FRTs & FFI

Author: BennoLossin

compiler/rustc_lint/messages.ftl

@@ -373,6 +373,7 @@ lint_improper_ctypes_enum_repr_help =
     consider adding a `#[repr(C)]`, `#[repr(transparent)]`, or integer `#[repr(...)]` attribute to this enum
 
 lint_improper_ctypes_enum_repr_reason = enum has no representation hint
+lint_improper_ctypes_field_representing_type_reason = field representing types have no C equivalent
 lint_improper_ctypes_fnptr_help = consider using an `extern fn(...) -> ...` function pointer instead
 
 lint_improper_ctypes_fnptr_reason = this function pointer has Rust-specific calling convention

compiler/rustc_lint/src/types/improper_ctypes.rs

@@ -569,6 +569,12 @@ impl<'a, 'tcx> ImproperCTypesVisitor<'a, 'tcx> {
                 }
             }
 
+            ty::Field(..) => FfiUnsafe {
+                ty,
+                reason: fluent::lint_improper_ctypes_field_representing_type_reason,
+                help: None,
+            },
+
             ty::Char => FfiUnsafe {
                 ty,
                 reason: fluent::lint_improper_ctypes_char_reason,