ir: Fix "this" argument generation to build a pointer to const, not a const pointer.

Author: emilio

src/ir/context.rs

@@ -1925,9 +1925,44 @@ impl BindgenContext {
         wrapped_id: TypeId,
         parent_id: Option<ItemId>,
         ty: &clang::Type,
+    ) -> TypeId {
+        self.build_wrapper(
+            with_id,
+            wrapped_id,
+            parent_id,
+            ty,
+            ty.is_const(),
+        )
+    }
+
+    /// A wrapper over a type that adds a const qualifier explicitly.
+    ///
+    /// Needed to handle const methods in C++, wrapping the type .
+    pub fn build_const_wrapper(
+        &mut self,
+        with_id: ItemId,
+        wrapped_id: TypeId,
+        parent_id: Option<ItemId>,
+        ty: &clang::Type,
+    ) -> TypeId {
+        self.build_wrapper(
+            with_id,
+            wrapped_id,
+            parent_id,
+            ty,
+            /* is_const = */ true,
+        )
+    }
+
+    fn build_wrapper(
+        &mut self,
+        with_id: ItemId,
+        wrapped_id: TypeId,
+        parent_id: Option<ItemId>,
+        ty: &clang::Type,
+        is_const: bool,
     ) -> TypeId {
         let spelling = ty.spelling();
-        let is_const = ty.is_const();
         let layout = ty.fallible_layout().ok();
         let type_kind = TypeKind::ResolvedTypeRef(wrapped_id);
         let ty = Type::new(Some(spelling), layout, type_kind, is_const);

src/ir/function.rs

@@ -402,14 +402,27 @@ impl FunctionSig {
             let is_virtual = is_method && cursor.method_is_virtual();
             let is_static = is_method && cursor.method_is_static();
             if !is_static && !is_virtual {
-                let class = Item::parse(cursor.semantic_parent(), None, ctx)
+                let parent = cursor.semantic_parent();
+                let class = Item::parse(parent, None, ctx)
                     .expect("Expected to parse the class");
                 // The `class` most likely is not finished parsing yet, so use
                 // the unchecked variant.
                 let class = class.as_type_id_unchecked();
 
+                let class = if is_const {
+                    let const_class_id = ctx.next_item_id();
+                    ctx.build_const_wrapper(
+                        const_class_id,
+                        class,
+                        None,
+                        &parent.cur_type(),
+                    )
+                } else {
+                    class
+                };
+
                 let ptr =
-                    Item::builtin_type(TypeKind::Pointer(class), is_const, ctx);
+                    Item::builtin_type(TypeKind::Pointer(class), false, ctx);
                 args.insert(0, (Some("this".into()), ptr));
             } else if is_virtual {
                 let void = Item::builtin_type(TypeKind::Void, false, ctx);