3 files changed, 9 insertions, 1 deletions
diff --git a/compiler/rustc_ast/src/ast.rs b/compiler/rustc_ast/src/ast.rs
index e41228bd501..098e2606a3b 100644
--- a/compiler/rustc_ast/src/ast.rs
+++ b/compiler/rustc_ast/src/ast.rs
@@ -2161,6 +2161,10 @@ impl TyKind {
             None
         }
     }
+
+    pub fn is_anon_adt(&self) -> bool {
+        matches!(self, TyKind::AnonStruct(..) | TyKind::AnonUnion(..))
+    }
 }
 
 /// Syntax used to declare a trait object.
diff --git a/compiler/rustc_builtin_macros/src/deriving/clone.rs b/compiler/rustc_builtin_macros/src/deriving/clone.rs
index 7bf19f61166..267405ac32e 100644
--- a/compiler/rustc_builtin_macros/src/deriving/clone.rs
+++ b/compiler/rustc_builtin_macros/src/deriving/clone.rs
@@ -110,7 +110,9 @@ fn cs_clone_simple(
                 && !seen_type_names.insert(name)
             {
                 // Already produced an assertion for this type.
-            } else {
+                // Anonymous structs or unions must be eliminated as they cannot be
+                // type parameters.
+            } else if !field.ty.kind.is_anon_adt() {
                 // let _: AssertParamIsClone<FieldTy>;
                 super::assert_ty_bounds(
                     cx,
diff --git a/compiler/rustc_builtin_macros/src/deriving/mod.rs b/compiler/rustc_builtin_macros/src/deriving/mod.rs
index a6f3252e7be..8a3375cba9d 100644
--- a/compiler/rustc_builtin_macros/src/deriving/mod.rs
+++ b/compiler/rustc_builtin_macros/src/deriving/mod.rs
@@ -123,6 +123,8 @@ fn assert_ty_bounds(
     span: Span,
     assert_path: &[Symbol],
 ) {
+    // Deny anonymous structs or unions to avoid wierd errors.
+    assert!(!ty.kind.is_anon_adt(), "Anonymous structs or unions cannot be type parameters");
     // Generate statement `let _: assert_path<ty>;`.
     let span = cx.with_def_site_ctxt(span);
     let assert_path = cx.path_all(span, true, cx.std_path(assert_path), vec![GenericArg::Type(ty)]);