diff --git a/Cargo.lock b/Cargo.lock
index 28684a310a3c7..544cb4faef222 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -2496,7 +2496,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "3742b2c103b9f06bc9fff0a37ff4912935851bee6d36f3c02bcc755bcfec228f"
 dependencies = [
  "lock_api",
- "parking_lot_core 0.9.3",
+ "parking_lot_core 0.9.4",
 ]
 
 [[package]]
@@ -2515,15 +2515,15 @@ dependencies = [
 
 [[package]]
 name = "parking_lot_core"
-version = "0.9.3"
+version = "0.9.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "09a279cbf25cb0757810394fbc1e359949b59e348145c643a939a525692e6929"
+checksum = "4dc9e0dc2adc1c69d09143aff38d3d30c5c3f0df0dad82e6d25547af174ebec0"
 dependencies = [
  "cfg-if 1.0.0",
  "libc",
  "redox_syscall",
  "smallvec",
- "windows-sys 0.36.1",
+ "windows-sys 0.42.0",
 ]
 
 [[package]]
@@ -2748,9 +2748,9 @@ dependencies = [
 
 [[package]]
 name = "psm"
-version = "0.1.16"
+version = "0.1.21"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "cd136ff4382c4753fc061cb9e4712ab2af263376b95bbd5bd8cd50c020b78e69"
+checksum = "5787f7cda34e3033a72192c018bc5883100330f362ef279a8cbccfce8bb4e874"
 dependencies = [
  "cc",
 ]
@@ -4651,9 +4651,9 @@ checksum = "a8f112729512f8e442d81f95a8a7ddf2b7c6b8a1a6f509a95864142b30cab2d3"
 
 [[package]]
 name = "stacker"
-version = "0.1.14"
+version = "0.1.15"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "90939d5171a4420b3ff5fbc8954d641e7377335454c259dcb80786f3f21dc9b4"
+checksum = "c886bd4480155fd3ef527d45e9ac8dd7118a898a46530b7b94c3e21866259fce"
 dependencies = [
  "cc",
  "cfg-if 1.0.0",
@@ -5473,17 +5473,25 @@ dependencies = [
 
 [[package]]
 name = "windows-sys"
-version = "0.36.1"
+version = "0.42.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "ea04155a16a59f9eab786fe12a4a450e75cdb175f9e0d80da1e17db09f55b8d2"
+checksum = "5a3e1820f08b8513f676f7ab6c1f99ff312fb97b553d30ff4dd86f9f15728aa7"
 dependencies = [
- "windows_aarch64_msvc 0.36.1",
- "windows_i686_gnu 0.36.1",
- "windows_i686_msvc 0.36.1",
- "windows_x86_64_gnu 0.36.1",
- "windows_x86_64_msvc 0.36.1",
+ "windows_aarch64_gnullvm",
+ "windows_aarch64_msvc 0.42.0",
+ "windows_i686_gnu 0.42.0",
+ "windows_i686_msvc 0.42.0",
+ "windows_x86_64_gnu 0.42.0",
+ "windows_x86_64_gnullvm",
+ "windows_x86_64_msvc 0.42.0",
 ]
 
+[[package]]
+name = "windows_aarch64_gnullvm"
+version = "0.42.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "41d2aa71f6f0cbe00ae5167d90ef3cfe66527d6f613ca78ac8024c3ccab9a19e"
+
 [[package]]
 name = "windows_aarch64_msvc"
 version = "0.28.0"
@@ -5492,9 +5500,9 @@ checksum = "52695a41e536859d5308cc613b4a022261a274390b25bd29dfff4bf08505f3c2"
 
 [[package]]
 name = "windows_aarch64_msvc"
-version = "0.36.1"
+version = "0.42.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "9bb8c3fd39ade2d67e9874ac4f3db21f0d710bee00fe7cab16949ec184eeaa47"
+checksum = "dd0f252f5a35cac83d6311b2e795981f5ee6e67eb1f9a7f64eb4500fbc4dcdb4"
 
 [[package]]
 name = "windows_i686_gnu"
@@ -5504,9 +5512,9 @@ checksum = "f54725ac23affef038fecb177de6c9bf065787c2f432f79e3c373da92f3e1d8a"
 
 [[package]]
 name = "windows_i686_gnu"
-version = "0.36.1"
+version = "0.42.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "180e6ccf01daf4c426b846dfc66db1fc518f074baa793aa7d9b9aaeffad6a3b6"
+checksum = "fbeae19f6716841636c28d695375df17562ca208b2b7d0dc47635a50ae6c5de7"
 
 [[package]]
 name = "windows_i686_msvc"
@@ -5516,9 +5524,9 @@ checksum = "51d5158a43cc43623c0729d1ad6647e62fa384a3d135fd15108d37c683461f64"
 
 [[package]]
 name = "windows_i686_msvc"
-version = "0.36.1"
+version = "0.42.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "e2e7917148b2812d1eeafaeb22a97e4813dfa60a3f8f78ebe204bcc88f12f024"
+checksum = "84c12f65daa39dd2babe6e442988fc329d6243fdce47d7d2d155b8d874862246"
 
 [[package]]
 name = "windows_x86_64_gnu"
@@ -5528,9 +5536,15 @@ checksum = "bc31f409f565611535130cfe7ee8e6655d3fa99c1c61013981e491921b5ce954"
 
 [[package]]
 name = "windows_x86_64_gnu"
-version = "0.36.1"
+version = "0.42.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "bf7b1b21b5362cbc318f686150e5bcea75ecedc74dd157d874d754a2ca44b0ed"
+
+[[package]]
+name = "windows_x86_64_gnullvm"
+version = "0.42.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "4dcd171b8776c41b97521e5da127a2d86ad280114807d0b2ab1e462bc764d9e1"
+checksum = "09d525d2ba30eeb3297665bd434a54297e4170c7f1a44cad4ef58095b4cd2028"
 
 [[package]]
 name = "windows_x86_64_msvc"
@@ -5540,9 +5554,9 @@ checksum = "3f2b8c7cbd3bfdddd9ab98769f9746a7fad1bca236554cd032b78d768bc0e89f"
 
 [[package]]
 name = "windows_x86_64_msvc"
-version = "0.36.1"
+version = "0.42.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "c811ca4a8c853ef420abd8592ba53ddbbac90410fab6903b3e79972a631f7680"
+checksum = "f40009d85759725a34da6d89a94e63d7bdc50a862acf0dbc7c8e488f1edcb6f5"
 
 [[package]]
 name = "xattr"
diff --git a/compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs b/compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs
index 8987a51757cd5..7f26e970e3094 100644
--- a/compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs
+++ b/compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs
@@ -724,13 +724,19 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
             borrow_span,
             &self.describe_any_place(borrow.borrowed_place.as_ref()),
         );
-
-        borrow_spans.var_span_label(
+        borrow_spans.var_subdiag(
             &mut err,
-            {
+            |var_span| {
+                use crate::session_diagnostics::CaptureVarCause::*;
                 let place = &borrow.borrowed_place;
                 let desc_place = self.describe_any_place(place.as_ref());
-                format!("borrow occurs due to use of {}{}", desc_place, borrow_spans.describe())
+                match borrow_spans {
+                    UseSpans::ClosureUse { generator_kind, .. } => match generator_kind {
+                        Some(_) => BorrowUsePlaceGenerator { place: desc_place, var_span },
+                        None => BorrowUsePlaceClosure { place: desc_place, var_span },
+                    },
+                    _ => BorrowUsePlace { place: desc_place, var_span },
+                }
             },
             "mutable",
         );
diff --git a/compiler/rustc_borrowck/src/diagnostics/mod.rs b/compiler/rustc_borrowck/src/diagnostics/mod.rs
index 534d9ecae6e6f..61518378e3d0c 100644
--- a/compiler/rustc_borrowck/src/diagnostics/mod.rs
+++ b/compiler/rustc_borrowck/src/diagnostics/mod.rs
@@ -623,6 +623,26 @@ impl UseSpans<'_> {
         }
     }
 
+    /// Add a subdiagnostic to the use of the captured variable, if it exists.
+    pub(super) fn var_subdiag(
+        self,
+        err: &mut Diagnostic,
+        f: impl Fn(Span) -> crate::session_diagnostics::CaptureVarCause,
+        kind_desc: impl Into<String>,
+    ) {
+        if let UseSpans::ClosureUse { capture_kind_span, path_span, .. } = self {
+            if capture_kind_span == path_span {
+                err.subdiagnostic(f(capture_kind_span));
+            } else {
+                err.subdiagnostic(crate::session_diagnostics::CaptureVarKind {
+                    kind_desc: kind_desc.into(),
+                    kind_span: capture_kind_span,
+                });
+                err.subdiagnostic(f(path_span));
+            }
+        }
+    }
+
     /// Returns `false` if this place is not used in a closure.
     pub(super) fn for_closure(&self) -> bool {
         match *self {
diff --git a/compiler/rustc_borrowck/src/session_diagnostics.rs b/compiler/rustc_borrowck/src/session_diagnostics.rs
index fe24f85fae10a..824f20a31bb09 100644
--- a/compiler/rustc_borrowck/src/session_diagnostics.rs
+++ b/compiler/rustc_borrowck/src/session_diagnostics.rs
@@ -148,3 +148,33 @@ pub(crate) enum RequireStaticErr {
         multi_span: MultiSpan,
     },
 }
+
+#[derive(Subdiagnostic)]
+#[label(borrowck_capture_kind_label)]
+pub(crate) struct CaptureVarKind {
+    pub kind_desc: String,
+    #[primary_span]
+    pub kind_span: Span,
+}
+
+#[derive(Subdiagnostic)]
+pub(crate) enum CaptureVarCause {
+    #[label(borrowck_var_borrow_by_use_place)]
+    BorrowUsePlace {
+        place: String,
+        #[primary_span]
+        var_span: Span,
+    },
+    #[label(borrowck_var_borrow_by_use_place_in_generator)]
+    BorrowUsePlaceGenerator {
+        place: String,
+        #[primary_span]
+        var_span: Span,
+    },
+    #[label(borrowck_var_borrow_by_use_place_in_closure)]
+    BorrowUsePlaceClosure {
+        place: String,
+        #[primary_span]
+        var_span: Span,
+    },
+}
diff --git a/compiler/rustc_codegen_llvm/src/consts.rs b/compiler/rustc_codegen_llvm/src/consts.rs
index dd3c43ba5ca7c..bf5ac4e503e3f 100644
--- a/compiler/rustc_codegen_llvm/src/consts.rs
+++ b/compiler/rustc_codegen_llvm/src/consts.rs
@@ -19,6 +19,7 @@ use rustc_middle::mir::mono::MonoItem;
 use rustc_middle::ty::layout::LayoutOf;
 use rustc_middle::ty::{self, Instance, Ty};
 use rustc_middle::{bug, span_bug};
+use rustc_session::config::Lto;
 use rustc_target::abi::{
     AddressSpace, Align, HasDataLayout, Primitive, Scalar, Size, WrappingRange,
 };
@@ -303,7 +304,8 @@ impl<'ll> CodegenCx<'ll, '_> {
                 // ThinLTO can't handle this workaround in all cases, so we don't
                 // emit the attrs. Instead we make them unnecessary by disallowing
                 // dynamic linking when linker plugin based LTO is enabled.
-                !self.tcx.sess.opts.cg.linker_plugin_lto.enabled();
+                !self.tcx.sess.opts.cg.linker_plugin_lto.enabled() &&
+                self.tcx.sess.lto() != Lto::Thin;
 
             // If this assertion triggers, there's something wrong with commandline
             // argument validation.
diff --git a/compiler/rustc_data_structures/Cargo.toml b/compiler/rustc_data_structures/Cargo.toml
index 5152d5ab0465c..5afce15e26bfc 100644
--- a/compiler/rustc_data_structures/Cargo.toml
+++ b/compiler/rustc_data_structures/Cargo.toml
@@ -23,7 +23,7 @@ rustc_macros = { path = "../rustc_macros" }
 rustc_serialize = { path = "../rustc_serialize" }
 smallvec = { version = "1.8.1", features = ["const_generics", "union", "may_dangle"] }
 stable_deref_trait = "1.0.0"
-stacker = "0.1.14"
+stacker = "0.1.15"
 tempfile = "3.2"
 thin-vec = "0.2.9"
 tracing = "0.1"
diff --git a/compiler/rustc_error_messages/locales/en-US/borrowck.ftl b/compiler/rustc_error_messages/locales/en-US/borrowck.ftl
index 67f2156f32e50..80fc4c6e4f5d3 100644
--- a/compiler/rustc_error_messages/locales/en-US/borrowck.ftl
+++ b/compiler/rustc_error_messages/locales/en-US/borrowck.ftl
@@ -58,3 +58,15 @@ borrowck_returned_lifetime_short =
 
 borrowck_used_impl_require_static =
     the used `impl` has a `'static` requirement
+
+borrowck_capture_kind_label =
+    capture is {$kind_desc} because of use here
+
+borrowck_var_borrow_by_use_place_in_generator =
+    borrow occurs due to use of {$place} in closure in generator
+
+borrowck_var_borrow_by_use_place_in_closure =
+    borrow occurs due to use of {$place} in closure
+
+borrowck_var_borrow_by_use_place =
+    borrow occurs due to use of {$place}
diff --git a/compiler/rustc_hir_analysis/src/collect/lifetimes.rs b/compiler/rustc_hir_analysis/src/collect/lifetimes.rs
index 3d07f3fbc674d..c64177eea3f83 100644
--- a/compiler/rustc_hir_analysis/src/collect/lifetimes.rs
+++ b/compiler/rustc_hir_analysis/src/collect/lifetimes.rs
@@ -18,7 +18,7 @@ use rustc_middle::bug;
 use rustc_middle::hir::map::Map;
 use rustc_middle::hir::nested_filter;
 use rustc_middle::middle::resolve_lifetime::*;
-use rustc_middle::ty::{self, DefIdTree, TyCtxt};
+use rustc_middle::ty::{self, DefIdTree, TyCtxt, TypeSuperVisitable, TypeVisitor};
 use rustc_span::def_id::DefId;
 use rustc_span::symbol::{sym, Ident};
 use rustc_span::Span;
@@ -1781,7 +1781,7 @@ fn is_late_bound_map(tcx: TyCtxt<'_>, def_id: LocalDefId) -> Option<&FxIndexSet<
 
     let mut late_bound = FxIndexSet::default();
 
-    let mut constrained_by_input = ConstrainedCollector::default();
+    let mut constrained_by_input = ConstrainedCollector { regions: Default::default(), tcx };
     for arg_ty in decl.inputs {
         constrained_by_input.visit_ty(arg_ty);
     }
@@ -1834,12 +1834,65 @@ fn is_late_bound_map(tcx: TyCtxt<'_>, def_id: LocalDefId) -> Option<&FxIndexSet<
     debug!(?late_bound);
     return Some(tcx.arena.alloc(late_bound));
 
-    #[derive(Default)]
-    struct ConstrainedCollector {
+    /// Visits a `ty::Ty` collecting information about what generic parameters are constrained.
+    ///
+    /// The visitor does not operate on `hir::Ty` so that it can be called on the rhs of a `type Alias<...> = ...;`
+    /// which may live in a separate crate so there would not be any hir available. Instead we use the `type_of`
+    /// query to obtain a `ty::Ty` which will be present even in cross crate scenarios. It also naturally
+    /// handles cycle detection as we go through the query system.
+    ///
+    /// This is necessary in the first place for the following case:
+    /// ```
+    /// type Alias<'a, T> = <T as Trait<'a>>::Assoc;
+    /// fn foo<'a>(_: Alias<'a, ()>) -> Alias<'a, ()> { ... }
+    /// ```
+    ///
+    /// If we conservatively considered `'a` unconstrained then we could break users who had written code before
+    /// we started correctly handling aliases. If we considered `'a` constrained then it would become late bound
+    /// causing an error during astconv as the `'a` is not constrained by the input type `<() as Trait<'a>>::Assoc`
+    /// but appears in the output type `<() as Trait<'a>>::Assoc`.
+    ///
+    /// We must therefore "look into" the `Alias` to see whether we should consider `'a` constrained or not.
+    ///
+    /// See #100508 #85533 #47511 for additional context
+    struct ConstrainedCollectorPostAstConv {
+        arg_is_constrained: Box<[bool]>,
+    }
+
+    use std::ops::ControlFlow;
+    use ty::Ty;
+    impl<'tcx> TypeVisitor<'tcx> for ConstrainedCollectorPostAstConv {
+        fn visit_ty(&mut self, t: Ty<'tcx>) -> ControlFlow<!> {
+            match t.kind() {
+                ty::Param(param_ty) => {
+                    self.arg_is_constrained[param_ty.index as usize] = true;
+                }
+                ty::Projection(_) => return ControlFlow::Continue(()),
+                _ => (),
+            }
+            t.super_visit_with(self)
+        }
+
+        fn visit_const(&mut self, _: ty::Const<'tcx>) -> ControlFlow<!> {
+            ControlFlow::Continue(())
+        }
+
+        fn visit_region(&mut self, r: ty::Region<'tcx>) -> ControlFlow<!> {
+            debug!("r={:?}", r.kind());
+            if let ty::RegionKind::ReEarlyBound(region) = r.kind() {
+                self.arg_is_constrained[region.index as usize] = true;
+            }
+
+            ControlFlow::Continue(())
+        }
+    }
+
+    struct ConstrainedCollector<'tcx> {
+        tcx: TyCtxt<'tcx>,
         regions: FxHashSet<LocalDefId>,
     }
 
-    impl<'v> Visitor<'v> for ConstrainedCollector {
+    impl<'v> Visitor<'v> for ConstrainedCollector<'_> {
         fn visit_ty(&mut self, ty: &'v hir::Ty<'v>) {
             match ty.kind {
                 hir::TyKind::Path(
@@ -1850,6 +1903,47 @@ fn is_late_bound_map(tcx: TyCtxt<'_>, def_id: LocalDefId) -> Option<&FxIndexSet<
                     // (defined above)
                 }
 
+                hir::TyKind::Path(hir::QPath::Resolved(
+                    None,
+                    hir::Path { res: Res::Def(DefKind::TyAlias, alias_def), segments, span },
+                )) => {
+                    // See comments on `ConstrainedCollectorPostAstConv` for why this arm does not just consider
+                    // substs to be unconstrained.
+                    let generics = self.tcx.generics_of(alias_def);
+                    let mut walker = ConstrainedCollectorPostAstConv {
+                        arg_is_constrained: vec![false; generics.params.len()].into_boxed_slice(),
+                    };
+                    walker.visit_ty(self.tcx.type_of(alias_def));
+
+                    match segments.last() {
+                        Some(hir::PathSegment { args: Some(args), .. }) => {
+                            let tcx = self.tcx;
+                            for constrained_arg in
+                                args.args.iter().enumerate().flat_map(|(n, arg)| {
+                                    match walker.arg_is_constrained.get(n) {
+                                        Some(true) => Some(arg),
+                                        Some(false) => None,
+                                        None => {
+                                            tcx.sess.delay_span_bug(
+                                                *span,
+                                                format!(
+                                                    "Incorrect generic arg count for alias {:?}",
+                                                    alias_def
+                                                ),
+                                            );
+                                            None
+                                        }
+                                    }
+                                })
+                            {
+                                self.visit_generic_arg(constrained_arg);
+                            }
+                        }
+                        Some(_) => (),
+                        None => bug!("Path with no segments or self type"),
+                    }
+                }
+
                 hir::TyKind::Path(hir::QPath::Resolved(None, ref path)) => {
                     // consider only the lifetimes on the final
                     // segment; I am not sure it's even currently
diff --git a/compiler/rustc_middle/src/ty/error.rs b/compiler/rustc_middle/src/ty/error.rs
index 4e6cdb786025e..dc13374f992eb 100644
--- a/compiler/rustc_middle/src/ty/error.rs
+++ b/compiler/rustc_middle/src/ty/error.rs
@@ -430,7 +430,9 @@ impl<'tcx> TyCtxt<'tcx> {
                     (ty::Projection(_), ty::Projection(_)) => {
                         diag.note("an associated type was expected, but a different one was found");
                     }
-                    (ty::Param(p), ty::Projection(proj)) | (ty::Projection(proj), ty::Param(p)) => {
+                    (ty::Param(p), ty::Projection(proj)) | (ty::Projection(proj), ty::Param(p))
+                        if self.def_kind(proj.item_def_id) != DefKind::ImplTraitPlaceholder =>
+                    {
                         let generics = self.generics_of(body_owner_def_id);
                         let p_span = self.def_span(generics.type_param(p, self).def_id);
                         if !sp.contains(p_span) {
diff --git a/compiler/rustc_span/src/source_map.rs b/compiler/rustc_span/src/source_map.rs
index f9566eeee9465..3baa2e03cbad7 100644
--- a/compiler/rustc_span/src/source_map.rs
+++ b/compiler/rustc_span/src/source_map.rs
@@ -855,7 +855,8 @@ impl SourceMap {
     /// Returns a new span representing the next character after the end-point of this span.
     /// Special cases:
     /// - if span is a dummy one, returns the same span
-    /// - if next_point reached the end of source, return span with lo = hi
+    /// - if next_point reached the end of source, return a span exceeding the end of source,
+    ///   which means sm.span_to_snippet(next_point) will get `Err`
     /// - respect multi-byte characters
     pub fn next_point(&self, sp: Span) -> Span {
         if sp.is_dummy() {
@@ -864,9 +865,6 @@ impl SourceMap {
         let start_of_next_point = sp.hi().0;
 
         let width = self.find_width_of_character_at_span(sp, true);
-        if width == 0 {
-            return Span::new(sp.hi(), sp.hi(), sp.ctxt(), None);
-        }
         // If the width is 1, then the next span should only contain the next char besides current ending.
         // However, in the case of a multibyte character, where the width != 1, the next span should
         // span multiple bytes to include the whole character.
@@ -938,7 +936,7 @@ impl SourceMap {
         // Ensure indexes are also not malformed.
         if start_index > end_index || end_index > source_len - 1 {
             debug!("find_width_of_character_at_span: source indexes are malformed");
-            return 0;
+            return 1;
         }
 
         let src = local_begin.sf.external_src.borrow();
diff --git a/compiler/rustc_span/src/source_map/tests.rs b/compiler/rustc_span/src/source_map/tests.rs
index 1fd81018fa05c..3cab59e8dbe6c 100644
--- a/compiler/rustc_span/src/source_map/tests.rs
+++ b/compiler/rustc_span/src/source_map/tests.rs
@@ -511,16 +511,17 @@ fn test_next_point() {
     assert_eq!(span.lo().0, 4);
     assert_eq!(span.hi().0, 5);
 
-    // A non-empty span at the last byte should advance to create an empty
-    // span pointing at the end of the file.
+    // Reaching to the end of file, return a span that will get error with `span_to_snippet`
     let span = Span::with_root_ctxt(BytePos(4), BytePos(5));
     let span = sm.next_point(span);
     assert_eq!(span.lo().0, 5);
-    assert_eq!(span.hi().0, 5);
+    assert_eq!(span.hi().0, 6);
+    assert!(sm.span_to_snippet(span).is_err());
 
-    // Empty span pointing just past the last byte.
+    // Reaching to the end of file, return a span that will get error with `span_to_snippet`
     let span = Span::with_root_ctxt(BytePos(5), BytePos(5));
     let span = sm.next_point(span);
     assert_eq!(span.lo().0, 5);
-    assert_eq!(span.hi().0, 5);
+    assert_eq!(span.hi().0, 6);
+    assert!(sm.span_to_snippet(span).is_err());
 }
diff --git a/compiler/rustc_trait_selection/src/traits/project.rs b/compiler/rustc_trait_selection/src/traits/project.rs
index 7f829e46bbb1b..572f82117cc0e 100644
--- a/compiler/rustc_trait_selection/src/traits/project.rs
+++ b/compiler/rustc_trait_selection/src/traits/project.rs
@@ -2187,7 +2187,7 @@ fn confirm_impl_candidate<'cx, 'tcx>(
 // Verify that the trait item and its implementation have compatible substs lists
 fn check_substs_compatible<'tcx>(
     tcx: TyCtxt<'tcx>,
-    assoc_ty: &ty::AssocItem,
+    assoc_item: &ty::AssocItem,
     substs: ty::SubstsRef<'tcx>,
 ) -> bool {
     fn check_substs_compatible_inner<'tcx>(
@@ -2219,7 +2219,10 @@ fn check_substs_compatible<'tcx>(
         true
     }
 
-    check_substs_compatible_inner(tcx, tcx.generics_of(assoc_ty.def_id), substs.as_slice())
+    let generics = tcx.generics_of(assoc_item.def_id);
+    // Chop off any additional substs (RPITIT) substs
+    let substs = &substs[0..generics.count().min(substs.len())];
+    check_substs_compatible_inner(tcx, generics, substs)
 }
 
 fn confirm_impl_trait_in_trait_candidate<'tcx>(
@@ -2248,11 +2251,27 @@ fn confirm_impl_trait_in_trait_candidate<'tcx>(
         };
     }
 
-    let impl_fn_def_id = leaf_def.item.def_id;
     // Rebase from {trait}::{fn}::{opaque} to {impl}::{fn}::{opaque},
     // since `data.substs` are the impl substs.
     let impl_fn_substs =
         obligation.predicate.substs.rebase_onto(tcx, tcx.parent(trait_fn_def_id), data.substs);
+    let impl_fn_substs = translate_substs(
+        selcx.infcx(),
+        obligation.param_env,
+        data.impl_def_id,
+        impl_fn_substs,
+        leaf_def.defining_node,
+    );
+
+    if !check_substs_compatible(tcx, &leaf_def.item, impl_fn_substs) {
+        let err = tcx.ty_error_with_message(
+            obligation.cause.span,
+            "impl method and trait method have different parameters",
+        );
+        return Progress { term: err.into(), obligations };
+    }
+
+    let impl_fn_def_id = leaf_def.item.def_id;
 
     let cause = ObligationCause::new(
         obligation.cause.span,
diff --git a/src/bootstrap/Cargo.lock b/src/bootstrap/Cargo.lock
index baecca44cd987..e1a108cea9574 100644
--- a/src/bootstrap/Cargo.lock
+++ b/src/bootstrap/Cargo.lock
@@ -224,13 +224,13 @@ dependencies = [
 
 [[package]]
 name = "fd-lock"
-version = "3.0.6"
+version = "3.0.7"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "e11dcc7e4d79a8c89b9ab4c6f5c30b1fc4a83c420792da3542fd31179ed5f517"
+checksum = "0c93a581058d957dc4176875aad04f82f81613e6611d64aa1a9c755bdfb16711"
 dependencies = [
  "cfg-if",
  "rustix",
- "windows-sys",
+ "windows-sys 0.42.0",
 ]
 
 [[package]]
@@ -528,7 +528,7 @@ dependencies = [
  "io-lifetimes",
  "libc",
  "linux-raw-sys",
- "windows-sys",
+ "windows-sys 0.36.1",
 ]
 
 [[package]]
@@ -721,43 +721,100 @@ version = "0.36.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "ea04155a16a59f9eab786fe12a4a450e75cdb175f9e0d80da1e17db09f55b8d2"
 dependencies = [
- "windows_aarch64_msvc",
- "windows_i686_gnu",
- "windows_i686_msvc",
- "windows_x86_64_gnu",
- "windows_x86_64_msvc",
+ "windows_aarch64_msvc 0.36.1",
+ "windows_i686_gnu 0.36.1",
+ "windows_i686_msvc 0.36.1",
+ "windows_x86_64_gnu 0.36.1",
+ "windows_x86_64_msvc 0.36.1",
 ]
 
+[[package]]
+name = "windows-sys"
+version = "0.42.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "5a3e1820f08b8513f676f7ab6c1f99ff312fb97b553d30ff4dd86f9f15728aa7"
+dependencies = [
+ "windows_aarch64_gnullvm",
+ "windows_aarch64_msvc 0.42.0",
+ "windows_i686_gnu 0.42.0",
+ "windows_i686_msvc 0.42.0",
+ "windows_x86_64_gnu 0.42.0",
+ "windows_x86_64_gnullvm",
+ "windows_x86_64_msvc 0.42.0",
+]
+
+[[package]]
+name = "windows_aarch64_gnullvm"
+version = "0.42.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "41d2aa71f6f0cbe00ae5167d90ef3cfe66527d6f613ca78ac8024c3ccab9a19e"
+
 [[package]]
 name = "windows_aarch64_msvc"
 version = "0.36.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "9bb8c3fd39ade2d67e9874ac4f3db21f0d710bee00fe7cab16949ec184eeaa47"
 
+[[package]]
+name = "windows_aarch64_msvc"
+version = "0.42.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "dd0f252f5a35cac83d6311b2e795981f5ee6e67eb1f9a7f64eb4500fbc4dcdb4"
+
 [[package]]
 name = "windows_i686_gnu"
 version = "0.36.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "180e6ccf01daf4c426b846dfc66db1fc518f074baa793aa7d9b9aaeffad6a3b6"
 
+[[package]]
+name = "windows_i686_gnu"
+version = "0.42.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "fbeae19f6716841636c28d695375df17562ca208b2b7d0dc47635a50ae6c5de7"
+
 [[package]]
 name = "windows_i686_msvc"
 version = "0.36.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "e2e7917148b2812d1eeafaeb22a97e4813dfa60a3f8f78ebe204bcc88f12f024"
 
+[[package]]
+name = "windows_i686_msvc"
+version = "0.42.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "84c12f65daa39dd2babe6e442988fc329d6243fdce47d7d2d155b8d874862246"
+
 [[package]]
 name = "windows_x86_64_gnu"
 version = "0.36.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "4dcd171b8776c41b97521e5da127a2d86ad280114807d0b2ab1e462bc764d9e1"
 
+[[package]]
+name = "windows_x86_64_gnu"
+version = "0.42.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "bf7b1b21b5362cbc318f686150e5bcea75ecedc74dd157d874d754a2ca44b0ed"
+
+[[package]]
+name = "windows_x86_64_gnullvm"
+version = "0.42.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "09d525d2ba30eeb3297665bd434a54297e4170c7f1a44cad4ef58095b4cd2028"
+
 [[package]]
 name = "windows_x86_64_msvc"
 version = "0.36.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "c811ca4a8c853ef420abd8592ba53ddbbac90410fab6903b3e79972a631f7680"
 
+[[package]]
+name = "windows_x86_64_msvc"
+version = "0.42.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f40009d85759725a34da6d89a94e63d7bdc50a862acf0dbc7c8e488f1edcb6f5"
+
 [[package]]
 name = "xattr"
 version = "0.2.3"
diff --git a/src/bootstrap/Cargo.toml b/src/bootstrap/Cargo.toml
index 95e711737738a..f74738437ea3a 100644
--- a/src/bootstrap/Cargo.toml
+++ b/src/bootstrap/Cargo.toml
@@ -36,7 +36,7 @@ test = false
 
 [dependencies]
 cmake = "0.1.38"
-fd-lock = "3.0.6"
+fd-lock = "3.0.7"
 filetime = "0.2"
 getopts = "0.2.19"
 cc = "1.0.69"
diff --git a/src/test/codegen/auxiliary/static_dllimport_aux.rs b/src/test/codegen/auxiliary/static_dllimport_aux.rs
new file mode 100644
index 0000000000000..afb0dc42f443a
--- /dev/null
+++ b/src/test/codegen/auxiliary/static_dllimport_aux.rs
@@ -0,0 +1,13 @@
+use std::sync::atomic::{AtomicPtr, Ordering};
+
+#[inline(always)]
+pub fn memrchr() {
+    fn detect() {}
+
+    static CROSS_CRATE_STATIC_ITEM: AtomicPtr<()> = AtomicPtr::new(detect as *mut ());
+
+    unsafe {
+        let fun = CROSS_CRATE_STATIC_ITEM.load(Ordering::SeqCst);
+        std::mem::transmute::<*mut (), fn()>(fun)()
+    }
+}
diff --git a/src/test/codegen/issue-81408-dllimport-thinlto-windows.rs b/src/test/codegen/issue-81408-dllimport-thinlto-windows.rs
new file mode 100644
index 0000000000000..0b6ab4f7ecb3b
--- /dev/null
+++ b/src/test/codegen/issue-81408-dllimport-thinlto-windows.rs
@@ -0,0 +1,15 @@
+// compile-flags: -O -C lto=thin -C prefer-dynamic=no
+// only-windows
+// aux-build:static_dllimport_aux.rs
+
+// Test that on Windows, when performing ThinLTO, we do not mark cross-crate static items with
+// dllimport because lld does not fix the symbol names for us.
+
+extern crate static_dllimport_aux;
+
+// CHECK-LABEL: @{{.+}}CROSS_CRATE_STATIC_ITEM{{.+}} =
+// CHECK-SAME: external local_unnamed_addr global %"{{.+}}AtomicPtr
+
+pub fn main() {
+    static_dllimport_aux::memrchr();
+}
diff --git a/src/test/ui/abi/homogenous-floats-target-feature-mixup.rs b/src/test/ui/abi/homogenous-floats-target-feature-mixup.rs
new file mode 100644
index 0000000000000..d7f5e19219ed6
--- /dev/null
+++ b/src/test/ui/abi/homogenous-floats-target-feature-mixup.rs
@@ -0,0 +1,192 @@
+// This test check that even if we mixup target feature of function with homogenous floats,
+// the abi is sound and still produce the right answer.
+//
+// This is basically the same test as src/test/ui/simd/target-feature-mixup.rs but for floats and
+// without #[repr(simd)]
+
+// run-pass
+// ignore-emscripten
+// ignore-sgx no processes
+
+#![feature(avx512_target_feature)]
+
+#![allow(overflowing_literals)]
+#![allow(unused_variables)]
+
+use std::process::{Command, ExitStatus};
+use std::env;
+
+fn main() {
+    if let Some(level) = env::args().nth(1) {
+        return test::main(&level)
+    }
+
+    match std::env::var("TARGET") {
+        Ok(s) => {
+            // Skip this tests on i586-unknown-linux-gnu where sse2 is disabled
+            if s.contains("i586") {
+                return
+            }
+        }
+        Err(_) => return,
+    }
+
+    let me = env::current_exe().unwrap();
+    for level in ["sse", "avx", "avx512"].iter() {
+        let status = Command::new(&me).arg(level).status().unwrap();
+        if status.success() {
+            println!("success with {}", level);
+            continue
+        }
+
+        // We don't actually know if our computer has the requisite target features
+        // for the test below. Testing for that will get added to libstd later so
+        // for now just assume sigill means this is a machine that can't run this test.
+        if is_sigill(status) {
+            println!("sigill with {}, assuming spurious", level);
+            continue
+        }
+        panic!("invalid status at {}: {}", level, status);
+    }
+}
+
+#[cfg(unix)]
+fn is_sigill(status: ExitStatus) -> bool {
+    use std::os::unix::prelude::*;
+    status.signal() == Some(4)
+}
+
+#[cfg(windows)]
+fn is_sigill(status: ExitStatus) -> bool {
+    status.code() == Some(0xc000001d)
+}
+
+#[cfg(any(target_arch = "x86", target_arch = "x86_64"))]
+#[allow(nonstandard_style)]
+mod test {
+    #[derive(PartialEq, Debug, Clone, Copy)]
+    struct f32x2(f32, f32);
+
+    #[derive(PartialEq, Debug, Clone, Copy)]
+    struct f32x4(f32, f32, f32, f32);
+
+    #[derive(PartialEq, Debug, Clone, Copy)]
+    struct f32x8(f32, f32, f32, f32, f32, f32, f32, f32);
+
+    pub fn main(level: &str) {
+        unsafe {
+            main_normal(level);
+            main_sse(level);
+            if level == "sse" {
+                return
+            }
+            main_avx(level);
+            if level == "avx" {
+                return
+            }
+            main_avx512(level);
+        }
+    }
+
+    macro_rules! mains {
+        ($(
+            $(#[$attr:meta])*
+            unsafe fn $main:ident(level: &str) {
+                ...
+            }
+        )*) => ($(
+            $(#[$attr])*
+            unsafe fn $main(level: &str) {
+                let m128 = f32x2(1., 2.);
+                let m256 = f32x4(3., 4., 5., 6.);
+                let m512 = f32x8(7., 8., 9., 10., 11., 12., 13., 14.);
+                assert_eq!(id_sse_128(m128), m128);
+                assert_eq!(id_sse_256(m256), m256);
+                assert_eq!(id_sse_512(m512), m512);
+
+                if level == "sse" {
+                    return
+                }
+                assert_eq!(id_avx_128(m128), m128);
+                assert_eq!(id_avx_256(m256), m256);
+                assert_eq!(id_avx_512(m512), m512);
+
+                if level == "avx" {
+                    return
+                }
+                assert_eq!(id_avx512_128(m128), m128);
+                assert_eq!(id_avx512_256(m256), m256);
+                assert_eq!(id_avx512_512(m512), m512);
+            }
+        )*)
+    }
+
+    mains! {
+        unsafe fn main_normal(level: &str) { ... }
+        #[target_feature(enable = "sse2")]
+        unsafe fn main_sse(level: &str) { ... }
+        #[target_feature(enable = "avx")]
+        unsafe fn main_avx(level: &str) { ... }
+        #[target_feature(enable = "avx512bw")]
+        unsafe fn main_avx512(level: &str) { ... }
+    }
+
+    #[target_feature(enable = "sse2")]
+    unsafe fn id_sse_128(a: f32x2) -> f32x2 {
+        assert_eq!(a, f32x2(1., 2.));
+        a.clone()
+    }
+
+    #[target_feature(enable = "sse2")]
+    unsafe fn id_sse_256(a: f32x4) -> f32x4 {
+        assert_eq!(a, f32x4(3., 4., 5., 6.));
+        a.clone()
+    }
+
+    #[target_feature(enable = "sse2")]
+    unsafe fn id_sse_512(a: f32x8) -> f32x8 {
+        assert_eq!(a, f32x8(7., 8., 9., 10., 11., 12., 13., 14.));
+        a.clone()
+    }
+
+    #[target_feature(enable = "avx")]
+    unsafe fn id_avx_128(a: f32x2) -> f32x2 {
+        assert_eq!(a, f32x2(1., 2.));
+        a.clone()
+    }
+
+    #[target_feature(enable = "avx")]
+    unsafe fn id_avx_256(a: f32x4) -> f32x4 {
+        assert_eq!(a, f32x4(3., 4., 5., 6.));
+        a.clone()
+    }
+
+    #[target_feature(enable = "avx")]
+    unsafe fn id_avx_512(a: f32x8) -> f32x8 {
+        assert_eq!(a, f32x8(7., 8., 9., 10., 11., 12., 13., 14.));
+        a.clone()
+    }
+
+    #[target_feature(enable = "avx512bw")]
+    unsafe fn id_avx512_128(a: f32x2) -> f32x2 {
+        assert_eq!(a, f32x2(1., 2.));
+        a.clone()
+    }
+
+    #[target_feature(enable = "avx512bw")]
+    unsafe fn id_avx512_256(a: f32x4) -> f32x4 {
+        assert_eq!(a, f32x4(3., 4., 5., 6.));
+        a.clone()
+    }
+
+    #[target_feature(enable = "avx512bw")]
+    unsafe fn id_avx512_512(a: f32x8) -> f32x8 {
+        assert_eq!(a, f32x8(7., 8., 9., 10., 11., 12., 13., 14.));
+        a.clone()
+    }
+}
+
+#[cfg(not(any(target_arch = "x86", target_arch = "x86_64")))]
+mod test {
+    pub fn main(level: &str) {}
+}
diff --git a/src/test/ui/impl-trait/in-trait/generics-mismatch.rs b/src/test/ui/impl-trait/in-trait/generics-mismatch.rs
new file mode 100644
index 0000000000000..cc0fc720ebbfd
--- /dev/null
+++ b/src/test/ui/impl-trait/in-trait/generics-mismatch.rs
@@ -0,0 +1,17 @@
+#![feature(return_position_impl_trait_in_trait)]
+#![allow(incomplete_features)]
+
+struct U;
+
+trait Foo {
+    fn bar(&self) -> impl Sized;
+}
+
+impl Foo for U {
+    fn bar<T>(&self) {}
+    //~^ ERROR method `bar` has 1 type parameter but its trait declaration has 0 type parameters
+}
+
+fn main() {
+    U.bar();
+}
diff --git a/src/test/ui/impl-trait/in-trait/generics-mismatch.stderr b/src/test/ui/impl-trait/in-trait/generics-mismatch.stderr
new file mode 100644
index 0000000000000..cd42683e0224d
--- /dev/null
+++ b/src/test/ui/impl-trait/in-trait/generics-mismatch.stderr
@@ -0,0 +1,12 @@
+error[E0049]: method `bar` has 1 type parameter but its trait declaration has 0 type parameters
+  --> $DIR/generics-mismatch.rs:11:12
+   |
+LL |     fn bar(&self) -> impl Sized;
+   |           - expected 0 type parameters
+...
+LL |     fn bar<T>(&self) {}
+   |            ^ found 1 type parameter
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0049`.
diff --git a/src/test/ui/impl-trait/in-trait/specialization-broken.rs b/src/test/ui/impl-trait/in-trait/specialization-broken.rs
new file mode 100644
index 0000000000000..9d27d3710a601
--- /dev/null
+++ b/src/test/ui/impl-trait/in-trait/specialization-broken.rs
@@ -0,0 +1,26 @@
+// FIXME(compiler-errors): I'm not exactly sure if this is expected to pass or not.
+// But we fixed an ICE anyways.
+
+#![feature(specialization)]
+#![feature(return_position_impl_trait_in_trait)]
+#![allow(incomplete_features)]
+
+trait Foo {
+    fn bar(&self) -> impl Sized;
+}
+
+default impl<U> Foo for U
+where
+    U: Copy,
+{
+    fn bar(&self) -> U {
+        //~^ ERROR method `bar` has an incompatible type for trait
+        *self
+    }
+}
+
+impl Foo for i32 {}
+
+fn main() {
+    1i32.bar();
+}
diff --git a/src/test/ui/impl-trait/in-trait/specialization-broken.stderr b/src/test/ui/impl-trait/in-trait/specialization-broken.stderr
new file mode 100644
index 0000000000000..a30e6346b2927
--- /dev/null
+++ b/src/test/ui/impl-trait/in-trait/specialization-broken.stderr
@@ -0,0 +1,23 @@
+error[E0053]: method `bar` has an incompatible type for trait
+  --> $DIR/specialization-broken.rs:16:22
+   |
+LL | default impl<U> Foo for U
+   |              - this type parameter
+...
+LL |     fn bar(&self) -> U {
+   |                      ^
+   |                      |
+   |                      expected associated type, found type parameter `U`
+   |                      help: change the output type to match the trait: `impl Sized`
+   |
+note: type in trait
+  --> $DIR/specialization-broken.rs:9:22
+   |
+LL |     fn bar(&self) -> impl Sized;
+   |                      ^^^^^^^^^^
+   = note: expected fn pointer `fn(&U) -> impl Sized`
+              found fn pointer `fn(&U) -> U`
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0053`.
diff --git a/src/test/ui/impl-trait/in-trait/specialization-substs-remap.rs b/src/test/ui/impl-trait/in-trait/specialization-substs-remap.rs
new file mode 100644
index 0000000000000..c9ee877db8ec5
--- /dev/null
+++ b/src/test/ui/impl-trait/in-trait/specialization-substs-remap.rs
@@ -0,0 +1,24 @@
+// check-pass
+
+#![feature(specialization)]
+#![feature(return_position_impl_trait_in_trait)]
+#![allow(incomplete_features)]
+
+trait Foo {
+    fn bar(&self) -> impl Sized;
+}
+
+impl<U> Foo for U
+where
+    U: Copy,
+{
+    fn bar(&self) -> U {
+        *self
+    }
+}
+
+impl Foo for i32 {}
+
+fn main() {
+    let _: i32 = 1i32.bar();
+}
diff --git a/src/test/ui/issues/issue-47511.stderr b/src/test/ui/issues/issue-47511.stderr
deleted file mode 100644
index 9998ee0e8d0c6..0000000000000
--- a/src/test/ui/issues/issue-47511.stderr
+++ /dev/null
@@ -1,18 +0,0 @@
-error[E0581]: return type references an anonymous lifetime, which is not constrained by the fn input types
-  --> $DIR/issue-47511.rs:8:15
-   |
-LL | fn f(_: X) -> X {
-   |               ^
-   |
-   = note: lifetimes appearing in an associated or opaque type are not considered constrained
-   = note: consider introducing a named lifetime parameter
-
-error[E0581]: return type references lifetime `'a`, which is not constrained by the fn input types
-  --> $DIR/issue-47511.rs:12:23
-   |
-LL | fn g<'a>(_: X<'a>) -> X<'a> {
-   |                       ^^^^^
-
-error: aborting due to 2 previous errors
-
-For more information about this error, try `rustc --explain E0581`.
diff --git a/src/test/ui/late-bound-lifetimes/auxiliary/upstream_alias.rs b/src/test/ui/late-bound-lifetimes/auxiliary/upstream_alias.rs
new file mode 100644
index 0000000000000..5b9dc0e43087c
--- /dev/null
+++ b/src/test/ui/late-bound-lifetimes/auxiliary/upstream_alias.rs
@@ -0,0 +1,5 @@
+pub trait Trait<'a> {
+    type Assoc;
+}
+
+pub type Alias<'a, T> = <T as Trait<'a>>::Assoc;
diff --git a/src/test/ui/late-bound-lifetimes/cross_crate_alias.rs b/src/test/ui/late-bound-lifetimes/cross_crate_alias.rs
new file mode 100644
index 0000000000000..4154c27924323
--- /dev/null
+++ b/src/test/ui/late-bound-lifetimes/cross_crate_alias.rs
@@ -0,0 +1,10 @@
+// aux-build:upstream_alias.rs
+// check-pass
+
+extern crate upstream_alias;
+
+fn foo<'a, T: for<'b> upstream_alias::Trait<'b>>(_: upstream_alias::Alias<'a, T>) -> &'a () {
+    todo!()
+}
+
+fn main() {}
diff --git a/src/test/ui/late-bound-lifetimes/downgraded_to_early_through_alias.rs b/src/test/ui/late-bound-lifetimes/downgraded_to_early_through_alias.rs
new file mode 100644
index 0000000000000..e56a34218e231
--- /dev/null
+++ b/src/test/ui/late-bound-lifetimes/downgraded_to_early_through_alias.rs
@@ -0,0 +1,24 @@
+// check-pass
+
+trait Gats<'a> {
+    type Assoc;
+    type Assoc2;
+}
+
+trait Trait: for<'a> Gats<'a> {
+    fn foo<'a>(_: &mut <Self as Gats<'a>>::Assoc) -> <Self as Gats<'a>>::Assoc2;
+}
+
+impl<'a> Gats<'a> for () {
+    type Assoc = &'a u32;
+    type Assoc2 = ();
+}
+
+type GatsAssoc<'a, T> = <T as Gats<'a>>::Assoc;
+type GatsAssoc2<'a, T> = <T as Gats<'a>>::Assoc2;
+
+impl Trait for () {
+    fn foo<'a>(_: &mut GatsAssoc<'a, Self>) -> GatsAssoc2<'a, Self> {}
+}
+
+fn main() {}
diff --git a/src/test/ui/issues/issue-47511.rs b/src/test/ui/late-bound-lifetimes/issue-47511.rs
similarity index 52%
rename from src/test/ui/issues/issue-47511.rs
rename to src/test/ui/late-bound-lifetimes/issue-47511.rs
index eb4860e75d758..7894435154082 100644
--- a/src/test/ui/issues/issue-47511.rs
+++ b/src/test/ui/late-bound-lifetimes/issue-47511.rs
@@ -1,9 +1,4 @@
-// check-fail
-// known-bug: #47511
-
-// Regression test for #47511: anonymous lifetimes can appear
-// unconstrained in a return type, but only if they appear just once
-// in the input, as the input to a projection.
+// check-pass
 
 fn f(_: X) -> X {
     unimplemented!()
diff --git a/src/test/ui/late-bound-lifetimes/late_bound_through_alias.rs b/src/test/ui/late-bound-lifetimes/late_bound_through_alias.rs
new file mode 100644
index 0000000000000..91839673c1f7a
--- /dev/null
+++ b/src/test/ui/late-bound-lifetimes/late_bound_through_alias.rs
@@ -0,0 +1,16 @@
+// check-pass
+
+fn f(_: X) -> X {
+    unimplemented!()
+}
+
+fn g<'a>(_: X<'a>) -> X<'a> {
+    unimplemented!()
+}
+
+type X<'a> = &'a ();
+
+fn main() {
+    let _: for<'a> fn(X<'a>) -> X<'a> = g;
+    let _: for<'a> fn(X<'a>) -> X<'a> = f;
+}
diff --git a/src/test/ui/late-bound-lifetimes/mismatched_arg_count.rs b/src/test/ui/late-bound-lifetimes/mismatched_arg_count.rs
new file mode 100644
index 0000000000000..0b331e2039f25
--- /dev/null
+++ b/src/test/ui/late-bound-lifetimes/mismatched_arg_count.rs
@@ -0,0 +1,12 @@
+// ensures that we don't ICE when there are too many args supplied to the alias.
+
+trait Trait<'a> {
+    type Assoc;
+}
+
+type Alias<'a, T> = <T as Trait<'a>>::Assoc;
+
+fn bar<'a, T: Trait<'a>>(_: Alias<'a, 'a, T>) {}
+//~^ error: this type alias takes 1 lifetime argument but 2 lifetime arguments were supplied
+
+fn main() {}
diff --git a/src/test/ui/late-bound-lifetimes/mismatched_arg_count.stderr b/src/test/ui/late-bound-lifetimes/mismatched_arg_count.stderr
new file mode 100644
index 0000000000000..3704d9bb957ed
--- /dev/null
+++ b/src/test/ui/late-bound-lifetimes/mismatched_arg_count.stderr
@@ -0,0 +1,17 @@
+error[E0107]: this type alias takes 1 lifetime argument but 2 lifetime arguments were supplied
+  --> $DIR/mismatched_arg_count.rs:9:29
+   |
+LL | fn bar<'a, T: Trait<'a>>(_: Alias<'a, 'a, T>) {}
+   |                             ^^^^^     -- help: remove this lifetime argument
+   |                             |
+   |                             expected 1 lifetime argument
+   |
+note: type alias defined here, with 1 lifetime parameter: `'a`
+  --> $DIR/mismatched_arg_count.rs:7:6
+   |
+LL | type Alias<'a, T> = <T as Trait<'a>>::Assoc;
+   |      ^^^^^ --
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0107`.
diff --git a/src/test/ui/parser/issue-103451.rs b/src/test/ui/parser/issue-103451.rs
new file mode 100644
index 0000000000000..1fdb001488155
--- /dev/null
+++ b/src/test/ui/parser/issue-103451.rs
@@ -0,0 +1,5 @@
+// error-pattern: this file contains an unclosed delimiter
+// error-pattern: expected value, found struct `R`
+struct R { }
+struct S {
+    x: [u8; R
diff --git a/src/test/ui/parser/issue-103451.stderr b/src/test/ui/parser/issue-103451.stderr
new file mode 100644
index 0000000000000..eb3c92fb43d9b
--- /dev/null
+++ b/src/test/ui/parser/issue-103451.stderr
@@ -0,0 +1,32 @@
+error: this file contains an unclosed delimiter
+  --> $DIR/issue-103451.rs:5:15
+   |
+LL | struct S {
+   |          - unclosed delimiter
+LL |     x: [u8; R
+   |        -      ^
+   |        |
+   |        unclosed delimiter
+
+error: this file contains an unclosed delimiter
+  --> $DIR/issue-103451.rs:5:15
+   |
+LL | struct S {
+   |          - unclosed delimiter
+LL |     x: [u8; R
+   |        -      ^
+   |        |
+   |        unclosed delimiter
+
+error[E0423]: expected value, found struct `R`
+  --> $DIR/issue-103451.rs:5:13
+   |
+LL | struct R { }
+   | ------------ `R` defined here
+LL | struct S {
+LL |     x: [u8; R
+   |             ^ help: use struct literal syntax instead: `R {}`
+
+error: aborting due to 3 previous errors
+
+For more information about this error, try `rustc --explain E0423`.