Improve type safety for instance resolvers

Author: mhallin

src/macros/interface.rs

@@ -175,7 +175,7 @@ macro_rules! graphql_interface {
         let $ctxtvar = &$ctxtarg;
 
         $(
-            if let Some(_) = $resolver {
+            if let Some(_) = $resolver as Option<$srctype> {
                 return (<$srctype as $crate::GraphQLType<$ctxttype>>::name()).unwrap().to_owned();
             }
         )*

src/macros/tests/union.rs

@@ -38,7 +38,7 @@ graphql_object!(Concrete: () |&self| {
 
 graphql_union!(DefaultName: () |&self| {
     instance_resolvers: |&_| {
-        Concrete => match *self { DefaultName::Concrete(ref c) => Some(c) }
+        &Concrete => match *self { DefaultName::Concrete(ref c) => Some(c) }
     }
 });
 
@@ -57,27 +57,27 @@ graphql_union!(<T> WithGenerics<T>: () as "WithGenerics" |&self| {
 graphql_union!(DescriptionFirst: () |&self| {
     description: "A description"
     instance_resolvers: |&_| {
-        Concrete => match *self { DescriptionFirst::Concrete(ref c) => Some(c) }
+        &Concrete => match *self { DescriptionFirst::Concrete(ref c) => Some(c) }
     }
 });
 
 graphql_union!(ResolversFirst: () |&self| {
     instance_resolvers: |&_| {
-        Concrete => match *self { ResolversFirst::Concrete(ref c) => Some(c) }
+        &Concrete => match *self { ResolversFirst::Concrete(ref c) => Some(c) }
     }
     description: "A description"
 });
 
 graphql_union!(CommasWithTrailing: () |&self| {
     instance_resolvers: |&_| {
-        Concrete => match *self { CommasWithTrailing::Concrete(ref c) => Some(c) }
+        &Concrete => match *self { CommasWithTrailing::Concrete(ref c) => Some(c) }
     },
     description: "A description",
 });
 
 graphql_union!(ResolversWithTrailingComma: () |&self| {
     instance_resolvers: |&_| {
-        Concrete => match *self { ResolversWithTrailingComma::Concrete(ref c) => Some(c) },
+        &Concrete => match *self { ResolversWithTrailingComma::Concrete(ref c) => Some(c) },
     }
     description: "A description"
 });

src/macros/union.rs

@@ -42,7 +42,7 @@ macro_rules! graphql_union {
         let $ctxtvar = &$ctxtarg;
 
         $(
-            if let Some(_) = $resolver {
+            if let Some(_) = $resolver as Option<$srctype> {
                 return (<$srctype as $crate::GraphQLType<$ctxttype>>::name()).unwrap().to_owned();
             }
         )*

src/tests/schema.rs

@@ -27,8 +27,8 @@ graphql_interface!(<'a> &'a Character: Database as "Character" |&self| {
     }
 
     instance_resolvers: |&context| {
-        &'a Human => context.get_human(&self.id()),
-        &'a Droid => context.get_droid(&self.id()),
+        &Human => context.get_human(&self.id()),
+        &Droid => context.get_droid(&self.id()),
     }
 });