add helper methods to project MemoRef on some types

crates/graphql_network_protocol/src/graphql_network_protocol.rs

@@ -74,7 +74,7 @@ impl NetworkProtocol for GraphQLNetworkProtocol {
         let mut graphql_root_types = None;
 
         let (type_system_document, type_system_extension_documents) =
-            parse_graphql_schema(db).to_owned()?;
+            parse_graphql_schema(db).try_ok()?.split();
 
         let (mut result, mut directives, mut refetch_fields) =
             process_graphql_type_system_document(

crates/graphql_network_protocol/src/read_schema.rs

@@ -13,7 +13,7 @@ pub fn parse_graphql_schema<TNetworkProtocol: NetworkProtocol + 'static>(
     db: &IsographDatabase<TNetworkProtocol>,
 ) -> Result<
     (
-        MemoRef<GraphQLTypeSystemDocument>,
+        GraphQLTypeSystemDocument,
         BTreeMap<RelativePathToSourceFile, MemoRef<GraphQLTypeSystemExtensionDocument>>,
     ),
     WithLocation<SchemaParseError>,
@@ -35,18 +35,18 @@ pub fn parse_graphql_schema<TNetworkProtocol: NetworkProtocol + 'static>(
         .iter()
     {
         let extensions_document =
-            parse_schema_extensions_file(db, *schema_extension_source_id).to_owned()?;
+            parse_schema_extensions_file(db, *schema_extension_source_id).try_ok()?;
         schema_extensions.insert(*relative_path, extensions_document);
     }
 
-    Ok((db.intern(schema), schema_extensions))
+    Ok((schema, schema_extensions))
 }
 
 #[memo]
 pub fn parse_schema_extensions_file<TNetworkProtocol: NetworkProtocol + 'static>(
     db: &IsographDatabase<TNetworkProtocol>,
     schema_extension_source_id: SourceId<SchemaSource>,
-) -> Result<MemoRef<GraphQLTypeSystemExtensionDocument>, WithLocation<SchemaParseError>> {
+) -> Result<GraphQLTypeSystemExtensionDocument, WithLocation<SchemaParseError>> {
     let SchemaSource {
         content,
         text_source,
@@ -55,5 +55,5 @@ pub fn parse_schema_extensions_file<TNetworkProtocol: NetworkProtocol + 'static>
     let schema_extensions = parse_schema_extensions(content, *text_source)
         .map_err(|with_span| with_span.to_with_location(*text_source))?;
 
-    Ok(db.intern(schema_extensions))
+    Ok(schema_extensions)
 }

crates/pico/src/view.rs → crates/pico/src/field_view.rs

@@ -6,16 +6,16 @@ pub trait Counter: Singleton + Default + Copy + Eq + 'static {
     fn increment(self) -> Self;
 }
 
-pub type Projector<Db, T> = for<'a> fn(&'a Db) -> &'a T;
+pub type FieldProjector<Db, T> = for<'a> fn(&'a Db) -> &'a T;
 
-pub struct View<'a, Db: Database, T, C: Counter> {
+pub struct FieldView<'a, Db: Database, T, C: Counter> {
     db: &'a Db,
-    projector: Projector<Db, T>,
+    projector: FieldProjector<Db, T>,
     phantom: PhantomData<C>,
 }
 
-impl<'a, Db: Database, T, C: Counter> View<'a, Db, T, C> {
-    pub fn new(db: &'a Db, projector: Projector<Db, T>) -> Self {
+impl<'a, Db: Database, T, C: Counter> FieldView<'a, Db, T, C> {
+    pub fn new(db: &'a Db, projector: FieldProjector<Db, T>) -> Self {
         Self {
             db,
             projector,
@@ -44,16 +44,16 @@ impl<'a, Db: Database, T, C: Counter> View<'a, Db, T, C> {
     }
 }
 
-pub type ProjectorMut<Db, T> = for<'a> fn(&'a mut Db) -> &'a mut T;
+pub type FieldProjectorMut<Db, T> = for<'a> fn(&'a mut Db) -> &'a mut T;
 
-pub struct MutView<'a, Db: Database, T, C: Counter> {
+pub struct FieldViewMut<'a, Db: Database, T, C: Counter> {
     db: &'a mut Db,
-    projector: ProjectorMut<Db, T>,
+    projector: FieldProjectorMut<Db, T>,
     phantom: PhantomData<C>,
 }
 
-impl<'a, Db: Database, T, C: Counter> MutView<'a, Db, T, C> {
-    pub fn new(db: &'a mut Db, projector: ProjectorMut<Db, T>) -> Self {
+impl<'a, Db: Database, T, C: Counter> FieldViewMut<'a, Db, T, C> {
+    pub fn new(db: &'a mut Db, projector: FieldProjectorMut<Db, T>) -> Self {
         Self {
             db,
             projector,

crates/pico/src/lib.rs

@@ -4,23 +4,23 @@ mod derived_node;
 mod dyn_eq;
 mod epoch;
 mod execute_memoized_function;
+mod field_view;
 mod garbage_collection;
 mod index;
 mod intern;
 pub mod macro_fns;
 mod memo_ref;
 mod retained_query;
 mod source;
-mod view;
 mod with_serialize;
 
 pub use database::*;
 pub use derived_node::*;
 pub use dyn_eq::*;
 pub use execute_memoized_function::*;
+pub use field_view::*;
 pub use intern::*;
 pub use memo_ref::*;
 pub use retained_query::*;
 pub use source::*;
-pub use view::*;
 pub use with_serialize::*;

crates/pico/src/memo_ref.rs

@@ -1,13 +1,66 @@
-use std::{marker::PhantomData, ops::Deref};
+use std::{
+    any::Any,
+    hash::{Hash, Hasher},
+    marker::PhantomData,
+    ops::Deref,
+};
 
+use crate::{DatabaseDyn, DerivedNodeId, ParamId, dependency::NodeKind};
 use intern::InternId;
 
-use crate::{DatabaseDyn, DerivedNodeId, ParamId, dependency::NodeKind};
+type MemoRefProjectorStep = for<'a> fn(&'a dyn Any) -> &'a dyn Any;
+
+const MAX_PROJECTOR_STEPS: usize = 4;
+
+#[inline(always)]
+fn step_identity(value: &dyn Any) -> &dyn Any {
+    value
+}
+
+#[inline(always)]
+fn step_result_ok<T: 'static, E: 'static>(value: &dyn Any) -> &dyn Any {
+    match value
+        .downcast_ref::<Result<T, E>>()
+        .expect("MemoRef<Result<..>>: underlying value has unexpected type")
+    {
+        Ok(t) => t as &dyn Any,
+        Err(_) => unreachable!("Ok projection used only after Ok check"),
+    }
+}
+
+#[inline(always)]
+fn step_option_some<T: 'static>(value: &dyn Any) -> &dyn Any {
+    match value
+        .downcast_ref::<Option<T>>()
+        .expect("MemoRef<Option<..>>: underlying value has unexpected type")
+    {
+        Some(t) => t as &dyn Any,
+        None => unreachable!("Some projection used only after Some check"),
+    }
+}
+
+#[inline(always)]
+fn step_tuple_0<T0: 'static, T1: 'static>(value: &dyn Any) -> &dyn Any {
+    let (t0, _) = value
+        .downcast_ref::<(T0, T1)>()
+        .expect("MemoRef<(..)>: underlying value has unexpected type");
+    t0 as &dyn Any
+}
+
+#[inline(always)]
+fn step_tuple_1<T0: 'static, T1: 'static>(value: &dyn Any) -> &dyn Any {
+    let (_, t1) = value
+        .downcast_ref::<(T0, T1)>()
+        .expect("MemoRef<(..)>: underlying value has unexpected type");
+    t1 as &dyn Any
+}
 
 #[derive(Debug)]
 pub struct MemoRef<T> {
     pub(crate) db: *const dyn DatabaseDyn,
     pub(crate) derived_node_id: DerivedNodeId,
+    projectors: [MemoRefProjectorStep; MAX_PROJECTOR_STEPS],
+    projectors_len: u8,
     phantom: PhantomData<T>,
 }
 
@@ -27,12 +80,23 @@ impl<T> PartialEq for MemoRef<T> {
 
 impl<T> Eq for MemoRef<T> {}
 
+#[allow(clippy::unnecessary_cast)]
+impl<T> Hash for MemoRef<T> {
+    fn hash<H: Hasher>(&self, state: &mut H) {
+        let data_ptr = self.db as *const dyn DatabaseDyn as *const ();
+        data_ptr.hash(state);
+        self.derived_node_id.hash(state);
+    }
+}
+
 #[allow(clippy::unnecessary_cast)]
 impl<T: 'static + Clone> MemoRef<T> {
     pub fn new(db: &dyn DatabaseDyn, derived_node_id: DerivedNodeId) -> Self {
         Self {
             db: db as *const _ as *const dyn DatabaseDyn,
             derived_node_id,
+            projectors: [step_identity; MAX_PROJECTOR_STEPS],
+            projectors_len: 0,
             phantom: PhantomData,
         }
     }
@@ -63,6 +127,84 @@ impl<T: 'static> Deref for MemoRef<T> {
             NodeKind::Derived(self.derived_node_id),
             revision.time_updated,
         );
-        value.downcast_ref::<T>().unwrap()
+        if self.projectors_len == 0 {
+            return value
+                .downcast_ref::<T>()
+                .expect("MemoRef: projector chain produced unexpected type");
+        }
+        let mut any_ref = value;
+        let len = self.projectors_len as usize;
+        for step in &self.projectors[..len] {
+            any_ref = (step)(any_ref);
+        }
+        any_ref
+            .downcast_ref::<T>()
+            .expect("MemoRef: projector chain produced unexpected type")
+    }
+}
+
+impl<T: 'static, E: 'static + Clone> MemoRef<Result<T, E>> {
+    pub fn try_ok(self) -> Result<MemoRef<T>, E> {
+        match self.deref() {
+            Ok(_) => {
+                let mut next = MemoRef::<T> {
+                    db: self.db,
+                    derived_node_id: self.derived_node_id,
+                    projectors: self.projectors,
+                    projectors_len: self.projectors_len + 1,
+                    phantom: PhantomData,
+                };
+                let idx = self.projectors_len as usize;
+                next.projectors[idx] = step_result_ok::<T, E>;
+                Ok(next)
+            }
+            Err(err) => Err(err.clone()),
+        }
+    }
+}
+
+impl<T: 'static> MemoRef<Option<T>> {
+    pub fn try_some(self) -> Option<MemoRef<T>> {
+        match self.deref() {
+            Some(_) => {
+                let mut next = MemoRef::<T> {
+                    db: self.db,
+                    derived_node_id: self.derived_node_id,
+                    projectors: self.projectors,
+                    projectors_len: self.projectors_len + 1,
+                    phantom: PhantomData,
+                };
+                let idx = self.projectors_len as usize;
+                next.projectors[idx] = step_option_some::<T>;
+                Some(next)
+            }
+            None => None,
+        }
+    }
+}
+
+impl<T0: 'static, T1: 'static> MemoRef<(T0, T1)> {
+    pub fn split(self) -> (MemoRef<T0>, MemoRef<T1>) {
+        let mut left = MemoRef::<T0> {
+            db: self.db,
+            derived_node_id: self.derived_node_id,
+            projectors: self.projectors,
+            projectors_len: self.projectors_len + 1,
+            phantom: PhantomData,
+        };
+        let idx = self.projectors_len as usize;
+        left.projectors[idx] = step_tuple_0::<T0, T1>;
+
+        let mut right = MemoRef::<T1> {
+            db: self.db,
+            derived_node_id: self.derived_node_id,
+            projectors: self.projectors,
+            projectors_len: self.projectors_len + 1,
+            phantom: PhantomData,
+        };
+        let idx = self.projectors_len as usize;
+        right.projectors[idx] = step_tuple_1::<T0, T1>;
+
+        (left, right)
     }
 }

crates/pico/tests/intern.rs

@@ -39,23 +39,19 @@ enum ProcessInputError {
 }
 
 #[memo]
-fn first_letter(
-    db: &TestDatabase,
-    input_id: SourceId<Input>,
-) -> Result<MemoRef<char>, FirstLetterError> {
+fn first_letter(db: &TestDatabase, input_id: SourceId<Input>) -> Result<char, FirstLetterError> {
     db.get(input_id)
         .value
         .chars()
         .next()
         .ok_or(FirstLetterError::EmptyString)
-        .map(|v| db.intern(v))
 }
 
 #[memo]
 fn process_input(
     db: &TestDatabase,
     input_id: SourceId<Input>,
 ) -> Result<MemoRef<char>, ProcessInputError> {
-    let result = first_letter(db, input_id).to_owned()?;
+    let result = first_letter(db, input_id).try_ok()?;
     Ok(result)
 }