diff --git a/juniper/Cargo.toml b/juniper/Cargo.toml
index f981af04..1fdee863 100644
--- a/juniper/Cargo.toml
+++ b/juniper/Cargo.toml
@@ -35,18 +35,17 @@ default = [
 [dependencies]
 juniper_codegen = { version = "0.14.0", path = "../juniper_codegen"  }
 
+async-trait = "0.1.16"
+chrono = { version = "0.4.0", optional = true }
 fnv = "1.0.3"
+futures-preview = { version = "=0.3.0-alpha.19", optional = true }
 indexmap = { version = "1.0.0", features = ["serde-1"] }
 serde = { version = "1.0.8" }
 serde_derive = { version = "1.0.2" }
-
-chrono = { version = "0.4.0", optional = true }
 serde_json = { version="1.0.2", optional = true }
 url = { version = "2", optional = true }
 uuid = { version = "0.7", optional = true }
 
-futures-preview = { version = "=0.3.0-alpha.19", optional = true }
-
 [dev-dependencies]
 bencher = "0.1.2"
 serde_json = { version = "1.0.2" }
diff --git a/juniper/src/macros/common.rs b/juniper/src/macros/common.rs
index 9a6ddef3..88320cd6 100644
--- a/juniper/src/macros/common.rs
+++ b/juniper/src/macros/common.rs
@@ -96,25 +96,6 @@ macro_rules! __juniper_insert_generic {
     };
 }
 
-// TODO: remove me.
-#[doc(hidden)]
-#[macro_export]
-macro_rules! __juniper_extract_generic {
-    (<$name:ident>) => {
-        $name
-    };
-    (
-        <$generic:tt $(: $bound: tt)*>
-    ) => {
-        $generic
-    };
-    (
-        $scalar: ty
-    ) => {
-        $scalar
-    };
-}
-
 #[doc(hidden)]
 #[macro_export]
 macro_rules! __juniper_parse_object_header {
diff --git a/juniper/src/macros/scalar.rs b/juniper/src/macros/scalar.rs
index 4f3ae84e..32c8b988 100644
--- a/juniper/src/macros/scalar.rs
+++ b/juniper/src/macros/scalar.rs
@@ -423,12 +423,16 @@ macro_rules! graphql_scalar {
                 )
             {
 
-                fn resolve_async<'a>(
+                fn resolve_async<'a, 'async_trait>(
                     &'a self,
                     info: &'a Self::TypeInfo,
-                    selection_set: Option<&'a [$crate::Selection<$crate::__juniper_insert_generic!($($scalar)+)>]>,
-                    executor: &'a $crate::Executor<Self::Context, $crate::__juniper_insert_generic!($($scalar)+)>,
-                ) -> futures::future::BoxFuture<'a, $crate::Value<$crate::__juniper_insert_generic!($($scalar)+)>> {
+                    selection_set: Option<&'a [$crate::Selection<'a, $crate::__juniper_insert_generic!($($scalar)+)>]>,
+                    executor: &'a $crate::Executor<'a, Self::Context, $crate::__juniper_insert_generic!($($scalar)+)>,
+                ) -> futures::future::BoxFuture<'async_trait, $crate::Value<$crate::__juniper_insert_generic!($($scalar)+)>>
+                where
+                    'a: 'async_trait,
+                    Self: 'async_trait,
+                {
                     use $crate::GraphQLType;
                     use futures::future;
                     let v = self.resolve(info, selection_set, executor);
diff --git a/juniper/src/macros/tests/args.rs b/juniper/src/macros/tests/args.rs
index 99915094..95b8dacb 100644
--- a/juniper/src/macros/tests/args.rs
+++ b/juniper/src/macros/tests/args.rs
@@ -73,13 +73,17 @@ impl Root {
         0
     }
 
-    // TODO: enable once [RFC 2565](https://github.com/rust-lang/rust/issues/60406) is implemented
-    // fn attr_arg_descr(#[doc = "The arg"] arg: i32) -> i32 { 0 }
-    // fn attr_arg_descr_collapse(
-    //     #[doc = "The arg"]
-    //     #[doc = "and more details"]
-    //     arg: i32,
-    // ) -> i32 { 0 }
+// TODO: enable once [parameter attributes are supported by proc macros]
+//       (https://github.com/graphql-rust/juniper/pull/441)
+//     fn attr_arg_descr(
+//        #[graphql(description = "The arg")]
+//        arg: i32) -> i32
+//     { 0 }
+//    fn attr_arg_descr_collapse(
+//        #[graphql(description = "The first arg")]
+//        #[graphql(description = "and more details")]
+//         arg: i32,
+//     ) -> i32 { 0 }
 
     #[graphql(arguments(arg(default = 123,),))]
     fn arg_with_default(arg: i32) -> i32 {
@@ -559,7 +563,8 @@ fn introspect_field_multi_args_descr_trailing_comma() {
     });
 }
 
-// TODO: enable once [RFC 2565](https://github.com/rust-lang/rust/issues/60406) is implemented
+// TODO: enable once [parameter attributes are supported by proc macros]
+//       (https://github.com/graphql-rust/juniper/pull/441)
 // #[test]
 // fn introspect_field_attr_arg_descr() {
 //     run_args_info_query("attrArgDescr", |args| {
@@ -593,7 +598,8 @@ fn introspect_field_multi_args_descr_trailing_comma() {
 //     });
 // }
 
-// TODO: enable once [RFC 2565](https://github.com/rust-lang/rust/issues/60406) is implemented
+// TODO: enable once [parameter attributes are supported by proc macros]
+//       (https://github.com/graphql-rust/juniper/pull/441)
 // #[test]
 // fn introspect_field_attr_arg_descr_collapse() {
 //     run_args_info_query("attrArgDescrCollapse", |args| {
diff --git a/juniper/src/schema/schema.rs b/juniper/src/schema/schema.rs
index 14c3f2c2..5192dc20 100644
--- a/juniper/src/schema/schema.rs
+++ b/juniper/src/schema/schema.rs
@@ -77,6 +77,7 @@ where
 }
 
 #[cfg(feature = "async")]
+#[async_trait::async_trait]
 impl<'a, CtxT, S, QueryT, MutationT> crate::GraphQLTypeAsync<S>
     for RootNode<'a, QueryT, MutationT, S>
 where
@@ -85,16 +86,16 @@ where
     QueryT::TypeInfo: Send + Sync,
     MutationT: crate::GraphQLTypeAsync<S, Context = CtxT>,
     MutationT::TypeInfo: Send + Sync,
-    CtxT: Send + Sync,
-    for<'b> &'b S: ScalarRefValue<'b>,
+    CtxT: Send + Sync + 'a,
+    for<'c> &'c S: ScalarRefValue<'c>,
 {
-    fn resolve_field_async<'b>(
+    async fn resolve_field_async<'b>(
         &'b self,
-        info: &'b Self::TypeInfo,
+        info: &'b <Self as crate::GraphQLType<S>>::TypeInfo,
         field_name: &'b str,
-        arguments: &'b Arguments<S>,
-        executor: &'b Executor<Self::Context, S>,
-    ) -> crate::BoxFuture<'b, ExecutionResult<S>> {
+        arguments: &'b Arguments<'b, S>,
+        executor: &'b Executor<'b, <Self as crate::GraphQLType<S>>::Context, S>,
+    ) -> ExecutionResult<S> {
         use futures::future::{ready, FutureExt};
         match field_name {
             "__schema" | "__type" => {
diff --git a/juniper/src/types/async_await.rs b/juniper/src/types/async_await.rs
index ab7b95d4..bf06e190 100644
--- a/juniper/src/types/async_await.rs
+++ b/juniper/src/types/async_await.rs
@@ -12,6 +12,7 @@ use crate::BoxFuture;
 
 use super::base::{is_excluded, merge_key_into, Arguments, GraphQLType};
 
+#[async_trait::async_trait]
 pub trait GraphQLTypeAsync<S>: GraphQLType<S> + Send + Sync
 where
     Self::Context: Send + Sync,
@@ -19,28 +20,42 @@ where
     S: ScalarValue + Send + Sync,
     for<'b> &'b S: ScalarRefValue<'b>,
 {
-    fn resolve_field_async<'a>(
+    async fn resolve_field_async<'a>(
         &'a self,
         info: &'a Self::TypeInfo,
         field_name: &'a str,
-        arguments: &'a Arguments<S>,
-        executor: &'a Executor<Self::Context, S>,
-    ) -> BoxFuture<'a, ExecutionResult<S>> {
+        arguments: &'a Arguments<'a, S>,
+        executor: &'a Executor<'a, Self::Context, S>,
+    ) -> ExecutionResult<S> {
         panic!("resolve_field must be implemented by object types");
     }
 
-    fn resolve_async<'a>(
+    async fn resolve_async<'a>(
         &'a self,
         info: &'a Self::TypeInfo,
-        selection_set: Option<&'a [Selection<S>]>,
-        executor: &'a Executor<Self::Context, S>,
-    ) -> BoxFuture<'a, Value<S>> {
+        selection_set: Option<&'a [Selection<'a, S>]>,
+        executor: &'a Executor<'a, Self::Context, S>,
+    ) -> Value<S> {
         if let Some(selection_set) = selection_set {
-            resolve_selection_set_into_async(self, info, selection_set, executor)
+            resolve_selection_set_into_async(self, info, selection_set, executor).await
         } else {
             panic!("resolve() must be implemented by non-object output types");
         }
     }
+
+    async fn resolve_into_type_async<'a>(
+        &'a self,
+        info: &'a Self::TypeInfo,
+        type_name: &str,
+        selection_set: Option<&'a [Selection<'a, S>]>,
+        executor: &'a Executor<'a, Self::Context, S>,
+    ) -> ExecutionResult<S> {
+        if Self::name(info).unwrap() == type_name {
+            Ok(self.resolve_async(info, selection_set, executor).await)
+        } else {
+            panic!("resolve_into_type_async must be implemented by unions and interfaces");
+        }
+    }
 }
 
 // Wrapper function around resolve_selection_set_into_async_recursive.
@@ -160,7 +175,7 @@ where
                 let response_name = response_name.to_string();
                 let field_future = async move {
                     // TODO: implement custom future type instead of
-                    // two-level boxing.
+                    //       two-level boxing.
                     let res = instance
                         .resolve_field_async(info, f.name.item, &args, &sub_exec)
                         .await;
@@ -223,14 +238,14 @@ where
                 );
 
                 if let Some(ref type_condition) = fragment.type_condition {
-                    // FIXME: implement async version.
-
-                    let sub_result = instance.resolve_into_type(
-                        info,
-                        type_condition.item,
-                        Some(&fragment.selection_set[..]),
-                        &sub_exec,
-                    );
+                    let sub_result = instance
+                        .resolve_into_type_async(
+                            info,
+                            type_condition.item,
+                            Some(&fragment.selection_set[..]),
+                            &sub_exec,
+                        )
+                        .await;
 
                     if let Ok(Value::Object(obj)) = sub_result {
                         for (k, v) in obj {
diff --git a/juniper/src/types/containers.rs b/juniper/src/types/containers.rs
index 06634072..7f6d1374 100644
--- a/juniper/src/types/containers.rs
+++ b/juniper/src/types/containers.rs
@@ -257,6 +257,7 @@ where
 }
 
 #[cfg(feature = "async")]
+#[async_trait::async_trait]
 impl<S, T, CtxT> crate::GraphQLTypeAsync<S> for Vec<T>
 where
     T: crate::GraphQLTypeAsync<S, Context = CtxT>,
@@ -265,18 +266,18 @@ where
     CtxT: Send + Sync,
     for<'b> &'b S: ScalarRefValue<'b>,
 {
-    fn resolve_async<'a>(
+    async fn resolve_async<'a>(
         &'a self,
-        info: &'a Self::TypeInfo,
-        selection_set: Option<&'a [Selection<S>]>,
-        executor: &'a Executor<Self::Context, S>,
-    ) -> crate::BoxFuture<'a, Value<S>> {
-        let f = resolve_into_list_async(executor, info, self.iter());
-        Box::pin(f)
+        info: &'a <Self as crate::GraphQLType<S>>::TypeInfo,
+        selection_set: Option<&'a [Selection<'a, S>]>,
+        executor: &'a Executor<'a, <Self as crate::GraphQLType<S>>::Context, S>,
+    ) -> Value<S> {
+        resolve_into_list_async(executor, info, self.iter()).await
     }
 }
 
 #[cfg(feature = "async")]
+#[async_trait::async_trait]
 impl<S, T, CtxT> crate::GraphQLTypeAsync<S> for &[T]
 where
     T: crate::GraphQLTypeAsync<S, Context = CtxT>,
@@ -285,18 +286,18 @@ where
     CtxT: Send + Sync,
     for<'b> &'b S: ScalarRefValue<'b>,
 {
-    fn resolve_async<'a>(
+    async fn resolve_async<'a>(
         &'a self,
-        info: &'a Self::TypeInfo,
-        selection_set: Option<&'a [Selection<S>]>,
-        executor: &'a Executor<Self::Context, S>,
-    ) -> crate::BoxFuture<'a, Value<S>> {
-        let f = resolve_into_list_async(executor, info, self.iter());
-        Box::pin(f)
+        info: &'a <Self as crate::GraphQLType<S>>::TypeInfo,
+        selection_set: Option<&'a [Selection<'a, S>]>,
+        executor: &'a Executor<'a, <Self as crate::GraphQLType<S>>::Context, S>,
+    ) -> Value<S> {
+        resolve_into_list_async(executor, info, self.iter()).await
     }
 }
 
 #[cfg(feature = "async")]
+#[async_trait::async_trait]
 impl<S, T, CtxT> crate::GraphQLTypeAsync<S> for Option<T>
 where
     T: crate::GraphQLTypeAsync<S, Context = CtxT>,
@@ -305,18 +306,15 @@ where
     CtxT: Send + Sync,
     for<'b> &'b S: ScalarRefValue<'b>,
 {
-    fn resolve_async<'a>(
+    async fn resolve_async<'a>(
         &'a self,
-        info: &'a Self::TypeInfo,
-        selection_set: Option<&'a [Selection<S>]>,
-        executor: &'a Executor<Self::Context, S>,
-    ) -> crate::BoxFuture<'a, Value<S>> {
-        let f = async move {
-            match *self {
-                Some(ref obj) => executor.resolve_into_value_async(info, obj).await,
-                None => Value::null(),
-            }
-        };
-        Box::pin(f)
+        info: &'a <Self as crate::GraphQLType<S>>::TypeInfo,
+        selection_set: Option<&'a [Selection<'a, S>]>,
+        executor: &'a Executor<'a, <Self as crate::GraphQLType<S>>::Context, S>,
+    ) -> Value<S> {
+        match *self {
+            Some(ref obj) => executor.resolve_into_value_async(info, obj).await,
+            None => Value::null(),
+        }
     }
 }
diff --git a/juniper/src/types/pointers.rs b/juniper/src/types/pointers.rs
index 1e8478a1..ed1ecd02 100644
--- a/juniper/src/types/pointers.rs
+++ b/juniper/src/types/pointers.rs
@@ -137,31 +137,33 @@ where
 }
 
 #[cfg(feature = "async")]
+#[async_trait::async_trait]
 impl<'e, S, T> crate::GraphQLTypeAsync<S> for &'e T
 where
     S: ScalarValue + Send + Sync,
     T: crate::GraphQLTypeAsync<S>,
     T::TypeInfo: Send + Sync,
     T::Context: Send + Sync,
-    for<'b> &'b S: ScalarRefValue<'b>,
+    for<'c> &'c S: ScalarRefValue<'c>,
 {
-    fn resolve_field_async<'b>(
+    async fn resolve_field_async<'b>(
         &'b self,
-        info: &'b Self::TypeInfo,
+        info: &'b <Self as crate::GraphQLType<S>>::TypeInfo,
         field_name: &'b str,
-        arguments: &'b Arguments<S>,
-        executor: &'b Executor<Self::Context, S>,
-    ) -> crate::BoxFuture<'b, ExecutionResult<S>> {
+        arguments: &'b Arguments<'b, S>,
+        executor: &'b Executor<'b, <Self as crate::GraphQLType<S>>::Context, S>,
+    ) -> ExecutionResult<S> {
         crate::GraphQLTypeAsync::resolve_field_async(&**self, info, field_name, arguments, executor)
+            .await
     }
 
-    fn resolve_async<'a>(
+    async fn resolve_async<'a>(
         &'a self,
-        info: &'a Self::TypeInfo,
-        selection_set: Option<&'a [Selection<S>]>,
-        executor: &'a Executor<Self::Context, S>,
-    ) -> crate::BoxFuture<'a, Value<S>> {
-        crate::GraphQLTypeAsync::resolve_async(&**self, info, selection_set, executor)
+        info: &'a <Self as crate::GraphQLType<S>>::TypeInfo,
+        selection_set: Option<&'a [Selection<'a, S>]>,
+        executor: &'a Executor<'a, <Self as crate::GraphQLType<S>>::Context, S>,
+    ) -> Value<S> {
+        crate::GraphQLTypeAsync::resolve_async(&**self, info, selection_set, executor).await
     }
 }
 
diff --git a/juniper/src/types/scalars.rs b/juniper/src/types/scalars.rs
index dba13834..81d1c965 100644
--- a/juniper/src/types/scalars.rs
+++ b/juniper/src/types/scalars.rs
@@ -197,19 +197,19 @@ where
 }
 
 #[cfg(feature = "async")]
+#[async_trait::async_trait]
 impl<'e, S> crate::GraphQLTypeAsync<S> for &'e str
 where
     S: ScalarValue + Send + Sync,
     for<'b> &'b S: ScalarRefValue<'b>,
 {
-    fn resolve_async<'a>(
+    async fn resolve_async<'a>(
         &'a self,
-        info: &'a Self::TypeInfo,
-        selection_set: Option<&'a [Selection<S>]>,
-        executor: &'a Executor<Self::Context, S>,
-    ) -> crate::BoxFuture<'a, crate::Value<S>> {
-        use futures::future;
-        future::FutureExt::boxed(future::ready(self.resolve(info, selection_set, executor)))
+        info: &'a <Self as crate::GraphQLType<S>>::TypeInfo,
+        selection_set: Option<&'a [Selection<'a, S>]>,
+        executor: &'a Executor<'a, <Self as crate::GraphQLType<S>>::Context, S>,
+    ) -> crate::Value<S> {
+        self.resolve(info, selection_set, executor)
     }
 }
 
diff --git a/juniper_codegen/src/derive_enum.rs b/juniper_codegen/src/derive_enum.rs
index d1262e7d..607d2d1f 100644
--- a/juniper_codegen/src/derive_enum.rs
+++ b/juniper_codegen/src/derive_enum.rs
@@ -213,12 +213,16 @@ pub fn impl_enum(ast: &syn::DeriveInput, is_internal: bool) -> TokenStream {
                 __S: #juniper_path::ScalarValue + Send + Sync,
                 for<'__b> &'__b __S: #juniper_path::ScalarRefValue<'__b>
         {
-            fn resolve_async<'a>(
+            fn resolve_async<'a, 'async_trait>(
                 &'a self,
                 info: &'a Self::TypeInfo,
                 selection_set: Option<&'a [#juniper_path::Selection<__S>]>,
                 executor: &'a #juniper_path::Executor<Self::Context, __S>,
-            ) -> futures::future::BoxFuture<'a, #juniper_path::Value<__S>> {
+            ) -> futures::future::BoxFuture<'async_trait, #juniper_path::Value<__S>>
+             where
+                'a: 'async_trait,
+                Self: 'async_trait
+            {
                 use #juniper_path::GraphQLType;
                 use futures::future;
                 let v = self.resolve(info, selection_set, executor);
diff --git a/juniper_codegen/src/impl_union.rs b/juniper_codegen/src/impl_union.rs
index 58edade1..e873d5d3 100644
--- a/juniper_codegen/src/impl_union.rs
+++ b/juniper_codegen/src/impl_union.rs
@@ -1,7 +1,7 @@
 use proc_macro::TokenStream;
 
 use proc_macro_error::MacroError;
-use quote::{quote};
+use quote::quote;
 use syn::spanned::Spanned;
 
 use crate::util;
diff --git a/juniper_codegen/src/util.rs b/juniper_codegen/src/util.rs
index d6a71d59..40607de0 100644
--- a/juniper_codegen/src/util.rs
+++ b/juniper_codegen/src/util.rs
@@ -731,15 +731,31 @@ impl GraphQLTypeDefiniton {
             }
         });
 
+        let scalar = self
+            .scalar
+            .as_ref()
+            .map(|s| quote!( #s ))
+            .unwrap_or_else(|| {
+                if self.generic_scalar {
+                    // If generic_scalar is true, we always insert a generic scalar.
+                    // See more comments below.
+                    quote!(__S)
+                } else {
+                    quote!(#juniper_crate_name::DefaultScalarValue)
+                }
+            });
+
         let resolve_matches = self.fields.iter().map(|field| {
             let name = &field.name;
             let code = &field.resolver_code;
 
             if field.is_async {
-                // TODO: better error message with field/type name.
                 quote!(
                     #name => {
-                        panic!("Tried to resolve async field with a sync resolver");
+                        panic!("Tried to resolve async field {} on type {:?} with a sync resolver",
+                            #name,
+                            <Self as #juniper_crate_name::GraphQLType<#scalar>>::name(_info)
+                        );
                     },
                 )
             } else {
@@ -780,20 +796,6 @@ impl GraphQLTypeDefiniton {
             )
         });
 
-        let scalar = self
-            .scalar
-            .as_ref()
-            .map(|s| quote!( #s ))
-            .unwrap_or_else(|| {
-                if self.generic_scalar {
-                    // If generic_scalar is true, we always insert a generic scalar.
-                    // See more comments below.
-                    quote!(__S)
-                } else {
-                    quote!(#juniper_crate_name::DefaultScalarValue)
-                }
-            });
-
         // Preserve the original type_generics before modification,
         // since alteration makes them invalid if self.generic_scalar
         // is specified.
@@ -925,21 +927,27 @@ impl GraphQLTypeDefiniton {
                 impl#impl_generics #juniper_crate_name::GraphQLTypeAsync<#scalar> for #ty #type_generics_tokens
                     #where_async
                 {
-                    fn resolve_field_async<'b>(
+                    fn resolve_field_async<'b, 'async_trait>(
                         &'b self,
                         info: &'b Self::TypeInfo,
                         field: &'b str,
                         args: &'b #juniper_crate_name::Arguments<#scalar>,
                         executor: &'b #juniper_crate_name::Executor<Self::Context, #scalar>,
-                    ) -> futures::future::BoxFuture<'b, #juniper_crate_name::ExecutionResult<#scalar>>
-                        where #scalar: Send + Sync,
+                    ) -> futures::future::BoxFuture<'async_trait, #juniper_crate_name::ExecutionResult<#scalar>>
+                        where
+                        #scalar: Send + Sync,
+                        'b: 'async_trait,
+                        Self: 'async_trait,
                     {
                         use futures::future;
                         use #juniper_crate_name::GraphQLType;
                         match field {
                             #( #resolve_matches_async )*
                             _ => {
-                                panic!("Field {} not found on type {}", field, "Mutation");
+                                panic!("Field {} not found on type {:?}",
+                                    field,
+                                    <Self as #juniper_crate_name::GraphQLType<#scalar>>::name(info)
+                                );
                             }
                         }
                     }
@@ -989,7 +997,10 @@ impl GraphQLTypeDefiniton {
                     match field {
                         #( #resolve_matches )*
                         _ => {
-                            panic!("Field {} not found on type {}", field, "Mutation");
+                            panic!("Field {} not found on type {:?}",
+                                field,
+                                <Self as #juniper_crate_name::GraphQLType<#scalar>>::name(_info)
+                            );
                         }
                     }
                 }