From d0e4c679ff1772e7ec0f9ca983ac229ffd3db2dc Mon Sep 17 00:00:00 2001
From: Michael Goulet <michael@errs.io>
Date: Sat, 30 Jul 2022 01:33:51 +0000
Subject: Built-in implementation of Tuple trait

---
 compiler/rustc_middle/src/traits/mod.rs              | 11 +++++++++--
 compiler/rustc_middle/src/traits/select.rs           |  3 +++
 compiler/rustc_middle/src/traits/structural_impls.rs |  2 ++
 3 files changed, 14 insertions(+), 2 deletions(-)

(limited to 'compiler/rustc_middle/src')

diff --git a/compiler/rustc_middle/src/traits/mod.rs b/compiler/rustc_middle/src/traits/mod.rs
index 72b848c3ee2..53d22eb0070 100644
--- a/compiler/rustc_middle/src/traits/mod.rs
+++ b/compiler/rustc_middle/src/traits/mod.rs
@@ -634,6 +634,10 @@ pub enum ImplSource<'tcx, N> {
 
     /// ImplSource for a `const Drop` implementation.
     ConstDestruct(ImplSourceConstDestructData<N>),
+
+    /// ImplSource for a `std::marker::Tuple` implementation.
+    /// This has no nested predicates ever, so no data.
+    Tuple,
 }
 
 impl<'tcx, N> ImplSource<'tcx, N> {
@@ -648,7 +652,8 @@ impl<'tcx, N> ImplSource<'tcx, N> {
             ImplSource::Object(d) => d.nested,
             ImplSource::FnPointer(d) => d.nested,
             ImplSource::DiscriminantKind(ImplSourceDiscriminantKindData)
-            | ImplSource::Pointee(ImplSourcePointeeData) => Vec::new(),
+            | ImplSource::Pointee(ImplSourcePointeeData)
+            | ImplSource::Tuple => Vec::new(),
             ImplSource::TraitAlias(d) => d.nested,
             ImplSource::TraitUpcasting(d) => d.nested,
             ImplSource::ConstDestruct(i) => i.nested,
@@ -666,7 +671,8 @@ impl<'tcx, N> ImplSource<'tcx, N> {
             ImplSource::Object(d) => &d.nested,
             ImplSource::FnPointer(d) => &d.nested,
             ImplSource::DiscriminantKind(ImplSourceDiscriminantKindData)
-            | ImplSource::Pointee(ImplSourcePointeeData) => &[],
+            | ImplSource::Pointee(ImplSourcePointeeData)
+            | ImplSource::Tuple => &[],
             ImplSource::TraitAlias(d) => &d.nested,
             ImplSource::TraitUpcasting(d) => &d.nested,
             ImplSource::ConstDestruct(i) => &i.nested,
@@ -733,6 +739,7 @@ impl<'tcx, N> ImplSource<'tcx, N> {
                     nested: i.nested.into_iter().map(f).collect(),
                 })
             }
+            ImplSource::Tuple => ImplSource::Tuple,
         }
     }
 }
diff --git a/compiler/rustc_middle/src/traits/select.rs b/compiler/rustc_middle/src/traits/select.rs
index e836ba47eed..53af3e90534 100644
--- a/compiler/rustc_middle/src/traits/select.rs
+++ b/compiler/rustc_middle/src/traits/select.rs
@@ -160,6 +160,9 @@ pub enum SelectionCandidate<'tcx> {
 
     /// Implementation of `const Destruct`, optionally from a custom `impl const Drop`.
     ConstDestructCandidate(Option<DefId>),
+
+    /// Witnesses the fact that a type is a tuple.
+    TupleCandidate,
 }
 
 /// The result of trait evaluation. The order is important
diff --git a/compiler/rustc_middle/src/traits/structural_impls.rs b/compiler/rustc_middle/src/traits/structural_impls.rs
index 7fbd57ac735..c526344e1f2 100644
--- a/compiler/rustc_middle/src/traits/structural_impls.rs
+++ b/compiler/rustc_middle/src/traits/structural_impls.rs
@@ -34,6 +34,8 @@ impl<'tcx, N: fmt::Debug> fmt::Debug for traits::ImplSource<'tcx, N> {
             super::ImplSource::TraitUpcasting(ref d) => write!(f, "{:?}", d),
 
             super::ImplSource::ConstDestruct(ref d) => write!(f, "{:?}", d),
+
+            super::ImplSource::Tuple => write!(f, "ImplSource::Tuple"),
         }
     }
 }
-- 
cgit 1.4.1-3-g733a5