FRTs are not trivially Copy & Clone

Author: BennoLossin

compiler/rustc_middle/src/ty/sty.rs

@@ -1945,7 +1945,7 @@ impl<'tcx> Ty<'tcx> {
             ty::Coroutine(..) | ty::CoroutineWitness(..) => false,
 
             // Might be, but not "trivial" so just giving the safe answer.
-            ty::Adt(..) | ty::Closure(..) | ty::CoroutineClosure(..) => false,
+            ty::Adt(..) | ty::Field(..) | ty::Closure(..) | ty::CoroutineClosure(..) => false,
 
             ty::UnsafeBinder(_) => false,
 

compiler/rustc_next_trait_solver/src/solve/assembly/structural_traits.rs

@@ -221,6 +221,7 @@ where
         | ty::Foreign(..)
         | ty::Ref(_, _, Mutability::Mut)
         | ty::Adt(_, _)
+        | ty::Field(_, _)
         | ty::Alias(_, _)
         | ty::Param(_)
         | ty::Placeholder(..) => Err(NoSolution),

compiler/rustc_trait_selection/src/traits/select/candidate_assembly.rs

@@ -1206,7 +1206,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
             }
 
             // Fallback to whatever user-defined impls or param-env clauses exist in this case.
-            ty::Adt(..) | ty::Alias(..) | ty::Param(..) | ty::Placeholder(..) => {}
+            ty::Adt(..) | ty::Field(..) | ty::Alias(..) | ty::Param(..) | ty::Placeholder(..) => {}
 
             ty::Infer(ty::TyVar(_)) => {
                 candidates.ambiguous = true;

compiler/rustc_trait_selection/src/traits/select/mod.rs

@@ -2222,6 +2222,7 @@ impl<'tcx> SelectionContext<'_, 'tcx> {
             | ty::Slice(_)
             | ty::Dynamic(..)
             | ty::Adt(..)
+            | ty::Field(..)
             | ty::Alias(..)
             | ty::Param(..)
             | ty::Placeholder(..)

library/std/tests/field_projections/clone-copy.rs

@@ -0,0 +1,20 @@
+#![allow(incomplete_features)]
+#![feature(field_projections)]
+
+use std::field::field_of;
+
+struct MyStruct(());
+
+impl Clone for field_of!(MyStruct, 0) {
+    fn clone(&self) -> Self {
+        *self
+    }
+}
+
+impl Copy for field_of!(MyStruct, 0) {}
+
+fn assert_copy<T: Copy>() {}
+
+fn main() {
+    assert_copy::<field_of!(MyStruct, 0)>();
+}