1254 lines
44 KiB
Rust
1254 lines
44 KiB
Rust
// Relationship between objects represented on ASG
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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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//! Relationship betwen objects on the ASG.
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//!
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//! See (parent module)[super] for more information.
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use super::{
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Doc, Expr, Ident, Meta, Object, ObjectIndex, ObjectIndexRefined,
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ObjectKind, OiPairObjectInner, Pkg, Root,
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};
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use crate::{
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asg::{
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graph::{object::Tpl, AsgRelMut, ProposedRel},
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Asg, AsgError,
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},
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f::Map,
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span::Span,
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};
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use std::{fmt::Display, marker::PhantomData};
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pub use super::ObjectTy as ObjectRelTy;
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impl Display for ObjectRelTy {
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fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
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// At the time of writing,
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// this happens to be sufficient.
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std::fmt::Debug::fmt(self, f)
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}
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}
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/// Declare relations for an [`ObjectKind`].
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///
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/// This generates an [`ObjectRel`] type for the provided [`ObjectKind`] and
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/// binds it to the kind using [`ObjectRelatable`].
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///
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/// Each relationship must be explicitly specified as either a `tree` or
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/// `cross` edge.
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/// For more information on cross edges,
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/// see [`ObjectRel::is_cross_edge`].
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macro_rules! object_rel {
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(
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$(#[$attr:meta])+
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$from:ident -> {
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$($ety:ident $kind:ident $({$($impl:tt)*})?,)*
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}
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$(can_recurse($rec_obj:ident) if $rec_expr:expr)?
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) => {paste::paste! {
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/// Subset of [`ObjectKind`]s that are valid targets for edges from
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#[doc=concat!("[`", stringify!($from), "`].")]
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///
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$(#[$attr])+
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///
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/// See [`ObjectRel`] for more information.
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///
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/// [`ObjectKind`]: crate::asg::ObjectKind
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#[derive(Debug, PartialEq, Eq)]
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pub enum [<$from Rel>] {
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$($kind(ObjectIndex<$kind>),)*
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}
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impl ObjectRel<$from> for [<$from Rel>] {
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fn narrow_ref<OB: ObjectRelFrom<$from> + ObjectRelatable>(
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&self,
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) -> Option<ObjectIndex<OB>> {
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match *self {
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$(Self::$kind(oi) => oi.filter_rel(),)*
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}
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}
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/// The root of the graph by definition has no cross edges.
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fn is_cross_edge<S, T>(
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&self,
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#[allow(unused_variables)] // used only for `dyn` edges
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rel: &$crate::asg::graph::object::rel::DynObjectRel<S, T>
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) -> bool {
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match self {
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$(
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Self::$kind(..) => object_rel!(@is_cross_edge $ety rel),
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)*
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#[allow(unreachable_patterns)] // for empty Rel types
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_ => unreachable!(
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concat!(stringify!($from), "Rel is empty")
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),
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}
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}
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$(
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fn can_recurse(&self, asg: &Asg) -> bool {
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self.narrow_ref::<$from>()
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.map(|oi| oi.resolve(asg))
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.map(|$rec_obj| $rec_expr)
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.unwrap_or(false)
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}
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)?
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}
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impl ObjectRelatable for $from {
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type Rel = [<$from Rel>];
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fn rel_ty() -> ObjectRelTy {
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ObjectRelTy::$from
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}
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fn new_rel_dyn(
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ty: ObjectRelTy,
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#[allow(unused_variables)] // for empty Rel
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oi: ObjectIndex<Object>,
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) -> Option<[<$from Rel>]> {
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match ty {
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$(
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ObjectRelTy::$kind => {
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Some(Self::Rel::$kind(oi.must_narrow_into()))
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},
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)*
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_ => None,
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}
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}
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fn oi_rel_to_dyn<OB: ObjectRelatable>(
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#[allow(unused_variables)] // for empty Rel
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oi: ObjectIndex<Self>,
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) -> Option<$crate::asg::graph::object::ObjectIndexTo<OB>> {
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#[allow(unused_imports)]
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use $crate::asg::graph::object::ObjectIndexTo;
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match OB::rel_ty() {
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$(
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ObjectRelTy::$kind => {
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ObjectIndexTo::<$kind>::from(oi).reflexivity()
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},
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)*
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_ => None,
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}
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}
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}
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$(
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impl From<ObjectIndex<$kind>> for [<$from Rel>] {
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fn from(value: ObjectIndex<$kind>) -> Self {
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Self::$kind(value)
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}
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}
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object_rel!{ @impl_rel_to $from $ety $kind }
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)*
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impl From<[<$from Rel>]> for ObjectIndex<Object> {
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fn from(value: [<$from Rel>]) -> Self {
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match value {
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$(
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[<$from Rel>]::$kind(oi) => oi.widen(),
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)*
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}
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}
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}
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// This generates a specialized implementation _per target `$kind`_
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// and allows for the caller to override methods on the trait.
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// This takes advantage of trait specialization via
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// `min_specialization`;
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// see `AsgRelMut` for more information.
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$(
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impl AsgRelMut<$kind> for $from {
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$( $($impl)* )?
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}
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)*
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}};
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// Static edge types.
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(@is_cross_edge cross $_:ident) => { true };
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(@is_cross_edge tree $_:ident) => { false };
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// Dynamic edge type.
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//
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// We consider an edge to be a cross edge iff it contains a context
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// span.
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// If it were _not_ a cross edge,
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// then the edge would represent ownership,
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// and the span information on the target would be sufficient context
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// on its own;
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// an edge only needs supplemental span information if there is
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// another context in which that object is referenced.
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(@is_cross_edge dyn $rel:ident) => { $rel.ctx_span().is_some() };
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// Similar to above but providing _static_ information to the type
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// system.
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// The above could be rolled into this at some point.
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(@impl_rel_to $from:ident cross $kind:ident) => {};
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(@impl_rel_to $from:ident tree $kind:ident) => {
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impl ObjectTreeRelTo<$kind> for $from {}
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};
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(@impl_rel_to $from:ident dyn $kind:ident) => {
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// It _could_ be a tree edge;
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// we can't know statically.
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impl ObjectTreeRelTo<$kind> for $from {}
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};
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}
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/// A dynamic relationship (edge) from one object to another before it has
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/// been narrowed.
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///
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/// The source and target of this edge are usually [`ObjectIndex`]es,
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/// but it is made generic (`S, T`) to support mapping while retaining
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/// useful metadata,
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/// e.g. to resolve an object while retaining the edge information.
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#[derive(Debug, PartialEq)]
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pub struct DynObjectRel<S = ObjectIndex<Object>, T = ObjectIndex<Object>>(
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(ObjectRelTy, ObjectRelTy),
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(S, T),
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Option<Span>,
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);
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impl<S, T> DynObjectRel<S, T> {
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pub(in super::super) fn new(
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from_ty: ObjectRelTy,
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to_ty: ObjectRelTy,
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src: S,
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target: T,
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ctx_span: Option<Span>,
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) -> Self {
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Self((from_ty, to_ty), (src, target), ctx_span)
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}
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/// The type of the source edge.
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pub fn source_ty(&self) -> ObjectRelTy {
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match self {
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Self((ty, _), ..) => *ty,
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}
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}
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/// The type of the target edge.
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pub fn target_ty(&self) -> ObjectRelTy {
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match self {
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Self((_, ty), ..) => *ty,
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}
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}
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/// The source of this relationship.
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pub fn source(&self) -> &S {
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match self {
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Self(_, (oi, _), _) => oi,
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}
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}
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/// The target of this relationship.
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///
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/// This type generally originates as [`ObjectIndex`] but can be mapped
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/// over to retain the structured edge data.
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pub fn target(&self) -> &T {
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match self {
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Self(_, (_, oi), _) => oi,
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}
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}
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/// A [`Span`] associated with the _relationship_ between the source and
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/// target objects,
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/// if any.
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pub fn ctx_span(&self) -> Option<Span> {
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match self {
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Self(_, _, ctx_span) => *ctx_span,
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}
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}
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}
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impl<S> DynObjectRel<S, ObjectIndex<Object>> {
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/// Attempt to narrow the target into the [`ObjectRel`] of `O`.
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///
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/// See [`ObjectRelatable::new_rel_dyn`] for more information.
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///
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/// To exhaustively match against all possible [`ObjectKind`]s,
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/// see [`Self::refine_target`].
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pub fn narrow_target<O: ObjectKind + ObjectRelatable>(
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&self,
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) -> Option<O::Rel> {
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O::new_rel_dyn(self.target_ty(), *self.target())
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}
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/// Refine the target [`ObjectIndex<Object>`](ObjectIndex) into
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/// [`ObjectIndexRefined`] such that the returned variant has a
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/// narrowed [`ObjectIndex<O>`] type.
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///
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/// This allows converting a dynamic [`ObjectIndex`] into a statically
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/// known type where `O` is derived from [`Self::target_ty`].
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/// This avoids having to manually match on [`Self::target_ty`] and then
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/// use [`ObjectIndex::must_narrow_into`] on the matching
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/// [`ObjectKind`],
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/// since there is a risk of those getting out of sync.
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///
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/// In contrast to [`Self::narrow_target`],
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/// where the caller must specify the expected [`ObjectKind`],
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/// this allows for exhaustively matching against all possible objects.
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pub fn refine_target(&self) -> ObjectIndexRefined {
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macro_rules! narrow_each_rel_ty {
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( $($var:ident),+ ) => {
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match self.target_ty() {
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$(
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ObjectRelTy::$var => {
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ObjectIndexRefined::$var(
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self.target().must_narrow_into()
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)
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}
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)+
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}
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}
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}
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narrow_each_rel_ty!(Root, Pkg, Ident, Expr, Tpl, Meta, Doc)
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}
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/// Attempt to convert [`Self`] into an [`ObjectIndex`] with an
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/// [`ObjectKind`] of type `O`.
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///
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/// This method allows marrying a dynamically determined type with a
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/// context requiring a static type.
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/// If the type `O` does not match the type stored at runtime,
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/// [`None`] is returned.
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pub fn filter_into_target<O: ObjectKind + ObjectRelatable>(
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&self,
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) -> Option<ObjectIndex<O>> {
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if self.target_ty() == O::rel_ty() {
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Some(self.target().must_narrow_into())
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} else {
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None
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}
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}
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/// Pair the target [`ObjectIndex`] with its resolved [`Object`].
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///
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/// This allows the [`ObjectIndex`] to be refined alongside the inner
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/// [`ObjectKind`] so that callers can make use of the refined
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/// [`ObjectIndex`] without having to explicitly narrow themselves.
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/// While isn't any more or less safe than the manual alternative,
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/// it _does_ defend against logic bugs.
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pub fn resolve_target_oi_pair(
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self,
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asg: &Asg,
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) -> DynObjectRel<S, Object<OiPairObjectInner>> {
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self.map(|(soi, toi)| (soi, toi.resolve(asg).pair_oi(toi)))
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}
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/// Retrieve the target [`ObjectIndex`] as an [`ObjectIndexTo<OB>`](ObjectIndexTo),
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/// if the object can be related to objects of type `OB`.
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///
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/// This method may be confusing in that it represents another
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/// _possible_ relation on top of the relation represented by
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/// [`Self`].
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/// That is:
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///
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/// ```text
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/// OA -> OB [ -> OC]
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/// '______'
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/// Self
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/// ```
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///
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/// If this method returns [`Some`],
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/// that means that the target of this relation `OB` is an object
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/// _that is capable of being related to_ an object of type `OC`.
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pub fn target_oi_rel_to_dyn<OC: ObjectRelatable>(
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&self,
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) -> Option<ObjectIndexTo<OC>> {
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// TODO: A newtype ought to couple these in a way that we don't have
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// to trust this assumption!
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// This requires assuming that the target is of the target type,
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// which _should_ certainly be the case if originating from the graph,
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// but if it's not,
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// then later resolving the `ObjectIndex` with a mismatched type
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// will result in a panic.
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self.target_ty()
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.assuming_oi_maybe_rel_to_dyn(*self.target())
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}
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/// Dynamically determine whether this edge represents a cross edge.
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///
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/// This function is intended for _dynamic_ edge types,
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/// which cannot be determined statically;
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/// it should be used only in situations where the potential edge types
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/// are unbounded,
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/// e.g. on an iterator yielding generalized [`ObjectIndex`]es during
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/// a full graph traversal.
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/// You should otherwise use [`ObjectRel::is_cross_edge`].
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///
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/// For more information on cross edges,
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/// see [`ObjectRel::is_cross_edge`].
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pub fn is_cross_edge(&self) -> bool {
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/// Generate cross-edge mappings between ObjectRelTy and the associated
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/// ObjectRel.
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///
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/// This is intended to both reduce boilerplate and to eliminate typos.
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///
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/// This mess will be optimized away,
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/// but exists so that cross edge definitions can exist alongside
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/// other relationship definitions for each individual object type,
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/// rather than having to maintain them in aggregate here.
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macro_rules! ty_cross_edge {
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($($ty:ident),*) => {
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match self.source_ty() {
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$(
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ObjectRelTy::$ty => {
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self.narrow_target::<$ty>().is_some_and(
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|rel| rel.is_cross_edge(self)
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)
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},
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)*
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}
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}
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}
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ty_cross_edge!(Root, Pkg, Ident, Expr, Tpl, Meta, Doc)
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}
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|
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/// Dynamically determine whether this edge represents a permitted
|
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/// cycle.
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||
///
|
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/// A cycle is permitted in certain cases of recursion.
|
||
/// See [`ObjectRel::can_recurse`] for more information.
|
||
pub fn can_recurse(&self, asg: &Asg) -> bool {
|
||
macro_rules! ty_can_recurse {
|
||
($($ty:ident),*) => {
|
||
match self.source_ty() {
|
||
$(
|
||
ObjectRelTy::$ty => {
|
||
self.narrow_target::<$ty>().is_some_and(
|
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|rel| rel.can_recurse(asg)
|
||
)
|
||
},
|
||
)*
|
||
}
|
||
}
|
||
}
|
||
|
||
ty_can_recurse!(Root, Pkg, Ident, Expr, Tpl, Meta, Doc)
|
||
}
|
||
}
|
||
|
||
impl<T> DynObjectRel<ObjectIndex<Object>, T> {
|
||
/// Pair the source [`ObjectIndex`] with its resolved [`Object`].
|
||
///
|
||
/// This allows the [`ObjectIndex`] to be refined alongside the inner
|
||
/// [`ObjectKind`] so that callers can make use of the refined
|
||
/// [`ObjectIndex`] without having to explicitly narrow themselves.
|
||
/// While isn't any more or less safe than the manual alternative,
|
||
/// it _does_ defend against logic bugs.
|
||
pub fn resolve_source_oi_pair(
|
||
self,
|
||
asg: &Asg,
|
||
) -> DynObjectRel<Object<OiPairObjectInner>, T> {
|
||
self.map(|(soi, toi)| (soi.resolve(asg).pair_oi(soi), toi))
|
||
}
|
||
}
|
||
|
||
impl DynObjectRel<ObjectIndex<Object>, ObjectIndex<Object>> {
|
||
/// Pair the source and target [`ObjectIndex`]es with their respective
|
||
/// resolved [`Object`]s.
|
||
///
|
||
/// See [`Self::resolve_target_oi_pair`] and
|
||
/// [`Self::resolve_source_oi_pair`] for more information.
|
||
pub fn resolve_oi_pairs(
|
||
self,
|
||
asg: &Asg,
|
||
) -> DynObjectRel<Object<OiPairObjectInner>, Object<OiPairObjectInner>>
|
||
{
|
||
self.resolve_source_oi_pair(asg).resolve_target_oi_pair(asg)
|
||
}
|
||
}
|
||
|
||
impl<S, T, U, V> Map<(S, T), (U, V)> for DynObjectRel<S, T> {
|
||
type Target = DynObjectRel<U, V>;
|
||
|
||
fn map(self, f: impl FnOnce((S, T)) -> (U, V)) -> Self::Target {
|
||
match self {
|
||
Self(tys, x, ctx_span) => DynObjectRel(tys, f(x), ctx_span),
|
||
}
|
||
}
|
||
}
|
||
|
||
impl<T: Display> Display for DynObjectRel<T> {
|
||
fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
|
||
let Self((from_ty, to_ty), (s, t), _) = self;
|
||
|
||
write!(f, "dynamic edge {from_ty}->{to_ty} with {s}->{t}",)
|
||
}
|
||
}
|
||
|
||
/// Indicate that an [`ObjectKind`] `Self` can be related to
|
||
/// [`ObjectKind`] `OB` by creating an edge from `Self` to `OB`.
|
||
///
|
||
/// This trait defines a portion of the graph ontology,
|
||
/// allowing [`Self`] to be related to `OB` by creating a directed edge
|
||
/// from [`Self`] _to_ `OB`, as in:
|
||
///
|
||
/// ```text
|
||
/// (Self) -> (OB)
|
||
/// ```
|
||
///
|
||
/// While the data on the graph itself is dynamic and provided at runtime,
|
||
/// the systems that _construct_ the graph using the runtime data can be
|
||
/// statically analyzed by the type system to ensure that they only
|
||
/// construct graphs that adhere to this schema.
|
||
pub trait ObjectRelTo<OB: ObjectKind + ObjectRelatable> =
|
||
ObjectRelatable + AsgRelMut<OB>
|
||
where <Self as ObjectRelatable>::Rel: From<ObjectIndex<OB>>;
|
||
|
||
/// Reverse of [`ObjectRelTo`].
|
||
///
|
||
/// This is primarily useful for avoiding `where` clauses,
|
||
/// or for use in `impl Trait` specifications.
|
||
pub trait ObjectRelFrom<OA: ObjectKind + ObjectRelatable> =
|
||
ObjectRelatable where <OA as ObjectRelatable>::Rel: From<ObjectIndex<Self>>;
|
||
|
||
/// Indicate that an [`ObjectKind`] `Self` _could possibly take ownership
|
||
/// over_ an [`ObjectKind`] `OB`.
|
||
///
|
||
/// This is a stronger assertion than [`ObjectRelTo`];
|
||
/// see that trait for more information.
|
||
/// This trait is intended to be used in contexts where the distinction
|
||
/// between reference and ownership is important.
|
||
pub trait ObjectTreeRelTo<OB: ObjectKind + ObjectRelatable>:
|
||
ObjectRelTo<OB>
|
||
{
|
||
}
|
||
|
||
/// Identify [`Self::Rel`] as a sum type consisting of the subset of
|
||
/// [`Object`] variants representing the valid _target_ edges of
|
||
/// [`Self`].
|
||
///
|
||
/// This is used to derive [`ObjectRelTo``],
|
||
/// which can be used as a trait bound to assert a valid relationship
|
||
/// between two [`Object`]s.
|
||
pub trait ObjectRelatable: ObjectKind {
|
||
/// Sum type representing a subset of [`Object`] variants that are valid
|
||
/// targets for edges from [`Self`].
|
||
///
|
||
/// See [`ObjectRel`] for more information.
|
||
type Rel: ObjectRel<Self>;
|
||
|
||
/// The [`ObjectRelTy`] tag used to identify this [`ObjectKind`] as a
|
||
/// target of a relation.
|
||
fn rel_ty() -> ObjectRelTy;
|
||
|
||
/// Represent a relation to another [`ObjectKind`] that cannot be
|
||
/// statically known and must be handled at runtime.
|
||
///
|
||
/// A value of [`None`] means that the provided [`ObjectRelTy`] is not
|
||
/// valid for [`Self`].
|
||
/// If the caller is utilizing edge data that is already present on the graph,
|
||
/// then this means that the system is not properly upholding edge
|
||
/// invariants
|
||
/// (the graph's ontology)
|
||
/// and the system ought to panic;
|
||
/// this is a significant bug representing a problem with the
|
||
/// correctness of the system.
|
||
///
|
||
/// See [`ObjectRel`] for more information.
|
||
fn new_rel_dyn(
|
||
ty: ObjectRelTy,
|
||
oi: ObjectIndex<Object>,
|
||
) -> Option<Self::Rel>;
|
||
|
||
/// Cast the provided [`ObjectIndex`] into an [`ObjectIndexTo`] if it is
|
||
/// able to be related to the provided `OB`.
|
||
///
|
||
/// This is intended to be used in a dynamic context,
|
||
/// where the caller is not aware statically of the [`ObjectKind`]s
|
||
/// involved.
|
||
/// If it is _required_ that an object be relatable,
|
||
/// use [`ObjectRelTo`] to statically verify that assertion.
|
||
///
|
||
/// If the type `OB` is not a valid target of a relation from this type,
|
||
/// [`None`] will be returned.
|
||
fn oi_rel_to_dyn<OB: ObjectRelatable>(
|
||
oi: ObjectIndex<Self>,
|
||
) -> Option<ObjectIndexTo<OB>>;
|
||
}
|
||
|
||
impl<O: ObjectKind + ObjectRelatable> ObjectIndex<O> {
|
||
pub fn rel_ty(&self) -> ObjectRelTy {
|
||
O::rel_ty()
|
||
}
|
||
}
|
||
|
||
/// A relationship to another [`ObjectKind`].
|
||
///
|
||
/// This trait is intended to be implemented by enums that represent the
|
||
/// subset of [`ObjectKind`]s that are able to serve as edge targets for
|
||
/// the [`ObjectRelatable`] that utilizes it as its
|
||
/// [`ObjectRelatable::Rel`].
|
||
///
|
||
/// As described in the [module-level documentation](super),
|
||
/// the concrete [`ObjectKind`] of an edge is generally not able to be
|
||
/// determined statically outside of code paths that created the
|
||
/// [`Object`] anew.
|
||
/// But we _can_ at least narrow the types of [`ObjectKind`]s to those
|
||
/// [`ObjectRelTo`]s that we know are valid,
|
||
/// since the system is restricted (statically) to those edges when
|
||
/// performing operations on the graph.
|
||
///
|
||
/// This [`ObjectRel`] represents that subset of [`ObjectKind`]s.
|
||
/// A caller may decide to dispatch based on the type of edge it receives,
|
||
/// or it may filter edges with [`Self::narrow`] in conjunction with
|
||
/// [`Iterator::filter_map`]
|
||
/// (for example).
|
||
/// Since the wrapped value is an [`ObjectIndex`],
|
||
/// the system will eventually panic if it attempts to reference a node
|
||
/// that is not of the type expected by the edge,
|
||
/// which can only happen if the edge has an incorrect [`ObjectRelTy`],
|
||
/// meaning the graph is somehow corrupt
|
||
/// (because system invariants were not upheld).
|
||
///
|
||
/// This affords us both runtime memory safety and static guarantees that
|
||
/// the system is not able to generate an invalid graph that does not
|
||
/// adhere to the prescribed ontology,
|
||
/// provided that invariants are properly upheld by the
|
||
/// [`asg`](crate::asg) module.
|
||
pub trait ObjectRel<OA: ObjectKind + ObjectRelatable>:
|
||
Sized + Into<ObjectIndex<Object>>
|
||
{
|
||
/// Attempt to narrow into the [`ObjectKind`] `OB`.
|
||
///
|
||
/// Unlike [`Object`] nodes,
|
||
/// _this operation does not panic_,
|
||
/// instead returning an [`Option`].
|
||
/// If the relationship is of type `OB`,
|
||
/// then [`Some`] will be returned with an inner
|
||
/// [`ObjectIndex<OB>`](ObjectIndex).
|
||
/// If the narrowing fails,
|
||
/// [`None`] will be returned instead.
|
||
///
|
||
/// This return value is well-suited for [`Iterator::filter_map`] to
|
||
/// query for edges of particular kinds.
|
||
fn narrow<OB: ObjectRelFrom<OA> + ObjectRelatable>(
|
||
self,
|
||
) -> Option<ObjectIndex<OB>> {
|
||
self.narrow_ref()
|
||
}
|
||
|
||
/// Attempt to narrow into the [`ObjectKind`] `OB`.
|
||
///
|
||
/// This method is the same as [`Self::narrow`],
|
||
/// but taking a reference instead of ownership.
|
||
fn narrow_ref<OB: ObjectRelFrom<OA> + ObjectRelatable>(
|
||
&self,
|
||
) -> Option<ObjectIndex<OB>>;
|
||
|
||
/// Attempt to narrow into the [`ObjectKind`] `OB`,
|
||
/// but rather than returning the narrowed type,
|
||
/// return `Option<Self>`.
|
||
///
|
||
/// This can be used with [`Iterator::filter_map`].
|
||
/// By not being a [`bool`] predicate,
|
||
/// we're able to provide a default trait implementation based on
|
||
/// [`Self::narrow`] without requiring that [`Self`] implement
|
||
/// [`Copy`].
|
||
fn narrows_into<OB: ObjectRelFrom<OA> + ObjectRelatable>(
|
||
self,
|
||
) -> Option<Self>
|
||
where
|
||
Self: From<ObjectIndex<OB>>,
|
||
{
|
||
self.narrow::<OB>().map(Into::into)
|
||
}
|
||
|
||
/// Widen into an [`ObjectIndex`],
|
||
/// discarding static type information.
|
||
fn widen(self) -> ObjectIndex<Object> {
|
||
self.into()
|
||
}
|
||
|
||
/// Whether this relationship represents an ontological cross edge.
|
||
///
|
||
/// A _cross edge_ is an edge between two trees as described by the
|
||
/// graph's ontology.
|
||
/// Many objects on the graph represent trees,
|
||
/// but contain references to other trees.
|
||
/// Recognizing cross edges allows the system to understand when it is
|
||
/// following an edge between two trees,
|
||
/// which may require different behavior.
|
||
///
|
||
/// This contrasts to cross edges in the context of a graph traversal,
|
||
/// where a tree is determined by a walk of the graph and may not take
|
||
/// into consideration the meaning of edges.
|
||
///
|
||
/// _Because this is a property of the ontology rather than a structural
|
||
/// interpretation of the graph,
|
||
/// it must be manually verified by a human._
|
||
/// An incorrect flagging of cross edges here will result in certain
|
||
/// traversals being incorrect.
|
||
///
|
||
/// Implementation Context
|
||
/// ======================
|
||
/// It is important to understand why this method exists and how it may
|
||
/// be used so that implementations of this trait do the right thing
|
||
/// with regards to determining whether an edge ought to represent a
|
||
/// cross edge.
|
||
///
|
||
/// For example,
|
||
/// when generating a representation of an [`Expr`],
|
||
/// a walk of the graph ought not consider an [`Ident`] reference to
|
||
/// be part of the expression tree,
|
||
/// otherwise the referenced expression would be inlined.
|
||
/// Furthermore,
|
||
/// visiting the referenced [`Ident`] ought not inhibit a later walk,
|
||
/// since the walk must later traverse the [`Ident`] to reach the
|
||
/// [`Object`] that it represents.
|
||
/// Similarly,
|
||
/// if the [`Ident`] has already been visited by a previous walk,
|
||
/// we want to _re-visit_ it to output a reference as part of the
|
||
/// referencing [`Expr`].
|
||
///
|
||
/// However,
|
||
/// this behavior is not always desirable.
|
||
/// In the case of a topological sort of the graph for linking,
|
||
/// cross edges ought to count as visitations since that dependency
|
||
/// must be calculated before the expression that needs it,
|
||
/// and we don't want to re-calculate it again later on.
|
||
///
|
||
/// The cross-edge is therefore an ontological fact,
|
||
/// but its _interpretation_ is context-dependent.
|
||
///
|
||
/// Note that the ontology is not intended to support back edges,
|
||
/// since they produce cycles,
|
||
/// except for exceptional situations
|
||
/// (e.g. function recursion which will hopefully be removed from
|
||
/// the language in the future).
|
||
/// With that said,
|
||
/// if an edge could conceivably be a back edge and not be rejected
|
||
/// from circular dependency checks,
|
||
/// then do _not_ assume that it is a cross edge without further
|
||
/// analysis,
|
||
/// which may require introducing more context to this method.
|
||
///
|
||
/// Dynamic Cross Edges
|
||
/// ==================
|
||
/// Sometimes a cross edge cannot be determined statically due to
|
||
/// ontological compromises.
|
||
/// For example,
|
||
/// a [`Tpl`]->[`Ident`] edge could be a reference to another tree,
|
||
/// as in the case of template application,
|
||
/// or the template could be serving as a container for that
|
||
/// definition.
|
||
/// The former case is a cross edge,
|
||
/// but the ladder is not.
|
||
///
|
||
/// We could introduce a layer of indirection on the graph to
|
||
/// disambiguate,
|
||
/// but that adds complexity to the graph that many different
|
||
/// subsystems need to concern themselves with.
|
||
/// But cross edge determination is fairly isolated,
|
||
/// needed only by traversals.
|
||
///
|
||
/// Therefore,
|
||
/// this method also receives a [`DynObjectRel`] reference,
|
||
/// which contains edge information.
|
||
/// The edge can be augmented with data that helps to determine,
|
||
/// at runtime,
|
||
/// whether that particular edge is a cross edge.
|
||
///
|
||
/// The use of [`DynObjectRel`] is heavy and effectively makes this
|
||
/// method useless for callers that do not deal directly with raw
|
||
/// [`Asg`] data;
|
||
/// it may be useful to refine this further in the future to correct
|
||
/// that,
|
||
/// once all use cases are clear.
|
||
fn is_cross_edge<S, T>(&self, rel: &DynObjectRel<S, T>) -> bool;
|
||
|
||
/// Whether the provided relationship represents a valid recursive
|
||
/// target.
|
||
///
|
||
/// It is expected that this method will be consulted only when the
|
||
/// provided [`ObjectIndex`] would produce a cycle when added to some
|
||
/// path.
|
||
/// This means that the source and target object will be identical.
|
||
///
|
||
/// It is expected that a cycle should be able to be "cut" at this point
|
||
/// while still producing a valid topological ordering of the graph.
|
||
/// For example,
|
||
/// consider two mutually recursive functions `A` and `B`,
|
||
/// as shown here:
|
||
///
|
||
/// ```text
|
||
/// A -> B
|
||
/// ^----'
|
||
/// ```
|
||
///
|
||
/// There are two cycles that might be encountered:
|
||
///
|
||
/// - `A -> B -> A`, which would cut to `A -> B`; and
|
||
/// - `B -> A -> B`, which would cut to `B -> A`.
|
||
///
|
||
/// In both cases,
|
||
/// since both `A` and `B` are functions,
|
||
/// a valid ordering is produced.
|
||
///
|
||
/// Failure to uphold this invariant when designing the graph's ontology
|
||
/// will result in an invalid ordering of the graph,
|
||
/// which will compile a program that does not behave according to
|
||
/// its specification.
|
||
/// That is:
|
||
/// proper ordering is a requirement to uphold soundness.
|
||
///
|
||
/// Recursion will continue to be limited as TAMER progresses,
|
||
/// migrating to a more APL-like alternative to solving
|
||
/// otherwise-recursive problems and restricting remaining recursion
|
||
/// to that which can provably terminate.
|
||
fn can_recurse(&self, _asg: &Asg) -> bool {
|
||
false
|
||
}
|
||
}
|
||
|
||
/// An [`ObjectIndex`]-like object that is able to relate to
|
||
/// [`ObjectKind`] `OB`.
|
||
///
|
||
/// This serves primarily as an opaque [`ObjectIndex`] that we know can be
|
||
/// related to some other type of [`ObjectKind`] `OB`.
|
||
/// This allows for generic graph operations that operate on relationships
|
||
/// without having to know the type of the source object (`Self`).
|
||
pub trait ObjectIndexRelTo<OB: ObjectRelatable>: Sized + Clone + Copy {
|
||
/// The [`ObjectRelTy`] of the inner [`ObjectIndex`] before widening.
|
||
fn src_rel_ty(&self) -> ObjectRelTy;
|
||
|
||
/// Widen this type into a generic [`ObjectIndex`] with no
|
||
/// [`ObjectKind`] information.
|
||
///
|
||
/// See [`ObjectIndex::widen`] for more information.
|
||
fn widen(&self) -> ObjectIndex<Object>;
|
||
|
||
/// Request permission to add an edge from `self` to another object.
|
||
///
|
||
/// This gives the object ownership over the edges that are created,
|
||
/// in addition to the static guarantees provided by
|
||
/// [`ObjectIndexRelTo`].
|
||
/// Since [`ObjectIndexRelTo` supports dynamic source objects,
|
||
/// this allows calling code to be written in a concise manner that is
|
||
/// agnostic to the source type,
|
||
/// without sacrificing edge ownership.
|
||
///
|
||
/// For more information,
|
||
/// see [`AsgRelMut::pre_add_edge`].
|
||
///
|
||
/// _This should only be called by [`Asg`]_;
|
||
/// `commit` is expected to be a continuation that adds the edge to
|
||
/// the graph,
|
||
/// and the object represented by `self` may modify itself expecting
|
||
/// such an edge to be added.
|
||
fn pre_add_edge(
|
||
&self,
|
||
asg: &mut Asg,
|
||
to_oi: ObjectIndex<OB>,
|
||
ctx_span: Option<Span>,
|
||
) -> Result<(), AsgError>;
|
||
|
||
/// Check whether an edge exists from `self` to `to_oi`.
|
||
fn has_edge_to(&self, asg: &Asg, to_oi: ObjectIndex<OB>) -> bool {
|
||
asg.has_edge(*self, to_oi)
|
||
}
|
||
|
||
/// Iterate over the [`ObjectIndex`]es of the outgoing edges of `self`
|
||
/// that match the [`ObjectKind`] `OB`.
|
||
///
|
||
/// Since this trait only guarantees edges to `OB`,
|
||
/// only edges targeting that type will be returned;
|
||
/// other types of edges may or may not exist.
|
||
/// See also [`ObjectIndex::edges_filtered`].
|
||
fn edges_rel_to<'a>(
|
||
&self,
|
||
asg: &'a Asg,
|
||
) -> impl Iterator<Item = ObjectIndex<OB>> + 'a {
|
||
asg.edges_dyn(self.widen())
|
||
.filter_map(|rel| rel.filter_into_target())
|
||
}
|
||
|
||
/// Attempt to look up a locally bound [`Ident`] via a linear search of
|
||
/// `self`'s edges.
|
||
///
|
||
/// This should be used only when an index is not available,
|
||
/// and is currently restricted to tests.
|
||
///
|
||
/// Performance
|
||
/// ===========
|
||
/// _This is a linear (O(1)) search of the edges of the node
|
||
/// corresponding to `self`!_
|
||
/// At the time of writing,
|
||
/// edges are stored using index references in a manner similar to a
|
||
/// linked list (petgraph).
|
||
/// And for each such edge,
|
||
/// the target object must be resolved so that its
|
||
/// [`SymbolId`](crate::sym::SymbolId) may be retrieved and compared
|
||
/// against the provided `name`.
|
||
///
|
||
/// If the number of edges is small and the objects are fairly localized
|
||
/// in memory relative to `self`,
|
||
/// then this may not be a concern.
|
||
/// However,
|
||
/// if you've arrived at this method while investigating unfavorable
|
||
/// circumstances during profiling,
|
||
/// then you should consider caching like the global environment
|
||
/// (see [`Asg::lookup`]).
|
||
#[cfg(test)]
|
||
fn lookup_local_linear(
|
||
&self,
|
||
asg: &Asg,
|
||
name: crate::parse::util::SPair,
|
||
) -> Option<ObjectIndex<Ident>>
|
||
where
|
||
Self: ObjectIndexRelTo<Ident>,
|
||
{
|
||
// Rust fails to infer OB with `self.edges_rel_to` as of 2023-03
|
||
ObjectIndexRelTo::<Ident>::edges_rel_to(self, asg).find(|oi| {
|
||
oi.resolve(asg).name().map(|name| name.symbol())
|
||
== Some(name.symbol())
|
||
})
|
||
}
|
||
}
|
||
|
||
impl<O: ObjectRelatable, OB: ObjectRelatable> ObjectIndexRelTo<OB>
|
||
for ObjectIndex<O>
|
||
where
|
||
O: ObjectRelTo<OB>,
|
||
{
|
||
fn src_rel_ty(&self) -> ObjectRelTy {
|
||
O::rel_ty()
|
||
}
|
||
|
||
fn widen(&self) -> ObjectIndex<Object> {
|
||
ObjectIndex::<O>::widen(*self)
|
||
}
|
||
|
||
fn pre_add_edge(
|
||
&self,
|
||
asg: &mut Asg,
|
||
to_oi: ObjectIndex<OB>,
|
||
ctx_span: Option<Span>,
|
||
) -> Result<(), AsgError> {
|
||
O::pre_add_edge(
|
||
asg,
|
||
ProposedRel {
|
||
from_oi: self.widen().must_narrow_into::<O>(),
|
||
to_oi,
|
||
ctx_span,
|
||
},
|
||
)
|
||
}
|
||
}
|
||
|
||
impl<OB: ObjectRelatable> ObjectIndexRelTo<OB> for ObjectIndexTo<OB> {
|
||
fn src_rel_ty(&self) -> ObjectRelTy {
|
||
match self {
|
||
Self((_, ty), _) => *ty,
|
||
}
|
||
}
|
||
|
||
fn widen(&self) -> ObjectIndex<Object> {
|
||
*self.as_ref()
|
||
}
|
||
|
||
fn pre_add_edge(
|
||
&self,
|
||
asg: &mut Asg,
|
||
to_oi: ObjectIndex<OB>,
|
||
ctx_span: Option<Span>,
|
||
) -> Result<(), AsgError> {
|
||
macro_rules! pre_add_edge {
|
||
($ty:ident) => {
|
||
$ty::pre_add_edge(
|
||
asg,
|
||
ProposedRel {
|
||
from_oi: self.widen().must_narrow_into::<$ty>(),
|
||
to_oi,
|
||
ctx_span,
|
||
},
|
||
)
|
||
};
|
||
}
|
||
|
||
match self.src_rel_ty() {
|
||
ObjectRelTy::Root => pre_add_edge!(Root),
|
||
ObjectRelTy::Pkg => pre_add_edge!(Pkg),
|
||
ObjectRelTy::Ident => pre_add_edge!(Ident),
|
||
ObjectRelTy::Expr => pre_add_edge!(Expr),
|
||
ObjectRelTy::Tpl => pre_add_edge!(Tpl),
|
||
ObjectRelTy::Meta => pre_add_edge!(Meta),
|
||
ObjectRelTy::Doc => pre_add_edge!(Doc),
|
||
}
|
||
}
|
||
}
|
||
|
||
impl<OB: ObjectRelatable> ObjectIndexRelTo<OB> for ObjectIndexToTree<OB> {
|
||
fn src_rel_ty(&self) -> ObjectRelTy {
|
||
match self {
|
||
Self(oito) => oito.src_rel_ty(),
|
||
}
|
||
}
|
||
|
||
fn widen(&self) -> ObjectIndex<Object> {
|
||
match self {
|
||
Self(oito) => oito.widen(),
|
||
}
|
||
}
|
||
|
||
fn pre_add_edge(
|
||
&self,
|
||
asg: &mut Asg,
|
||
to_oi: ObjectIndex<OB>,
|
||
ctx_span: Option<Span>,
|
||
) -> Result<(), AsgError> {
|
||
match self {
|
||
Self(oito) => oito.pre_add_edge(asg, to_oi, ctx_span),
|
||
}
|
||
}
|
||
}
|
||
|
||
impl<OB: ObjectRelatable> From<ObjectIndexTo<OB>> for ObjectIndex<Object> {
|
||
fn from(oi_rel: ObjectIndexTo<OB>) -> Self {
|
||
oi_rel.widen()
|
||
}
|
||
}
|
||
|
||
impl<OB: ObjectRelatable> AsRef<ObjectIndex<Object>> for ObjectIndexTo<OB> {
|
||
fn as_ref(&self) -> &ObjectIndex<Object> {
|
||
match self {
|
||
Self((oi, _), _) => oi,
|
||
}
|
||
}
|
||
}
|
||
|
||
/// An [`ObjectIndex`]-like object that is able to create a _tree_ edge to
|
||
/// [`ObjectKind`] `OB`.
|
||
///
|
||
/// This allows for generic graph operations that operate on ownership
|
||
/// relationships without having to know the type of the source
|
||
/// object (`Self`).
|
||
///
|
||
/// This is a specialization of [`ObjectIndexRelTo`].
|
||
pub trait ObjectIndexTreeRelTo<OB: ObjectRelatable>:
|
||
ObjectIndexRelTo<OB> + Into<ObjectIndexToTree<OB>>
|
||
{
|
||
}
|
||
|
||
impl<OB: ObjectRelatable> ObjectIndexTreeRelTo<OB> for ObjectIndexToTree<OB> {}
|
||
|
||
impl<O: ObjectRelatable, OB: ObjectRelatable> ObjectIndexTreeRelTo<OB>
|
||
for ObjectIndex<O>
|
||
where
|
||
O: ObjectTreeRelTo<OB>,
|
||
{
|
||
}
|
||
|
||
pub use private::{ObjectIndexTo, ObjectIndexToTree};
|
||
|
||
/// Private inner module to ensure that nothing is able to bypass invariants
|
||
/// by constructing [`ObjectIndexTo`] manually.
|
||
mod private {
|
||
use std::hash::{Hash, Hasher};
|
||
|
||
use super::*;
|
||
|
||
/// Some [`ObjectIndex`] that is able to [`ObjectRelTo`] `OB`.
|
||
///
|
||
/// This type upholds the invariant that any [`ObjectIndex`] contained
|
||
/// within is [`ObjectRelTo`] `OB`.
|
||
/// This allows this object to serve in place of a concrete
|
||
/// [`ObjectIndex`] for graph operations that need only know whether
|
||
/// an object is relatable to another,
|
||
/// such as when adding edges.
|
||
///
|
||
/// This object is only needed when relations need to be manipulated on
|
||
/// a known target [`ObjectKind`] `OB`,
|
||
/// but the source [`ObjectKind`] is dynamic.
|
||
/// This is necessary because a generic [`Object`] must first be
|
||
/// narrowed before being able to be used in any graph operation so
|
||
/// that the ontology can be statically enforced.
|
||
///
|
||
/// See [`ObjectIndexRelTo`] for more information.
|
||
///
|
||
/// Constructing [`ObjectIndexTo`]
|
||
/// ==============================
|
||
/// This object is intended to be constructed using [`From`].
|
||
/// _Never construct this object in any other way;_
|
||
/// manually creating the struct will not uphold its invariants,
|
||
/// which can lead to an invalid graph construction,
|
||
/// which will in turn lead to internal system failures when trying
|
||
/// to operate on the graph data down the line.
|
||
/// There are no memory safety concerns.
|
||
#[derive(Debug)]
|
||
pub struct ObjectIndexTo<OB: ObjectRelatable>(
|
||
(ObjectIndex<Object>, ObjectRelTy),
|
||
PhantomData<OB>,
|
||
);
|
||
|
||
impl<OB: ObjectRelatable, O: ObjectRelatable> From<ObjectIndex<O>>
|
||
for ObjectIndexTo<OB>
|
||
where
|
||
O: ObjectRelTo<OB>,
|
||
{
|
||
fn from(oi: ObjectIndex<O>) -> Self {
|
||
Self(oi.widen_dyn_ty(), PhantomData::default())
|
||
}
|
||
}
|
||
|
||
impl<OB: ObjectRelatable> ObjectIndexTo<OB> {
|
||
pub fn span(&self) -> Span {
|
||
(*self).into()
|
||
}
|
||
|
||
/// Assert a reflexive relationship between `OB` and `OC`.
|
||
///
|
||
/// The types `OB` and `OC` are equivalent (and therefore reflexive)
|
||
/// iff they have matching `ObjectRelTy`s.
|
||
///
|
||
/// The sole purpose of this method is to satisfy Rust's type system
|
||
/// in dynamic situations where the type system is not able to
|
||
/// understand what we're doing,
|
||
/// where the type `OC` is more general than the type `OB`.
|
||
/// This method is always safe;
|
||
/// it will return [`None`] if the two types differ in runtime
|
||
/// value.
|
||
///
|
||
/// While the term "reflexive" is a binary relation in mathematics,
|
||
/// the term "reflexivity" originates from the Coq tactic.
|
||
///
|
||
/// For an example of where this is needed,
|
||
/// see [`ObjectRelatable::oi_rel_to_dyn`].
|
||
pub fn reflexivity<OC: ObjectRelatable>(
|
||
self,
|
||
) -> Option<ObjectIndexTo<OC>> {
|
||
let Self(parts, _) = self;
|
||
(OB::rel_ty() == OC::rel_ty())
|
||
.then_some(ObjectIndexTo(parts, PhantomData::default()))
|
||
}
|
||
}
|
||
|
||
// Ignore metadata that should always be consistent with the underlying
|
||
// `ObjectIndex`.
|
||
impl<OB: ObjectRelatable> PartialEq for ObjectIndexTo<OB> {
|
||
fn eq(&self, other: &Self) -> bool {
|
||
match (self, other) {
|
||
(Self((oi, _), _), Self((oi_other, _), _)) => oi == oi_other,
|
||
}
|
||
}
|
||
}
|
||
|
||
impl<OB: ObjectRelatable> Eq for ObjectIndexTo<OB> {}
|
||
|
||
// Ignore metadata that should always be consistent with the underlying
|
||
// `ObjectIndex`.
|
||
impl<OB: ObjectRelatable> Hash for ObjectIndexTo<OB> {
|
||
fn hash<H: Hasher>(&self, state: &mut H) {
|
||
match self {
|
||
Self((oi, _), _) => oi.hash(state),
|
||
}
|
||
}
|
||
}
|
||
|
||
// Deriving `Clone`/`Copy` as of 2023-03 was introducing a
|
||
// `Clone`/`Copy` bound on `OB`.
|
||
impl<OB: ObjectRelatable> Clone for ObjectIndexTo<OB> {
|
||
fn clone(&self) -> Self {
|
||
Self(self.0, self.1)
|
||
}
|
||
}
|
||
|
||
impl<OB: ObjectRelatable> Copy for ObjectIndexTo<OB> {}
|
||
|
||
impl<OB: ObjectRelatable> From<ObjectIndexTo<OB>> for Span {
|
||
fn from(oi: ObjectIndexTo<OB>) -> Self {
|
||
match oi {
|
||
ObjectIndexTo((oi, _), _) => oi.span(),
|
||
}
|
||
}
|
||
}
|
||
|
||
impl<OB: ObjectRelatable> From<ObjectIndexToTree<OB>> for ObjectIndexTo<OB> {
|
||
fn from(value: ObjectIndexToTree<OB>) -> Self {
|
||
match value {
|
||
ObjectIndexToTree(oit) => oit,
|
||
}
|
||
}
|
||
}
|
||
|
||
/// Some [`ObjectIndex`] that can create a _tree_ edge to `OB`.
|
||
///
|
||
/// This is a specialization of
|
||
/// (and contains)
|
||
/// [`ObjectIndexTo`];
|
||
/// see that for more information.
|
||
///
|
||
/// See also [`ObjectIndexTreeRelTo`].
|
||
#[derive(Debug)]
|
||
pub struct ObjectIndexToTree<OB: ObjectRelatable>(ObjectIndexTo<OB>);
|
||
|
||
impl<OB: ObjectRelatable, O: ObjectRelatable> From<ObjectIndex<O>>
|
||
for ObjectIndexToTree<OB>
|
||
where
|
||
O: ObjectTreeRelTo<OB>,
|
||
{
|
||
fn from(oi: ObjectIndex<O>) -> Self {
|
||
Self(oi.into())
|
||
}
|
||
}
|
||
|
||
// Deriving any of the below were introducing trait bounds on `OB`.
|
||
|
||
impl<OB: ObjectRelatable> PartialEq for ObjectIndexToTree<OB> {
|
||
fn eq(&self, other: &Self) -> bool {
|
||
match (self, other) {
|
||
(Self(oi), Self(oi_other)) => oi == oi_other,
|
||
}
|
||
}
|
||
}
|
||
|
||
impl<OB: ObjectRelatable> Eq for ObjectIndexToTree<OB> {}
|
||
|
||
impl<OB: ObjectRelatable> Hash for ObjectIndexToTree<OB> {
|
||
fn hash<H: Hasher>(&self, state: &mut H) {
|
||
match self {
|
||
Self(oi) => oi.hash(state),
|
||
}
|
||
}
|
||
}
|
||
|
||
impl<OB: ObjectRelatable> Clone for ObjectIndexToTree<OB> {
|
||
fn clone(&self) -> Self {
|
||
Self(self.0)
|
||
}
|
||
}
|
||
|
||
impl<OB: ObjectRelatable> Copy for ObjectIndexToTree<OB> {}
|
||
|
||
impl<OB: ObjectRelatable> From<ObjectIndexToTree<OB>> for Span {
|
||
fn from(oi: ObjectIndexToTree<OB>) -> Self {
|
||
match oi {
|
||
ObjectIndexToTree(inner) => inner.span(),
|
||
}
|
||
}
|
||
}
|
||
}
|