelatable + 'a>(
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&'a self,
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oi: ObjectIndex<impl ObjectKind + ObjectRelFrom<OI> + 'a>,
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) -> impl Iterator<Item = ObjectIndex<OI>> + 'a {
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self.graph
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.edges_directed(oi.into(), Direction::Incoming)
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.filter(|edge| edge.weight().0 == OI::rel_ty())
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.map(move |edge| ObjectIndex::<OI>::new(edge.source(), oi))
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}
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/// Check whether an edge exists from `from` to `to.
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#[inline]
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pub fn has_edge<OB: ObjectRelatable>(
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&self,
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from: impl ObjectIndexRelTo<OB>,
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to: ObjectIndex<OB>,
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) -> bool {
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self.graph.contains_edge(from.widen().into(), to.into())
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}
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pub(super) fn expect_obj<O: ObjectKind>(&self, oi: ObjectIndex<O>) -> &O {
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let obj_container =
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self.graph.node_weight(oi.into()).diagnostic_expect(
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|| diagnostic_node_missing_desc(oi),
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"invalid ObjectIndex: data are missing from the ASG",
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);
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obj_container.get()
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}
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/// Attempt to retrieve an identifier from the graph by name relative to
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/// the immediate environment `imm_env`.
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///
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/// Since only identifiers carry a name,
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/// this method cannot be used to retrieve all possible objects on the
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/// graph---for
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/// that, see [`Asg::get`].
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#[inline]
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pub fn lookup<O: ObjectRelatable>(
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&self,
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imm_env: impl ObjectIndexRelTo<O>,
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id: SPair,
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) -> Option<ObjectIndex<O>> {
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self.lookup_raw(imm_env, id)
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.and_then(EnvScopeKind::in_scope)
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.map(EnvScopeKind::into_inner)
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}
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/// Attempt to retrieve an identifier and its scope information from the
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/// graph by name relative to the immediate environment `imm_env`.
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///
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/// See [`Self::lookup`] for more information.
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#[inline]
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pub(super) fn lookup_raw<O: ObjectRelatable>(
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&self,
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imm_env: impl ObjectIndexRelTo<O>,
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id: SPair,
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) -> Option<EnvScopeKind<ObjectIndex<O>>> {
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// The type `O` is encoded into the index on [`Self::index`] and so
|
||
// should always be able to be narrowed into the expected type.
|
||
// If this invariant somehow does not hold,
|
||
// then the system will panic when the object is resolved.
|
||
// Maybe future Rust will have dependent types that allow for better
|
||
// static assurances.
|
||
self.index
|
||
.get(&(O::rel_ty(), id.symbol(), imm_env.widen()))
|
||
.map(|&eoi| {
|
||
eoi.map(|oi| oi.overwrite(id.span()).must_narrow_into::<O>())
|
||
})
|
||
}
|
||
}
|
||
|
||
fn diagnostic_node_missing_desc<O: ObjectKind>(
|
||
index: ObjectIndex<O>,
|
||
) -> Vec<AnnotatedSpan<'static>> {
|
||
vec![
|
||
index.internal_error("this object is missing from the ASG"),
|
||
index.help("this means that either an ObjectIndex was malformed, or"),
|
||
index.help(" the object no longer exists on the graph, both of"),
|
||
index.help(" which are unexpected and possibly represent data"),
|
||
index.help(" corruption."),
|
||
index.help("The system cannot proceed with confidence."),
|
||
]
|
||
}
|
||
|
||
#[cfg(test)]
|
||
mod test;
|