Upd

Author: tyranron

juniper/src/types/scalars.rs

@@ -1,4 +1,4 @@
-use std::{char, convert::identity, marker::PhantomData, rc::Rc, thread::JoinHandle};
+use std::{char, marker::PhantomData, rc::Rc, thread::JoinHandle};
 
 use derive_more::with_trait::{Deref, Display, From, Into};
 use serde::{Deserialize, Serialize};
@@ -65,6 +65,16 @@ type String = std::string::String;
 mod impl_string_scalar {
     use super::*;
 
+    impl<'s, S> FromScalarValue<'s, S> for String
+    where
+        S: TryScalarValueTo<'s, Self, Error: IntoFieldError<S>> + 's,
+    {
+        fn from_scalar_value(v: &'s S) -> FieldResult<Self, S> {
+            v.try_scalar_value_to()
+                .map_err(IntoFieldError::into_field_error)
+        }
+    }
+
     pub(super) fn to_output<S: ScalarValue>(v: &str) -> Value<S> {
         Value::scalar(v.to_owned())
     }
@@ -173,22 +183,19 @@ where
     })
 }
 
-
 #[graphql_scalar]
 #[graphql(name = "String", with = impl_arcstr_scalar, parse_token(String))]
 type ArcStr = arcstr::ArcStr;
 
 mod impl_arcstr_scalar {
     use super::ArcStr;
-    use crate::{IntoValue as _, Scalar, ScalarValue, Value, FieldResult};
+    use crate::{FieldResult, IntoValue as _, Scalar, ScalarValue, Value};
 
     pub(super) fn to_output<S: ScalarValue>(v: &ArcStr) -> Value<S> {
         v.into_value()
     }
-    
-    pub(super) fn from_input<S: ScalarValue>(
-        v: &Scalar<S>,
-    ) -> FieldResult<ArcStr, S> {
+
+    pub(super) fn from_input<S: ScalarValue>(v: &Scalar<S>) -> FieldResult<ArcStr, S> {
         if let Some(s) = v.downcast_type::<ArcStr>() {
             Ok(s.clone())
         } else {
@@ -203,15 +210,13 @@ type CompactString = compact_str::CompactString;
 
 mod impl_compactstring_scalar {
     use super::CompactString;
-    use crate::{IntoValue as _, Scalar, ScalarValue, FieldResult, Value};
+    use crate::{FieldResult, IntoValue as _, Scalar, ScalarValue, Value};
 
     pub(super) fn to_output<S: ScalarValue>(v: &CompactString) -> Value<S> {
         v.into_value()
     }
 
-    pub(super) fn from_input<S: ScalarValue>(
-        v: &Scalar<S>,
-    ) -> FieldResult<CompactString, S> {
+    pub(super) fn from_input<S: ScalarValue>(v: &Scalar<S>) -> FieldResult<CompactString, S> {
         if let Some(s) = v.downcast_type::<CompactString>() {
             Ok(s.clone())
         } else {
@@ -307,6 +312,16 @@ type Boolean = bool;
 mod impl_boolean_scalar {
     use super::*;
 
+    impl<'s, S> FromScalarValue<'s, S> for Boolean
+    where
+        S: TryScalarValueTo<'s, Self, Error: IntoFieldError<S>> + 's,
+    {
+        fn from_scalar_value(v: &'s S) -> FieldResult<Self, S> {
+            v.try_scalar_value_to()
+                .map_err(IntoFieldError::into_field_error)
+        }
+    }
+
     pub(super) fn to_output<S: ScalarValue>(v: &Boolean) -> Value<S> {
         Value::scalar(*v)
     }
@@ -324,6 +339,16 @@ type Int = i32;
 mod impl_int_scalar {
     use super::*;
 
+    impl<'s, S> FromScalarValue<'s, S> for Int
+    where
+        S: TryScalarValueTo<'s, Self, Error: IntoFieldError<S>> + 's,
+    {
+        fn from_scalar_value(v: &'s S) -> FieldResult<Self, S> {
+            v.try_scalar_value_to()
+                .map_err(IntoFieldError::into_field_error)
+        }
+    }
+
     pub(super) fn to_output<S: ScalarValue>(v: &Int) -> Value<S> {
         Value::scalar(*v)
     }
@@ -346,6 +371,16 @@ type Float = f64;
 mod impl_float_scalar {
     use super::*;
 
+    impl<'s, S> FromScalarValue<'s, S> for Float
+    where
+        S: TryScalarValueTo<'s, Self, Error: IntoFieldError<S>> + 's,
+    {
+        fn from_scalar_value(v: &'s S) -> FieldResult<Self, S> {
+            v.try_scalar_value_to()
+                .map_err(IntoFieldError::into_field_error)
+        }
+    }
+
     pub(super) fn to_output<S: ScalarValue>(v: &Float) -> Value<S> {
         Value::scalar(*v)
     }

juniper/src/value/scalar.rs

@@ -270,25 +270,7 @@ pub trait ScalarValue:
     #[must_use]
     fn downcast_type<T: Any>(&self) -> Option<&T>;
 
-    /// Tries to represent this [`ScalarValue`] as the specified type `T`.
-    ///
-    /// This method could be used instead of other helpers in case the [`TryScalarValueTo::Error`]
-    /// is needed.
-    ///
-    /// # Implementation
-    ///
-    /// This method is an ergonomic alias for the [`TryScalarValueTo<T>`] conversion.
-    ///
-    /// Implementations should not implement this method, but rather implement the
-    /// [`TryScalarValueTo<T>`] conversion directly.
-    fn try_to2<'a, T>(&'a self) -> Result<T, <Self as TryScalarValueTo<'a, T>>::Error>
-    where
-        T: 'a,
-        Self: TryScalarValueTo<'a, T, Error: IntoFieldError<Self>>,
-    {
-        self.try_scalar_value_to()
-    }
-
+    /// TODO: renew docs
     /// Tries to represent this [`ScalarValue`] as the specified type `T`.
     ///
     /// This method could be used instead of other helpers in case the [`TryScalarValueTo::Error`]

juniper_codegen/src/graphql_scalar/mod.rs

@@ -250,6 +250,8 @@ impl Attr {
         if attr.description.is_none() {
             attr.description = Description::parse_from_doc_attrs(attrs)?;
         }
+        
+        // TODO: check whether `__builtin` is from inside `juniper` crate only.
 
         Ok(attr)
     }
@@ -492,7 +494,7 @@ impl Definition {
     ///
     /// [`FromScalarValue`]: juniper::FromScalarValue
     /// [1]: https://spec.graphql.org/October2021#sec-Scalars
-    fn impl_from_scalar_value_tokens(&self) -> TokenStream {
+    fn impl_from_scalar_value_tokens(&self) -> Option<TokenStream> {
         let scalar = &self.scalar;
 
         let ref_lt = quote! { '___a };
@@ -509,20 +511,16 @@ impl Definition {
                 ..
             } => {
                 if from_input == &parse_quote! { __builtin } {
-                    quote! {
-                        ::juniper::TryScalarValueTo::try_scalar_value_to(input)
-                            .map_err(::juniper::executor::IntoFieldError::<#scalar>::into_field_error)
-                    }
-                } else {
-                    quote! {
-                        use ::juniper::macros::helper::ToResultCall as _;
-
-                        let input = ::juniper::ScalarValue::try_to(input)?;
-                        let func: fn(_) -> _ = #from_input;
-                        (&&func)
-                            .__to_result_call(input)
-                            .map_err(::juniper::executor::IntoFieldError::<#scalar>::into_field_error)
-                    }
+                    return None;
+                }
+                quote! {
+                    use ::juniper::macros::helper::ToResultCall as _;
+
+                    let input = ::juniper::ScalarValue::try_to(input)?;
+                    let func: fn(_) -> _ = #from_input;
+                    (&&func)
+                        .__to_result_call(input)
+                        .map_err(::juniper::executor::IntoFieldError::<#scalar>::into_field_error)
                 }
             }
             Methods::Delegated { field, .. } => {
@@ -542,7 +540,7 @@ impl Definition {
 
         let (lt_impl_gens, _, where_clause) = generics.split_for_impl();
 
-        quote! {
+        Some(quote! {
             #[automatically_derived]
             impl #lt_impl_gens ::juniper::FromScalarValue<#ref_lt, #scalar> for #ty #where_clause {
                 fn from_scalar_value(
@@ -551,7 +549,7 @@ impl Definition {
                     #body
                 }
             }
-        }
+        })
     }
 
     /// Returns generated code implementing [`FromInputValue`] trait for this