From cc4a0293697ca5dce8a518f6d5aa0036a1bd94d1 Mon Sep 17 00:00:00 2001
From: Deadbeef <ent3rm4n@gmail.com>
Date: Fri, 14 Jun 2024 12:16:15 +0000
Subject: [PATCH 1/4] implement new effects desugaring

---
 core/src/lib.rs    |  1 +
 core/src/marker.rs | 38 ++++++++++++++++++++++++++++++++++++++
 2 files changed, 39 insertions(+)

diff --git a/core/src/lib.rs b/core/src/lib.rs
index d1692729a31b4..cfadfb0233ea7 100644
--- a/core/src/lib.rs
+++ b/core/src/lib.rs
@@ -231,6 +231,7 @@
 #![feature(let_chains)]
 #![feature(link_llvm_intrinsics)]
 #![feature(macro_metavar_expr)]
+#![feature(marker_trait_attr)]
 #![feature(min_exhaustive_patterns)]
 #![feature(min_specialization)]
 #![feature(multiple_supertrait_upcastable)]
diff --git a/core/src/marker.rs b/core/src/marker.rs
index 0fedb8835d1ae..b3f3cc021261f 100644
--- a/core/src/marker.rs
+++ b/core/src/marker.rs
@@ -1027,3 +1027,41 @@ pub trait FnPtr: Copy + Clone {
 pub macro SmartPointer($item:item) {
     /* compiler built-in */
 }
+
+#[doc(hidden)]
+#[unstable(
+    feature = "effect_types",
+    issue = "none",
+    reason = "internal module for implementing effects"
+)]
+#[allow(missing_debug_implementations)] // these unit structs don't need `Debug` impls.
+#[cfg(not(bootstrap))]
+// TODO docs
+pub mod effects {
+    #[lang = "EffectsNoRuntime"]
+    pub struct NoRuntime;
+    #[lang = "EffectsMaybe"]
+    pub struct Maybe;
+    #[lang = "EffectsRuntime"]
+    pub struct Runtime;
+
+    #[lang = "EffectsCompat"]
+    pub trait Compat<#[rustc_runtime] const RUNTIME: bool> {}
+
+    impl Compat<false> for NoRuntime {}
+    impl Compat<true> for Runtime {}
+    impl<#[rustc_runtime] const RUNTIME: bool> Compat<RUNTIME> for Maybe {}
+
+    #[lang = "EffectsTyCompat"]
+    #[marker]
+    pub trait TyCompat<T> {}
+
+    impl<T> TyCompat<T> for T {}
+    impl<T> TyCompat<T> for Maybe {}
+
+    #[lang = "EffectsMin"]
+    pub trait Min {
+        #[lang = "EffectsMinOutput"]
+        type Output;
+    }
+}

From 47492c9ec941a1698125185372a6bfb82d364bad Mon Sep 17 00:00:00 2001
From: Deadbeef <ent3rm4n@gmail.com>
Date: Mon, 24 Jun 2024 16:25:17 +0000
Subject: [PATCH 2/4] Implement `Min` trait in new solver

---
 core/src/marker.rs | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/core/src/marker.rs b/core/src/marker.rs
index b3f3cc021261f..b71bedaa1948f 100644
--- a/core/src/marker.rs
+++ b/core/src/marker.rs
@@ -1054,14 +1054,15 @@ pub mod effects {
 
     #[lang = "EffectsTyCompat"]
     #[marker]
-    pub trait TyCompat<T> {}
+    pub trait TyCompat<T: ?Sized> {}
 
-    impl<T> TyCompat<T> for T {}
-    impl<T> TyCompat<T> for Maybe {}
+    impl<T: ?Sized> TyCompat<T> for T {}
+    impl<T: ?Sized> TyCompat<T> for Maybe {}
+    impl<T: ?Sized> TyCompat<Maybe> for T {}
 
     #[lang = "EffectsMin"]
     pub trait Min {
         #[lang = "EffectsMinOutput"]
-        type Output;
+        type Output: ?Sized;
     }
 }

From db228b821dda3240d1e1f7e8e2dc75eb2c484d52 Mon Sep 17 00:00:00 2001
From: Deadbeef <ent3rm4n@gmail.com>
Date: Tue, 25 Jun 2024 09:57:31 +0000
Subject: [PATCH 3/4] general fixups and turn `TODO`s into `FIXME`s

---
 core/src/marker.rs | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/core/src/marker.rs b/core/src/marker.rs
index b71bedaa1948f..042acbf20b1a0 100644
--- a/core/src/marker.rs
+++ b/core/src/marker.rs
@@ -1028,6 +1028,9 @@ pub macro SmartPointer($item:item) {
     /* compiler built-in */
 }
 
+// Support traits and types for the desugaring of const traits and
+// `~const` bounds. Not supposed to be used by anything other than
+// the compiler.
 #[doc(hidden)]
 #[unstable(
     feature = "effect_types",
@@ -1036,7 +1039,6 @@ pub macro SmartPointer($item:item) {
 )]
 #[allow(missing_debug_implementations)] // these unit structs don't need `Debug` impls.
 #[cfg(not(bootstrap))]
-// TODO docs
 pub mod effects {
     #[lang = "EffectsNoRuntime"]
     pub struct NoRuntime;

From 729a10a00b8311b6cdb4e46c59b9033692a0976b Mon Sep 17 00:00:00 2001
From: Deadbeef <ent3rm4n@gmail.com>
Date: Wed, 26 Jun 2024 16:36:42 +0000
Subject: [PATCH 4/4] address review comments

---
 core/src/marker.rs | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/core/src/marker.rs b/core/src/marker.rs
index 042acbf20b1a0..9f5818f675d86 100644
--- a/core/src/marker.rs
+++ b/core/src/marker.rs
@@ -1062,9 +1062,14 @@ pub mod effects {
     impl<T: ?Sized> TyCompat<T> for Maybe {}
     impl<T: ?Sized> TyCompat<Maybe> for T {}
 
-    #[lang = "EffectsMin"]
-    pub trait Min {
-        #[lang = "EffectsMinOutput"]
+    #[lang = "EffectsIntersection"]
+    pub trait Intersection {
+        #[lang = "EffectsIntersectionOutput"]
         type Output: ?Sized;
     }
+
+    // FIXME(effects): remove this after next trait solver lands
+    impl Intersection for () {
+        type Output = Maybe;
+    }
 }