move impl documentation to their actual locations

compiler/rustc_target/src/abi/mod.rs

@@ -121,7 +121,6 @@ pub fn unadjusted_abi_align(self) -> Align {
     ///
     /// Currently, that means that the type is pointer-sized, pointer-aligned,
     /// and has a initialized (non-union), scalar ABI.
-    // Please also update compiler/rustc_trait_selection/src/solve/trait_goals.rs if the criteria changes
     pub fn is_pointer_like(self, data_layout: &TargetDataLayout) -> bool {
         self.size() == data_layout.pointer_size
             && self.align().abi == data_layout.pointer_align.abi

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

@@ -120,6 +120,8 @@ pub(in crate::solve) fn instantiate_constituent_tys_for_sized_trait<'tcx>(
     ty: Ty<'tcx>,
 ) -> Result<Vec<ty::Binder<'tcx, Ty<'tcx>>>, NoSolution> {
     match *ty.kind() {
+        // impl Sized for u*, i*, bool, f*, FnDef, FnPtr, *(const/mut) T, char, &mut? T, [T; N], dyn* Trait, !
+        // impl Sized for Coroutine, CoroutineWitness, Closure, CoroutineClosure
         ty::Infer(ty::IntVar(_) | ty::FloatVar(_))
         | ty::Uint(_)
         | ty::Int(_)
@@ -152,8 +154,10 @@ pub(in crate::solve) fn instantiate_constituent_tys_for_sized_trait<'tcx>(
             bug!("unexpected type `{ty}`")
         }
 
+        // impl Sized for (T1, T2, .., Tn) where T1: Sized, T2: Sized, .. Tn: Sized
         ty::Tuple(tys) => Ok(tys.iter().map(ty::Binder::dummy).collect()),
 
+        // impl Sized for Adt where T: Sized forall T in field types
         ty::Adt(def, args) => {
             let sized_crit = def.sized_constraint(ecx.tcx());
             Ok(sized_crit.iter_instantiated(ecx.tcx(), args).map(ty::Binder::dummy).collect())
@@ -167,6 +171,7 @@ pub(in crate::solve) fn instantiate_constituent_tys_for_copy_clone_trait<'tcx>(
     ty: Ty<'tcx>,
 ) -> Result<Vec<ty::Binder<'tcx, Ty<'tcx>>>, NoSolution> {
     match *ty.kind() {
+        // impl Copy/Clone for FnDef, FnPtr
         ty::FnDef(..) | ty::FnPtr(_) | ty::Error(_) => Ok(vec![]),
 
         // Implementations are provided in core
@@ -196,12 +201,16 @@ pub(in crate::solve) fn instantiate_constituent_tys_for_copy_clone_trait<'tcx>(
             bug!("unexpected type `{ty}`")
         }
 
+        // impl Copy/Clone for (T1, T2, .., Tn) where T1: Copy/Clone, T2: Copy/Clone, .. Tn: Copy/Clone
         ty::Tuple(tys) => Ok(tys.iter().map(ty::Binder::dummy).collect()),
 
+        // impl Copy/Clone for Closure where Self::TupledUpvars: Copy/Clone
         ty::Closure(_, args) => Ok(vec![ty::Binder::dummy(args.as_closure().tupled_upvars_ty())]),
 
         ty::CoroutineClosure(..) => Err(NoSolution),
 
+        // only when `coroutine_clone` is enabled and the coroutine is movable
+        // impl Copy/Clone for Coroutine where T: Copy/Clone forall T in (upvars, witnesses)
         ty::Coroutine(def_id, args) => match ecx.tcx().coroutine_movability(def_id) {
             Movability::Static => Err(NoSolution),
             Movability::Movable => {
@@ -217,6 +226,7 @@ pub(in crate::solve) fn instantiate_constituent_tys_for_copy_clone_trait<'tcx>(
             }
         },
 
+        // impl Copy/Clone for CoroutineWitness where T: Copy/Clone forall T in coroutine_hidden_types
         ty::CoroutineWitness(def_id, args) => Ok(ecx
             .tcx()
             .coroutine_hidden_types(def_id)

compiler/rustc_trait_selection/src/solve/trait_goals.rs

@@ -188,16 +188,6 @@ fn consider_trait_alias_candidate(
         })
     }
 
-    /// ```rust,ignore (not valid rust syntax)
-    /// impl Sized for u*, i*, bool, f*, FnPtr, FnDef, *(const/mut) T, char, &mut? T, [T; N], dyn* Trait, !
-    ///
-    /// impl Sized for (T1, T2, .., Tn) where T1: Sized, T2: Sized, .. Tn: Sized
-    ///
-    /// impl Sized for Adt where T: Sized forall T in field types
-    /// ```
-    ///
-    /// note that `[T; N]` is unconditionally sized since `T: Sized` is required for the array type to be
-    /// well-formed.
     fn consider_builtin_sized_candidate(
         ecx: &mut EvalCtxt<'_, 'tcx>,
         goal: Goal<'tcx, Self>,
@@ -212,20 +202,6 @@ fn consider_builtin_sized_candidate(
         )
     }
 
-    /// ```rust,ignore (not valid rust syntax)
-    /// impl Copy/Clone for FnDef, FnPtr
-    ///
-    /// impl Copy/Clone for (T1, T2, .., Tn) where T1: Copy/Clone, T2: Copy/Clone, .. Tn: Copy/Clone
-    ///
-    /// impl Copy/Clone for Closure where T: Copy/Clone forall T in upvars
-    ///
-    /// // only when `coroutine_clone` is enabled and the coroutine is movable
-    /// impl Copy/Clone for Coroutine where T: Copy/Clone forall T in (upvars, witnesses)
-    ///
-    /// impl Copy/Clone for CoroutineWitness where T: Copy/Clone forall T in coroutine_hidden_types
-    /// ```
-    ///
-    /// Some built-in types don't have built-in impls because they can be implemented within the standard library.
     fn consider_builtin_copy_clone_candidate(
         ecx: &mut EvalCtxt<'_, 'tcx>,
         goal: Goal<'tcx, Self>,
@@ -240,9 +216,6 @@ fn consider_builtin_copy_clone_candidate(
         )
     }
 
-    /// Implements `PointerLike` for types that are pointer-sized, pointer-aligned,
-    /// and have a initialized (non-union), scalar ABI.
-    // Please also update compiler/rustc_target/src/abi/mod.rs if the criteria changes
     fn consider_builtin_pointer_like_candidate(
         ecx: &mut EvalCtxt<'_, 'tcx>,
         goal: Goal<'tcx, Self>,
@@ -272,18 +245,13 @@ fn consider_builtin_pointer_like_candidate(
         }
     }
 
-    /// ```rust,ignore (not valid rust syntax)
-    /// impl FnPtr for FnPtr {}
-    /// impl !FnPtr for T where T != FnPtr && T is rigid {}
-    /// ```
-    ///
-    /// Note: see [`Ty::is_known_rigid`] for what it means for the type to be rigid.
     fn consider_builtin_fn_ptr_trait_candidate(
         ecx: &mut EvalCtxt<'_, 'tcx>,
         goal: Goal<'tcx, Self>,
     ) -> QueryResult<'tcx> {
         let self_ty = goal.predicate.self_ty();
         match goal.predicate.polarity {
+            // impl FnPtr for FnPtr {}
             ty::ImplPolarity::Positive => {
                 if self_ty.is_fn_ptr() {
                     ecx.evaluate_added_goals_and_make_canonical_response(Certainty::Yes)
@@ -291,6 +259,7 @@ fn consider_builtin_fn_ptr_trait_candidate(
                     Err(NoSolution)
                 }
             }
+            //  impl !FnPtr for T where T != FnPtr && T is rigid {}
             ty::ImplPolarity::Negative => {
                 // If a type is rigid and not a fn ptr, then we know for certain
                 // that it does *not* implement `FnPtr`.