Fix null function pointer due to renaming of "new"

Previously, when the binding generator renamed "new" to "_new", the previous
name is forgotten, and "_new" is used as an argument to
`godot_method_bind_get_method`, leading to null function pointer for that
method.

This fixes the problem, and makes it harder for further renamings to cause
similiar bugs.

Author: toasteater

bindings_generator/src/api.rs

@@ -105,15 +105,27 @@ pub struct GodotMethod {
     pub arguments: Vec<GodotArgument>,
 }
 
+#[derive(Copy, Clone, Eq, PartialEq, Ord, PartialOrd, Hash, Debug)]
+pub struct MethodName<'a> {
+    pub rust_name: &'a str,
+    pub original_name: &'a str,
+}
+
 impl GodotMethod {
-    pub fn get_name(&self) -> &str {
+    pub fn get_name(&self) -> MethodName {
         // GDScript and NativeScript have ::new methods but we want to reserve
         // the name for the constructors.
         if &self.name == "new" {
-            return "_new";
+            return MethodName {
+                rust_name: "_new",
+                original_name: "new",
+            };
         }
 
-        &self.name
+        MethodName {
+            rust_name: &self.name,
+            original_name: &self.name,
+        }
     }
 
     pub fn get_return_type(&self) -> Ty {

bindings_generator/src/methods.rs

@@ -27,7 +27,7 @@ pub struct {name}MethodTable {{
     )?;
 
     for method in &class.methods {
-        let method_name = method.get_name();
+        let MethodName { rust_name: method_name, .. } = method.get_name();
         if method_name == "free" {
             continue;
         }
@@ -49,14 +49,14 @@ impl {name}MethodTable {{
         name = class.name
     )?;
     for method in &class.methods {
-        let method_name = method.get_name();
+        let MethodName { rust_name: method_name, .. } = method.get_name();
         if method_name == "free" {
             continue;
         }
         writeln!(
             output,
             "            {}: 0 as *mut sys::godot_method_bind,",
-            method.get_name()
+            method_name,
         )?;
     }
     let lookup_name: String = if has_underscore {
@@ -97,14 +97,15 @@ impl {name}MethodTable {{
         lookup_name = lookup_name,
     )?;
     for method in &class.methods {
-        let method_name = method.get_name();
+        let MethodName { rust_name: method_name, original_name } = method.get_name();
         if method_name == "free" {
             continue;
         }
 
         writeln!(output,
-r#"            table.{method_name} = (gd_api.godot_method_bind_get_method)(class_name, "{method_name}\0".as_ptr() as *const c_char );"#,
-            method_name = method_name
+r#"            table.{method_name} = (gd_api.godot_method_bind_get_method)(class_name, "{original_name}\0".as_ptr() as *const c_char );"#,
+            method_name = method_name,
+            original_name = original_name,
         )?;
     }
 
@@ -124,7 +125,7 @@ pub fn generate_method_impl(
     class: &GodotClass,
     method: &GodotMethod,
 ) -> GeneratorResult {
-    let method_name = method.get_name();
+    let MethodName { rust_name: method_name, .. } = method.get_name();
 
     if skip_method(&method_name) {
         return Ok(());
@@ -259,7 +260,7 @@ pub fn generate_methods(
 ) -> GeneratorResult {
     if let Some(class) = api.find_class(class_name) {
         'method: for method in &class.methods {
-            let method_name = method.get_name();
+            let MethodName { rust_name: method_name, .. } = method.get_name();
 
             if skip_method(&method_name) {
                 continue;

test/src/lib.rs

@@ -22,6 +22,7 @@ pub extern "C" fn run_tests(
     status &= gdnative::test_vector3_variants();
 
     status &= test_constructor();
+    status &= test_underscore_method_binding();
 
     gdnative::Variant::from_bool(status).forget()
 }
@@ -44,6 +45,21 @@ fn test_constructor() -> bool {
     return true;
 }
 
+fn test_underscore_method_binding() -> bool {
+    println!(" -- test_underscore_method_binding");
+
+    let ok = std::panic::catch_unwind(|| {
+        let table = gdnative::NativeScriptMethodTable::get(get_api());
+        assert_ne!(0, table._new as usize);
+    }).is_ok();
+
+    if !ok {
+        godot_error!("   !! Test test_underscore_method_binding failed");
+    }
+
+    ok
+}
+
 godot_gdnative_init!();
 godot_nativescript_init!();
 godot_gdnative_terminate!();