Auto merge of #54714 - eddyb:fine-grained-feats, r=<try>

[WIP] Require specific feature names in `#[allow_internal_unstable]`.

I opened this with just a hacky commit to test the perf impact of one implementation strategy.

Author: bors

Diff for: src/librustc/hir/lowering.rs

@@ -652,6 +652,7 @@ impl<'a> LoweringContext<'a> {
             def_site: Some(span),
             format: source_map::CompilerDesugaring(reason),
             allow_internal_unstable: true,
+            _allow_internal_unstable_features: <_>::default(),
             allow_internal_unsafe: false,
             local_inner_macros: false,
             edition: source_map::hygiene::default_edition(),

Diff for: src/librustc/ich/impls_syntax.rs

@@ -395,6 +395,7 @@ impl_stable_hash_for!(struct ::syntax_pos::hygiene::ExpnInfo {
     def_site,
     format,
     allow_internal_unstable,
+    _allow_internal_unstable_features,
     allow_internal_unsafe,
     local_inner_macros,
     edition

Diff for: src/librustc_allocator/expand.rs

@@ -102,6 +102,7 @@ impl<'a> Folder for ExpandAllocatorDirectives<'a> {
             def_site: None,
             format: MacroAttribute(Symbol::intern(name)),
             allow_internal_unstable: true,
+            _allow_internal_unstable_features: <_>::default(),
             allow_internal_unsafe: false,
             local_inner_macros: false,
             edition: hygiene::default_edition(),

Diff for: src/libsyntax/ext/derive.rs

@@ -63,6 +63,7 @@ pub fn add_derived_markers<T>(cx: &mut ExtCtxt, span: Span, traits: &[ast::Path]
         def_site: None,
         format: ExpnFormat::MacroAttribute(Symbol::intern(&pretty_name)),
         allow_internal_unstable: true,
+        _allow_internal_unstable_features: <_>::default(),
         allow_internal_unsafe: false,
         local_inner_macros: false,
         edition: hygiene::default_edition(),

Diff for: src/libsyntax/ext/expand.rs

@@ -568,6 +568,7 @@ impl<'a, 'b> MacroExpander<'a, 'b> {
             def_site: None,
             format: MacroAttribute(Symbol::intern(&attr.path.to_string())),
             allow_internal_unstable: false,
+            _allow_internal_unstable_features: <_>::default(),
             allow_internal_unsafe: false,
             local_inner_macros: false,
             edition: ext.edition(),
@@ -757,6 +758,7 @@ impl<'a, 'b> MacroExpander<'a, 'b> {
                 def_site: def_site_span,
                 format: macro_bang_format(path),
                 allow_internal_unstable,
+                _allow_internal_unstable_features: <_>::default(),
                 allow_internal_unsafe,
                 local_inner_macros,
                 edition,
@@ -808,6 +810,7 @@ impl<'a, 'b> MacroExpander<'a, 'b> {
                         def_site: tt_span,
                         format: macro_bang_format(path),
                         allow_internal_unstable,
+                        _allow_internal_unstable_features: <_>::default(),
                         allow_internal_unsafe: false,
                         local_inner_macros: false,
                         edition: hygiene::default_edition(),
@@ -849,6 +852,7 @@ impl<'a, 'b> MacroExpander<'a, 'b> {
                         format: macro_bang_format(path),
                         // FIXME probably want to follow macro_rules macros here.
                         allow_internal_unstable,
+                        _allow_internal_unstable_features: <_>::default(),
                         allow_internal_unsafe: false,
                         local_inner_macros: false,
                         edition,
@@ -924,6 +928,7 @@ impl<'a, 'b> MacroExpander<'a, 'b> {
             def_site: None,
             format: MacroAttribute(pretty_name),
             allow_internal_unstable: false,
+            _allow_internal_unstable_features: <_>::default(),
             allow_internal_unsafe: false,
             local_inner_macros: false,
             edition: ext.edition(),

Diff for: src/libsyntax/std_inject.rs

@@ -30,6 +30,7 @@ fn ignored_span(sp: Span) -> Span {
         def_site: None,
         format: MacroAttribute(Symbol::intern("std_inject")),
         allow_internal_unstable: true,
+        _allow_internal_unstable_features: <_>::default(),
         allow_internal_unsafe: false,
         local_inner_macros: false,
         edition: hygiene::default_edition(),

Diff for: src/libsyntax/test.rs

@@ -294,6 +294,7 @@ fn generate_test_harness(sess: &ParseSess,
         def_site: None,
         format: MacroAttribute(Symbol::intern("test_case")),
         allow_internal_unstable: true,
+        _allow_internal_unstable_features: <_>::default(),
         allow_internal_unsafe: false,
         local_inner_macros: false,
         edition: hygiene::default_edition(),

Diff for: src/libsyntax_ext/proc_macro_registrar.rs

@@ -358,6 +358,7 @@ fn mk_registrar(cx: &mut ExtCtxt,
         def_site: None,
         format: MacroAttribute(Symbol::intern("proc_macro")),
         allow_internal_unstable: true,
+        _allow_internal_unstable_features: <_>::default(),
         allow_internal_unsafe: false,
         local_inner_macros: false,
         edition: hygiene::default_edition(),

Diff for: src/libsyntax_ext/test.rs

@@ -77,6 +77,7 @@ pub fn expand_test_or_bench(
             def_site: None,
             format: MacroAttribute(Symbol::intern("test")),
             allow_internal_unstable: true,
+            _allow_internal_unstable_features: <_>::default(),
             allow_internal_unsafe: false,
             local_inner_macros: false,
             edition: hygiene::default_edition(),

Diff for: src/libsyntax_ext/test_case.rs

@@ -52,6 +52,7 @@ pub fn expand(
             def_site: None,
             format: MacroAttribute(Symbol::intern("test_case")),
             allow_internal_unstable: true,
+            _allow_internal_unstable_features: <_>::default(),
             allow_internal_unsafe: false,
             local_inner_macros: false,
             edition: hygiene::default_edition(),

Diff for: src/libsyntax_pos/hygiene.rs

@@ -534,6 +534,11 @@ impl fmt::Debug for SyntaxContext {
     }
 }
 
+// HACK(eddyb) only testing the performance impact of using more memory.
+// Also, `[u8; 19]` doesn't implement the right traits, so instead I've
+// approximated `[u8; 19]` to `[u32; 5]` which can be written as a tuple:
+type UnstableFeatures = (((u32, u32), (u32, u32)), u32); // [u8; (145 + 7) / 8];
+
 /// Extra information for tracking spans of macro and syntax sugar expansion
 #[derive(Clone, Hash, Debug, RustcEncodable, RustcDecodable)]
 pub struct ExpnInfo {
@@ -558,6 +563,8 @@ pub struct ExpnInfo {
     /// features internally without forcing the whole crate to opt-in
     /// to them.
     pub allow_internal_unstable: bool,
+    // HACK(eddyb) only testing the performance impact of using more memory.
+    pub _allow_internal_unstable_features: UnstableFeatures,
     /// Whether the macro is allowed to use `unsafe` internally
     /// even if the user crate has `#![forbid(unsafe_code)]`.
     pub allow_internal_unsafe: bool,