Replace "codegen" with "derive"

serde_derive/src/de.rs

@@ -1090,7 +1090,7 @@ fn deserialize_internally_tagged_variant(
         Style::Newtype | Style::Struct => {
             deserialize_untagged_variant(params, variant, item_attrs, deserializer)
         }
-        Style::Tuple => unreachable!("checked in serde_codegen_internals"),
+        Style::Tuple => unreachable!("checked in serde_derive_internals"),
     }
 }
 

serde_derive/src/lib.rs

@@ -18,7 +18,7 @@ extern crate syn;
 #[macro_use]
 extern crate quote;
 
-extern crate serde_codegen_internals as internals;
+extern crate serde_derive_internals as internals;
 
 extern crate proc_macro;
 use proc_macro::TokenStream;

serde_derive/src/ser.rs

@@ -490,7 +490,7 @@ fn serialize_internally_tagged_variant(
                 &type_name,
             )
         }
-        Style::Tuple => unreachable!("checked in serde_codegen_internals"),
+        Style::Tuple => unreachable!("checked in serde_derive_internals"),
     }
 }