Updates from PR comments

6 files changed, 30 insertions, 72 deletions

diff --git a/src/codegen/mod.rs b/src/codegen/mod.rs
index 0039a859..d07e27a7 100644
--- a/src/codegen/mod.rs
+++ b/src/codegen/mod.rs
@@ -49,7 +49,6 @@ use crate::{Entry, HashMap, HashSet};
 use std;
 use std::borrow::Cow;
 use std::cell::Cell;
-use std::collections::HashSet as CollectionHashSet;
 use std::collections::VecDeque;
 use std::fmt::Write;
 use std::iter;
@@ -3922,8 +3921,7 @@ impl CodeGenerator for ObjCInterface {
                 }
             };
             result.push(struct_block);
-            let mut protocol_set: CollectionHashSet<ItemId> =
-                CollectionHashSet::new();
+            let mut protocol_set: HashSet<ItemId> = Default::default();
             for protocol_id in self.conforms_to.iter() {
                 protocol_set.insert(*protocol_id);
                 let protocol_name = ctx.rust_ident(
@@ -3967,8 +3965,7 @@ impl CodeGenerator for ObjCInterface {
                     };
                     result.push(impl_trait);
                     for protocol_id in parent.conforms_to.iter() {
-                        if !protocol_set.contains(protocol_id) {
-                            protocol_set.insert(*protocol_id);
+                        if protocol_set.insert(*protocol_id) {
                             let protocol_name = ctx.rust_ident(
                                 ctx.resolve_type(
                                     protocol_id.expect_type_id(ctx),
@@ -3995,15 +3992,16 @@ impl CodeGenerator for ObjCInterface {
                         };
                         result.push(from_block);
 
+                        let error_msg = format!("This {} cannot be downcasted to {}", parent_struct_name, child_struct_name);
                         let try_into_block = quote! {
                             impl std::convert::TryFrom<#parent_struct> for #class_name {
-                                type Error = String;
+                                type Error = &'static str;
                                 fn try_from(parent: #parent_struct) -> Result<#class_name, Self::Error> {
                                     let is_kind_of : bool = unsafe { msg_send!(parent, isKindOfClass:class!(#class_name))};
                                     if is_kind_of {
                                         Ok(#class_name(parent.0))
                                     } else {
-                                        Err(format!("This {} is not an cannot be downcasted to {}", #parent_struct_name, #child_struct_name))
+                                        Err(#error_msg)
                                     }
                                 }
                             }
diff --git a/tests/expectations/tests/libclang-3.9/objc_inheritance.rs b/tests/expectations/tests/libclang-3.9/objc_inheritance.rs
index 76b758ec..f2049a88 100644
--- a/tests/expectations/tests/libclang-3.9/objc_inheritance.rs
+++ b/tests/expectations/tests/libclang-3.9/objc_inheritance.rs
@@ -50,17 +50,14 @@ impl From<Bar> for Foo {
     }
 }
 impl std::convert::TryFrom<Foo> for Bar {
-    type Error = String;
+    type Error = &'static str;
     fn try_from(parent: Foo) -> Result<Bar, Self::Error> {
         let is_kind_of: bool =
             unsafe { msg_send!(parent, isKindOfClass: class!(Bar)) };
         if is_kind_of {
             Ok(Bar(parent.0))
         } else {
-            Err(format!(
-                "This {} is not an cannot be downcasted to {}",
-                "Foo", "Bar"
-            ))
+            Err("This Foo cannot be downcasted to Bar")
         }
     }
 }
@@ -70,19 +67,15 @@ impl From<Baz> for Bar {
         Bar(child.0)
     }
 }
-
 impl std::convert::TryFrom<Bar> for Baz {
-    type Error = String;
+    type Error = &'static str;
     fn try_from(parent: Bar) -> Result<Baz, Self::Error> {
         let is_kind_of: bool =
             unsafe { msg_send!(parent, isKindOfClass: class!(Baz)) };
         if is_kind_of {
             Ok(Baz(parent.0))
         } else {
-            Err(format!(
-                "This {} is not an cannot be downcasted to {}",
-                "Bar", "Baz"
-            ))
+            Err("This Bar cannot be downcasted to Baz")
         }
     }
 }
@@ -93,17 +86,14 @@ impl From<Baz> for Foo {
     }
 }
 impl std::convert::TryFrom<Foo> for Baz {
-    type Error = String;
+    type Error = &'static str;
     fn try_from(parent: Foo) -> Result<Baz, Self::Error> {
         let is_kind_of: bool =
             unsafe { msg_send!(parent, isKindOfClass: class!(Baz)) };
         if is_kind_of {
             Ok(Baz(parent.0))
         } else {
-            Err(format!(
-                "This {} is not an cannot be downcasted to {}",
-                "Foo", "Baz"
-            ))
+            Err("This Foo cannot be downcasted to Baz")
         }
     }
 }
diff --git a/tests/expectations/tests/libclang-4/objc_inheritance.rs b/tests/expectations/tests/libclang-4/objc_inheritance.rs
index a84f6f37..5f07dbaa 100644
--- a/tests/expectations/tests/libclang-4/objc_inheritance.rs
+++ b/tests/expectations/tests/libclang-4/objc_inheritance.rs
@@ -49,17 +49,14 @@ impl From<Bar> for Foo {
     }
 }
 impl std::convert::TryFrom<Foo> for Bar {
-    type Error = String;
+    type Error = &'static str;
     fn try_from(parent: Foo) -> Result<Bar, Self::Error> {
         let is_kind_of: bool =
             unsafe { msg_send!(parent, isKindOfClass: class!(Bar)) };
         if is_kind_of {
             Ok(Bar(parent.0))
         } else {
-            Err(format!(
-                "This {} is not an cannot be downcasted to {}",
-                "Foo", "Bar"
-            ))
+            Err("This Foo cannot be downcasted to Bar")
         }
     }
 }
@@ -87,17 +84,14 @@ impl From<Baz> for Bar {
     }
 }
 impl std::convert::TryFrom<Bar> for Baz {
-    type Error = String;
+    type Error = &'static str;
     fn try_from(parent: Bar) -> Result<Baz, Self::Error> {
         let is_kind_of: bool =
             unsafe { msg_send!(parent, isKindOfClass: class!(Baz)) };
         if is_kind_of {
             Ok(Baz(parent.0))
         } else {
-            Err(format!(
-                "This {} is not an cannot be downcasted to {}",
-                "Bar", "Baz"
-            ))
+            Err("This Bar cannot be downcasted to Baz")
         }
     }
 }
@@ -108,17 +102,14 @@ impl From<Baz> for Foo {
     }
 }
 impl std::convert::TryFrom<Foo> for Baz {
-    type Error = String;
+    type Error = &'static str;
     fn try_from(parent: Foo) -> Result<Baz, Self::Error> {
         let is_kind_of: bool =
             unsafe { msg_send!(parent, isKindOfClass: class!(Baz)) };
         if is_kind_of {
             Ok(Baz(parent.0))
         } else {
-            Err(format!(
-                "This {} is not an cannot be downcasted to {}",
-                "Foo", "Baz"
-            ))
+            Err("This Foo cannot be downcasted to Baz")
         }
     }
 }
diff --git a/tests/expectations/tests/libclang-5/objc_inheritance.rs b/tests/expectations/tests/libclang-5/objc_inheritance.rs
index a84f6f37..42c961e7 100644
--- a/tests/expectations/tests/libclang-5/objc_inheritance.rs
+++ b/tests/expectations/tests/libclang-5/objc_inheritance.rs
@@ -56,10 +56,7 @@ impl std::convert::TryFrom<Foo> for Bar {
         if is_kind_of {
             Ok(Bar(parent.0))
         } else {
-            Err(format!(
-                "This {} is not an cannot be downcasted to {}",
-                "Foo", "Bar"
-            ))
+            Err("This Foo cannot be downcasted to Bar")
         }
     }
 }
@@ -87,17 +84,14 @@ impl From<Baz> for Bar {
     }
 }
 impl std::convert::TryFrom<Bar> for Baz {
-    type Error = String;
+    type Error = &'static str;
     fn try_from(parent: Bar) -> Result<Baz, Self::Error> {
         let is_kind_of: bool =
             unsafe { msg_send!(parent, isKindOfClass: class!(Baz)) };
         if is_kind_of {
             Ok(Baz(parent.0))
         } else {
-            Err(format!(
-                "This {} is not an cannot be downcasted to {}",
-                "Bar", "Baz"
-            ))
+            Err("This Bar cannot be downcasted to Baz")
         }
     }
 }
@@ -108,17 +102,14 @@ impl From<Baz> for Foo {
     }
 }
 impl std::convert::TryFrom<Foo> for Baz {
-    type Error = String;
+    type Error = &'static str;
     fn try_from(parent: Foo) -> Result<Baz, Self::Error> {
         let is_kind_of: bool =
             unsafe { msg_send!(parent, isKindOfClass: class!(Baz)) };
         if is_kind_of {
             Ok(Baz(parent.0))
         } else {
-            Err(format!(
-                "This {} is not an cannot be downcasted to {}",
-                "Foo", "Baz"
-            ))
+            Err("This Foo cannot be downcasted to Baz")
         }
     }
 }
diff --git a/tests/expectations/tests/libclang-9/objc_inheritance.rs b/tests/expectations/tests/libclang-9/objc_inheritance.rs
index a84f6f37..5f07dbaa 100644
--- a/tests/expectations/tests/libclang-9/objc_inheritance.rs
+++ b/tests/expectations/tests/libclang-9/objc_inheritance.rs
@@ -49,17 +49,14 @@ impl From<Bar> for Foo {
     }
 }
 impl std::convert::TryFrom<Foo> for Bar {
-    type Error = String;
+    type Error = &'static str;
     fn try_from(parent: Foo) -> Result<Bar, Self::Error> {
         let is_kind_of: bool =
             unsafe { msg_send!(parent, isKindOfClass: class!(Bar)) };
         if is_kind_of {
             Ok(Bar(parent.0))
         } else {
-            Err(format!(
-                "This {} is not an cannot be downcasted to {}",
-                "Foo", "Bar"
-            ))
+            Err("This Foo cannot be downcasted to Bar")
         }
     }
 }
@@ -87,17 +84,14 @@ impl From<Baz> for Bar {
     }
 }
 impl std::convert::TryFrom<Bar> for Baz {
-    type Error = String;
+    type Error = &'static str;
     fn try_from(parent: Bar) -> Result<Baz, Self::Error> {
         let is_kind_of: bool =
             unsafe { msg_send!(parent, isKindOfClass: class!(Baz)) };
         if is_kind_of {
             Ok(Baz(parent.0))
         } else {
-            Err(format!(
-                "This {} is not an cannot be downcasted to {}",
-                "Bar", "Baz"
-            ))
+            Err("This Bar cannot be downcasted to Baz")
         }
     }
 }
@@ -108,17 +102,14 @@ impl From<Baz> for Foo {
     }
 }
 impl std::convert::TryFrom<Foo> for Baz {
-    type Error = String;
+    type Error = &'static str;
     fn try_from(parent: Foo) -> Result<Baz, Self::Error> {
         let is_kind_of: bool =
             unsafe { msg_send!(parent, isKindOfClass: class!(Baz)) };
         if is_kind_of {
             Ok(Baz(parent.0))
         } else {
-            Err(format!(
-                "This {} is not an cannot be downcasted to {}",
-                "Foo", "Baz"
-            ))
+            Err("This Foo cannot be downcasted to Baz")
         }
     }
 }
diff --git a/tests/expectations/tests/objc_protocol_inheritance.rs b/tests/expectations/tests/objc_protocol_inheritance.rs
index 14570e1e..598273ba 100644
--- a/tests/expectations/tests/objc_protocol_inheritance.rs
+++ b/tests/expectations/tests/objc_protocol_inheritance.rs
@@ -52,17 +52,14 @@ impl From<Bar> for Foo {
     }
 }
 impl std::convert::TryFrom<Foo> for Bar {
-    type Error = String;
+    type Error = &'static str;
     fn try_from(parent: Foo) -> Result<Bar, Self::Error> {
         let is_kind_of: bool =
             unsafe { msg_send!(parent, isKindOfClass: class!(Bar)) };
         if is_kind_of {
             Ok(Bar(parent.0))
         } else {
-            Err(format!(
-                "This {} is not an cannot be downcasted to {}",
-                "Foo", "Bar"
-            ))
+            Err("This Foo cannot be downcasted to Bar")
         }
     }
 }