Auto merge of #113126 - Bryanskiy:delete_old, r=petrochenkov

Replace old private-in-public diagnostic with type privacy lints

Next part of RFC https://github.com/rust-lang/rust/issues/48054.

r? `@petrochenkov`

compiler/rustc_error_codes/src/error_codes/E0445.md

@@ -1,10 +1,10 @@
+#### Note: this error code is no longer emitted by the compiler.
+
 A private trait was used on a public type parameter bound.
 
-Erroneous code examples:
-
-```compile_fail,E0445
-#![deny(private_in_public)]
+Previously erroneous code examples:
 
+```
 trait Foo {
     fn dummy(&self) { }
 }

compiler/rustc_error_codes/src/error_codes/E0446.md

@@ -1,16 +1,16 @@
-A private type was used in a public type signature.
+A private type or trait was used in a public associated type signature.
 
 Erroneous code example:
 
 ```compile_fail,E0446
-#![deny(private_in_public)]
-struct Bar(u32);
+struct Bar;
 
-mod foo {
-    use crate::Bar;
-    pub fn bar() -> Bar { // error: private type in public interface
-        Bar(0)
-    }
+pub trait PubTr {
+    type Alias;
+}
+
+impl PubTr for u8 {
+    type Alias = Bar; // error private type in public interface
 }
 
 fn main() {}
@@ -22,13 +22,14 @@ This is done by using pub(crate) or pub(in crate::my_mod::etc)
 Example:
 
 ```
-struct Bar(u32);
+struct Bar;
 
-mod foo {
-    use crate::Bar;
-    pub(crate) fn bar() -> Bar { // only public to crate root
-        Bar(0)
-    }
+pub(crate) trait PubTr { // only public to crate root
+    type Alias;
+}
+
+impl PubTr for u8 {
+    type Alias = Bar;
 }
 
 fn main() {}
@@ -38,12 +39,15 @@ The other way to solve this error is to make the private type public.
 Example:
 
 ```
-pub struct Bar(u32); // we set the Bar type public
-mod foo {
-    use crate::Bar;
-    pub fn bar() -> Bar { // ok!
-        Bar(0)
-    }
+
+pub struct Bar; // we set the Bar trait public
+
+pub trait PubTr {
+    type Alias;
+}
+
+impl PubTr for u8 {
+    type Alias = Bar;
 }
 
 fn main() {}