Add `internal_features` lint

It lints against features that are inteded to be internal to the
compiler and standard library. Implements MCP #596.

We allow `internal_features` in the standard library and compiler as those
use many features and this _is_ the standard library from the "internal to the compiler and
standard library" after all.

Marking some features as internal wasn't exactly the most scientific approach, I just marked some
mostly obvious features. While there is a categorization in the macro,
it's not very well upheld (should probably be fixed in another PR).

We always pass `-Ainternal_features` in the testsuite
About 400 UI tests and several other tests use internal features.
Instead of throwing the attribute on each one, just always allow them.
There's nothing wrong with testing internal features^^

20 files changed, 37 insertions, 0 deletions

diff --git a/compiler/rustc_error_codes/src/error_codes/E0092.md b/compiler/rustc_error_codes/src/error_codes/E0092.md
index 5cbe2a188b0..84ec0656d1a 100644
--- a/compiler/rustc_error_codes/src/error_codes/E0092.md
+++ b/compiler/rustc_error_codes/src/error_codes/E0092.md
@@ -4,6 +4,7 @@ Erroneous code example:
 
 ```compile_fail,E0092
 #![feature(intrinsics)]
+#![allow(internal_features)]
 
 extern "rust-intrinsic" {
     fn atomic_foo(); // error: unrecognized atomic operation
@@ -17,6 +18,7 @@ functions are defined in `compiler/rustc_codegen_llvm/src/intrinsic.rs` and in
 
 ```
 #![feature(intrinsics)]
+#![allow(internal_features)]
 
 extern "rust-intrinsic" {
     fn atomic_fence_seqcst(); // ok!
diff --git a/compiler/rustc_error_codes/src/error_codes/E0093.md b/compiler/rustc_error_codes/src/error_codes/E0093.md
index b1683cf4fc4..2bda4d74f72 100644
--- a/compiler/rustc_error_codes/src/error_codes/E0093.md
+++ b/compiler/rustc_error_codes/src/error_codes/E0093.md
@@ -4,6 +4,7 @@ Erroneous code example:
 
 ```compile_fail,E0093
 #![feature(intrinsics)]
+#![allow(internal_features)]
 
 extern "rust-intrinsic" {
     fn foo(); // error: unrecognized intrinsic function: `foo`
@@ -22,6 +23,7 @@ functions are defined in `compiler/rustc_codegen_llvm/src/intrinsic.rs` and in
 
 ```
 #![feature(intrinsics)]
+#![allow(internal_features)]
 
 extern "rust-intrinsic" {
     fn atomic_fence_seqcst(); // ok!
diff --git a/compiler/rustc_error_codes/src/error_codes/E0094.md b/compiler/rustc_error_codes/src/error_codes/E0094.md
index cc546bdbb3b..67a8c3678c5 100644
--- a/compiler/rustc_error_codes/src/error_codes/E0094.md
+++ b/compiler/rustc_error_codes/src/error_codes/E0094.md
@@ -4,6 +4,7 @@ Erroneous code example:
 
 ```compile_fail,E0094
 #![feature(intrinsics)]
+#![allow(internal_features)]
 
 extern "rust-intrinsic" {
     #[rustc_safe_intrinsic]
@@ -18,6 +19,7 @@ Example:
 
 ```
 #![feature(intrinsics)]
+#![allow(internal_features)]
 
 extern "rust-intrinsic" {
     #[rustc_safe_intrinsic]
diff --git a/compiler/rustc_error_codes/src/error_codes/E0208.md b/compiler/rustc_error_codes/src/error_codes/E0208.md
index c6db9b5d61b..2b811b4b850 100644
--- a/compiler/rustc_error_codes/src/error_codes/E0208.md
+++ b/compiler/rustc_error_codes/src/error_codes/E0208.md
@@ -8,6 +8,7 @@ Erroneous code example:
 ```compile_fail
 // NOTE: this feature is perma-unstable and should *only* be used for
 //       testing purposes.
+#![allow(internal_features)]
 #![feature(rustc_attrs)]
 
 #[rustc_variance]
diff --git a/compiler/rustc_error_codes/src/error_codes/E0211.md b/compiler/rustc_error_codes/src/error_codes/E0211.md
index 8c2462ebd9b..70f14fffae6 100644
--- a/compiler/rustc_error_codes/src/error_codes/E0211.md
+++ b/compiler/rustc_error_codes/src/error_codes/E0211.md
@@ -5,6 +5,7 @@ used. Erroneous code examples:
 
 ```compile_fail
 #![feature(intrinsics)]
+#![allow(internal_features)]
 
 extern "rust-intrinsic" {
     #[rustc_safe_intrinsic]
@@ -41,6 +42,7 @@ For the first code example, please check the function definition. Example:
 
 ```
 #![feature(intrinsics)]
+#![allow(internal_features)]
 
 extern "rust-intrinsic" {
     #[rustc_safe_intrinsic]
diff --git a/compiler/rustc_error_codes/src/error_codes/E0230.md b/compiler/rustc_error_codes/src/error_codes/E0230.md
index cfb72e74319..87ea90e73c9 100644
--- a/compiler/rustc_error_codes/src/error_codes/E0230.md
+++ b/compiler/rustc_error_codes/src/error_codes/E0230.md
@@ -5,6 +5,7 @@ compiled:
 
 ```compile_fail,E0230
 #![feature(rustc_attrs)]
+#![allow(internal_features)]
 
 #[rustc_on_unimplemented = "error on `{Self}` with params `<{A},{B}>`"] // error
 trait BadAnnotation<A> {}
diff --git a/compiler/rustc_error_codes/src/error_codes/E0231.md b/compiler/rustc_error_codes/src/error_codes/E0231.md
index 23a0a88ecdd..a1aaf90df49 100644
--- a/compiler/rustc_error_codes/src/error_codes/E0231.md
+++ b/compiler/rustc_error_codes/src/error_codes/E0231.md
@@ -5,6 +5,7 @@ compiled:
 
 ```compile_fail,E0231
 #![feature(rustc_attrs)]
+#![allow(internal_features)]
 
 #[rustc_on_unimplemented = "error on `{Self}` with params `<{A},{}>`"] // error!
 trait BadAnnotation<A> {}
diff --git a/compiler/rustc_error_codes/src/error_codes/E0232.md b/compiler/rustc_error_codes/src/error_codes/E0232.md
index b310caefa6e..0e50cf589ee 100644
--- a/compiler/rustc_error_codes/src/error_codes/E0232.md
+++ b/compiler/rustc_error_codes/src/error_codes/E0232.md
@@ -5,6 +5,7 @@ compiled:
 
 ```compile_fail,E0232
 #![feature(rustc_attrs)]
+#![allow(internal_features)]
 
 #[rustc_on_unimplemented(lorem="")] // error!
 trait BadAnnotation {}
diff --git a/compiler/rustc_error_codes/src/error_codes/E0264.md b/compiler/rustc_error_codes/src/error_codes/E0264.md
index e2a27f7b106..d7906076229 100644
--- a/compiler/rustc_error_codes/src/error_codes/E0264.md
+++ b/compiler/rustc_error_codes/src/error_codes/E0264.md
@@ -4,6 +4,7 @@ Erroneous code example:
 
 ```compile_fail,E0264
 #![feature(lang_items)]
+#![allow(internal_features)]
 
 extern "C" {
     #[lang = "cake"] // error: unknown external lang item: `cake`
@@ -16,6 +17,7 @@ A list of available external lang items is available in
 
 ```
 #![feature(lang_items)]
+#![allow(internal_features)]
 
 extern "C" {
     #[lang = "panic_impl"] // ok!
diff --git a/compiler/rustc_error_codes/src/error_codes/E0539.md b/compiler/rustc_error_codes/src/error_codes/E0539.md
index c53d60a5f47..cd28afbc48d 100644
--- a/compiler/rustc_error_codes/src/error_codes/E0539.md
+++ b/compiler/rustc_error_codes/src/error_codes/E0539.md
@@ -4,6 +4,7 @@ Erroneous code example:
 
 ```compile_fail,E0539
 #![feature(staged_api)]
+#![allow(internal_features)]
 #![stable(since = "1.0.0", feature = "test")]
 
 #[deprecated(note)] // error!
@@ -28,6 +29,7 @@ To fix these issues you need to give required key-value pairs.
 
 ```
 #![feature(staged_api)]
+#![allow(internal_features)]
 #![stable(since = "1.0.0", feature = "test")]
 
 #[deprecated(since = "1.39.0", note = "reason")] // ok!
diff --git a/compiler/rustc_error_codes/src/error_codes/E0542.md b/compiler/rustc_error_codes/src/error_codes/E0542.md
index c69e574179b..be186dbd2cc 100644
--- a/compiler/rustc_error_codes/src/error_codes/E0542.md
+++ b/compiler/rustc_error_codes/src/error_codes/E0542.md
@@ -4,6 +4,7 @@ Erroneous code example:
 
 ```compile_fail,E0542
 #![feature(staged_api)]
+#![allow(internal_features)]
 #![stable(since = "1.0.0", feature = "test")]
 
 #[stable(feature = "_stable_fn")] // invalid
@@ -23,6 +24,7 @@ To fix this issue, you need to provide the `since` field. Example:
 
 ```
 #![feature(staged_api)]
+#![allow(internal_features)]
 #![stable(since = "1.0.0", feature = "test")]
 
 #[stable(feature = "_stable_fn", since = "1.0.0")] // ok!
diff --git a/compiler/rustc_error_codes/src/error_codes/E0543.md b/compiler/rustc_error_codes/src/error_codes/E0543.md
index d0b2e2f7a7d..5051c72a151 100644
--- a/compiler/rustc_error_codes/src/error_codes/E0543.md
+++ b/compiler/rustc_error_codes/src/error_codes/E0543.md
@@ -4,6 +4,7 @@ Erroneous code example:
 
 ```compile_fail,E0543
 #![feature(staged_api)]
+#![allow(internal_features)]
 #![stable(since = "1.0.0", feature = "test")]
 
 #[stable(since = "0.1.0", feature = "_deprecated_fn")]
@@ -17,6 +18,7 @@ To fix this issue, you need to provide the `note` field. Example:
 
 ```
 #![feature(staged_api)]
+#![allow(internal_features)]
 #![stable(since = "1.0.0", feature = "test")]
 
 #[stable(since = "0.1.0", feature = "_deprecated_fn")]
diff --git a/compiler/rustc_error_codes/src/error_codes/E0544.md b/compiler/rustc_error_codes/src/error_codes/E0544.md
index 2227e2a06bf..202401f9d45 100644
--- a/compiler/rustc_error_codes/src/error_codes/E0544.md
+++ b/compiler/rustc_error_codes/src/error_codes/E0544.md
@@ -4,6 +4,7 @@ Erroneous code example:
 
 ```compile_fail,E0544
 #![feature(staged_api)]
+#![allow(internal_features)]
 #![stable(since = "1.0.0", feature = "rust1")]
 
 #[stable(feature = "rust1", since = "1.0.0")]
@@ -15,6 +16,7 @@ To fix this issue, ensure that each item has at most one stability attribute.
 
 ```
 #![feature(staged_api)]
+#![allow(internal_features)]
 #![stable(since = "1.0.0", feature = "rust1")]
 
 #[stable(feature = "test", since = "2.0.0")] // ok!
diff --git a/compiler/rustc_error_codes/src/error_codes/E0545.md b/compiler/rustc_error_codes/src/error_codes/E0545.md
index 7aba084f4d3..880378ebd3a 100644
--- a/compiler/rustc_error_codes/src/error_codes/E0545.md
+++ b/compiler/rustc_error_codes/src/error_codes/E0545.md
@@ -4,6 +4,7 @@ Erroneous code example:
 
 ```compile_fail,E0545
 #![feature(staged_api)]
+#![allow(internal_features)]
 #![stable(since = "1.0.0", feature = "test")]
 
 #[unstable(feature = "_unstable_fn", issue = "0")] // invalid
@@ -18,6 +19,7 @@ Example:
 
 ```
 #![feature(staged_api)]
+#![allow(internal_features)]
 #![stable(since = "1.0.0", feature = "test")]
 
 #[unstable(feature = "_unstable_fn", issue = "none")] // ok!
diff --git a/compiler/rustc_error_codes/src/error_codes/E0546.md b/compiler/rustc_error_codes/src/error_codes/E0546.md
index a33dcb7a9ac..8c98eaa07bb 100644
--- a/compiler/rustc_error_codes/src/error_codes/E0546.md
+++ b/compiler/rustc_error_codes/src/error_codes/E0546.md
@@ -4,6 +4,7 @@ Erroneous code example:
 
 ```compile_fail,E0546
 #![feature(staged_api)]
+#![allow(internal_features)]
 #![stable(since = "1.0.0", feature = "test")]
 
 #[unstable(issue = "none")] // invalid
@@ -17,6 +18,7 @@ To fix this issue, you need to provide the `feature` field. Example:
 
 ```
 #![feature(staged_api)]
+#![allow(internal_features)]
 #![stable(since = "1.0.0", feature = "test")]
 
 #[unstable(feature = "unstable_fn", issue = "none")] // ok!
diff --git a/compiler/rustc_error_codes/src/error_codes/E0547.md b/compiler/rustc_error_codes/src/error_codes/E0547.md
index 4950325df64..5b0f7cd44cf 100644
--- a/compiler/rustc_error_codes/src/error_codes/E0547.md
+++ b/compiler/rustc_error_codes/src/error_codes/E0547.md
@@ -4,6 +4,7 @@ Erroneous code example:
 
 ```compile_fail,E0547
 #![feature(staged_api)]
+#![allow(internal_features)]
 #![stable(since = "1.0.0", feature = "test")]
 
 #[unstable(feature = "_unstable_fn")] // invalid
@@ -17,6 +18,7 @@ To fix this issue, you need to provide the `issue` field. Example:
 
 ```
 #![feature(staged_api)]
+#![allow(internal_features)]
 #![stable(since = "1.0.0", feature = "test")]
 
 #[unstable(feature = "_unstable_fn", issue = "none")] // ok!
diff --git a/compiler/rustc_error_codes/src/error_codes/E0549.md b/compiler/rustc_error_codes/src/error_codes/E0549.md
index 70e458a9867..cc6a47fe253 100644
--- a/compiler/rustc_error_codes/src/error_codes/E0549.md
+++ b/compiler/rustc_error_codes/src/error_codes/E0549.md
@@ -5,6 +5,7 @@ Erroneous code example:
 
 ```compile_fail,E0549
 #![feature(staged_api)]
+#![allow(internal_features)]
 #![stable(since = "1.0.0", feature = "test")]
 
 #[deprecated(
@@ -19,6 +20,7 @@ Example:
 
 ```
 #![feature(staged_api)]
+#![allow(internal_features)]
 #![stable(since = "1.0.0", feature = "test")]
 
 #[stable(since = "1.0.0", feature = "test")]
diff --git a/compiler/rustc_error_codes/src/error_codes/E0622.md b/compiler/rustc_error_codes/src/error_codes/E0622.md
index 3ba3ed10e5c..5d71ee9949d 100644
--- a/compiler/rustc_error_codes/src/error_codes/E0622.md
+++ b/compiler/rustc_error_codes/src/error_codes/E0622.md
@@ -4,6 +4,8 @@ Erroneous code example:
 
 ```compile_fail,E0622
 #![feature(intrinsics)]
+#![allow(internal_features)]
+
 extern "rust-intrinsic" {
     pub static breakpoint: fn(); // error: intrinsic must be a function
 }
@@ -17,6 +19,8 @@ error, just declare a function. Example:
 
 ```no_run
 #![feature(intrinsics)]
+#![allow(internal_features)]
+
 extern "rust-intrinsic" {
     pub fn breakpoint(); // ok!
 }
diff --git a/compiler/rustc_error_codes/src/error_codes/E0773.md b/compiler/rustc_error_codes/src/error_codes/E0773.md
index b19a58bf33d..aa65a475a4f 100644
--- a/compiler/rustc_error_codes/src/error_codes/E0773.md
+++ b/compiler/rustc_error_codes/src/error_codes/E0773.md
@@ -5,6 +5,7 @@ Erroneous code example:
 ```compile_fail,E0773
 #![feature(decl_macro)]
 #![feature(rustc_attrs)]
+#![allow(internal_features)]
 
 #[rustc_builtin_macro]
 pub macro test($item:item) {
@@ -24,6 +25,7 @@ To fix the issue, remove the duplicate declaration:
 ```
 #![feature(decl_macro)]
 #![feature(rustc_attrs)]
+#![allow(internal_features)]
 
 #[rustc_builtin_macro]
 pub macro test($item:item) {
diff --git a/compiler/rustc_error_codes/src/error_codes/E0789.md b/compiler/rustc_error_codes/src/error_codes/E0789.md
index 89b7cd422fe..2c0018cc799 100644
--- a/compiler/rustc_error_codes/src/error_codes/E0789.md
+++ b/compiler/rustc_error_codes/src/error_codes/E0789.md
@@ -10,6 +10,7 @@ Erroneous code example:
 //       used outside of the compiler and standard library.
 #![feature(rustc_attrs)]
 #![feature(staged_api)]
+#![allow(internal_features)]
 
 #![unstable(feature = "foo_module", reason = "...", issue = "123")]