allow concrete self types in consts

src/librustdoc/clean/utils.rs

@@ -601,7 +601,7 @@ pub fn register_res(cx: &DocContext<'_>, res: Res) -> DefId {
         },
         Res::Def(DefKind::TraitAlias, i) => (i, TypeKind::TraitAlias),
         Res::SelfTy(Some(def_id), _) => (def_id, TypeKind::Trait),
-        Res::SelfTy(_, Some(impl_def_id)) => return impl_def_id,
+        Res::SelfTy(_, Some((impl_def_id, _))) => return impl_def_id,
         _ => return res.def_id(),
     };
     if did.is_local() {

src/test/ui/const-generics/min_const_generics/self-ty-in-const-1.rs

@@ -0,0 +1,27 @@
+#![feature(min_const_generics)]
+
+trait Foo {
+    fn t1() -> [u8; std::mem::size_of::<Self>()]; //~ERROR generic parameters
+}
+
+struct Bar<T>(T);
+
+impl Bar<u8> {
+    fn t2() -> [u8; std::mem::size_of::<Self>()] { todo!() } // ok
+}
+
+impl<T> Bar<T> {
+    fn t3() -> [u8; std::mem::size_of::<Self>()] {} //~ERROR generic `Self`
+}
+
+trait Baz {
+    fn hey();
+}
+
+impl Baz for u16 {
+    fn hey() {
+        let _: [u8; std::mem::size_of::<Self>()]; // ok
+    }
+}
+
+fn main() {}

src/test/ui/const-generics/min_const_generics/self-ty-in-const-1.stderr

@@ -0,0 +1,24 @@
+error: generic parameters must not be used inside of non trivial constant values
+  --> $DIR/self-ty-in-const-1.rs:4:41
+   |
+LL |     fn t1() -> [u8; std::mem::size_of::<Self>()];
+   |                                         ^^^^ non-trivial anonymous constants must not depend on the parameter `Self`
+   |
+   = help: it is currently only allowed to use either `Self` or `{ Self }` as generic constants
+
+error: generic `Self` types are currently not permitted in anonymous constants
+  --> $DIR/self-ty-in-const-1.rs:14:41
+   |
+LL |     fn t3() -> [u8; std::mem::size_of::<Self>()] {}
+   |                                         ^^^^
+   |
+note: not a concrete type
+  --> $DIR/self-ty-in-const-1.rs:13:1
+   |
+LL | / impl<T> Bar<T> {
+LL | |     fn t3() -> [u8; std::mem::size_of::<Self>()] {}
+LL | | }
+   | |_^
+
+error: aborting due to 2 previous errors
+

src/test/ui/const-generics/min_const_generics/self-ty-in-const-2.rs

@@ -0,0 +1,21 @@
+#![feature(min_const_generics)]
+
+struct Bar<T>(T);
+
+trait Baz {
+    fn hey();
+}
+
+impl Baz for u16 {
+    fn hey() {
+        let _: [u8; std::mem::size_of::<Self>()]; // ok
+    }
+}
+
+impl<T> Baz for Bar<T> {
+    fn hey() {
+        let _: [u8; std::mem::size_of::<Self>()]; //~ERROR generic `Self`
+    }
+}
+
+fn main() {}

src/test/ui/const-generics/min_const_generics/self-ty-in-const-2.stderr

@@ -0,0 +1,18 @@
+error: generic `Self` types are currently not permitted in anonymous constants
+  --> $DIR/self-ty-in-const-2.rs:17:41
+   |
+LL |         let _: [u8; std::mem::size_of::<Self>()];
+   |                                         ^^^^
+   |
+note: not a concrete type
+  --> $DIR/self-ty-in-const-2.rs:15:1
+   |
+LL | / impl<T> Baz for Bar<T> {
+LL | |     fn hey() {
+LL | |         let _: [u8; std::mem::size_of::<Self>()];
+LL | |     }
+LL | | }
+   | |_^
+
+error: aborting due to previous error
+