Address code review comments

compiler/rustc_ast_passes/src/ast_validation.rs

@@ -19,7 +19,6 @@ use rustc_session::lint::builtin::{
     DEPRECATED_WHERE_CLAUSE_LOCATION, MISSING_ABI, PATTERNS_IN_FNS_WITHOUT_BODY,
 };
 use rustc_session::lint::{BuiltinLintDiagnostics, LintBuffer};
-use rustc_session::parse::feature_err;
 use rustc_session::Session;
 use rustc_span::source_map::Spanned;
 use rustc_span::symbol::{kw, sym, Ident};
@@ -754,19 +753,7 @@ impl<'a> AstValidator<'a> {
                     self.maybe_lint_missing_abi(sig_span, ty.id);
                 }
             }
-            TyKind::TraitObject(ref bounds, syntax, ..) => {
+            TyKind::TraitObject(ref bounds, ..) => {
-                if syntax == TraitObjectSyntax::DynStar
-                    && !self.session.features_untracked().dyn_star
-                {
-                    feature_err(
-                        &self.session.parse_sess,
-                        sym::dyn_star,
-                        ty.span,
-                        "dyn* trait objects are unstable",
-                    )
-                    .emit();
-                }
-
                 let mut any_lifetime_bounds = false;
                 for bound in bounds {
                     if let GenericBound::Outlives(ref lifetime) = *bound {

compiler/rustc_ast_passes/src/feature_gate.rs

@@ -573,6 +573,9 @@ impl<'a> Visitor<'a> for PostExpansionVisitor<'a> {
             ast::TyKind::Never => {
                 gate_feature_post!(&self, never_type, ty.span, "the `!` type is experimental");
             }
+            ast::TyKind::TraitObject(_, ast::TraitObjectSyntax::DynStar, ..) => {
+                gate_feature_post!(&self, dyn_star, ty.span, "dyn* trait objects are unstable");
+            }
             _ => {}
         }
         visit::walk_ty(self, ty)

compiler/rustc_codegen_cranelift/src/value_and_place.rs

@@ -816,6 +816,7 @@ pub(crate) fn assert_assignable<'tcx>(
             // fn(&T) -> for<'l> fn(&'l T) is allowed
         }
         (&ty::Dynamic(from_traits, _, _from_kind), &ty::Dynamic(to_traits, _, _to_kind)) => {
+            // FIXME(dyn-star): Do the right thing with DynKinds
             for (from, to) in from_traits.iter().zip(to_traits) {
                 let from =
                     fx.tcx.normalize_erasing_late_bound_regions(ParamEnv::reveal_all(), from);

compiler/rustc_codegen_ssa/src/mir/block.rs

@@ -367,7 +367,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
         bx.ret(llval);
     }
 
-    #[tracing::instrument(level = "debug", skip(self, helper, bx))]
+    #[tracing::instrument(level = "trace", skip(self, helper, bx))]
     fn codegen_drop_terminator(
         &mut self,
         helper: TerminatorCodegenHelper<'tcx>,

compiler/rustc_const_eval/src/interpret/cast.rs

@@ -113,11 +113,10 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
                 if let ty::Dynamic(data, _, ty::DynStar) = cast_ty.kind() {
                     // Initial cast from sized to dyn trait
                     let vtable = self.get_vtable_ptr(src.layout.ty, data.principal())?;
-                    let ptr = self.read_immediate(src)?.to_scalar();
+                    let vtable = Scalar::from_maybe_pointer(vtable, self);
-                    // FIXME(dyn-star): This should not use new_dyn_trait, but
+                    let data = self.read_immediate(src)?.to_scalar();
-                    // it does exactly the same thing (makes a scalar pair)...
+                    let _assert_pointer_sized = data.to_pointer(self)?;
-                    // so maybe we should just duplicate/rename the function.
+                    let val = Immediate::ScalarPair(data, vtable);
-                    let val = Immediate::new_dyn_trait(ptr, vtable, &*self.tcx);
                     self.write_immediate(val, dest)?;
                 } else {
                     bug!()
@@ -327,7 +326,7 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
                 let new_vptr = self.get_vtable_ptr(ty, data_b.principal())?;
                 self.write_immediate(Immediate::new_dyn_trait(old_data, new_vptr, self), dest)
             }
-            (_, &ty::Dynamic(ref data, _, _repr)) => {
+            (_, &ty::Dynamic(ref data, _, ty::Dyn)) => {
                 // Initial cast from sized to dyn trait
                 let vtable = self.get_vtable_ptr(src_pointee_ty, data.principal())?;
                 let ptr = self.read_scalar(src)?;

compiler/rustc_const_eval/src/transform/validate.rs

@@ -570,7 +570,7 @@ impl<'a, 'tcx> Visitor<'tcx> for TypeChecker<'a, 'tcx> {
                         }
                     }
                     CastKind::DynStar => {
-                        // FIXME: make sure nothing needs to be done here.
+                        // FIXME(dyn-star): make sure nothing needs to be done here.
                     }
                     // Nothing to check here
                     CastKind::PointerFromExposedAddress

compiler/rustc_feature/src/active.rs

@@ -381,7 +381,7 @@ declare_features! (
     /// Allows `#[doc(masked)]`.
     (active, doc_masked, "1.21.0", Some(44027), None),
     /// Allows `dyn* Trait` objects.
-    (active, dyn_star, "1.65.0", Some(91611), None),
+    (incomplete, dyn_star, "CURRENT_RUSTC_VERSION", Some(91611), None),
     /// Allows `X..Y` patterns.
     (active, exclusive_range_pattern, "1.11.0", Some(37854), None),
     /// Allows exhaustive pattern matching on types that contain uninhabited types.

compiler/rustc_middle/src/ty/layout.rs

@@ -626,11 +626,11 @@ impl<'tcx> LayoutCx<'tcx, TyCtxt<'tcx>> {
             }
 
             ty::Dynamic(_, _, ty::DynStar) => {
-                let mut pointer = scalar_unit(Int(dl.ptr_sized_integer(), false));
+                let mut data = scalar_unit(Int(dl.ptr_sized_integer(), false));
-                pointer.valid_range_mut().start = 1;
+                data.valid_range_mut().start = 0;
                 let mut vtable = scalar_unit(Pointer);
                 vtable.valid_range_mut().start = 1;
-                tcx.intern_layout(self.scalar_pair(pointer, vtable))
+                tcx.intern_layout(self.scalar_pair(data, vtable))
             }
 
             // Arrays and slices.
@@ -2474,8 +2474,7 @@ where
 
                     match tcx.struct_tail_erasing_lifetimes(pointee, cx.param_env()).kind() {
                         ty::Slice(_) | ty::Str => TyMaybeWithLayout::Ty(tcx.types.usize),
-                        // FIXME(eholk): Do the right thing with trait object representation
+                        ty::Dynamic(_, _, ty::Dyn) => {
-                        ty::Dynamic(_, _, _repr) => {
                             TyMaybeWithLayout::Ty(tcx.mk_imm_ref(
                                 tcx.lifetimes.re_static,
                                 tcx.mk_array(tcx.types.usize, 3),
@@ -3379,7 +3378,7 @@ impl<'tcx> LayoutCx<'tcx, TyCtxt<'tcx>> {
         Ok(self.tcx.arena.alloc(fn_abi))
     }
 
-    #[tracing::instrument(level = "debug", skip(self))]
+    #[tracing::instrument(level = "trace", skip(self))]
     fn fn_abi_adjust_for_abi(
         &self,
         fn_abi: &mut FnAbi<'tcx, Ty<'tcx>>,

compiler/rustc_monomorphize/src/collector.rs

@@ -699,7 +699,9 @@ impl<'a, 'tcx> MirVisitor<'tcx> for MirNeighborCollector<'a, 'tcx> {
                 // This could also be a different Unsize instruction, like
                 // from a fixed sized array to a slice. But we are only
                 // interested in things that produce a vtable.
-                if (target_ty.is_trait() || target_ty.is_dyn_star()) && !source_ty.is_trait() {
+                if (target_ty.is_trait() && !source_ty.is_trait())
+                    || (target_ty.is_dyn_star() && !source_ty.is_dyn_star())
+                {
                     create_mono_items_for_vtable_methods(
                         self.tcx,
                         target_ty,

compiler/rustc_parse/src/parser/ty.rs

@@ -579,9 +579,7 @@ impl<'a> Parser<'a> {
         self.bump(); // `dyn`
 
         // parse dyn* types
-        let dyn_star = matches!(self.token.kind, TokenKind::BinOp(token::Star));
+        let syntax = if self.eat(&TokenKind::BinOp(token::Star)) {
-        let syntax = if dyn_star {
-            self.bump(); // `*`
             TraitObjectSyntax::DynStar
         } else {
             TraitObjectSyntax::Dyn

compiler/rustc_symbol_mangling/src/typeid/typeid_itanium_cxx_abi.rs

@@ -627,10 +627,13 @@ fn encode_ty<'tcx>(
         }
 
         // Trait types
-        ty::Dynamic(predicates, region, _repr) => {
+        ty::Dynamic(predicates, region, kind) => {
             // u3dynI<element-type1[..element-typeN]>E, where <element-type> is <predicate>, as
             // vendor extended type.
-            let mut s = String::from("u3dynI");
+            let mut s = String::from(match kind {
+                ty::Dyn => "u3dynI",
+                ty::DynStar => "u7dynstarI",
+            });
             s.push_str(&encode_predicates(tcx, predicates, dict, options));
             s.push_str(&encode_region(tcx, *region, dict, options));
             s.push('E');

compiler/rustc_symbol_mangling/src/v0.rs

@@ -479,8 +479,12 @@ impl<'tcx> Printer<'tcx> for &mut SymbolMangler<'tcx> {
                 })?;
             }
 
-            ty::Dynamic(predicates, r, _repr) => {
+            ty::Dynamic(predicates, r, kind) => {
-                self.push("D");
+                self.push(match kind {
+                    ty::Dyn => "D",
+                    // FIXME(dyn-star): need to update v0 mangling docs
+                    ty::DynStar => "D*",
+                });
                 self = self.print_dyn_existential(predicates)?;
                 self = r.print(self)?;
             }

compiler/rustc_trait_selection/src/traits/error_reporting/suggestions.rs

@@ -1067,7 +1067,7 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> {
         self_ty: Ty<'tcx>,
         object_ty: Ty<'tcx>,
     ) {
-        let ty::Dynamic(predicates, _, _) = object_ty.kind() else { return; };
+        let ty::Dynamic(predicates, _, ty::Dyn) = object_ty.kind() else { return; };
         let self_ref_ty = self.tcx.mk_imm_ref(self.tcx.lifetimes.re_erased, self_ty);
 
         for predicate in predicates.iter() {
@@ -1365,7 +1365,7 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> {
         let trait_pred = self.resolve_vars_if_possible(trait_pred);
         let ty = trait_pred.skip_binder().self_ty();
         let is_object_safe = match ty.kind() {
-            ty::Dynamic(predicates, _, _) => {
+            ty::Dynamic(predicates, _, ty::Dyn) => {
                 // If the `dyn Trait` is not object safe, do not suggest `Box<dyn Trait>`.
                 predicates
                     .principal_def_id()

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

@@ -890,9 +890,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
         let mut nested = vec![];
         match (source.kind(), target.kind()) {
             // Trait+Kx+'a -> Trait+Ky+'b (auto traits and lifetime subtyping).
-            (&ty::Dynamic(ref data_a, r_a, repr_a), &ty::Dynamic(ref data_b, r_b, repr_b))
+            (&ty::Dynamic(ref data_a, r_a, ty::Dyn), &ty::Dynamic(ref data_b, r_b, ty::Dyn)) => {
-                if repr_a == repr_b =>
-            {
                 // See `assemble_candidates_for_unsizing` for more info.
                 // We already checked the compatibility of auto traits within `assemble_candidates_for_unsizing`.
                 let iter = data_a
@@ -911,7 +909,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
                             .map(ty::Binder::dummy),
                     );
                 let existential_predicates = tcx.mk_poly_existential_predicates(iter);
-                let source_trait = tcx.mk_dynamic(existential_predicates, r_b, repr_b);
+                let source_trait = tcx.mk_dynamic(existential_predicates, r_b, ty::Dyn);
 
                 // Require that the traits involved in this upcast are **equal**;
                 // only the **lifetime bound** is changed.
@@ -938,7 +936,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
             }
 
             // `T` -> `Trait`
-            (_, &ty::Dynamic(ref data, r, _repr)) => {
+            (_, &ty::Dynamic(ref data, r, ty::Dyn)) => {
                 let mut object_dids = data.auto_traits().chain(data.principal_def_id());
                 if let Some(did) = object_dids.find(|did| !tcx.is_object_safe(*did)) {
                     return Err(TraitNotObjectSafe(did));

compiler/rustc_traits/src/chalk/lowering.rs

@@ -326,7 +326,8 @@ impl<'tcx> LowerInto<'tcx, chalk_ir::Ty<RustInterner<'tcx>>> for Ty<'tcx> {
                     )),
                 })
             }
-            ty::Dynamic(predicates, region, _repr) => chalk_ir::TyKind::Dyn(chalk_ir::DynTy {
+            // FIXME(dyn-star): handle the dynamic kind (dyn or dyn*)
+            ty::Dynamic(predicates, region, _kind) => chalk_ir::TyKind::Dyn(chalk_ir::DynTy {
                 bounds: predicates.lower_into(interner),
                 lifetime: region.lower_into(interner),
             }),

compiler/rustc_type_ir/src/sty.rs

@@ -19,26 +19,33 @@ use rustc_data_structures::stable_hasher::HashStable;
 use rustc_serialize::{Decodable, Decoder, Encodable};
 
 /// Specifies how a trait object is represented.
-#[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, Debug, Encodable, Decodable)]
+#[derive(
+    Clone,
+    Copy,
+    PartialEq,
+    Eq,
+    PartialOrd,
+    Ord,
+    Hash,
+    Debug,
+    Encodable,
+    Decodable,
+    HashStable_Generic
+)]
 pub enum DynKind {
     /// An unsized `dyn Trait` object
     Dyn,
     /// A sized `dyn* Trait` object
+    ///
+    /// These objects are represented as a `(data, vtable)` pair where `data` is a ptr-sized value
+    /// (often a pointer to the real object, but not necessarily) and `vtable` is a pointer to
+    /// the vtable for `dyn* Trait`. The representation is essentially the same as `&dyn Trait`
+    /// or similar, but the drop function included in the vtable is responsible for freeing the
+    /// underlying storage if needed. This allows a `dyn*` object to be treated agnostically with
+    /// respect to whether it points to a `Box<T>`, `Rc<T>`, etc.
     DynStar,
 }
 
-// Manually implemented because deriving HashStable requires rustc_query_system, which would
-// create a cyclic dependency.
-impl<CTX> HashStable<CTX> for DynKind {
-    fn hash_stable(
-        &self,
-        hcx: &mut CTX,
-        hasher: &mut rustc_data_structures::stable_hasher::StableHasher,
-    ) {
-        std::mem::discriminant(self).hash_stable(hcx, hasher);
-    }
-}
-
 /// Defines the kinds of types used by the type system.
 ///
 /// Types written by the user start out as `hir::TyKind` and get

compiler/rustc_typeck/src/check/cast.rs

@@ -105,7 +105,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
 
         Ok(match *t.kind() {
             ty::Slice(_) | ty::Str => Some(PointerKind::Length),
-            ty::Dynamic(ref tty, ..) => Some(PointerKind::VTable(tty.principal_def_id())),
+            ty::Dynamic(ref tty, _, ty::Dyn) => Some(PointerKind::VTable(tty.principal_def_id())),
             ty::Adt(def, substs) if def.is_struct() => match def.non_enum_variant().fields.last() {
                 None => Some(PointerKind::Thin),
                 Some(f) => {
@@ -142,6 +142,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             | ty::Generator(..)
             | ty::Adt(..)
             | ty::Never
+            | ty::Dynamic(_, _, ty::DynStar)
             | ty::Error(_) => {
                 let reported = self
                     .tcx
@@ -246,7 +247,7 @@ fn check_dyn_star_cast<'tcx>(
     let cause = ObligationCause::new(
         expr.span,
         fcx.body_id,
-        // FIXME: Use a better obligation cause code
+        // FIXME(dyn-star): Use a better obligation cause code
         ObligationCauseCode::MiscObligation,
     );
 
@@ -927,10 +928,10 @@ impl<'a, 'tcx> CastCheck<'tcx> {
 
             (Int(_) | Float, Int(_) | Float) => Ok(CastKind::NumericCast),
 
-            // FIXME: this needs more conditions...
+            // FIXME(dyn-star): this needs more conditions...
             (_, DynStar) => Ok(CastKind::DynStarCast),
 
-            // FIXME: do we want to allow dyn* upcasting or other casts?
+            // FIXME(dyn-star): do we want to allow dyn* upcasting or other casts?
             (DynStar, _) => Err(CastError::IllegalCast),
         }
     }

src/test/ui/dyn-star/const.rs

@@ -1,6 +1,6 @@
 // run-pass
 #![feature(dyn_star)]
-#![allow(unused)]
+#![allow(unused, incomplete_features)]
 
 use std::fmt::Debug;
 

src/test/ui/dyn-star/drop.rs

@@ -1,6 +1,7 @@
 // run-pass
 // check-run-results
 #![feature(dyn_star)]
+#![allow(incomplete_features)]
 
 use std::fmt::Debug;
 

src/test/ui/dyn-star/error.rs

@@ -1,4 +1,5 @@
 #![feature(dyn_star)]
+#![allow(incomplete_features)]
 
 use std::fmt::Debug;
 

src/test/ui/dyn-star/error.stderr

@@ -1,5 +1,5 @@
 error[E0277]: the trait bound `{integer}: Foo` is not satisfied
-  --> $DIR/error.rs:9:27
+  --> $DIR/error.rs:10:27
    |
 LL |     let dyn_i: dyn* Foo = i as dyn* Foo;
    |                           ^ the trait `Foo` is not implemented for `{integer}`

src/test/ui/dyn-star/make-dyn-star.rs

@@ -1,5 +1,6 @@
 // run-pass
 #![feature(dyn_star)]
+#![allow(incomplete_features)]
 
 use std::fmt::Debug;
 

src/test/ui/dyn-star/method.rs

@@ -1,5 +1,6 @@
 // run-pass
 #![feature(dyn_star)]
+#![allow(incomplete_features)]
 
 trait Foo {
     fn get(&self) -> usize;

src/test/ui/dyn-star/syntax.rs

@@ -3,6 +3,7 @@
 // check-pass
 
 #![feature(dyn_star)]
+#![allow(incomplete_features)]
 
 pub fn dyn_star_parameter(_: dyn* Send) {
 }

src/tools/clippy/clippy_lints/src/transmute/utils.rs

@@ -2,18 +2,11 @@ use rustc_hir::Expr;
 use rustc_lint::LateContext;
 use rustc_middle::ty::{cast::CastKind, Ty};
 use rustc_span::DUMMY_SP;
-use rustc_typeck::check::{
+use rustc_typeck::check::{cast::{self, CastCheckResult}, FnCtxt, Inherited};
-    cast::{self, CastCheckResult},
-    FnCtxt, Inherited,
-};
 
 // check if the component types of the transmuted collection and the result have different ABI,
 // size or alignment
-pub(super) fn is_layout_incompatible<'tcx>(
+pub(super) fn is_layout_incompatible<'tcx>(cx: &LateContext<'tcx>, from: Ty<'tcx>, to: Ty<'tcx>) -> bool {
-    cx: &LateContext<'tcx>,
-    from: Ty<'tcx>,
-    to: Ty<'tcx>,
-) -> bool {
     if let Ok(from) = cx.tcx.try_normalize_erasing_regions(cx.param_env, from)
         && let Ok(to) = cx.tcx.try_normalize_erasing_regions(cx.param_env, to)
         && let Ok(from_layout) = cx.tcx.layout_of(cx.param_env.and(from))
@@ -36,9 +29,7 @@ pub(super) fn can_be_expressed_as_pointer_cast<'tcx>(
     from_ty: Ty<'tcx>,
     to_ty: Ty<'tcx>,
 ) -> bool {
-    use CastKind::{
+    use CastKind::{AddrPtrCast, ArrayPtrCast, FnPtrAddrCast, FnPtrPtrCast, PtrAddrCast, PtrPtrCast};
-        AddrPtrCast, ArrayPtrCast, FnPtrAddrCast, FnPtrPtrCast, PtrAddrCast, PtrPtrCast,
-    };
     matches!(
         check_cast(cx, e, from_ty, to_ty),
         Some(PtrPtrCast | PtrAddrCast | AddrPtrCast | ArrayPtrCast | FnPtrPtrCast | FnPtrAddrCast)
@@ -49,12 +40,7 @@ pub(super) fn can_be_expressed_as_pointer_cast<'tcx>(
 /// the cast. In certain cases, including some invalid casts from array references
 /// to pointers, this may cause additional errors to be emitted and/or ICE error
 /// messages. This function will panic if that occurs.
-fn check_cast<'tcx>(
+fn check_cast<'tcx>(cx: &LateContext<'tcx>, e: &'tcx Expr<'_>, from_ty: Ty<'tcx>, to_ty: Ty<'tcx>) -> Option<CastKind> {
-    cx: &LateContext<'tcx>,
-    e: &'tcx Expr<'_>,
-    from_ty: Ty<'tcx>,
-    to_ty: Ty<'tcx>,
-) -> Option<CastKind> {
     let hir_id = e.hir_id;
     let local_def_id = hir_id.owner;
 
@@ -62,7 +48,10 @@ fn check_cast<'tcx>(
         let fn_ctxt = FnCtxt::new(&inherited, cx.param_env, hir_id);
 
         // If we already have errors, we can't be sure we can pointer cast.
-        assert!(!fn_ctxt.errors_reported_since_creation(), "Newly created FnCtxt contained errors");
+        assert!(
+            !fn_ctxt.errors_reported_since_creation(),
+            "Newly created FnCtxt contained errors"
+        );
 
         if let CastCheckResult::Deferred(check) = cast::check_cast(
             &fn_ctxt, e, from_ty, to_ty,

src/tools/clippy/clippy_utils/src/qualify_min_const_fn.rs

@@ -18,11 +18,7 @@ use std::borrow::Cow;
 
 type McfResult = Result<(), (Span, Cow<'static, str>)>;
 
-pub fn is_min_const_fn<'a, 'tcx>(
+pub fn is_min_const_fn<'a, 'tcx>(tcx: TyCtxt<'tcx>, body: &'a Body<'tcx>, msrv: Option<RustcVersion>) -> McfResult {
-    tcx: TyCtxt<'tcx>,
-    body: &'a Body<'tcx>,
-    msrv: Option<RustcVersion>,
-) -> McfResult {
     let def_id = body.source.def_id();
     let mut current = def_id;
     loop {
@@ -37,18 +33,10 @@ pub fn is_min_const_fn<'a, 'tcx>(
                 | ty::PredicateKind::ConstEquate(..)
                 | ty::PredicateKind::Trait(..)
                 | ty::PredicateKind::TypeWellFormedFromEnv(..) => continue,
-                ty::PredicateKind::ObjectSafe(_) => {
+                ty::PredicateKind::ObjectSafe(_) => panic!("object safe predicate on function: {:#?}", predicate),
-                    panic!("object safe predicate on function: {:#?}", predicate)
+                ty::PredicateKind::ClosureKind(..) => panic!("closure kind predicate on function: {:#?}", predicate),
-                }
+                ty::PredicateKind::Subtype(_) => panic!("subtype predicate on function: {:#?}", predicate),
-                ty::PredicateKind::ClosureKind(..) => {
+                ty::PredicateKind::Coerce(_) => panic!("coerce predicate on function: {:#?}", predicate),
-                    panic!("closure kind predicate on function: {:#?}", predicate)
-                }
-                ty::PredicateKind::Subtype(_) => {
-                    panic!("subtype predicate on function: {:#?}", predicate)
-                }
-                ty::PredicateKind::Coerce(_) => {
-                    panic!("coerce predicate on function: {:#?}", predicate)
-                }
             }
         }
         match predicates.parent {
@@ -89,23 +77,22 @@ fn check_ty<'tcx>(tcx: TyCtxt<'tcx>, ty: Ty<'tcx>, span: Span) -> McfResult {
         match ty.kind() {
             ty::Ref(_, _, hir::Mutability::Mut) => {
                 return Err((span, "mutable references in const fn are unstable".into()));
-            }
+            },
             ty::Opaque(..) => return Err((span, "`impl Trait` in const fn is unstable".into())),
             ty::FnPtr(..) => {
                 return Err((span, "function pointers in const fn are unstable".into()));
-            }
+            },
             ty::Dynamic(preds, _, _) => {
                 for pred in preds.iter() {
                     match pred.skip_binder() {
-                        ty::ExistentialPredicate::AutoTrait(_)
+                        ty::ExistentialPredicate::AutoTrait(_) | ty::ExistentialPredicate::Projection(_) => {
-                        | ty::ExistentialPredicate::Projection(_) => {
                             return Err((
                                 span,
                                 "trait bounds other than `Sized` \
                                  on const fn parameters are unstable"
                                     .into(),
                             ));
-                        }
+                        },
                         ty::ExistentialPredicate::Trait(trait_ref) => {
                             if Some(trait_ref.def_id) != tcx.lang_items().sized_trait() {
                                 return Err((
@@ -115,11 +102,11 @@ fn check_ty<'tcx>(tcx: TyCtxt<'tcx>, ty: Ty<'tcx>, span: Span) -> McfResult {
                                         .into(),
                                 ));
                             }
-                        }
+                        },
                     }
                 }
-            }
+            },
-            _ => {}
+            _ => {},
         }
     }
     Ok(())
@@ -133,13 +120,10 @@ fn check_rvalue<'tcx>(
     span: Span,
 ) -> McfResult {
     match rvalue {
-        Rvalue::ThreadLocalRef(_) => {
+        Rvalue::ThreadLocalRef(_) => Err((span, "cannot access thread local storage in const fn".into())),
-            Err((span, "cannot access thread local storage in const fn".into()))
+        Rvalue::Len(place) | Rvalue::Discriminant(place) | Rvalue::Ref(_, _, place) | Rvalue::AddressOf(_, place) => {
-        }
+            check_place(tcx, *place, span, body)
-        Rvalue::Len(place)
+        },
-        | Rvalue::Discriminant(place)
-        | Rvalue::Ref(_, _, place)
-        | Rvalue::AddressOf(_, place) => check_place(tcx, *place, span, body),
         Rvalue::CopyForDeref(place) => check_place(tcx, *place, span, body),
         Rvalue::Repeat(operand, _)
         | Rvalue::Use(operand)
@@ -152,9 +136,7 @@ fn check_rvalue<'tcx>(
         ) => check_operand(tcx, operand, span, body),
         Rvalue::Cast(
             CastKind::Pointer(
-                PointerCast::UnsafeFnPointer
+                PointerCast::UnsafeFnPointer | PointerCast::ClosureFnPointer(_) | PointerCast::ReifyFnPointer,
-                | PointerCast::ClosureFnPointer(_)
-                | PointerCast::ReifyFnPointer,
             ),
             _,
             _,
@@ -164,10 +146,7 @@ fn check_rvalue<'tcx>(
                 deref_ty.ty
             } else {
                 // We cannot allow this for now.
-                return Err((
+                return Err((span, "unsizing casts are only allowed for references right now".into()));
-                    span,
-                    "unsizing casts are only allowed for references right now".into(),
-                ));
             };
             let unsized_ty = tcx.struct_tail_erasing_lifetimes(pointee_ty, tcx.param_env(def_id));
             if let ty::Slice(_) | ty::Str = unsized_ty.kind() {
@@ -178,14 +157,14 @@ fn check_rvalue<'tcx>(
                 // We just can't allow trait objects until we have figured out trait method calls.
                 Err((span, "unsizing casts are not allowed in const fn".into()))
             }
-        }
+        },
         Rvalue::Cast(CastKind::PointerExposeAddress, _, _) => {
             Err((span, "casting pointers to ints is unstable in const fn".into()))
-        }
+        },
         Rvalue::Cast(CastKind::DynStar, _, _) => {
             // FIXME(dyn-star)
             unimplemented!()
-        }
+        },
         // binops are fine on integers
         Rvalue::BinaryOp(_, box (lhs, rhs)) | Rvalue::CheckedBinaryOp(_, box (lhs, rhs)) => {
             check_operand(tcx, lhs, span, body)?;
@@ -194,12 +173,13 @@ fn check_rvalue<'tcx>(
             if ty.is_integral() || ty.is_bool() || ty.is_char() {
                 Ok(())
             } else {
-                Err((span, "only int, `bool` and `char` operations are stable in const fn".into()))
+                Err((
+                    span,
+                    "only int, `bool` and `char` operations are stable in const fn".into(),
+                ))
             }
-        }
+        },
-        Rvalue::NullaryOp(NullOp::SizeOf | NullOp::AlignOf, _) | Rvalue::ShallowInitBox(_, _) => {
+        Rvalue::NullaryOp(NullOp::SizeOf | NullOp::AlignOf, _) | Rvalue::ShallowInitBox(_, _) => Ok(()),
-            Ok(())
-        }
         Rvalue::UnaryOp(_, operand) => {
             let ty = operand.ty(body, tcx);
             if ty.is_integral() || ty.is_bool() {
@@ -207,13 +187,13 @@ fn check_rvalue<'tcx>(
             } else {
                 Err((span, "only int and `bool` operations are stable in const fn".into()))
             }
-        }
+        },
         Rvalue::Aggregate(_, operands) => {
             for operand in operands {
                 check_operand(tcx, operand, span, body)?;
             }
             Ok(())
-        }
+        },
     }
 }
 
@@ -228,7 +208,7 @@ fn check_statement<'tcx>(
         StatementKind::Assign(box (place, rval)) => {
             check_place(tcx, *place, span, body)?;
             check_rvalue(tcx, body, def_id, rval, span)
-        }
+        },
 
         StatementKind::FakeRead(box (_, place)) => check_place(tcx, *place, span, body),
         // just an assignment
@@ -238,15 +218,13 @@ fn check_statement<'tcx>(
 
         StatementKind::Intrinsic(box NonDivergingIntrinsic::Assume(op)) => check_operand(tcx, op, span, body),
 
-        StatementKind::CopyNonOverlapping(box rustc_middle::mir::CopyNonOverlapping {
+        StatementKind::Intrinsic(box NonDivergingIntrinsic::CopyNonOverlapping(
-            dst,
+            rustc_middle::mir::CopyNonOverlapping { dst, src, count },
-            src,
+        )) => {
-            count,
-        }) => {
             check_operand(tcx, dst, span, body)?;
             check_operand(tcx, src, span, body)?;
             check_operand(tcx, count, span, body)
-        }
+        },
         // These are all NOPs
         StatementKind::StorageLive(_)
         | StatementKind::StorageDead(_)
@@ -257,12 +235,7 @@ fn check_statement<'tcx>(
     }
 }
 
-fn check_operand<'tcx>(
+fn check_operand<'tcx>(tcx: TyCtxt<'tcx>, operand: &Operand<'tcx>, span: Span, body: &Body<'tcx>) -> McfResult {
-    tcx: TyCtxt<'tcx>,
-    operand: &Operand<'tcx>,
-    span: Span,
-    body: &Body<'tcx>,
-) -> McfResult {
     match operand {
         Operand::Move(place) | Operand::Copy(place) => check_place(tcx, *place, span, body),
         Operand::Constant(c) => match c.check_static_ptr(tcx) {
@@ -272,12 +245,7 @@ fn check_operand<'tcx>(
     }
 }
 
-fn check_place<'tcx>(
+fn check_place<'tcx>(tcx: TyCtxt<'tcx>, place: Place<'tcx>, span: Span, body: &Body<'tcx>) -> McfResult {
-    tcx: TyCtxt<'tcx>,
-    place: Place<'tcx>,
-    span: Span,
-    body: &Body<'tcx>,
-) -> McfResult {
     let mut cursor = place.projection.as_ref();
     while let [ref proj_base @ .., elem] = *cursor {
         cursor = proj_base;
@@ -290,12 +258,12 @@ fn check_place<'tcx>(
                         return Err((span, "accessing union fields is unstable".into()));
                     }
                 }
-            }
+            },
             ProjectionElem::ConstantIndex { .. }
             | ProjectionElem::Downcast(..)
             | ProjectionElem::Subslice { .. }
             | ProjectionElem::Deref
-            | ProjectionElem::Index(_) => {}
+            | ProjectionElem::Index(_) => {},
         }
     }
 
@@ -321,16 +289,18 @@ fn check_terminator<'a, 'tcx>(
         TerminatorKind::DropAndReplace { place, value, .. } => {
             check_place(tcx, *place, span, body)?;
             check_operand(tcx, value, span, body)
-        }
+        },
 
-        TerminatorKind::SwitchInt { discr, switch_ty: _, targets: _ } => {
+        TerminatorKind::SwitchInt {
-            check_operand(tcx, discr, span, body)
+            discr,
-        }
+            switch_ty: _,
+            targets: _,
+        } => check_operand(tcx, discr, span, body),
 
         TerminatorKind::Abort => Err((span, "abort is not stable in const fn".into())),
         TerminatorKind::GeneratorDrop | TerminatorKind::Yield { .. } => {
             Err((span, "const fn generators are unstable".into()))
-        }
+        },
 
         TerminatorKind::Call {
             func,
@@ -375,15 +345,17 @@ fn check_terminator<'a, 'tcx>(
             } else {
                 Err((span, "can only call other const fns within const fn".into()))
             }
-        }
+        },
 
-        TerminatorKind::Assert { cond, expected: _, msg: _, target: _, cleanup: _ } => {
+        TerminatorKind::Assert {
-            check_operand(tcx, cond, span, body)
+            cond,
-        }
+            expected: _,
+            msg: _,
+            target: _,
+            cleanup: _,
+        } => check_operand(tcx, cond, span, body),
 
-        TerminatorKind::InlineAsm { .. } => {
+        TerminatorKind::InlineAsm { .. } => Err((span, "cannot use inline assembly in const fn".into())),
-            Err((span, "cannot use inline assembly in const fn".into()))
-        }
     }
 }
 

src/tools/clippy/clippy_utils/src/ty.rs

@@ -14,9 +14,8 @@ use rustc_lint::LateContext;
 use rustc_middle::mir::interpret::{ConstValue, Scalar};
 use rustc_middle::ty::subst::{GenericArg, GenericArgKind, Subst};
 use rustc_middle::ty::{
-    self, AdtDef, Binder, BoundRegion, DefIdTree, FnSig, IntTy, ParamEnv, Predicate, PredicateKind,
+    self, AdtDef, Binder, BoundRegion, DefIdTree, FnSig, IntTy, ParamEnv, Predicate, PredicateKind, ProjectionTy,
-    ProjectionTy, Region, RegionKind, Ty, TyCtxt, TypeSuperVisitable, TypeVisitable, TypeVisitor,
+    Region, RegionKind, Ty, TyCtxt, TypeSuperVisitable, TypeVisitable, TypeVisitor, UintTy, VariantDef, VariantDiscr,
-    UintTy, VariantDef, VariantDiscr,
 };
 use rustc_span::symbol::Ident;
 use rustc_span::{sym, Span, Symbol, DUMMY_SP};
@@ -167,7 +166,9 @@ pub fn implements_trait_with_env<'tcx>(
     }
     let ty_params = tcx.mk_substs(ty_params.iter());
     tcx.infer_ctxt().enter(|infcx| {
-        infcx.type_implements_trait(trait_id, ty, ty_params, param_env).must_apply_modulo_regions()
+        infcx
+            .type_implements_trait(trait_id, ty, ty_params, param_env)
+            .must_apply_modulo_regions()
     })
 }
 
@@ -184,14 +185,11 @@ pub fn is_must_use_ty<'tcx>(cx: &LateContext<'tcx>, ty: Ty<'tcx>) -> bool {
     match ty.kind() {
         ty::Adt(adt, _) => cx.tcx.has_attr(adt.did(), sym::must_use),
         ty::Foreign(did) => cx.tcx.has_attr(*did, sym::must_use),
-        ty::Slice(ty)
+        ty::Slice(ty) | ty::Array(ty, _) | ty::RawPtr(ty::TypeAndMut { ty, .. }) | ty::Ref(_, ty, _) => {
-        | ty::Array(ty, _)
-        | ty::RawPtr(ty::TypeAndMut { ty, .. })
-        | ty::Ref(_, ty, _) => {
             // for the Array case we don't need to care for the len == 0 case
             // because we don't want to lint functions returning empty arrays
             is_must_use_ty(cx, *ty)
-        }
+        },
         ty::Tuple(substs) => substs.iter().any(|ty| is_must_use_ty(cx, ty)),
         ty::Opaque(def_id, _) => {
             for (predicate, _) in cx.tcx.explicit_item_bounds(*def_id) {
@@ -202,7 +200,7 @@ pub fn is_must_use_ty<'tcx>(cx: &LateContext<'tcx>, ty: Ty<'tcx>) -> bool {
                 }
             }
             false
-        }
+        },
         ty::Dynamic(binder, _, _) => {
             for predicate in binder.iter() {
                 if let ty::ExistentialPredicate::Trait(ref trait_ref) = predicate.skip_binder() {
@@ -212,7 +210,7 @@ pub fn is_must_use_ty<'tcx>(cx: &LateContext<'tcx>, ty: Ty<'tcx>) -> bool {
                 }
             }
             false
-        }
+        },
         _ => false,
     }
 }
@@ -222,11 +220,7 @@ pub fn is_must_use_ty<'tcx>(cx: &LateContext<'tcx>, ty: Ty<'tcx>) -> bool {
 // not succeed
 /// Checks if `Ty` is normalizable. This function is useful
 /// to avoid crashes on `layout_of`.
-pub fn is_normalizable<'tcx>(
+pub fn is_normalizable<'tcx>(cx: &LateContext<'tcx>, param_env: ty::ParamEnv<'tcx>, ty: Ty<'tcx>) -> bool {
-    cx: &LateContext<'tcx>,
-    param_env: ty::ParamEnv<'tcx>,
-    ty: Ty<'tcx>,
-) -> bool {
     is_normalizable_helper(cx, param_env, ty, &mut FxHashMap::default())
 }
 
@@ -246,14 +240,15 @@ fn is_normalizable_helper<'tcx>(
         if infcx.at(&cause, param_env).normalize(ty).is_ok() {
             match ty.kind() {
                 ty::Adt(def, substs) => def.variants().iter().all(|variant| {
-                    variant.fields.iter().all(|field| {
+                    variant
-                        is_normalizable_helper(cx, param_env, field.ty(cx.tcx, substs), cache)
+                        .fields
-                    })
+                        .iter()
+                        .all(|field| is_normalizable_helper(cx, param_env, field.ty(cx.tcx, substs), cache))
                 }),
                 _ => ty.walk().all(|generic_arg| match generic_arg.unpack() {
                     GenericArgKind::Type(inner_ty) if inner_ty != ty => {
                         is_normalizable_helper(cx, param_env, inner_ty, cache)
-                    }
+                    },
                     _ => true, // if inner_ty == ty, we've already checked it
                 }),
             }
@@ -278,9 +273,7 @@ pub fn is_recursively_primitive_type(ty: Ty<'_>) -> bool {
     match *ty.kind() {
         ty::Bool | ty::Char | ty::Int(_) | ty::Uint(_) | ty::Float(_) | ty::Str => true,
         ty::Ref(_, inner, _) if *inner.kind() == ty::Str => true,
-        ty::Array(inner_type, _) | ty::Slice(inner_type) => {
+        ty::Array(inner_type, _) | ty::Slice(inner_type) => is_recursively_primitive_type(inner_type),
-            is_recursively_primitive_type(inner_type)
-        }
         ty::Tuple(inner_types) => inner_types.iter().all(is_recursively_primitive_type),
         _ => false,
     }
@@ -320,9 +313,11 @@ pub fn is_type_diagnostic_item(cx: &LateContext<'_>, ty: Ty<'_>, diag_item: Symb
 /// Returns `false` if the `LangItem` is not defined.
 pub fn is_type_lang_item(cx: &LateContext<'_>, ty: Ty<'_>, lang_item: hir::LangItem) -> bool {
     match ty.kind() {
-        ty::Adt(adt, _) => {
+        ty::Adt(adt, _) => cx
-            cx.tcx.lang_items().require(lang_item).map_or(false, |li| li == adt.did())
+            .tcx
-        }
+            .lang_items()
+            .require(lang_item)
+            .map_or(false, |li| li == adt.did()),
         _ => false,
     }
 }
@@ -347,11 +342,7 @@ pub fn match_type(cx: &LateContext<'_>, ty: Ty<'_>, path: &[&str]) -> bool {
 /// deallocate memory. For these types, and composites containing them, changing the drop order
 /// won't result in any observable side effects.
 pub fn needs_ordered_drop<'tcx>(cx: &LateContext<'tcx>, ty: Ty<'tcx>) -> bool {
-    fn needs_ordered_drop_inner<'tcx>(
+    fn needs_ordered_drop_inner<'tcx>(cx: &LateContext<'tcx>, ty: Ty<'tcx>, seen: &mut FxHashSet<Ty<'tcx>>) -> bool {
-        cx: &LateContext<'tcx>,
-        ty: Ty<'tcx>,
-        seen: &mut FxHashSet<Ty<'tcx>>,
-    ) -> bool {
         if !seen.insert(ty) {
             return false;
         }
@@ -402,7 +393,11 @@ pub fn needs_ordered_drop<'tcx>(cx: &LateContext<'tcx>, ty: Ty<'tcx>) -> bool {
 /// removed.
 pub fn peel_mid_ty_refs(ty: Ty<'_>) -> (Ty<'_>, usize) {
     fn peel(ty: Ty<'_>, count: usize) -> (Ty<'_>, usize) {
-        if let ty::Ref(_, ty, _) = ty.kind() { peel(*ty, count + 1) } else { (ty, count) }
+        if let ty::Ref(_, ty, _) = ty.kind() {
+            peel(*ty, count + 1)
+        } else {
+            (ty, count)
+        }
     }
     peel(ty, 0)
 }
@@ -457,18 +452,17 @@ pub fn same_type_and_consts<'tcx>(a: Ty<'tcx>, b: Ty<'tcx>) -> bool {
                 return false;
             }
 
-            substs_a.iter().zip(substs_b.iter()).all(|(arg_a, arg_b)| {
+            substs_a
-                match (arg_a.unpack(), arg_b.unpack()) {
+                .iter()
-                    (GenericArgKind::Const(inner_a), GenericArgKind::Const(inner_b)) => {
+                .zip(substs_b.iter())
-                        inner_a == inner_b
+                .all(|(arg_a, arg_b)| match (arg_a.unpack(), arg_b.unpack()) {
-                    }
+                    (GenericArgKind::Const(inner_a), GenericArgKind::Const(inner_b)) => inner_a == inner_b,
                     (GenericArgKind::Type(type_a), GenericArgKind::Type(type_b)) => {
                         same_type_and_consts(type_a, type_b)
-                    }
+                    },
                     _ => true,
-                }
+                })
-            })
+        },
-        }
         _ => a == b,
     }
 }
@@ -484,10 +478,7 @@ pub fn is_uninit_value_valid_for_ty(cx: &LateContext<'_>, ty: Ty<'_>) -> bool {
 }
 
 /// Gets an iterator over all predicates which apply to the given item.
-pub fn all_predicates_of(
+pub fn all_predicates_of(tcx: TyCtxt<'_>, id: DefId) -> impl Iterator<Item = &(Predicate<'_>, Span)> {
-    tcx: TyCtxt<'_>,
-    id: DefId,
-) -> impl Iterator<Item = &(Predicate<'_>, Span)> {
     let mut next_id = Some(id);
     iter::from_fn(move || {
         next_id.take().map(|id| {
@@ -517,7 +508,7 @@ impl<'tcx> ExprFnSig<'tcx> {
                 } else {
                     Some(sig.input(i))
                 }
-            }
+            },
             Self::Closure(_, sig) => Some(sig.input(0).map_bound(|ty| ty.tuple_fields()[i])),
             Self::Trait(inputs, _, _) => Some(inputs.map_bound(|ty| ty.tuple_fields()[i])),
         }
@@ -526,10 +517,7 @@ impl<'tcx> ExprFnSig<'tcx> {
     /// Gets the argument type at the given offset. For closures this will also get the type as
     /// written. This will return `None` when the index is out of bounds only for variadic
     /// functions, otherwise this will panic.
-    pub fn input_with_hir(
+    pub fn input_with_hir(self, i: usize) -> Option<(Option<&'tcx hir::Ty<'tcx>>, Binder<'tcx, Ty<'tcx>>)> {
-        self,
-        i: usize,
-    ) -> Option<(Option<&'tcx hir::Ty<'tcx>>, Binder<'tcx, Ty<'tcx>>)> {
         match self {
             Self::Sig(sig, _) => {
                 if sig.c_variadic() {
@@ -540,7 +528,7 @@ impl<'tcx> ExprFnSig<'tcx> {
                 } else {
                     Some((None, sig.input(i)))
                 }
-            }
+            },
             Self::Closure(decl, sig) => Some((
                 decl.and_then(|decl| decl.inputs.get(i)),
                 sig.input(0).map_bound(|ty| ty.tuple_fields()[i]),
@@ -559,15 +547,17 @@ impl<'tcx> ExprFnSig<'tcx> {
     }
 
     pub fn predicates_id(&self) -> Option<DefId> {
-        if let ExprFnSig::Sig(_, id) | ExprFnSig::Trait(_, _, id) = *self { id } else { None }
+        if let ExprFnSig::Sig(_, id) | ExprFnSig::Trait(_, _, id) = *self {
+            id
+        } else {
+            None
+        }
     }
 }
 
 /// If the expression is function like, get the signature for it.
 pub fn expr_sig<'tcx>(cx: &LateContext<'tcx>, expr: &Expr<'_>) -> Option<ExprFnSig<'tcx>> {
-    if let Res::Def(DefKind::Fn | DefKind::Ctor(_, CtorKind::Fn) | DefKind::AssocFn, id) =
+    if let Res::Def(DefKind::Fn | DefKind::Ctor(_, CtorKind::Fn) | DefKind::AssocFn, id) = path_res(cx, expr) {
-        path_res(cx, expr)
-    {
         Some(ExprFnSig::Sig(cx.tcx.fn_sig(id), Some(id)))
     } else {
         ty_sig(cx, cx.typeck_results().expr_ty_adjusted(expr).peel_refs())
@@ -581,14 +571,12 @@ pub fn ty_sig<'tcx>(cx: &LateContext<'tcx>, ty: Ty<'tcx>) -> Option<ExprFnSig<'t
     }
     match *ty.kind() {
         ty::Closure(id, subs) => {
-            let decl = id.as_local().and_then(|id| {
+            let decl = id
-                cx.tcx.hir().fn_decl_by_hir_id(cx.tcx.hir().local_def_id_to_hir_id(id))
+                .as_local()
-            });
+                .and_then(|id| cx.tcx.hir().fn_decl_by_hir_id(cx.tcx.hir().local_def_id_to_hir_id(id)));
             Some(ExprFnSig::Closure(decl, subs.as_closure().sig()))
-        }
+        },
-        ty::FnDef(id, subs) => {
+        ty::FnDef(id, subs) => Some(ExprFnSig::Sig(cx.tcx.bound_fn_sig(id).subst(cx.tcx, subs), Some(id))),
-            Some(ExprFnSig::Sig(cx.tcx.bound_fn_sig(id).subst(cx.tcx, subs), Some(id)))
-        }
         ty::Opaque(id, _) => sig_from_bounds(cx, ty, cx.tcx.item_bounds(id), cx.tcx.opt_parent(id)),
         ty::FnPtr(sig) => Some(ExprFnSig::Sig(sig, None)),
         ty::Dynamic(bounds, _, _) => {
@@ -601,19 +589,16 @@ pub fn ty_sig<'tcx>(cx: &LateContext<'tcx>, ty: Ty<'tcx>) -> Option<ExprFnSig<'t
                 {
                     let output = bounds
                         .projection_bounds()
-                        .find(|p| {
+                        .find(|p| lang_items.fn_once_output().map_or(false, |id| id == p.item_def_id()))
-                            lang_items.fn_once_output().map_or(false, |id| id == p.item_def_id())
-                        })
                         .map(|p| p.map_bound(|p| p.term.ty().unwrap()));
                     Some(ExprFnSig::Trait(bound.map_bound(|b| b.substs.type_at(0)), output, None))
-                }
+                },
                 _ => None,
             }
-        }
+        },
         ty::Projection(proj) => match cx.tcx.try_normalize_erasing_regions(cx.param_env, ty) {
             Ok(normalized_ty) if normalized_ty != ty => ty_sig(cx, normalized_ty),
-            _ => sig_for_projection(cx, proj)
+            _ => sig_for_projection(cx, proj).or_else(|| sig_from_bounds(cx, ty, cx.param_env.caller_bounds(), None)),
-                .or_else(|| sig_from_bounds(cx, ty, cx.param_env.caller_bounds(), None)),
         },
         ty::Param(_) => sig_from_bounds(cx, ty, cx.param_env.caller_bounds(), None),
         _ => None,
@@ -644,7 +629,7 @@ fn sig_from_bounds<'tcx>(
                     return None;
                 }
                 inputs = Some(i);
-            }
+            },
             PredicateKind::Projection(p)
                 if Some(p.projection_ty.item_def_id) == lang_items.fn_once_output()
                     && p.projection_ty.self_ty() == ty =>
@@ -654,7 +639,7 @@ fn sig_from_bounds<'tcx>(
                     return None;
                 }
                 output = Some(pred.kind().rebind(p.term.ty().unwrap()));
-            }
+            },
             _ => (),
         }
     }
@@ -662,10 +647,7 @@ fn sig_from_bounds<'tcx>(
     inputs.map(|ty| ExprFnSig::Trait(ty, output, predicates_id))
 }
 
-fn sig_for_projection<'tcx>(
+fn sig_for_projection<'tcx>(cx: &LateContext<'tcx>, ty: ProjectionTy<'tcx>) -> Option<ExprFnSig<'tcx>> {
-    cx: &LateContext<'tcx>,
-    ty: ProjectionTy<'tcx>,
-) -> Option<ExprFnSig<'tcx>> {
     let mut inputs = None;
     let mut output = None;
     let lang_items = cx.tcx.lang_items();
@@ -691,10 +673,8 @@ fn sig_for_projection<'tcx>(
                     return None;
                 }
                 inputs = Some(i);
-            }
+            },
-            PredicateKind::Projection(p)
+            PredicateKind::Projection(p) if Some(p.projection_ty.item_def_id) == lang_items.fn_once_output() => {
-                if Some(p.projection_ty.item_def_id) == lang_items.fn_once_output() =>
-            {
                 if output.is_some() {
                     // Multiple different fn trait impls. Is this even allowed?
                     return None;
@@ -703,7 +683,7 @@ fn sig_for_projection<'tcx>(
                     pred.map_bound(|pred| pred.kind().rebind(p.term.ty().unwrap()))
                         .subst(cx.tcx, ty.substs),
                 );
-            }
+            },
             _ => (),
         }
     }
@@ -797,10 +777,7 @@ pub fn for_each_top_level_late_bound_region<B>(
                 ControlFlow::Continue(())
             }
         }
-        fn visit_binder<T: TypeVisitable<'tcx>>(
+        fn visit_binder<T: TypeVisitable<'tcx>>(&mut self, t: &Binder<'tcx, T>) -> ControlFlow<Self::BreakTy> {
-            &mut self,
-            t: &Binder<'tcx, T>,
-        ) -> ControlFlow<Self::BreakTy> {
             self.index += 1;
             let res = t.super_visit_with(self);
             self.index -= 1;
@@ -814,27 +791,19 @@ pub fn for_each_top_level_late_bound_region<B>(
 pub fn variant_of_res<'tcx>(cx: &LateContext<'tcx>, res: Res) -> Option<&'tcx VariantDef> {
     match res {
         Res::Def(DefKind::Struct, id) => Some(cx.tcx.adt_def(id).non_enum_variant()),
-        Res::Def(DefKind::Variant, id) => {
+        Res::Def(DefKind::Variant, id) => Some(cx.tcx.adt_def(cx.tcx.parent(id)).variant_with_id(id)),
-            Some(cx.tcx.adt_def(cx.tcx.parent(id)).variant_with_id(id))
+        Res::Def(DefKind::Ctor(CtorOf::Struct, _), id) => Some(cx.tcx.adt_def(cx.tcx.parent(id)).non_enum_variant()),
-        }
-        Res::Def(DefKind::Ctor(CtorOf::Struct, _), id) => {
-            Some(cx.tcx.adt_def(cx.tcx.parent(id)).non_enum_variant())
-        }
         Res::Def(DefKind::Ctor(CtorOf::Variant, _), id) => {
             let var_id = cx.tcx.parent(id);
             Some(cx.tcx.adt_def(cx.tcx.parent(var_id)).variant_with_id(var_id))
-        }
+        },
         Res::SelfCtor(id) => Some(cx.tcx.type_of(id).ty_adt_def().unwrap().non_enum_variant()),
         _ => None,
     }
 }
 
 /// Checks if the type is a type parameter implementing `FnOnce`, but not `FnMut`.
-pub fn ty_is_fn_once_param<'tcx>(
+pub fn ty_is_fn_once_param<'tcx>(tcx: TyCtxt<'_>, ty: Ty<'tcx>, predicates: &'tcx [Predicate<'_>]) -> bool {
-    tcx: TyCtxt<'_>,
-    ty: Ty<'tcx>,
-    predicates: &'tcx [Predicate<'_>],
-) -> bool {
     let ty::Param(ty) = *ty.kind() else {
         return false;
     };