Use field_visibility callback for new-type aliases

The `field_visibility` callback is now called in case of alias new-type and new-type-deref with the type name and field_name set to `"0"`

bindgen-tests/tests/headers/issue-2966.h

@@ -0,0 +1,6 @@
+// bindgen-flags: --default-alias-style=new_type
+// bindgen-parse-callbacks: type-visibility
+
+typedef const char *  pub_var1;
+typedef const char *  pubcrate_var2;
+typedef const char *  private_var3;

bindgen-tests/tests/parse_callbacks/mod.rs

@@ -93,8 +93,8 @@ struct FieldVisibility {
 }
 
 /// Implements the `field_visibility` function of the trait by checking if the
-/// field name starts with `private_`. If it does it makes it private, if it
-/// doesn't it makes it public, taking into account the default visibility.
+/// field name starts with `private_`. If it does, it makes it private, if it
+/// doesn't, it makes it public, taking into account the default visibility.
 impl ParseCallbacks for FieldVisibility {
     fn field_visibility(
         &self,
@@ -113,6 +113,28 @@ impl ParseCallbacks for FieldVisibility {
     }
 }
 
+#[derive(Debug)]
+struct TypeVisibility;
+
+/// Implements the `field_visibility` function of the trait by checking the
+/// type name. Depending on name prefix, it will return a different visibility.
+impl ParseCallbacks for TypeVisibility {
+    fn field_visibility(
+        &self,
+        FieldInfo { type_name, .. }: FieldInfo,
+    ) -> Option<FieldVisibilityKind> {
+        if type_name.starts_with("private_") {
+            Some(FieldVisibilityKind::Private)
+        } else if type_name.starts_with("pubcrate_") {
+            Some(FieldVisibilityKind::PublicCrate)
+        } else if type_name.starts_with("pub_") {
+            Some(FieldVisibilityKind::Public)
+        } else {
+            None
+        }
+    }
+}
+
 #[derive(Debug)]
 pub(super) struct WrapAsVariadicFn;
 
@@ -129,6 +151,7 @@ pub fn lookup(cb: &str) -> Box<dyn ParseCallbacks> {
             Box::new(BlocklistedTypeImplementsTrait)
         }
         "wrap-as-variadic-fn" => Box::new(WrapAsVariadicFn),
+        "type-visibility" => Box::new(TypeVisibility),
         call_back => {
             if let Some(prefix) =
                 call_back.strip_prefix("remove-function-prefix-")

bindgen/codegen/mod.rs

@@ -1100,13 +1100,21 @@ impl CodeGenerator for Type {
                     });
                 }
 
-                let access_spec =
-                    access_specifier(ctx.options().default_visibility);
                 tokens.append_all(match alias_style {
                     AliasVariation::TypeAlias => quote! {
                         = #inner_rust_type ;
                     },
                     AliasVariation::NewType | AliasVariation::NewTypeDeref => {
+                        let visibility = ctx
+                            .options()
+                            .last_callback(|cb| {
+                                cb.field_visibility(FieldInfo {
+                                    type_name: &item.canonical_name(ctx),
+                                    field_name: "0",
+                                })
+                            })
+                            .unwrap_or(ctx.options().default_visibility);
+                        let access_spec = access_specifier(visibility);
                         quote! {
                             (#access_spec #inner_rust_type) ;
                         }