Reject enum literals for custom scalar values

bluejay-validator/src/value/input_coercion.rs

@@ -193,6 +193,14 @@ fn coerce_custom_scalar_value<'a, const CONST: bool, V: Value<CONST>>(
     value: &'a V,
     path: Path<'a>,
 ) -> Result<(), Vec<Error<'a, CONST, V>>> {
+    if matches!(value.as_ref(), ValueReference::Enum(_)) {
+        return Err(vec![Error::NoImplicitConversion {
+            value,
+            input_type_name: cstd.name().to_string(),
+            path,
+        }]);
+    }
+
     cstd.coerce_input(value).map_err(|message| {
         vec![Error::CustomScalarInvalidValue {
             value,

bluejay-validator/tests/snapshots/executable_integration_test__error@value_is_valid.graphql.snap

@@ -29,6 +29,22 @@ Error: Object with multiple entries for field name
     │                                      ╰─── Entry for field
 ────╯
 
+Error: No implicit conversion of enum to Int
+    ╭─[ value_is_valid.graphql:22:25 ]
+    │
+ 22 │     intArgField(intArg: SomeEnumValue)
+    │                         ──────┬──────  
+    │                               ╰──────── No implicit conversion to Int
+────╯
+
+Error: No implicit conversion of enum to CustomScalar
+    ╭─[ value_is_valid.graphql:27:38 ]
+    │
+ 27 │   customScalarField(customScalarArg: SomeEnumValue)
+    │                                      ──────┬──────  
+    │                                            ╰──────── No implicit conversion to CustomScalar
+────╯
+
 Error: No implicit conversion of string to Int
    ╭─[ value_is_valid.graphql:2:23 ]
    │

bluejay-validator/tests/test_data/executable/error/value_is_valid.graphql

@@ -16,3 +16,13 @@ query inputFieldDoesNotExist {
 query duplicateInputField {
   findDog(complex: { name: "Fido", name: "Fido" }) { name }
 }
+
+query enumLiteralForBuiltinScalar {
+  arguments {
+    intArgField(intArg: SomeEnumValue)
+  }
+}
+
+query enumLiteralForCustomScalar {
+  customScalarField(customScalarArg: SomeEnumValue)
+}

bluejay-validator/tests/test_data/executable/schema.graphql

@@ -9,8 +9,11 @@ type Query {
   oneOf(oneOfArg: OneOfInput!): String
   oneOfList(oneOfListArg: [OneOfInput]!): String
   nestedOneOf(nestedOneOfArg: NestedOneOfInput!): String
+  customScalarField(customScalarArg: CustomScalar!): String
 }
 
+scalar CustomScalar
+
 input OneOfInput @oneOf {
   oneOfField: String
   anotherField: String