From a68453ce6bea99f7f5df0b2f1bb97ba160e235fa Mon Sep 17 00:00:00 2001
From: Hans Wennborg <hans@chromium.org>
Date: Wed, 27 Aug 2025 14:05:50 +0200
Subject: [PATCH 1/2] Get the type's definition in CompInfo::from_ty

In https://github.com/llvm/llvm-project/pull/147835, Clang's AST changed
so that a TagType's decl will not necessarily refer to the type's
definition, but to the exact declaration which produced the type.

For example, in

  typedef struct S T;
  struct S {
    int x;
  };

the 'struct S' type would refer to the incomplete type decl in the
typedef, causing CompInfo to fail to see the type's definition.

This patch inserts a call to use the definition when available. It fixes
the original test case in
https://github.com/rust-lang/rust-bindgen/issues/3275 and most of the
test failures caused by the Clang change but not all.
---
 bindgen/ir/comp.rs | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/bindgen/ir/comp.rs b/bindgen/ir/comp.rs
index 0b50bf3244..f0c4e6f03c 100644
--- a/bindgen/ir/comp.rs
+++ b/bindgen/ir/comp.rs
@@ -1234,6 +1234,12 @@ impl CompInfo {
         );
 
         let mut cursor = ty.declaration();
+
+        // If there is a definition, that's what we want.
+        if let Some(def) = cursor.definition() {
+            cursor = def;
+        }
+
         let mut kind = Self::kind_from_cursor(&cursor);
         if kind.is_err() {
             if let Some(location) = location {

From 2e7bbcfdbb487100f58d682a39dda3583fbde517 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Emilio=20Cobos=20=C3=81lvarez?= <emilio@crisal.io>
Date: Wed, 27 Aug 2025 15:57:15 +0200
Subject: [PATCH 2/2] clang: Push the fix for #3277 into Type::declaration.

Fixes #3264.
---
 .../expectations/tests/nested-class-field.rs  | 22 +++++++++++++++++++
 .../tests/headers/nested-class-field.hpp      |  7 ++++++
 bindgen/clang.rs                              | 10 ++++-----
 bindgen/ir/comp.rs                            |  6 -----
 4 files changed, 34 insertions(+), 11 deletions(-)
 create mode 100644 bindgen-tests/tests/expectations/tests/nested-class-field.rs
 create mode 100644 bindgen-tests/tests/headers/nested-class-field.hpp

diff --git a/bindgen-tests/tests/expectations/tests/nested-class-field.rs b/bindgen-tests/tests/expectations/tests/nested-class-field.rs
new file mode 100644
index 0000000000..91500f4142
--- /dev/null
+++ b/bindgen-tests/tests/expectations/tests/nested-class-field.rs
@@ -0,0 +1,22 @@
+#![allow(dead_code, non_snake_case, non_camel_case_types, non_upper_case_globals)]
+#[repr(C)]
+#[derive(Debug, Default, Copy, Clone)]
+pub struct A {
+    pub _address: u8,
+}
+#[allow(clippy::unnecessary_operation, clippy::identity_op)]
+const _: () = {
+    ["Size of A"][::std::mem::size_of::<A>() - 1usize];
+    ["Alignment of A"][::std::mem::align_of::<A>() - 1usize];
+};
+#[repr(C)]
+#[derive(Debug, Default, Copy, Clone)]
+pub struct A_I {
+    pub i: ::std::os::raw::c_int,
+}
+#[allow(clippy::unnecessary_operation, clippy::identity_op)]
+const _: () = {
+    ["Size of A_I"][::std::mem::size_of::<A_I>() - 4usize];
+    ["Alignment of A_I"][::std::mem::align_of::<A_I>() - 4usize];
+    ["Offset of field: A_I::i"][::std::mem::offset_of!(A_I, i) - 0usize];
+};
diff --git a/bindgen-tests/tests/headers/nested-class-field.hpp b/bindgen-tests/tests/headers/nested-class-field.hpp
new file mode 100644
index 0000000000..295ebe8129
--- /dev/null
+++ b/bindgen-tests/tests/headers/nested-class-field.hpp
@@ -0,0 +1,7 @@
+class A {
+  class I;
+};
+
+class A::I {
+  int i;
+};
diff --git a/bindgen/clang.rs b/bindgen/clang.rs
index e52fed0d4a..1e8326ed82 100644
--- a/bindgen/clang.rs
+++ b/bindgen/clang.rs
@@ -1211,11 +1211,11 @@ impl Type {
 
     /// Get a cursor pointing to this type's declaration.
     pub(crate) fn declaration(&self) -> Cursor {
-        unsafe {
-            Cursor {
-                x: clang_getTypeDeclaration(self.x),
-            }
-        }
+        let decl = Cursor {
+            x: unsafe { clang_getTypeDeclaration(self.x) },
+        };
+        // Prior to clang 22, the declaration pointed to the definition.
+        decl.definition().unwrap_or(decl)
     }
 
     /// Get the canonical declaration of this type, if it is available.
diff --git a/bindgen/ir/comp.rs b/bindgen/ir/comp.rs
index f0c4e6f03c..0b50bf3244 100644
--- a/bindgen/ir/comp.rs
+++ b/bindgen/ir/comp.rs
@@ -1234,12 +1234,6 @@ impl CompInfo {
         );
 
         let mut cursor = ty.declaration();
-
-        // If there is a definition, that's what we want.
-        if let Some(def) = cursor.definition() {
-            cursor = def;
-        }
-
         let mut kind = Self::kind_from_cursor(&cursor);
         if kind.is_err() {
             if let Some(location) = location {