8 files changed, 47 insertions, 12 deletions
diff --git a/compiler/rustc_middle/src/hir/map/mod.rs b/compiler/rustc_middle/src/hir/map/mod.rs
index 883554f959c..48bae7a2d4e 100644
--- a/compiler/rustc_middle/src/hir/map/mod.rs
+++ b/compiler/rustc_middle/src/hir/map/mod.rs
@@ -485,7 +485,9 @@ impl<'hir> Map<'hir> {
             BodyOwnerKind::Static(mt) => ConstContext::Static(mt),
 
             BodyOwnerKind::Fn if self.tcx.is_constructor(def_id.to_def_id()) => return None,
-            BodyOwnerKind::Fn if self.tcx.is_const_fn_raw(def_id.to_def_id()) => {
+            BodyOwnerKind::Fn | BodyOwnerKind::Closure
+                if self.tcx.is_const_fn_raw(def_id.to_def_id()) =>
+            {
                 ConstContext::ConstFn
             }
             BodyOwnerKind::Fn if self.tcx.is_const_default_method(def_id.to_def_id()) => {
diff --git a/compiler/rustc_middle/src/thir.rs b/compiler/rustc_middle/src/thir.rs
index ac903010c8d..5f320708c84 100644
--- a/compiler/rustc_middle/src/thir.rs
+++ b/compiler/rustc_middle/src/thir.rs
@@ -9,6 +9,7 @@
 //! [rustc dev guide]: https://rustc-dev-guide.rust-lang.org/thir.html
 
 use rustc_ast::{InlineAsmOptions, InlineAsmTemplatePiece};
+use rustc_errors::{DiagnosticArgValue, IntoDiagnosticArg};
 use rustc_hir as hir;
 use rustc_hir::def_id::DefId;
 use rustc_hir::RangeEnd;
@@ -575,6 +576,12 @@ impl<'tcx> Pat<'tcx> {
     }
 }
 
+impl<'tcx> IntoDiagnosticArg for Pat<'tcx> {
+    fn into_diagnostic_arg(self) -> DiagnosticArgValue<'static> {
+        format!("{}", self).into_diagnostic_arg()
+    }
+}
+
 #[derive(Clone, Debug, HashStable)]
 pub struct Ascription<'tcx> {
     pub annotation: CanonicalUserTypeAnnotation<'tcx>,
diff --git a/compiler/rustc_middle/src/traits/select.rs b/compiler/rustc_middle/src/traits/select.rs
index ec69864c951..1cc9fd526b4 100644
--- a/compiler/rustc_middle/src/traits/select.rs
+++ b/compiler/rustc_middle/src/traits/select.rs
@@ -131,7 +131,9 @@ pub enum SelectionCandidate<'tcx> {
 
     /// Implementation of a `Fn`-family trait by one of the anonymous types
     /// generated for an `||` expression.
-    ClosureCandidate,
+    ClosureCandidate {
+        is_const: bool,
+    },
 
     /// Implementation of a `Generator` trait by one of the anonymous types
     /// generated for a generator.
diff --git a/compiler/rustc_middle/src/ty/_match.rs b/compiler/rustc_middle/src/ty/_match.rs
index cd147d7e558..b9c5a4e0d0d 100644
--- a/compiler/rustc_middle/src/ty/_match.rs
+++ b/compiler/rustc_middle/src/ty/_match.rs
@@ -89,7 +89,9 @@ impl<'tcx> TypeRelation<'tcx> for Match<'tcx> {
                 Err(TypeError::Sorts(relate::expected_found(self, a, b)))
             }
 
-            (&ty::Error(_), _) | (_, &ty::Error(_)) => Ok(self.tcx().ty_error()),
+            (&ty::Error(guar), _) | (_, &ty::Error(guar)) => {
+                Ok(self.tcx().ty_error_with_guaranteed(guar))
+            }
 
             _ => relate::super_relate_tys(self, a, b),
         }
diff --git a/compiler/rustc_middle/src/ty/error.rs b/compiler/rustc_middle/src/ty/error.rs
index 50554cf9a82..5d394f71f0d 100644
--- a/compiler/rustc_middle/src/ty/error.rs
+++ b/compiler/rustc_middle/src/ty/error.rs
@@ -2,10 +2,10 @@ use crate::traits::{ObligationCause, ObligationCauseCode};
 use crate::ty::diagnostics::suggest_constraining_type_param;
 use crate::ty::print::{with_forced_trimmed_paths, FmtPrinter, Printer};
 use crate::ty::{self, BoundRegionKind, Region, Ty, TyCtxt};
-use hir::def::DefKind;
 use rustc_errors::Applicability::{MachineApplicable, MaybeIncorrect};
 use rustc_errors::{pluralize, Diagnostic, MultiSpan};
 use rustc_hir as hir;
+use rustc_hir::def::{CtorOf, DefKind};
 use rustc_hir::def_id::DefId;
 use rustc_span::symbol::{sym, Symbol};
 use rustc_span::{BytePos, Span};
@@ -319,7 +319,11 @@ impl<'tcx> Ty<'tcx> {
                     .into()
                 }
             }
-            ty::FnDef(..) => "fn item".into(),
+            ty::FnDef(def_id, ..) => match tcx.def_kind(def_id) {
+                DefKind::Ctor(CtorOf::Struct, _) => "struct constructor".into(),
+                DefKind::Ctor(CtorOf::Variant, _) => "enum constructor".into(),
+                _ => "fn item".into(),
+            },
             ty::FnPtr(_) => "fn pointer".into(),
             ty::Dynamic(ref inner, ..) if let Some(principal) = inner.principal() => {
                 format!("trait object `dyn {}`", tcx.def_path_str(principal.def_id())).into()
@@ -366,7 +370,11 @@ impl<'tcx> Ty<'tcx> {
                 _ => "reference",
             }
             .into(),
-            ty::FnDef(..) => "fn item".into(),
+            ty::FnDef(def_id, ..) => match tcx.def_kind(def_id) {
+                DefKind::Ctor(CtorOf::Struct, _) => "struct constructor".into(),
+                DefKind::Ctor(CtorOf::Variant, _) => "enum constructor".into(),
+                _ => "fn item".into(),
+            },
             ty::FnPtr(_) => "fn pointer".into(),
             ty::Dynamic(..) => "trait object".into(),
             ty::Closure(..) => "closure".into(),
diff --git a/compiler/rustc_middle/src/ty/mod.rs b/compiler/rustc_middle/src/ty/mod.rs
index fa571d480b6..993e95b3514 100644
--- a/compiler/rustc_middle/src/ty/mod.rs
+++ b/compiler/rustc_middle/src/ty/mod.rs
@@ -2465,8 +2465,10 @@ impl<'tcx> TyCtxt<'tcx> {
 
     #[inline]
     pub fn is_const_fn_raw(self, def_id: DefId) -> bool {
-        matches!(self.def_kind(def_id), DefKind::Fn | DefKind::AssocFn | DefKind::Ctor(..))
-            && self.constness(def_id) == hir::Constness::Const
+        matches!(
+            self.def_kind(def_id),
+            DefKind::Fn | DefKind::AssocFn | DefKind::Ctor(..) | DefKind::Closure
+        ) && self.constness(def_id) == hir::Constness::Const
     }
 
     #[inline]
diff --git a/compiler/rustc_middle/src/ty/print/pretty.rs b/compiler/rustc_middle/src/ty/print/pretty.rs
index c49e75d68ad..a91e8de5f21 100644
--- a/compiler/rustc_middle/src/ty/print/pretty.rs
+++ b/compiler/rustc_middle/src/ty/print/pretty.rs
@@ -283,6 +283,8 @@ pub trait PrettyPrinter<'tcx>:
     /// This is typically the case for all non-`'_` regions.
     fn should_print_region(&self, region: ty::Region<'tcx>) -> bool;
 
+    fn reset_type_limit(&mut self) {}
+
     // Defaults (should not be overridden):
 
     /// If possible, this returns a global path resolving to `def_id` that is visible
@@ -1981,6 +1983,10 @@ impl<'tcx> PrettyPrinter<'tcx> for FmtPrinter<'_, 'tcx> {
         self.0.ty_infer_name_resolver.as_ref().and_then(|func| func(id))
     }
 
+    fn reset_type_limit(&mut self) {
+        self.printed_type_count = 0;
+    }
+
     fn const_infer_name(&self, id: ty::ConstVid<'tcx>) -> Option<Symbol> {
         self.0.const_infer_name_resolver.as_ref().and_then(|func| func(id))
     }
@@ -2722,11 +2728,15 @@ define_print_and_forward_display! {
     }
 
     ty::SubtypePredicate<'tcx> {
-        p!(print(self.a), " <: ", print(self.b))
+        p!(print(self.a), " <: ");
+        cx.reset_type_limit();
+        p!(print(self.b))
     }
 
     ty::CoercePredicate<'tcx> {
-        p!(print(self.a), " -> ", print(self.b))
+        p!(print(self.a), " -> ");
+        cx.reset_type_limit();
+        p!(print(self.b))
     }
 
     ty::TraitPredicate<'tcx> {
@@ -2738,7 +2748,9 @@ define_print_and_forward_display! {
     }
 
     ty::ProjectionPredicate<'tcx> {
-        p!(print(self.projection_ty), " == ", print(self.term))
+        p!(print(self.projection_ty), " == ");
+        cx.reset_type_limit();
+        p!(print(self.term))
     }
 
     ty::Term<'tcx> {
diff --git a/compiler/rustc_middle/src/ty/relate.rs b/compiler/rustc_middle/src/ty/relate.rs
index 4d34ca3d66b..65fd8d9753d 100644
--- a/compiler/rustc_middle/src/ty/relate.rs
+++ b/compiler/rustc_middle/src/ty/relate.rs
@@ -414,7 +414,7 @@ pub fn super_relate_tys<'tcx, R: TypeRelation<'tcx>>(
             bug!("bound types encountered in super_relate_tys")
         }
 
-        (&ty::Error(_), _) | (_, &ty::Error(_)) => Ok(tcx.ty_error()),
+        (&ty::Error(guar), _) | (_, &ty::Error(guar)) => Ok(tcx.ty_error_with_guaranteed(guar)),
 
         (&ty::Never, _)
         | (&ty::Char, _)