Generate opaque type for template param dependent bit field width

libclang's API does not provide a straightforward way to check for
this, and calling clang_getFieldDeclBitWidth is actively unsafe in
this case. See https://github.com/llvm/llvm-project/issues/56644

We probably can't generate reasonable bindings for such a type, so
make the binding opaque.

Ideally libclang would report if the bit width could not be
evaluated. Unfortunately making such a change would mean bumping the
minimum libclang version from 6.0 to 15.0.

Instead, add logic to traverse the AST subtree starting from the
field's bit width specifier looking for template parameters. If we
find one, we make the resulting type opaque.

2 files changed, 29 insertions, 0 deletions

diff --git a/tests/expectations/tests/issue-2239-template-dependent-bit-width.rs b/tests/expectations/tests/issue-2239-template-dependent-bit-width.rs
new file mode 100644
index 00000000..75ec9e43
--- /dev/null
+++ b/tests/expectations/tests/issue-2239-template-dependent-bit-width.rs
@@ -0,0 +1,19 @@
+#![allow(
+    dead_code,
+    non_snake_case,
+    non_camel_case_types,
+    non_upper_case_globals
+)]
+
+#[repr(C)]
+#[derive(Debug, Default, Copy, Clone)]
+pub struct b {
+    pub _address: u8,
+}
+pub type b_td<a> = a;
+pub type b_ta<a> = a;
+#[repr(C)]
+#[derive(Debug, Default, Copy, Clone)]
+pub struct b_foo {
+    pub _address: u8,
+}
diff --git a/tests/headers/issue-2239-template-dependent-bit-width.hpp b/tests/headers/issue-2239-template-dependent-bit-width.hpp
new file mode 100644
index 00000000..4e6feb3f
--- /dev/null
+++ b/tests/headers/issue-2239-template-dependent-bit-width.hpp
@@ -0,0 +1,10 @@
+template <class a> class b {
+    typedef a td;
+    using ta = a;
+    struct foo {
+        a foo : sizeof(a);
+        a : sizeof(a);
+        td : sizeof(td);
+        ta : sizeof(ta);
+    };
+};