tamer: asg::graph::Asg{Object=>Rel}Mut: Trait-level target type

This allows for a declarative matching on edge targets using the trait
system, rather than having to convert the type to a runtime value to match
on (which doesn't make a whole lot of sense).

See a commit to follow shortly (with Tpl) for an example use case.

DEV-13163

tamer/src/asg/graph.rs

@@ -393,7 +393,7 @@ fn diagnostic_node_missing_desc<O: ObjectKind>(
     ]
 }
 
-/// Mutation of an [`Object`] or its edges on the [`Asg`].
+/// Mutation of an [`Object`]'s relationships (edges) on the [`Asg`].
 ///
 /// This trait is intended to delegate certain responsibilities to
 ///   [`ObjectKind`]s so that they may enforce their own invariants with
@@ -403,7 +403,7 @@ fn diagnostic_node_missing_desc<O: ObjectKind>(
 ///   trait,
 ///     but the current module structure together with Rust's visibility
 ///     with sibling modules doesn't seem to make that possible.
-pub trait AsgObjectMut: ObjectKind {
+pub trait AsgRelMut<OB: ObjectRelatable>: ObjectKind {
     /// Allow an object to handle or reject the creation of an edge from it
     ///   to another object.
     ///
@@ -434,7 +434,7 @@ pub trait AsgObjectMut: ObjectKind {
     /// Unlike the type of [`Asg::add_edge`],
     ///   the source [`ObjectIndex`] has been narrowed to the appropriate
     ///   type for you.
-    fn pre_add_edge<OB: ObjectKind + ObjectRelatable>(
+    fn pre_add_edge(
         asg: &mut Asg,
         _from_oi: ObjectIndex<Self>,
         _to_oi: ObjectIndex<OB>,

tamer/src/asg/graph/object.rs

@@ -114,8 +114,8 @@
 //!   follow an edge to an unexpected [`ObjectKind`].
 //!
 //! In addition to these static guarantees,
-//!   [`AsgObjectMut`](super::AsgObjectMut) is utilized by [`Asg`] to
-//!   consult an object before an edge is added _from_ it,
+//!   [`AsgRelMut`](super::AsgRelMut) is utilized by [`Asg`] to consult an
+//!   object before an edge is added _from_ it,
 //!     allowing objects to assert ownership over their edges and cache
 //!     information about them as the graph is being built.
 
@@ -162,7 +162,7 @@ pub use tpl::Tpl;
 /// Often-needed exports for [`ObjectKind`]s.
 pub mod prelude {
     pub use super::{
-        super::{super::error::AsgError, Asg, AsgObjectMut},
+        super::{super::error::AsgError, Asg, AsgRelMut},
         Object, ObjectIndex, ObjectIndexRelTo, ObjectKind, ObjectRel,
         ObjectRelFrom, ObjectRelTo, ObjectRelTy, ObjectRelatable,
         ObjectTreeRelTo,

tamer/src/asg/graph/object/doc.rs

@@ -92,4 +92,4 @@ object_rel! {
     }
 }
 
-impl AsgObjectMut for Doc {}
+impl<OB: ObjectRelatable> AsgRelMut<OB> for Doc {}

tamer/src/asg/graph/object/expr.rs

@@ -269,4 +269,4 @@ impl ObjectIndex<Expr> {
     }
 }
 
-impl AsgObjectMut for Expr {}
+impl<OB: ObjectRelatable> AsgRelMut<OB> for Expr {}

tamer/src/asg/graph/object/ident.rs

@@ -1406,7 +1406,7 @@ impl ObjectIndex<Ident> {
     }
 }
 
-impl AsgObjectMut for Ident {}
+impl<OB: ObjectRelatable> AsgRelMut<OB> for Ident {}
 
 #[cfg(test)]
 mod test;

tamer/src/asg/graph/object/meta.rs

@@ -307,4 +307,4 @@ impl ObjectIndex<Meta> {
     }
 }
 
-impl AsgObjectMut for Meta {}
+impl<OB: ObjectRelatable> AsgRelMut<OB> for Meta {}

tamer/src/asg/graph/object/pkg.rs

@@ -148,4 +148,4 @@ impl ObjectIndex<Pkg> {
     }
 }
 
-impl AsgObjectMut for Pkg {}
+impl<OB: ObjectRelatable> AsgRelMut<OB> for Pkg {}

tamer/src/asg/graph/object/rel.rs

@@ -27,7 +27,7 @@ use super::{
 };
 use crate::{
     asg::{
-        graph::{object::Tpl, AsgObjectMut},
+        graph::{object::Tpl, AsgRelMut},
         Asg, AsgError,
     },
     f::Functor,
@@ -504,7 +504,8 @@ impl<T: Display> Display for DynObjectRel<T> {
 ///   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 where <Self as ObjectRelatable>::Rel: From<ObjectIndex<OB>>;
+    ObjectRelatable + AsgRelMut<OB>
+    where <Self as ObjectRelatable>::Rel: From<ObjectIndex<OB>>;
 
 /// Reverse of [`ObjectRelTo`].
 ///
@@ -532,7 +533,7 @@ pub trait ObjectTreeRelTo<OB: ObjectKind + ObjectRelatable>:
 /// 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 + AsgObjectMut {
+pub trait ObjectRelatable: ObjectKind {
     /// Sum type representing a subset of [`Object`] variants that are valid
     ///   targets for edges from [`Self`].
     ///
@@ -840,7 +841,7 @@ pub trait ObjectIndexRelTo<OB: ObjectRelatable>: Sized + Clone + Copy {
     ///     without sacrificing edge ownership.
     ///
     /// For more information,
-    ///   see [`AsgObjectMut::pre_add_edge`].
+    ///   see [`AsgRelMut::pre_add_edge`].
     ///
     /// _This should only be called by [`Asg`]_;
     ///   `commit` is expected to be a continuation that adds the edge to

tamer/src/asg/graph/object/root.rs

@@ -71,4 +71,4 @@ impl ObjectIndex<Root> {
     }
 }
 
-impl AsgObjectMut for Root {}
+impl<OB: ObjectRelatable> AsgRelMut<OB> for Root {}

tamer/src/asg/graph/object/tpl.rs

@@ -132,4 +132,4 @@ impl ObjectIndex<Tpl> {
     }
 }
 
-impl AsgObjectMut for Tpl {}
+impl<OB: ObjectRelatable> AsgRelMut<OB> for Tpl {}