diff --git a/compiler/rustc_ast_lowering/src/lib.rs b/compiler/rustc_ast_lowering/src/lib.rs
index ce81a0ae9596b..bd1876d428475 100644
--- a/compiler/rustc_ast_lowering/src/lib.rs
+++ b/compiler/rustc_ast_lowering/src/lib.rs
@@ -1817,9 +1817,11 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
 
         let opaque_ty_span = self.mark_span_with_reason(DesugaringKind::Async, span, None);
 
-        let opaque_ty_def_id = self.local_def_id(opaque_ty_node_id);
         let fn_def_id = self.local_def_id(fn_node_id);
 
+        let opaque_ty_def_id =
+            self.create_def(fn_def_id, opaque_ty_node_id, DefPathData::ImplTrait);
+
         // When we create the opaque type for this async fn, it is going to have
         // to capture all the lifetimes involved in the signature (including in the
         // return type). This is done by introducing lifetime parameters for:
diff --git a/compiler/rustc_hir_analysis/src/check/compare_method.rs b/compiler/rustc_hir_analysis/src/check/compare_method.rs
index e68df228c6b51..bf4e5126bfa10 100644
--- a/compiler/rustc_hir_analysis/src/check/compare_method.rs
+++ b/compiler/rustc_hir_analysis/src/check/compare_method.rs
@@ -14,10 +14,8 @@ use rustc_infer::traits::util;
 use rustc_middle::ty::error::{ExpectedFound, TypeError};
 use rustc_middle::ty::util::ExplicitSelf;
 use rustc_middle::ty::{
-    self, AssocItem, DefIdTree, TraitRef, Ty, TypeFoldable, TypeFolder, TypeSuperFoldable,
-    TypeVisitable,
+    self, DefIdTree, InternalSubsts, Ty, TypeFoldable, TypeFolder, TypeSuperFoldable, TypeVisitable,
 };
-use rustc_middle::ty::{FnSig, InternalSubsts};
 use rustc_middle::ty::{GenericParamDefKind, ToPredicate, TyCtxt};
 use rustc_span::Span;
 use rustc_trait_selection::traits::error_reporting::TypeErrCtxtExt;
@@ -51,11 +49,11 @@ pub(crate) fn compare_impl_method<'tcx>(
         return;
     }
 
-    if let Err(_) = compare_number_of_generics(tcx, impl_m, impl_m_span, trait_m, trait_item_span) {
+    if let Err(_) = compare_number_of_generics(tcx, impl_m, trait_m, trait_item_span, false) {
         return;
     }
 
-    if let Err(_) = compare_generic_param_kinds(tcx, impl_m, trait_m) {
+    if let Err(_) = compare_generic_param_kinds(tcx, impl_m, trait_m, false) {
         return;
     }
 
@@ -144,9 +142,9 @@ pub(crate) fn compare_impl_method<'tcx>(
 #[instrument(level = "debug", skip(tcx, impl_m_span, impl_trait_ref))]
 fn compare_predicate_entailment<'tcx>(
     tcx: TyCtxt<'tcx>,
-    impl_m: &AssocItem,
+    impl_m: &ty::AssocItem,
     impl_m_span: Span,
-    trait_m: &AssocItem,
+    trait_m: &ty::AssocItem,
     impl_trait_ref: ty::TraitRef<'tcx>,
 ) -> Result<(), ErrorGuaranteed> {
     let trait_to_impl_substs = impl_trait_ref.substs;
@@ -157,8 +155,7 @@ fn compare_predicate_entailment<'tcx>(
     // FIXME(@lcnr): remove that after removing `cause.body_id` from
     // obligations.
     let impl_m_hir_id = tcx.hir().local_def_id_to_hir_id(impl_m.def_id.expect_local());
-    // We sometimes modify the span further down.
-    let mut cause = ObligationCause::new(
+    let cause = ObligationCause::new(
         impl_m_span,
         impl_m_hir_id,
         ObligationCauseCode::CompareImplItemObligation {
@@ -291,30 +288,19 @@ fn compare_predicate_entailment<'tcx>(
     // type would be more appropriate. In other places we have a `Vec<Span>`
     // corresponding to their `Vec<Predicate>`, but we don't have that here.
     // Fixing this would improve the output of test `issue-83765.rs`.
-    let mut result = ocx.sup(&cause, param_env, trait_fty, impl_fty);
-
-    // HACK(RPITIT): #101614. When we are trying to infer the hidden types for
-    // RPITITs, we need to equate the output tys instead of just subtyping. If
-    // we just use `sup` above, we'll end up `&'static str <: _#1t`, which causes
-    // us to infer `_#1t = #'_#2r str`, where `'_#2r` is unconstrained, which gets
-    // fixed up to `ReEmpty`, and which is certainly not what we want.
-    if trait_fty.has_infer_types() {
-        result =
-            result.and_then(|()| ocx.eq(&cause, param_env, trait_sig.output(), impl_sig.output()));
-    }
+    let result = ocx.sup(&cause, param_env, trait_fty, impl_fty);
 
     if let Err(terr) = result {
         debug!(?terr, "sub_types failed: impl ty {:?}, trait ty {:?}", impl_fty, trait_fty);
 
         let emitted = report_trait_method_mismatch(
-            tcx,
-            &mut cause,
             &infcx,
+            cause,
             terr,
             (trait_m, trait_fty),
             (impl_m, impl_fty),
-            &trait_sig,
-            &impl_trait_ref,
+            trait_sig,
+            impl_trait_ref,
         );
         return Err(emitted);
     }
@@ -352,11 +338,15 @@ pub fn collect_trait_impl_trait_tys<'tcx>(
     let impl_trait_ref = tcx.impl_trait_ref(impl_m.impl_container(tcx).unwrap()).unwrap();
     let param_env = tcx.param_env(def_id);
 
+    // First, check a few of the same thing as `compare_impl_method`, just so we don't ICE during substitutions later.
+    compare_number_of_generics(tcx, impl_m, trait_m, tcx.hir().span_if_local(impl_m.def_id), true)?;
+    compare_generic_param_kinds(tcx, impl_m, trait_m, true)?;
+
     let trait_to_impl_substs = impl_trait_ref.substs;
 
     let impl_m_hir_id = tcx.hir().local_def_id_to_hir_id(impl_m.def_id.expect_local());
     let return_span = tcx.hir().fn_decl_by_hir_id(impl_m_hir_id).unwrap().output.span();
-    let mut cause = ObligationCause::new(
+    let cause = ObligationCause::new(
         return_span,
         impl_m_hir_id,
         ObligationCauseCode::CompareImplItemObligation {
@@ -376,6 +366,7 @@ pub fn collect_trait_impl_trait_tys<'tcx>(
     let infcx = &tcx.infer_ctxt().build();
     let ocx = ObligationCtxt::new(infcx);
 
+    // Normalize the impl signature with fresh variables for lifetime inference.
     let norm_cause = ObligationCause::misc(return_span, impl_m_hir_id);
     let impl_sig = ocx.normalize(
         norm_cause.clone(),
@@ -388,6 +379,10 @@ pub fn collect_trait_impl_trait_tys<'tcx>(
     );
     let impl_return_ty = impl_sig.output();
 
+    // Normalize the trait signature with liberated bound vars, passing it through
+    // the ImplTraitInTraitCollector, which gathers all of the RPITITs and replaces
+    // them with inference variables.
+    // We will use these inference variables to collect the hidden types of RPITITs.
     let mut collector = ImplTraitInTraitCollector::new(&ocx, return_span, param_env, impl_m_hir_id);
     let unnormalized_trait_sig = tcx
         .liberate_late_bound_regions(
@@ -448,14 +443,13 @@ pub fn collect_trait_impl_trait_tys<'tcx>(
             // emit an error now because `compare_predicate_entailment` will not report the error
             // when normalization fails.
             let emitted = report_trait_method_mismatch(
-                tcx,
-                &mut cause,
                 infcx,
+                cause,
                 terr,
                 (trait_m, trait_fty),
                 (impl_m, impl_fty),
-                &trait_sig,
-                &impl_trait_ref,
+                trait_sig,
+                impl_trait_ref,
             );
             return Err(emitted);
         }
@@ -625,23 +619,21 @@ impl<'tcx> TypeFolder<'tcx> for ImplTraitInTraitCollector<'_, 'tcx> {
 }
 
 fn report_trait_method_mismatch<'tcx>(
-    tcx: TyCtxt<'tcx>,
-    cause: &mut ObligationCause<'tcx>,
     infcx: &InferCtxt<'tcx>,
+    mut cause: ObligationCause<'tcx>,
     terr: TypeError<'tcx>,
-    (trait_m, trait_fty): (&AssocItem, Ty<'tcx>),
-    (impl_m, impl_fty): (&AssocItem, Ty<'tcx>),
-    trait_sig: &FnSig<'tcx>,
-    impl_trait_ref: &TraitRef<'tcx>,
+    (trait_m, trait_fty): (&ty::AssocItem, Ty<'tcx>),
+    (impl_m, impl_fty): (&ty::AssocItem, Ty<'tcx>),
+    trait_sig: ty::FnSig<'tcx>,
+    impl_trait_ref: ty::TraitRef<'tcx>,
 ) -> ErrorGuaranteed {
+    let tcx = infcx.tcx;
     let (impl_err_span, trait_err_span) =
         extract_spans_for_error_reporting(&infcx, terr, &cause, impl_m, trait_m);
 
-    cause.span = impl_err_span;
-
     let mut diag = struct_span_err!(
         tcx.sess,
-        cause.span(),
+        impl_err_span,
         E0053,
         "method `{}` has an incompatible type for trait",
         trait_m.name
@@ -712,6 +704,7 @@ fn report_trait_method_mismatch<'tcx>(
         _ => {}
     }
 
+    cause.span = impl_err_span;
     infcx.err_ctxt().note_type_err(
         &mut diag,
         &cause,
@@ -922,9 +915,9 @@ fn compare_self_type<'tcx>(
 fn compare_number_of_generics<'tcx>(
     tcx: TyCtxt<'tcx>,
     impl_: &ty::AssocItem,
-    _impl_span: Span,
     trait_: &ty::AssocItem,
     trait_span: Option<Span>,
+    delay: bool,
 ) -> Result<(), ErrorGuaranteed> {
     let trait_own_counts = tcx.generics_of(trait_.def_id).own_counts();
     let impl_own_counts = tcx.generics_of(impl_.def_id).own_counts();
@@ -1054,7 +1047,7 @@ fn compare_number_of_generics<'tcx>(
                 err.span_label(*span, "`impl Trait` introduces an implicit type parameter");
             }
 
-            let reported = err.emit();
+            let reported = err.emit_unless(delay);
             err_occurred = Some(reported);
         }
     }
@@ -1306,6 +1299,7 @@ fn compare_generic_param_kinds<'tcx>(
     tcx: TyCtxt<'tcx>,
     impl_item: &ty::AssocItem,
     trait_item: &ty::AssocItem,
+    delay: bool,
 ) -> Result<(), ErrorGuaranteed> {
     assert_eq!(impl_item.kind, trait_item.kind);
 
@@ -1363,7 +1357,7 @@ fn compare_generic_param_kinds<'tcx>(
             err.span_label(impl_header_span, "");
             err.span_label(param_impl_span, make_param_message("found", param_impl));
 
-            let reported = err.emit();
+            let reported = err.emit_unless(delay);
             return Err(reported);
         }
     }
@@ -1489,9 +1483,9 @@ pub(crate) fn compare_ty_impl<'tcx>(
     debug!("compare_impl_type(impl_trait_ref={:?})", impl_trait_ref);
 
     let _: Result<(), ErrorGuaranteed> = (|| {
-        compare_number_of_generics(tcx, impl_ty, impl_ty_span, trait_ty, trait_item_span)?;
+        compare_number_of_generics(tcx, impl_ty, trait_ty, trait_item_span, false)?;
 
-        compare_generic_param_kinds(tcx, impl_ty, trait_ty)?;
+        compare_generic_param_kinds(tcx, impl_ty, trait_ty, false)?;
 
         let sp = tcx.def_span(impl_ty.def_id);
         compare_type_predicate_entailment(tcx, impl_ty, sp, trait_ty, impl_trait_ref)?;
diff --git a/compiler/rustc_mir_build/src/build/block.rs b/compiler/rustc_mir_build/src/build/block.rs
index db05592ed0ea5..49d7136a2f1ff 100644
--- a/compiler/rustc_mir_build/src/build/block.rs
+++ b/compiler/rustc_mir_build/src/build/block.rs
@@ -1,4 +1,3 @@
-use crate::build::matches::ArmHasGuard;
 use crate::build::ForGuard::OutsideGuard;
 use crate::build::{BlockAnd, BlockAndExtension, BlockFrame, Builder};
 use rustc_middle::middle::region::Scope;
@@ -231,7 +230,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
                                         visibility_scope,
                                         remainder_span,
                                         pattern,
-                                        ArmHasGuard(false),
+                                        None,
                                         Some((None, initializer_span)),
                                     );
                                     this.visit_primary_bindings(
@@ -308,7 +307,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
                                             visibility_scope,
                                             remainder_span,
                                             pattern,
-                                            ArmHasGuard(false),
+                                            None,
                                             Some((None, initializer_span)),
                                         );
                                         this.expr_into_pattern(block, &pattern, init)
@@ -324,7 +323,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
                                 visibility_scope,
                                 remainder_span,
                                 pattern,
-                                ArmHasGuard(false),
+                                None,
                                 None,
                             );
                             block.unit()
diff --git a/compiler/rustc_mir_build/src/build/expr/into.rs b/compiler/rustc_mir_build/src/build/expr/into.rs
index efb6eba7e576f..33e4fa58399e2 100644
--- a/compiler/rustc_mir_build/src/build/expr/into.rs
+++ b/compiler/rustc_mir_build/src/build/expr/into.rs
@@ -108,7 +108,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
             ExprKind::Let { expr, ref pat } => {
                 let scope = this.local_scope();
                 let (true_block, false_block) = this.in_if_then_scope(scope, expr_span, |this| {
-                    this.lower_let_expr(block, &this.thir[expr], pat, scope, None, expr_span)
+                    this.lower_let_expr(block, &this.thir[expr], pat, scope, None, expr_span, true)
                 });
 
                 this.cfg.push_assign_constant(
diff --git a/compiler/rustc_mir_build/src/build/matches/mod.rs b/compiler/rustc_mir_build/src/build/matches/mod.rs
index dfd8649cb97e7..802704d6ca77d 100644
--- a/compiler/rustc_mir_build/src/build/matches/mod.rs
+++ b/compiler/rustc_mir_build/src/build/matches/mod.rs
@@ -84,6 +84,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
                 break_scope,
                 Some(variable_source_info.scope),
                 variable_source_info.span,
+                true,
             ),
             _ => {
                 let temp_scope = temp_scope_override.unwrap_or_else(|| this.local_scope());
@@ -357,7 +358,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
                         None,
                         arm.span,
                         &arm.pattern,
-                        ArmHasGuard(arm.guard.is_some()),
+                        arm.guard.as_ref(),
                         opt_scrutinee_place,
                     );
 
@@ -645,7 +646,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
         mut visibility_scope: Option<SourceScope>,
         scope_span: Span,
         pattern: &Pat<'tcx>,
-        has_guard: ArmHasGuard,
+        guard: Option<&Guard<'tcx>>,
         opt_match_place: Option<(Option<&Place<'tcx>>, Span)>,
     ) -> Option<SourceScope> {
         self.visit_primary_bindings(
@@ -667,12 +668,16 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
                     var,
                     ty,
                     user_ty,
-                    has_guard,
+                    ArmHasGuard(guard.is_some()),
                     opt_match_place.map(|(x, y)| (x.cloned(), y)),
                     pattern.span,
                 );
             },
         );
+        if let Some(Guard::IfLet(guard_pat, _)) = guard {
+            // FIXME: pass a proper `opt_match_place`
+            self.declare_bindings(visibility_scope, scope_span, guard_pat, None, None);
+        }
         visibility_scope
     }
 
@@ -1766,6 +1771,8 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
 // Pat binding - used for `let` and function parameters as well.
 
 impl<'a, 'tcx> Builder<'a, 'tcx> {
+    /// If the bindings have already been declared, set `declare_bindings` to
+    /// `false` to avoid duplicated bindings declaration. Used for if-let guards.
     pub(crate) fn lower_let_expr(
         &mut self,
         mut block: BasicBlock,
@@ -1774,6 +1781,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
         else_target: region::Scope,
         source_scope: Option<SourceScope>,
         span: Span,
+        declare_bindings: bool,
     ) -> BlockAnd<()> {
         let expr_span = expr.span;
         let expr_place_builder = unpack!(block = self.lower_scrutinee(block, expr, expr_span));
@@ -1797,13 +1805,9 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
         let otherwise_post_guard_block = otherwise_candidate.pre_binding_block.unwrap();
         self.break_for_else(otherwise_post_guard_block, else_target, self.source_info(expr_span));
 
-        self.declare_bindings(
-            source_scope,
-            pat.span.to(span),
-            pat,
-            ArmHasGuard(false),
-            opt_expr_place,
-        );
+        if declare_bindings {
+            self.declare_bindings(source_scope, pat.span.to(span), pat, None, opt_expr_place);
+        }
 
         let post_guard_block = self.bind_pattern(
             self.source_info(pat.span),
@@ -1984,7 +1988,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
                     Guard::IfLet(ref pat, scrutinee) => {
                         let s = &this.thir[scrutinee];
                         guard_span = s.span;
-                        this.lower_let_expr(block, s, pat, match_scope, None, arm.span)
+                        this.lower_let_expr(block, s, pat, match_scope, None, arm.span, false)
                     }
                 });
 
diff --git a/compiler/rustc_mir_build/src/build/mod.rs b/compiler/rustc_mir_build/src/build/mod.rs
index 437ac8d82a1a3..0b76122913ebe 100644
--- a/compiler/rustc_mir_build/src/build/mod.rs
+++ b/compiler/rustc_mir_build/src/build/mod.rs
@@ -924,7 +924,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
                         scope,
                         expr.span,
                         &pat,
-                        matches::ArmHasGuard(false),
+                        None,
                         Some((Some(&place), span)),
                     );
                     let place_builder = PlaceBuilder::from(local);
diff --git a/compiler/rustc_resolve/src/def_collector.rs b/compiler/rustc_resolve/src/def_collector.rs
index b1cee06849dd9..4aed5d1ea3a34 100644
--- a/compiler/rustc_resolve/src/def_collector.rs
+++ b/compiler/rustc_resolve/src/def_collector.rs
@@ -131,12 +131,9 @@ impl<'a, 'b> visit::Visitor<'a> for DefCollector<'a, 'b> {
 
     fn visit_fn(&mut self, fn_kind: FnKind<'a>, span: Span, _: NodeId) {
         if let FnKind::Fn(_, _, sig, _, generics, body) = fn_kind {
-            if let Async::Yes { closure_id, return_impl_trait_id, .. } = sig.header.asyncness {
+            if let Async::Yes { closure_id, .. } = sig.header.asyncness {
                 self.visit_generics(generics);
 
-                let return_impl_trait_id =
-                    self.create_def(return_impl_trait_id, DefPathData::ImplTrait, span);
-
                 // For async functions, we need to create their inner defs inside of a
                 // closure to match their desugared representation. Besides that,
                 // we must mirror everything that `visit::walk_fn` below does.
@@ -144,9 +141,7 @@ impl<'a, 'b> visit::Visitor<'a> for DefCollector<'a, 'b> {
                 for param in &sig.decl.inputs {
                     self.visit_param(param);
                 }
-                self.with_parent(return_impl_trait_id, |this| {
-                    this.visit_fn_ret_ty(&sig.decl.output)
-                });
+                self.visit_fn_ret_ty(&sig.decl.output);
                 // If this async fn has no body (i.e. it's an async fn signature in a trait)
                 // then the closure_def will never be used, and we should avoid generating a
                 // def-id for it.
diff --git a/library/core/src/primitive_docs.rs b/library/core/src/primitive_docs.rs
index 331714a993c60..d6e9da187e80a 100644
--- a/library/core/src/primitive_docs.rs
+++ b/library/core/src/primitive_docs.rs
@@ -1493,11 +1493,13 @@ mod prim_ref {}
 /// However, a direct cast back is not possible. You need to use `transmute`:
 ///
 /// ```rust
+/// # #[cfg(not(miri))] { // FIXME: use strict provenance APIs once they are stable, then remove this `cfg`
 /// # let fnptr: fn(i32) -> i32 = |x| x+2;
 /// # let fnptr_addr = fnptr as usize;
 /// let fnptr = fnptr_addr as *const ();
 /// let fnptr: fn(i32) -> i32 = unsafe { std::mem::transmute(fnptr) };
 /// assert_eq!(fnptr(40), 42);
+/// # }
 /// ```
 ///
 /// Crucially, we `as`-cast to a raw pointer before `transmute`ing to a function pointer.
diff --git a/library/core/src/ptr/const_ptr.rs b/library/core/src/ptr/const_ptr.rs
index 969029e262e02..76603e1018d19 100644
--- a/library/core/src/ptr/const_ptr.rs
+++ b/library/core/src/ptr/const_ptr.rs
@@ -112,11 +112,13 @@ impl<T: ?Sized> *const T {
     ///
     /// ```
     /// #![feature(ptr_to_from_bits)]
+    /// # #[cfg(not(miri))] { // doctest does not work with strict provenance
     /// let array = [13, 42];
     /// let p0: *const i32 = &array[0];
     /// assert_eq!(<*const _>::from_bits(p0.to_bits()), p0);
     /// let p1: *const i32 = &array[1];
     /// assert_eq!(p1.to_bits() - p0.to_bits(), 4);
+    /// # }
     /// ```
     #[unstable(feature = "ptr_to_from_bits", issue = "91126")]
     #[deprecated(
@@ -140,9 +142,11 @@ impl<T: ?Sized> *const T {
     ///
     /// ```
     /// #![feature(ptr_to_from_bits)]
+    /// # #[cfg(not(miri))] { // doctest does not work with strict provenance
     /// use std::ptr::NonNull;
     /// let dangling: *const u8 = NonNull::dangling().as_ptr();
     /// assert_eq!(<*const u8>::from_bits(1), dangling);
+    /// # }
     /// ```
     #[unstable(feature = "ptr_to_from_bits", issue = "91126")]
     #[deprecated(
diff --git a/library/core/src/ptr/mut_ptr.rs b/library/core/src/ptr/mut_ptr.rs
index d1b3a63443379..b03cad18e4aed 100644
--- a/library/core/src/ptr/mut_ptr.rs
+++ b/library/core/src/ptr/mut_ptr.rs
@@ -117,12 +117,14 @@ impl<T: ?Sized> *mut T {
     ///
     /// ```
     /// #![feature(ptr_to_from_bits)]
+    /// # #[cfg(not(miri))] { // doctest does not work with strict provenance
     /// let mut array = [13, 42];
     /// let mut it = array.iter_mut();
     /// let p0: *mut i32 = it.next().unwrap();
     /// assert_eq!(<*mut _>::from_bits(p0.to_bits()), p0);
     /// let p1: *mut i32 = it.next().unwrap();
     /// assert_eq!(p1.to_bits() - p0.to_bits(), 4);
+    /// }
     /// ```
     #[unstable(feature = "ptr_to_from_bits", issue = "91126")]
     #[deprecated(
@@ -146,9 +148,11 @@ impl<T: ?Sized> *mut T {
     ///
     /// ```
     /// #![feature(ptr_to_from_bits)]
+    /// # #[cfg(not(miri))] { // doctest does not work with strict provenance
     /// use std::ptr::NonNull;
     /// let dangling: *mut u8 = NonNull::dangling().as_ptr();
     /// assert_eq!(<*mut u8>::from_bits(1), dangling);
+    /// }
     /// ```
     #[unstable(feature = "ptr_to_from_bits", issue = "91126")]
     #[deprecated(
diff --git a/library/std/src/primitive_docs.rs b/library/std/src/primitive_docs.rs
index 331714a993c60..d6e9da187e80a 100644
--- a/library/std/src/primitive_docs.rs
+++ b/library/std/src/primitive_docs.rs
@@ -1493,11 +1493,13 @@ mod prim_ref {}
 /// However, a direct cast back is not possible. You need to use `transmute`:
 ///
 /// ```rust
+/// # #[cfg(not(miri))] { // FIXME: use strict provenance APIs once they are stable, then remove this `cfg`
 /// # let fnptr: fn(i32) -> i32 = |x| x+2;
 /// # let fnptr_addr = fnptr as usize;
 /// let fnptr = fnptr_addr as *const ();
 /// let fnptr: fn(i32) -> i32 = unsafe { std::mem::transmute(fnptr) };
 /// assert_eq!(fnptr(40), 42);
+/// # }
 /// ```
 ///
 /// Crucially, we `as`-cast to a raw pointer before `transmute`ing to a function pointer.
diff --git a/library/unwind/src/libunwind.rs b/library/unwind/src/libunwind.rs
index a218910f0ec4d..0fa11f3761ad7 100644
--- a/library/unwind/src/libunwind.rs
+++ b/library/unwind/src/libunwind.rs
@@ -27,7 +27,10 @@ pub type _Unwind_Trace_Fn =
 #[cfg(target_arch = "x86")]
 pub const unwinder_private_data_size: usize = 5;
 
-#[cfg(target_arch = "x86_64")]
+#[cfg(all(target_arch = "x86_64", not(target_os = "windows")))]
+pub const unwinder_private_data_size: usize = 2;
+
+#[cfg(all(target_arch = "x86_64", target_os = "windows"))]
 pub const unwinder_private_data_size: usize = 6;
 
 #[cfg(all(target_arch = "arm", not(any(target_os = "ios", target_os = "watchos"))))]
diff --git a/src/test/ui/impl-trait/in-trait/trait-more-generics-than-impl.rs b/src/test/ui/impl-trait/in-trait/trait-more-generics-than-impl.rs
new file mode 100644
index 0000000000000..0bbe50ea6fd37
--- /dev/null
+++ b/src/test/ui/impl-trait/in-trait/trait-more-generics-than-impl.rs
@@ -0,0 +1,17 @@
+#![feature(return_position_impl_trait_in_trait)]
+#![allow(incomplete_features)]
+
+struct S;
+
+trait Foo {
+    fn bar<T>() -> impl Sized;
+}
+
+impl Foo for S {
+    fn bar() -> impl Sized {}
+    //~^ ERROR method `bar` has 0 type parameters but its trait declaration has 1 type parameter
+}
+
+fn main() {
+    S::bar();
+}
diff --git a/src/test/ui/impl-trait/in-trait/trait-more-generics-than-impl.stderr b/src/test/ui/impl-trait/in-trait/trait-more-generics-than-impl.stderr
new file mode 100644
index 0000000000000..8ff54cad95139
--- /dev/null
+++ b/src/test/ui/impl-trait/in-trait/trait-more-generics-than-impl.stderr
@@ -0,0 +1,12 @@
+error[E0049]: method `bar` has 0 type parameters but its trait declaration has 1 type parameter
+  --> $DIR/trait-more-generics-than-impl.rs:11:11
+   |
+LL |     fn bar<T>() -> impl Sized;
+   |            - expected 1 type parameter
+...
+LL |     fn bar() -> impl Sized {}
+   |           ^ found 0 type parameters
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0049`.
diff --git a/src/test/ui/rfc-2294-if-let-guard/run-pass.rs b/src/test/ui/rfc-2294-if-let-guard/run-pass.rs
index 3da57989df2b5..a303a0d1fcee3 100644
--- a/src/test/ui/rfc-2294-if-let-guard/run-pass.rs
+++ b/src/test/ui/rfc-2294-if-let-guard/run-pass.rs
@@ -30,4 +30,11 @@ fn main() {
         Some(x) if let Foo::Qux(y) = qux(x) => assert_eq!(y, 84),
         _ => panic!(),
     }
+
+    // issue #88015
+    #[allow(irrefutable_let_patterns)]
+    match () {
+        () | () if let x = 42 => assert_eq!(x, 42),
+        _ => panic!()
+    }
 }