From 778abc7a00dff4271b48a5cd0fa256b9c28965f3 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Le=C3=B3n=20Orell=20Valerian=20Liehr?= <me@fmease.dev>
Date: Fri, 12 May 2023 01:36:37 +0200
Subject: [PATCH] properly pretty-print inherent projections

---
 .../rustc_const_eval/src/util/type_name.rs    |  3 ++-
 compiler/rustc_middle/src/ty/print/pretty.rs  | 22 ++++++++++++++++++-
 compiler/rustc_symbol_mangling/src/legacy.rs  |  4 +++-
 compiler/rustc_symbol_mangling/src/v0.rs      |  3 ++-
 4 files changed, 28 insertions(+), 4 deletions(-)

diff --git a/compiler/rustc_const_eval/src/util/type_name.rs b/compiler/rustc_const_eval/src/util/type_name.rs
index 4e80a28518668..11ad5b49df2ef 100644
--- a/compiler/rustc_const_eval/src/util/type_name.rs
+++ b/compiler/rustc_const_eval/src/util/type_name.rs
@@ -58,11 +58,12 @@ impl<'tcx> Printer<'tcx> for AbsolutePathPrinter<'tcx> {
             // Types with identity (print the module path).
             ty::Adt(ty::AdtDef(Interned(&ty::AdtDefData { did: def_id, .. }, _)), substs)
             | ty::FnDef(def_id, substs)
-            | ty::Alias(_, ty::AliasTy { def_id, substs, .. })
+            | ty::Alias(ty::Projection | ty::Opaque, ty::AliasTy { def_id, substs, .. })
             | ty::Closure(def_id, substs)
             | ty::Generator(def_id, substs, _) => self.print_def_path(def_id, substs),
             ty::Foreign(def_id) => self.print_def_path(def_id, &[]),
 
+            ty::Alias(ty::Inherent, _) => bug!("type_name: unexpected inherent projection"),
             ty::GeneratorWitness(_) => bug!("type_name: unexpected `GeneratorWitness`"),
             ty::GeneratorWitnessMIR(..) => bug!("type_name: unexpected `GeneratorWitnessMIR`"),
         }
diff --git a/compiler/rustc_middle/src/ty/print/pretty.rs b/compiler/rustc_middle/src/ty/print/pretty.rs
index a8193c3e5591f..e381c1812eda6 100644
--- a/compiler/rustc_middle/src/ty/print/pretty.rs
+++ b/compiler/rustc_middle/src/ty/print/pretty.rs
@@ -1164,6 +1164,22 @@ pub trait PrettyPrinter<'tcx>:
         traits.entry(trait_ref).or_default().extend(proj_ty);
     }
 
+    fn pretty_print_inherent_projection(
+        self,
+        alias_ty: &ty::AliasTy<'tcx>,
+    ) -> Result<Self::Path, Self::Error> {
+        let def_key = self.tcx().def_key(alias_ty.def_id);
+        self.path_generic_args(
+            |cx| {
+                cx.path_append(
+                    |cx| cx.path_qualified(alias_ty.self_ty(), None),
+                    &def_key.disambiguated_data,
+                )
+            },
+            &alias_ty.substs[1..],
+        )
+    }
+
     fn ty_infer_name(&self, _: ty::TyVid) -> Option<Symbol> {
         None
     }
@@ -2821,7 +2837,11 @@ define_print_and_forward_display! {
     }
 
     ty::AliasTy<'tcx> {
-        p!(print_def_path(self.def_id, self.substs));
+        if let DefKind::Impl { of_trait: false } = cx.tcx().def_kind(cx.tcx().parent(self.def_id)) {
+            p!(pretty_print_inherent_projection(self))
+        } else {
+            p!(print_def_path(self.def_id, self.substs));
+        }
     }
 
     ty::ClosureKind {
diff --git a/compiler/rustc_symbol_mangling/src/legacy.rs b/compiler/rustc_symbol_mangling/src/legacy.rs
index a3f262905c74f..254ede4e6a00a 100644
--- a/compiler/rustc_symbol_mangling/src/legacy.rs
+++ b/compiler/rustc_symbol_mangling/src/legacy.rs
@@ -220,7 +220,7 @@ impl<'tcx> Printer<'tcx> for &mut SymbolPrinter<'tcx> {
         match *ty.kind() {
             // Print all nominal types as paths (unlike `pretty_print_type`).
             ty::FnDef(def_id, substs)
-            | ty::Alias(_, ty::AliasTy { def_id, substs, .. })
+            | ty::Alias(ty::Projection | ty::Opaque, ty::AliasTy { def_id, substs, .. })
             | ty::Closure(def_id, substs)
             | ty::Generator(def_id, substs, _) => self.print_def_path(def_id, substs),
 
@@ -241,6 +241,8 @@ impl<'tcx> Printer<'tcx> for &mut SymbolPrinter<'tcx> {
                 Ok(self)
             }
 
+            ty::Alias(ty::Inherent, _) => panic!("unexpected inherent projection"),
+
             _ => self.pretty_print_type(ty),
         }
     }
diff --git a/compiler/rustc_symbol_mangling/src/v0.rs b/compiler/rustc_symbol_mangling/src/v0.rs
index 2235524129e62..4cccc6398927c 100644
--- a/compiler/rustc_symbol_mangling/src/v0.rs
+++ b/compiler/rustc_symbol_mangling/src/v0.rs
@@ -433,7 +433,7 @@ impl<'tcx> Printer<'tcx> for &mut SymbolMangler<'tcx> {
             // Mangle all nominal types as paths.
             ty::Adt(ty::AdtDef(Interned(&ty::AdtDefData { did: def_id, .. }, _)), substs)
             | ty::FnDef(def_id, substs)
-            | ty::Alias(_, ty::AliasTy { def_id, substs, .. })
+            | ty::Alias(ty::Projection | ty::Opaque, ty::AliasTy { def_id, substs, .. })
             | ty::Closure(def_id, substs)
             | ty::Generator(def_id, substs, _) => {
                 self = self.print_def_path(def_id, substs)?;
@@ -482,6 +482,7 @@ impl<'tcx> Printer<'tcx> for &mut SymbolMangler<'tcx> {
                 self = r.print(self)?;
             }
 
+            ty::Alias(ty::Inherent, _) => bug!("symbol_names: unexpected inherent projection"),
             ty::GeneratorWitness(_) => bug!("symbol_names: unexpected `GeneratorWitness`"),
             ty::GeneratorWitnessMIR(..) => bug!("symbol_names: unexpected `GeneratorWitnessMIR`"),
         }