diff --git a/derive/src/enum.rs b/derive/src/enum.rs
index 2c2e15f1..e3e5859b 100644
--- a/derive/src/enum.rs
+++ b/derive/src/enum.rs
@@ -61,7 +61,7 @@ pub fn generate(enum_args: &args::Enum, input: &DeriveInput) -> Result<TokenStre
             .unwrap_or_else(|| quote! {None});
         enum_items.push(quote! { #(#item_attrs)* #item_ident});
         items.push(quote! {
-            #crate_name::EnumItem {
+            #crate_name::resolver_utils::EnumItem {
                 name: #gql_item_name,
                 value: #ident::#item_ident,
             }
@@ -77,8 +77,8 @@ pub fn generate(enum_args: &args::Enum, input: &DeriveInput) -> Result<TokenStre
 
     let expanded = quote! {
         #[allow(clippy::all, clippy::pedantic)]
-        impl #crate_name::EnumType for #ident {
-            fn items() -> &'static [#crate_name::EnumItem<#ident>] {
+        impl #crate_name::resolver_utils::EnumType for #ident {
+            fn items() -> &'static [#crate_name::resolver_utils::EnumItem<#ident>] {
                 &[#(#items),*]
             }
         }
@@ -107,18 +107,18 @@ pub fn generate(enum_args: &args::Enum, input: &DeriveInput) -> Result<TokenStre
         #[allow(clippy::all, clippy::pedantic)]
         impl #crate_name::InputValueType for #ident {
             fn parse(value: Option<#crate_name::Value>) -> #crate_name::InputValueResult<Self> {
-                #crate_name::EnumType::parse_enum(value.unwrap_or_default())
+                #crate_name::resolver_utils::parse_enum(value.unwrap_or_default())
             }
 
             fn to_value(&self) -> #crate_name::Value {
-                #crate_name::EnumType::to_value(self)
+                #crate_name::resolver_utils::enum_value(*self)
             }
         }
 
         #[#crate_name::async_trait::async_trait]
         impl #crate_name::OutputValueType for #ident {
             async fn resolve(&self, _: &#crate_name::ContextSelectionSet<'_>, _field: &#crate_name::Positioned<#crate_name::parser::types::Field>) -> #crate_name::Result<#crate_name::serde_json::Value> {
-                Ok(#crate_name::EnumType::to_value(self).into_json().unwrap())
+                Ok(#crate_name::resolver_utils::enum_value(*self).into_json().unwrap())
             }
         }
     };
diff --git a/src/lib.rs b/src/lib.rs
index 58419891..03fdf8d6 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -105,16 +105,15 @@ mod look_ahead;
 mod model;
 mod request;
 mod response;
-mod scalars;
 mod schema;
 mod serialize_resp;
 mod subscription;
-mod types;
 mod validation;
 
 pub mod extensions;
 pub mod guard;
 pub mod validators;
+pub mod types;
 
 #[doc(hidden)]
 pub mod resolver_utils;
@@ -145,15 +144,11 @@ pub use parser::{types::ConstValue as Value, Pos, Positioned};
 pub use registry::CacheControl;
 pub use request::Request;
 pub use response::Response;
-pub use scalars::{Any, Json, OutputJson, ID};
 pub use schema::{Schema, SchemaBuilder, SchemaEnv};
 pub use serde_json::Number;
 pub use subscription::SimpleBroker;
-pub use types::{
-    connection, EmptyMutation, EmptySubscription, MaybeUndefined, MergedObject,
-    MergedObjectSubscriptionTail, MergedObjectTail, Upload,
-};
 pub use validation::ValidationMode;
+pub use types::*;
 
 /// Result type
 pub type Result<T> = std::result::Result<T, Error>;
@@ -168,8 +163,6 @@ pub mod registry;
 pub use base::{InputObjectType, InputValueType, OutputValueType};
 #[doc(hidden)]
 pub use subscription::SubscriptionType;
-#[doc(hidden)]
-pub use types::{EnumItem, EnumType};
 
 /// Define a GraphQL object with methods
 ///
diff --git a/src/resolver_utils/enum.rs b/src/resolver_utils/enum.rs
new file mode 100644
index 00000000..f7ad3afc
--- /dev/null
+++ b/src/resolver_utils/enum.rs
@@ -0,0 +1,45 @@
+use crate::parser::types::Name;
+use crate::{InputValueError, InputValueResult, Type, Value};
+
+/// A variant of an enum.
+pub struct EnumItem<T> {
+    /// The name of the variant.
+    pub name: &'static str,
+    /// The value of the variant.
+    pub value: T,
+}
+
+/// An enum value.
+pub trait EnumType: Type + Sized + Eq + Send + Copy + Sized + 'static {
+    /// Get a list of the variants of the enum value.
+    fn items() -> &'static [EnumItem<Self>];
+}
+
+/// Parse a value as an enum value.
+///
+/// This can be used to implement `InputValueType::parse`.
+pub fn parse_enum<T: EnumType>(value: Value) -> InputValueResult<T> {
+    let value = match &value {
+        Value::Enum(s) => s,
+        Value::String(s) => s.as_str(),
+        _ => return Err(InputValueError::ExpectedType(value)),
+    };
+    
+    T::items()
+        .iter()
+        .find(|item| item.name == value)
+        .map(|item| item.value)
+        .ok_or_else(|| InputValueError::Custom(format!(
+            r#"Enumeration type "{}" does not contain the value "{}""#,
+            T::type_name(),
+            value,
+        )))
+}
+
+/// Convert the enum value into a GraphQL value.
+///
+/// This can be used to implement `InputValueType::to_value` or `OutputValueType::resolve`.
+pub fn enum_value<T: EnumType>(value: T) -> Value {
+    let item = T::items().iter().find(|item| item.value == value).unwrap();
+    Value::Enum(Name::new_unchecked(item.name.to_owned()))
+}
diff --git a/src/resolver_utils/mod.rs b/src/resolver_utils/mod.rs
index a3984912..2210a754 100644
--- a/src/resolver_utils/mod.rs
+++ b/src/resolver_utils/mod.rs
@@ -1,5 +1,7 @@
 //! Utilities for implementing `OutputValueType::resolve`.
 
 mod object;
+mod r#enum;
 
 pub use object::*;
+pub use r#enum::*;
diff --git a/src/scalars/mod.rs b/src/scalars/mod.rs
deleted file mode 100644
index d6081810..00000000
--- a/src/scalars/mod.rs
+++ /dev/null
@@ -1,84 +0,0 @@
-mod any;
-mod bool;
-mod datetime;
-mod floats;
-mod id;
-mod integers;
-mod json;
-mod naive_time;
-mod string;
-mod uuid;
-
-#[cfg(feature = "bson")]
-mod bson;
-#[cfg(feature = "chrono_tz")]
-mod chrono_tz;
-#[cfg(feature = "url")]
-mod url;
-
-pub use any::Any;
-pub use id::ID;
-pub use json::{Json, OutputJson};
-
-#[cfg(test)]
-mod tests {
-    use super::ID;
-    use crate::Type;
-    use bson::oid::ObjectId;
-    use chrono::{DateTime, FixedOffset, Local, NaiveDate, NaiveTime, Utc};
-    use uuid::Uuid;
-
-    #[test]
-    fn test_scalar_type() {
-        assert_eq!(<bool as Type>::type_name(), "Boolean");
-        assert_eq!(<bool as Type>::qualified_type_name(), "Boolean!");
-
-        assert_eq!(<i32 as Type>::type_name(), "Int");
-        assert_eq!(<i32 as Type>::qualified_type_name(), "Int!");
-
-        assert_eq!(<f32 as Type>::type_name(), "Float");
-        assert_eq!(<f32 as Type>::qualified_type_name(), "Float!");
-
-        assert_eq!(<&str as Type>::type_name(), "String");
-        assert_eq!(<&str as Type>::qualified_type_name(), "String!");
-
-        assert_eq!(<String as Type>::type_name(), "String");
-        assert_eq!(<String as Type>::qualified_type_name(), "String!");
-
-        assert_eq!(<ID as Type>::type_name(), "ID");
-        assert_eq!(<ID as Type>::qualified_type_name(), "ID!");
-
-        assert_eq!(<NaiveDate as Type>::type_name(), "NaiveDate");
-        assert_eq!(<NaiveDate as Type>::qualified_type_name(), "NaiveDate!");
-
-        assert_eq!(<NaiveTime as Type>::type_name(), "NaiveTime");
-        assert_eq!(<NaiveTime as Type>::qualified_type_name(), "NaiveTime!");
-
-        assert_eq!(<DateTime::<Utc> as Type>::type_name(), "DateTime");
-        assert_eq!(
-            <DateTime::<Utc> as Type>::qualified_type_name(),
-            "DateTime!"
-        );
-
-        assert_eq!(<DateTime::<Local> as Type>::type_name(), "DateTime");
-        assert_eq!(
-            <DateTime::<Local> as Type>::qualified_type_name(),
-            "DateTime!"
-        );
-
-        assert_eq!(<DateTime::<FixedOffset> as Type>::type_name(), "DateTime");
-        assert_eq!(
-            <DateTime::<FixedOffset> as Type>::qualified_type_name(),
-            "DateTime!"
-        );
-
-        assert_eq!(<Uuid as Type>::type_name(), "UUID");
-        assert_eq!(<Uuid as Type>::qualified_type_name(), "UUID!");
-
-        #[cfg(feature = "bson")]
-        {
-            assert_eq!(<ObjectId as Type>::type_name(), "ObjectId");
-            assert_eq!(<ObjectId as Type>::qualified_type_name(), "ObjectId!");
-        }
-    }
-}
diff --git a/src/scalars/any.rs b/src/types/any.rs
similarity index 100%
rename from src/scalars/any.rs
rename to src/types/any.rs
diff --git a/src/types/enum.rs b/src/types/enum.rs
deleted file mode 100644
index 3fedb84d..00000000
--- a/src/types/enum.rs
+++ /dev/null
@@ -1,44 +0,0 @@
-use crate::parser::types::Name;
-use crate::{InputValueError, InputValueResult, Type, Value};
-
-#[allow(missing_docs)]
-pub struct EnumItem<T> {
-    pub name: &'static str,
-    pub value: T,
-}
-
-#[allow(missing_docs)]
-#[async_trait::async_trait]
-pub trait EnumType: Type + Sized + Eq + Send + Copy + Sized + 'static {
-    fn items() -> &'static [EnumItem<Self>];
-
-    fn parse_enum(value: Value) -> InputValueResult<Self> {
-        let value = match &value {
-            Value::Enum(s) => s,
-            Value::String(s) => s.as_str(),
-            _ => return Err(InputValueError::ExpectedType(value)),
-        };
-
-        let items = Self::items();
-        for item in items {
-            if item.name == value {
-                return Ok(item.value);
-            }
-        }
-        Err(InputValueError::Custom(format!(
-            r#"Enumeration type "{}" does not contain the value "{}""#,
-            Self::type_name(),
-            value
-        )))
-    }
-
-    fn to_value(&self) -> Value {
-        let items = Self::items();
-        for item in items {
-            if item.value == *self {
-                return Value::Enum(Name::new_unchecked(item.name.to_owned()));
-            }
-        }
-        unreachable!()
-    }
-}
diff --git a/src/scalars/bool.rs b/src/types/external/bool.rs
similarity index 100%
rename from src/scalars/bool.rs
rename to src/types/external/bool.rs
diff --git a/src/scalars/bson.rs b/src/types/external/bson.rs
similarity index 100%
rename from src/scalars/bson.rs
rename to src/types/external/bson.rs
diff --git a/src/scalars/chrono_tz.rs b/src/types/external/chrono_tz.rs
similarity index 100%
rename from src/scalars/chrono_tz.rs
rename to src/types/external/chrono_tz.rs
diff --git a/src/scalars/datetime.rs b/src/types/external/datetime.rs
similarity index 100%
rename from src/scalars/datetime.rs
rename to src/types/external/datetime.rs
diff --git a/src/scalars/floats.rs b/src/types/external/floats.rs
similarity index 100%
rename from src/scalars/floats.rs
rename to src/types/external/floats.rs
diff --git a/src/scalars/integers.rs b/src/types/external/integers.rs
similarity index 100%
rename from src/scalars/integers.rs
rename to src/types/external/integers.rs
diff --git a/src/types/list.rs b/src/types/external/list.rs
similarity index 100%
rename from src/types/list.rs
rename to src/types/external/list.rs
diff --git a/src/types/external/mod.rs b/src/types/external/mod.rs
new file mode 100644
index 00000000..6253253b
--- /dev/null
+++ b/src/types/external/mod.rs
@@ -0,0 +1,16 @@
+//! Implementations of `Type`, `ScalarType`, etc on external types.
+
+mod string;
+mod list;
+mod optional;
+mod bool;
+mod integers;
+mod floats;
+mod url;
+mod uuid;
+mod datetime;
+
+#[cfg(feature = "bson")]
+mod bson;
+#[cfg(feature = "chrono_tz")]
+mod chrono_tz;
diff --git a/src/scalars/naive_time.rs b/src/types/external/naive_time.rs
similarity index 100%
rename from src/scalars/naive_time.rs
rename to src/types/external/naive_time.rs
diff --git a/src/types/optional.rs b/src/types/external/optional.rs
similarity index 100%
rename from src/types/optional.rs
rename to src/types/external/optional.rs
diff --git a/src/scalars/string.rs b/src/types/external/string.rs
similarity index 100%
rename from src/scalars/string.rs
rename to src/types/external/string.rs
diff --git a/src/scalars/url.rs b/src/types/external/url.rs
similarity index 100%
rename from src/scalars/url.rs
rename to src/types/external/url.rs
diff --git a/src/scalars/uuid.rs b/src/types/external/uuid.rs
similarity index 100%
rename from src/scalars/uuid.rs
rename to src/types/external/uuid.rs
diff --git a/src/scalars/id.rs b/src/types/id.rs
similarity index 90%
rename from src/scalars/id.rs
rename to src/types/id.rs
index 13abc2a4..81bd3bc8 100644
--- a/src/scalars/id.rs
+++ b/src/types/id.rs
@@ -10,7 +10,7 @@ use std::ops::{Deref, DerefMut};
 ///
 /// The input is a `&str`, `String`, `usize` or `uuid::UUID`, and the output is a string.
 #[derive(Clone, Ord, PartialOrd, Eq, PartialEq, Hash, Debug, Serialize, Deserialize)]
-pub struct ID(String);
+pub struct ID(pub String);
 
 impl Deref for ID {
     type Target = String;
@@ -26,18 +26,15 @@ impl DerefMut for ID {
     }
 }
 
-impl<T> From<T> for ID
-where
-    T: std::fmt::Display,
-{
+impl<T: std::fmt::Display> From<T> for ID {
     fn from(value: T) -> Self {
         ID(value.to_string())
     }
 }
 
-impl Into<String> for ID {
-    fn into(self) -> String {
-        self.0
+impl From<ID> for String {
+    fn from(id: ID) -> Self {
+        id.0
     }
 }
 
@@ -55,7 +52,7 @@ macro_rules! try_from_integers {
     };
 }
 
-try_from_integers!(i8, i16, i32, i64, u8, u16, u32, u64, isize, usize);
+try_from_integers!(i8, i16, i32, i64, i128, u8, u16, u32, u64, u128, isize, usize);
 
 impl TryFrom<ID> for uuid::Uuid {
     type Error = uuid::Error;
diff --git a/src/scalars/json.rs b/src/types/json.rs
similarity index 100%
rename from src/scalars/json.rs
rename to src/types/json.rs
diff --git a/src/types/mod.rs b/src/types/mod.rs
index f55a5309..30a62bfe 100644
--- a/src/types/mod.rs
+++ b/src/types/mod.rs
@@ -1,19 +1,26 @@
+//! Useful GraphQL types.
+
 pub mod connection;
 
+mod any;
+mod json;
 mod empty_mutation;
 mod empty_subscription;
-mod r#enum;
-mod list;
 mod maybe_undefined;
 mod merged_object;
-mod optional;
 mod query_root;
 mod upload;
+mod id;
 
+mod external;
+
+pub use any::Any;
+pub use json::{Json, OutputJson};
 pub use empty_mutation::EmptyMutation;
 pub use empty_subscription::EmptySubscription;
 pub use maybe_undefined::MaybeUndefined;
 pub use merged_object::{MergedObject, MergedObjectSubscriptionTail, MergedObjectTail};
-pub use query_root::QueryRoot;
-pub use r#enum::{EnumItem, EnumType};
 pub use upload::Upload;
+pub use id::ID;
+
+pub(crate) use query_root::QueryRoot;
diff --git a/src/types/query_root.rs b/src/types/query_root.rs
index 011d27c2..ddea49b9 100644
--- a/src/types/query_root.rs
+++ b/src/types/query_root.rs
@@ -1,9 +1,8 @@
 use crate::model::{__Schema, __Type};
 use crate::parser::types::Field;
 use crate::resolver_utils::{resolve_object, ObjectType};
-use crate::scalars::Any;
 use crate::{
-    registry, Context, ContextSelectionSet, Error, GQLSimpleObject, OutputValueType, Positioned,
+    registry, Any, Context, ContextSelectionSet, Error, GQLSimpleObject, OutputValueType, Positioned,
     QueryError, Result, Type,
 };
 
@@ -17,9 +16,9 @@ struct Service {
     sdl: Option<String>,
 }
 
-pub struct QueryRoot<T> {
-    pub inner: T,
-    pub disable_introspection: bool,
+pub(crate) struct QueryRoot<T> {
+    pub(crate) inner: T,
+    pub(crate) disable_introspection: bool,
 }
 
 impl<T: Type> Type for QueryRoot<T> {