add a boilerplate reducing macro

examples/hello_world/implementation.rs

@@ -1,6 +1,7 @@
-use crate::class_table::{self, ClassTableQueryContext};
+use crate::class_table;
 use crate::compiler::{CompilerQueryContext, Interner};
 use salsa::dyn_descriptor::DynDescriptor;
+use salsa::query_context_storage;
 use salsa::BaseQueryContext;
 use salsa::Query;
 use salsa::QueryTable;
@@ -14,41 +15,13 @@ pub struct QueryContextImpl {
     execution_stack: RefCell<Vec<DynDescriptor>>,
 }
 
-// The intention is that plus the impl of `ClassTableQueryContext`
+query_context_storage! {
-// below will eventually be generated by a macro, so that you just
+    struct QueryContextImplStorage for storage in QueryContextImpl {
-// have to name the queries.
+        impl class_table::ClassTableQueryContext {
-
+            fn all_classes() for class_table::AllClasses;
-#[allow(non_snake_case)]
+            fn all_fields() for class_table::AllFields;
-#[derive(Default)]
+            fn fields() for class_table::Fields;
-struct QueryContextImplStorage {
+        }
-    AllClasses: <class_table::AllClasses as Query<QueryContextImpl>>::Storage,
-    AllFields: <class_table::AllFields as Query<QueryContextImpl>>::Storage,
-    Fields: <class_table::Fields as Query<QueryContextImpl>>::Storage,
-}
-
-impl ClassTableQueryContext for QueryContextImpl {
-    fn all_classes(&self) -> QueryTable<'_, Self, class_table::AllClasses> {
-        QueryTable::new(
-            self,
-            &self.storage.AllClasses,
-            DynDescriptor::from_key::<Self, class_table::AllClasses>,
-        )
-    }
-
-    fn all_fields(&self) -> QueryTable<'_, Self, class_table::AllFields> {
-        QueryTable::new(
-            self,
-            &self.storage.AllFields,
-            DynDescriptor::from_key::<Self, class_table::AllFields>,
-        )
-    }
-
-    fn fields(&self) -> QueryTable<'_, Self, class_table::Fields> {
-        QueryTable::new(
-            self,
-            &self.storage.Fields,
-            DynDescriptor::from_key::<Self, class_table::Fields>,
-        )
     }
 }
 

src/lib.rs

@@ -190,3 +190,52 @@ macro_rules! query_definition {
         }
     }
 }
+
+#[macro_export]
+macro_rules! query_context_storage {
+    (
+        $(#[$attr:meta])*
+        $v:vis struct $Storage:ident for $storage_field:ident in $QueryContext:ty {
+            $(
+                impl $TraitName:path {
+                    $(
+                        fn $query_method:ident() for $QueryType:path;
+                    )*
+                }
+            )*
+        }
+    ) => {
+        #[allow(non_snake_case)]
+        #[derive(Default)]
+        $(#[$attr])*
+        $v struct $Storage {
+            $(
+                $(
+                    $query_method: <$QueryType as $crate::Query<$QueryContext>>::Storage,
+                )*
+            )*
+        }
+
+        $(
+            impl $TraitName for $QueryContext {
+                $(
+                    fn $query_method(
+                        &self,
+                    ) -> $crate::QueryTable<'_, Self, $QueryType> {
+                        QueryTable::new(
+                            self,
+                            &self.$storage_field.$query_method,
+
+                            // FIXME: we should not hardcode the descriptor like this.
+                            // Have to think of the best fix.
+                            $crate::dyn_descriptor::DynDescriptor::from_key::<
+                                Self,
+                                $QueryType,
+                            >,
+                        )
+                }
+                )*
+            }
+        )*
+    };
+}