remove support for rustc_safe_intrinsic attribute; use rustc_intrinsic functions instead

compiler/rustc_error_codes/src/error_codes/E0094.md

@@ -3,13 +3,15 @@ An invalid number of generic parameters was passed to an intrinsic function.
 Erroneous code example:
 
 ```compile_fail,E0094
-#![feature(intrinsics, rustc_attrs)]
+#![feature(intrinsics)]
 #![allow(internal_features)]
 
-extern "rust-intrinsic" {
-    #[rustc_safe_intrinsic]
-    fn size_of<T, U>() -> usize; // error: intrinsic has wrong number
-                                 //        of type parameters
+#[rustc_intrinsic]
+#[rustc_intrinsic_must_be_overridden]
+fn size_of<T, U>() -> usize // error: intrinsic has wrong number
+                            //        of type parameters
+{
+    loop {}
 }
 ```
 
@@ -18,11 +20,13 @@ and verify with the function declaration in the Rust source code.
 Example:
 
 ```
-#![feature(intrinsics, rustc_attrs)]
+#![feature(intrinsics)]
 #![allow(internal_features)]
 
-extern "rust-intrinsic" {
-    #[rustc_safe_intrinsic]
-    fn size_of<T>() -> usize; // ok!
+#[rustc_intrinsic]
+#[rustc_intrinsic_must_be_overridden]
+fn size_of<T>() -> usize // ok!
+{
+    loop {}
 }
 ```

compiler/rustc_error_codes/src/error_codes/E0211.md

@@ -4,12 +4,11 @@ You used a function or type which doesn't fit the requirements for where it was
 used. Erroneous code examples:
 
 ```compile_fail
-#![feature(intrinsics, rustc_attrs)]
+#![feature(intrinsics)]
 #![allow(internal_features)]
 
 extern "rust-intrinsic" {
-    #[rustc_safe_intrinsic]
-    fn size_of<T>(); // error: intrinsic has wrong type
+    fn unreachable(); // error: intrinsic has wrong type
 }
 
 // or:
@@ -41,12 +40,11 @@ impl Foo {
 For the first code example, please check the function definition. Example:
 
 ```
-#![feature(intrinsics, rustc_attrs)]
+#![feature(intrinsics)]
 #![allow(internal_features)]
 
 extern "rust-intrinsic" {
-    #[rustc_safe_intrinsic]
-    fn size_of<T>() -> usize; // ok!
+    fn unreachable() -> !; // ok!
 }
 ```