Auto merge of #58098 - oli-obk:maybe_allow_internal_unstable, r=petrochenkov

Require a list of features in `#[allow_internal_unstable]`

The blanket-permission slip is not great and will likely give us trouble some point down the road.

Author: bors

src/liballoc/macros.rs

@@ -34,7 +34,8 @@
 #[cfg(not(test))]
 #[macro_export]
 #[stable(feature = "rust1", since = "1.0.0")]
-#[allow_internal_unstable]
+#[cfg_attr(not(stage0), allow_internal_unstable(box_syntax))]
+#[cfg_attr(stage0, allow_internal_unstable)]
 macro_rules! vec {
     ($elem:expr; $n:expr) => (
         $crate::vec::from_elem($elem, $n)

src/libcore/macros.rs

@@ -1,6 +1,7 @@
 /// Entry point of thread panic, for details, see std::macros
 #[macro_export]
-#[allow_internal_unstable]
+#[cfg_attr(not(stage0), allow_internal_unstable(core_panic, __rust_unstable_column))]
+#[cfg_attr(stage0, allow_internal_unstable)]
 #[stable(feature = "core", since = "1.6.0")]
 macro_rules! panic {
     () => (
@@ -409,7 +410,8 @@ macro_rules! write {
 /// ```
 #[macro_export]
 #[stable(feature = "rust1", since = "1.0.0")]
-#[allow_internal_unstable]
+#[cfg_attr(stage0, allow_internal_unstable)]
+#[cfg_attr(not(stage0), allow_internal_unstable(format_args_nl))]
 macro_rules! writeln {
     ($dst:expr) => (
         write!($dst, "\n")

src/librustc/hir/lowering.rs

@@ -44,6 +44,7 @@ use crate::middle::cstore::CrateStore;
 use rustc_data_structures::fx::FxHashSet;
 use rustc_data_structures::indexed_vec::IndexVec;
 use rustc_data_structures::thin_vec::ThinVec;
+use rustc_data_structures::sync::Lrc;
 use crate::session::Session;
 use crate::session::config::nightly_options;
 use crate::util::common::FN_OUTPUT_NAME;
@@ -681,13 +682,20 @@ impl<'a> LoweringContext<'a> {
         Ident::with_empty_ctxt(Symbol::gensym(s))
     }
 
-    fn allow_internal_unstable(&self, reason: CompilerDesugaringKind, span: Span) -> Span {
+    /// Reuses the span but adds information like the kind of the desugaring and features that are
+    /// allowed inside this span.
+    fn mark_span_with_reason(
+        &self,
+        reason: CompilerDesugaringKind,
+        span: Span,
+        allow_internal_unstable: Option<Lrc<[Symbol]>>,
+    ) -> Span {
         let mark = Mark::fresh(Mark::root());
         mark.set_expn_info(source_map::ExpnInfo {
             call_site: span,
             def_site: Some(span),
             format: source_map::CompilerDesugaring(reason),
-            allow_internal_unstable: true,
+            allow_internal_unstable,
             allow_internal_unsafe: false,
             local_inner_macros: false,
             edition: source_map::hygiene::default_edition(),
@@ -964,7 +972,13 @@ impl<'a> LoweringContext<'a> {
             attrs: ThinVec::new(),
         };
 
-        let unstable_span = self.allow_internal_unstable(CompilerDesugaringKind::Async, span);
+        let unstable_span = self.mark_span_with_reason(
+            CompilerDesugaringKind::Async,
+            span,
+            Some(vec![
+                Symbol::intern("gen_future"),
+            ].into()),
+        );
         let gen_future = self.expr_std_path(
             unstable_span, &["future", "from_generator"], None, ThinVec::new());
         hir::ExprKind::Call(P(gen_future), hir_vec![generator])
@@ -1360,9 +1374,10 @@ impl<'a> LoweringContext<'a> {
         // desugaring that explicitly states that we don't want to track that.
         // Not tracking it makes lints in rustc and clippy very fragile as
         // frequently opened issues show.
-        let exist_ty_span = self.allow_internal_unstable(
+        let exist_ty_span = self.mark_span_with_reason(
             CompilerDesugaringKind::ExistentialReturnType,
             span,
+            None,
         );
 
         let exist_ty_def_index = self
@@ -3927,8 +3942,13 @@ impl<'a> LoweringContext<'a> {
             }),
             ExprKind::TryBlock(ref body) => {
                 self.with_catch_scope(body.id, |this| {
-                    let unstable_span =
-                        this.allow_internal_unstable(CompilerDesugaringKind::TryBlock, body.span);
+                    let unstable_span = this.mark_span_with_reason(
+                        CompilerDesugaringKind::TryBlock,
+                        body.span,
+                        Some(vec![
+                            Symbol::intern("try_trait"),
+                        ].into()),
+                    );
                     let mut block = this.lower_block(body, true).into_inner();
                     let tail = block.expr.take().map_or_else(
                         || {
@@ -4360,9 +4380,10 @@ impl<'a> LoweringContext<'a> {
                 // expand <head>
                 let head = self.lower_expr(head);
                 let head_sp = head.span;
-                let desugared_span = self.allow_internal_unstable(
+                let desugared_span = self.mark_span_with_reason(
                     CompilerDesugaringKind::ForLoop,
                     head_sp,
+                    None,
                 );
 
                 let iter = self.str_to_ident("iter");
@@ -4525,8 +4546,13 @@ impl<'a> LoweringContext<'a> {
                 //                 return Try::from_error(From::from(err)),
                 // }
 
-                let unstable_span =
-                    self.allow_internal_unstable(CompilerDesugaringKind::QuestionMark, e.span);
+                let unstable_span = self.mark_span_with_reason(
+                    CompilerDesugaringKind::QuestionMark,
+                    e.span,
+                    Some(vec![
+                        Symbol::intern("try_trait")
+                    ].into()),
+                );
 
                 // `Try::into_result(<expr>)`
                 let discr = {

src/librustc/middle/stability.rs

@@ -561,11 +561,6 @@ impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
     /// deprecated. If the item is indeed deprecated, we will emit a deprecation lint attached to
     /// `id`.
     pub fn eval_stability(self, def_id: DefId, id: Option<NodeId>, span: Span) -> EvalResult {
-        if span.allows_unstable() {
-            debug!("stability: skipping span={:?} since it is internal", span);
-            return EvalResult::Allow;
-        }
-
         let lint_deprecated = |def_id: DefId,
                                id: NodeId,
                                note: Option<Symbol>,
@@ -694,6 +689,10 @@ impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
 
         match stability {
             Some(&Stability { level: attr::Unstable { reason, issue }, feature, .. }) => {
+                if span.allows_unstable(&feature.as_str()) {
+                    debug!("stability: skipping span={:?} since it is internal", span);
+                    return EvalResult::Allow;
+                }
                 if self.stability().active_features.contains(&feature) {
                     return EvalResult::Allow;
                 }

src/librustc_allocator/expand.rs

@@ -91,7 +91,9 @@ impl MutVisitor for ExpandAllocatorDirectives<'_> {
             call_site: item.span, // use the call site of the static
             def_site: None,
             format: MacroAttribute(Symbol::intern(name)),
-            allow_internal_unstable: true,
+            allow_internal_unstable: Some(vec![
+                Symbol::intern("rustc_attrs"),
+            ].into()),
             allow_internal_unsafe: false,
             local_inner_macros: false,
             edition: hygiene::default_edition(),

src/librustc_data_structures/macros.rs

@@ -1,7 +1,8 @@
 /// A simple static assertion macro. The first argument should be a unique
 /// ALL_CAPS identifier that describes the condition.
 #[macro_export]
-#[allow_internal_unstable]
+#[cfg_attr(stage0, allow_internal_unstable)]
+#[cfg_attr(not(stage0), allow_internal_unstable(type_ascription))]
 macro_rules! static_assert {
     ($name:ident: $test:expr) => {
         // Use the bool to access an array such that if the bool is false, the access

src/librustc_metadata/creader.rs

@@ -570,7 +570,7 @@ impl<'a> CrateLoader<'a> {
                 ProcMacro::Bang { name, client } => {
                     (name, SyntaxExtension::ProcMacro {
                         expander: Box::new(BangProcMacro { client }),
-                        allow_internal_unstable: false,
+                        allow_internal_unstable: None,
                         edition: root.edition,
                     })
                 }

src/librustc_metadata/cstore_impl.rs

@@ -425,7 +425,9 @@ impl cstore::CStore {
             let client = proc_macro::bridge::client::Client::expand1(proc_macro::quote);
             let ext = SyntaxExtension::ProcMacro {
                 expander: Box::new(BangProcMacro { client }),
-                allow_internal_unstable: true,
+                allow_internal_unstable: Some(vec![
+                    Symbol::intern("proc_macro_def_site"),
+                ].into()),
                 edition: data.root.edition,
             };
             return LoadedMacro::ProcMacro(Lrc::new(ext));

src/librustc_mir/transform/qualify_consts.rs

@@ -909,7 +909,7 @@ impl<'a, 'tcx> Visitor<'tcx> for Qualifier<'a, 'tcx, 'tcx> {
                                     // Check `#[unstable]` const fns or `#[rustc_const_unstable]`
                                     // functions without the feature gate active in this crate in
                                     // order to report a better error message than the one below.
-                                    if self.span.allows_unstable() {
+                                    if self.span.allows_unstable(&feature.as_str()) {
                                         // `allow_internal_unstable` can make such calls stable.
                                         is_const_fn = true;
                                     } else {

src/librustc_plugin/registry.rs

@@ -110,8 +110,8 @@ impl<'a> Registry<'a> {
                     edition,
                 }
             }
-            IdentTT(ext, _, allow_internal_unstable) => {
-                IdentTT(ext, Some(self.krate_span), allow_internal_unstable)
+            IdentTT { expander, span: _, allow_internal_unstable } => {
+                IdentTT { expander, span: Some(self.krate_span), allow_internal_unstable }
             }
             _ => extension,
         }));
@@ -126,7 +126,7 @@ impl<'a> Registry<'a> {
         self.register_syntax_extension(Symbol::intern(name), NormalTT {
             expander: Box::new(expander),
             def_info: None,
-            allow_internal_unstable: false,
+            allow_internal_unstable: None,
             allow_internal_unsafe: false,
             local_inner_macros: false,
             unstable_feature: None,