Auto merge of #64466 - Centril:rollup-s3nlb9e, r=Centril

Rollup of 4 pull requests

Successful merges:

 - #61797 (Stabilise weak_ptr_eq)
 - #64290 (Provide a span if main function is not present in crate)
 - #64406 (Ban non-extern rust intrinsics)
 - #64462 (feature_gate: Remove dead code from attribute checking)

Failed merges:

r? @ghost

src/liballoc/rc.rs

@@ -1832,8 +1832,9 @@ impl<T: ?Sized> Weak<T> {
         }
     }
 
-    /// Returns `true` if the two `Weak`s point to the same value (not just values
-    /// that compare as equal).
+    /// Returns `true` if the two `Weak`s point to the same value (not just
+    /// values that compare as equal), or if both don't point to any value
+    /// (because they were created with `Weak::new()`).
     ///
     /// # Notes
     ///
@@ -1843,7 +1844,6 @@ impl<T: ?Sized> Weak<T> {
     /// # Examples
     ///
     /// ```
-    /// #![feature(weak_ptr_eq)]
     /// use std::rc::Rc;
     ///
     /// let first_rc = Rc::new(5);
@@ -1861,7 +1861,6 @@ impl<T: ?Sized> Weak<T> {
     /// Comparing `Weak::new`.
     ///
     /// ```
-    /// #![feature(weak_ptr_eq)]
     /// use std::rc::{Rc, Weak};
     ///
     /// let first = Weak::new();
@@ -1873,7 +1872,7 @@ impl<T: ?Sized> Weak<T> {
     /// assert!(!first.ptr_eq(&third));
     /// ```
     #[inline]
-    #[unstable(feature = "weak_ptr_eq", issue = "55981")]
+    #[stable(feature = "weak_ptr_eq", since = "1.39.0")]
     pub fn ptr_eq(&self, other: &Self) -> bool {
         self.ptr.as_ptr() == other.ptr.as_ptr()
     }

src/liballoc/sync.rs

@@ -1550,19 +1550,18 @@ impl<T: ?Sized> Weak<T> {
         }
     }
 
-    /// Returns `true` if the two `Weak`s point to the same value (not just values
-    /// that compare as equal).
+    /// Returns `true` if the two `Weak`s point to the same value (not just
+    /// values that compare as equal), or if both don't point to any value
+    /// (because they were created with `Weak::new()`).
     ///
     /// # Notes
     ///
     /// Since this compares pointers it means that `Weak::new()` will equal each
     /// other, even though they don't point to any value.
     ///
-    ///
     /// # Examples
     ///
     /// ```
-    /// #![feature(weak_ptr_eq)]
     /// use std::sync::Arc;
     ///
     /// let first_rc = Arc::new(5);
@@ -1580,7 +1579,6 @@ impl<T: ?Sized> Weak<T> {
     /// Comparing `Weak::new`.
     ///
     /// ```
-    /// #![feature(weak_ptr_eq)]
     /// use std::sync::{Arc, Weak};
     ///
     /// let first = Weak::new();
@@ -1592,7 +1590,7 @@ impl<T: ?Sized> Weak<T> {
     /// assert!(!first.ptr_eq(&third));
     /// ```
     #[inline]
-    #[unstable(feature = "weak_ptr_eq", issue = "55981")]
+    #[stable(feature = "weak_ptr_eq", since = "1.39.0")]
     pub fn ptr_eq(&self, other: &Self) -> bool {
         self.ptr.as_ptr() == other.ptr.as_ptr()
     }

src/librustc/middle/entry.rs

@@ -16,16 +16,16 @@ struct EntryContext<'a, 'tcx> {
 
     map: &'a hir_map::Map<'tcx>,
 
-    /// The top-level function called 'main'.
+    /// The top-level function called `main`.
     main_fn: Option<(HirId, Span)>,
 
-    /// The function that has attribute named 'main'.
+    /// The function that has attribute named `main`.
     attr_main_fn: Option<(HirId, Span)>,
 
     /// The function that has the attribute 'start' on it.
     start_fn: Option<(HirId, Span)>,
 
-    /// The functions that one might think are 'main' but aren't, e.g.
+    /// The functions that one might think are `main` but aren't, e.g.
     /// main functions not defined at the top level. For diagnostics.
     non_main_fns: Vec<(HirId, Span)> ,
 }
@@ -88,7 +88,7 @@ fn entry_point_type(item: &Item, at_root: bool) -> EntryPointType {
                 EntryPointType::MainAttr
             } else if item.ident.name == sym::main {
                 if at_root {
-                    // This is a top-level function so can be 'main'.
+                    // This is a top-level function so can be `main`.
                     EntryPointType::MainNamed
                 } else {
                     EntryPointType::OtherMain
@@ -109,7 +109,7 @@ fn find_item(item: &Item, ctxt: &mut EntryContext<'_, '_>, at_root: bool) {
                 ctxt.main_fn = Some((item.hir_id, item.span));
             } else {
                 span_err!(ctxt.session, item.span, E0136,
-                          "multiple 'main' functions");
+                          "multiple `main` functions");
             }
         },
         EntryPointType::OtherMain => {
@@ -130,7 +130,7 @@ fn find_item(item: &Item, ctxt: &mut EntryContext<'_, '_>, at_root: bool) {
             if ctxt.start_fn.is_none() {
                 ctxt.start_fn = Some((item.hir_id, item.span));
             } else {
-                struct_span_err!(ctxt.session, item.span, E0138, "multiple 'start' functions")
+                struct_span_err!(ctxt.session, item.span, E0138, "multiple `start` functions")
                     .span_label(ctxt.start_fn.unwrap().1, "previous `start` function here")
                     .span_label(item.span, "multiple `start` functions")
                     .emit();
@@ -148,34 +148,48 @@ fn configure_main(tcx: TyCtxt<'_>, visitor: &EntryContext<'_, '_>) -> Option<(De
     } else if let Some((hir_id, _)) = visitor.main_fn {
         Some((tcx.hir().local_def_id(hir_id), EntryFnType::Main))
     } else {
-        // There is no main function.
-        let mut err = struct_err!(tcx.sess, E0601,
-            "`main` function not found in crate `{}`", tcx.crate_name(LOCAL_CRATE));
-        if !visitor.non_main_fns.is_empty() {
-            // There were some functions named 'main' though. Try to give the user a hint.
-            err.note("the main function must be defined at the crate level \
-                      but you have one or more functions named 'main' that are not \
-                      defined at the crate level. Either move the definition or \
-                      attach the `#[main]` attribute to override this behavior.");
-            for &(_, span) in &visitor.non_main_fns {
-                err.span_note(span, "here is a function named 'main'");
-            }
-            err.emit();
-        } else {
-            if let Some(ref filename) = tcx.sess.local_crate_source_file {
-                err.note(&format!("consider adding a `main` function to `{}`", filename.display()));
-            }
-            if tcx.sess.teach(&err.get_code().unwrap()) {
-                err.note("If you don't know the basics of Rust, you can go look to the Rust Book \
-                          to get started: https://doc.rust-lang.org/book/");
-            }
-            err.emit();
-        }
-
+        no_main_err(tcx, visitor);
         None
     }
 }
 
+fn no_main_err(tcx: TyCtxt<'_>, visitor: &EntryContext<'_, '_>) {
+    // There is no main function.
+    let mut err = struct_err!(tcx.sess, E0601,
+        "`main` function not found in crate `{}`", tcx.crate_name(LOCAL_CRATE));
+    let filename = &tcx.sess.local_crate_source_file;
+    let note = if !visitor.non_main_fns.is_empty() {
+        for &(_, span) in &visitor.non_main_fns {
+            err.span_note(span, "here is a function named `main`");
+        }
+        err.note("you have one or more functions named `main` not defined at the crate level");
+        err.help("either move the `main` function definitions or attach the `#[main]` attribute \
+                  to one of them");
+        // There were some functions named `main` though. Try to give the user a hint.
+        format!("the main function must be defined at the crate level{}",
+                 filename.as_ref().map(|f| format!(" (in `{}`)", f.display())).unwrap_or_default())
+    } else if let Some(filename) = filename {
+        format!("consider adding a `main` function to `{}`", filename.display())
+    } else {
+        String::from("consider adding a `main` function at the crate level")
+    };
+    let sp = tcx.hir().krate().span;
+    // The file may be empty, which leads to the diagnostic machinery not emitting this
+    // note. This is a relatively simple way to detect that case and emit a span-less
+    // note instead.
+    if let Ok(_) = tcx.sess.source_map().lookup_line(sp.lo()) {
+        err.set_span(sp);
+        err.span_label(sp, &note);
+    } else {
+        err.note(&note);
+    }
+    if tcx.sess.teach(&err.get_code().unwrap()) {
+        err.note("If you don't know the basics of Rust, you can go look to the Rust Book \
+                  to get started: https://doc.rust-lang.org/book/");
+    }
+    err.emit();
+}
+
 pub fn find_entry_point(tcx: TyCtxt<'_>) -> Option<(DefId, EntryFnType)> {
     tcx.entry_fn(LOCAL_CRATE)
 }

src/librustc_interface/passes.rs

@@ -41,7 +41,6 @@ use syntax::mut_visit::MutVisitor;
 use syntax::parse::{self, PResult};
 use syntax::util::node_count::NodeCounter;
 use syntax::symbol::Symbol;
-use syntax::feature_gate::AttributeType;
 use syntax_pos::FileName;
 use syntax_ext;
 
@@ -219,7 +218,6 @@ impl BoxedResolver {
 
 pub struct PluginInfo {
     syntax_exts: Vec<NamedSyntaxExtension>,
-    attributes: Vec<(Symbol, AttributeType)>,
 }
 
 pub fn register_plugins<'a>(
@@ -312,12 +310,9 @@ pub fn register_plugins<'a>(
     }
 
     *sess.plugin_llvm_passes.borrow_mut() = llvm_passes;
-    *sess.plugin_attributes.borrow_mut() = attributes.clone();
+    *sess.plugin_attributes.borrow_mut() = attributes;
 
-    Ok((krate, PluginInfo {
-        syntax_exts,
-        attributes,
-    }))
+    Ok((krate, PluginInfo { syntax_exts }))
 }
 
 fn configure_and_expand_inner<'a>(
@@ -329,7 +324,6 @@ fn configure_and_expand_inner<'a>(
     crate_loader: &'a mut CrateLoader<'a>,
     plugin_info: PluginInfo,
 ) -> Result<(ast::Crate, Resolver<'a>)> {
-    let attributes = plugin_info.attributes;
     time(sess, "pre ast expansion lint checks", || {
         lint::check_ast_crate(
             sess,
@@ -522,7 +516,6 @@ fn configure_and_expand_inner<'a>(
             &krate,
             &sess.parse_sess,
             &sess.features_untracked(),
-            &attributes,
             sess.opts.unstable_features,
         );
     });

src/librustc_typeck/check/mod.rs

@@ -1088,6 +1088,8 @@ fn check_fn<'a, 'tcx>(
 
     let span = body.value.span;
 
+    fn_maybe_err(fcx.tcx, span, fn_sig.abi);
+
     if body.generator_kind.is_some() && can_be_generator.is_some() {
         let yield_ty = fcx.next_ty_var(TypeVariableOrigin {
             kind: TypeVariableOriginKind::TypeInference,
@@ -1439,6 +1441,14 @@ fn check_opaque_for_cycles<'tcx>(
     }
 }
 
+// Forbid defining intrinsics in Rust code,
+// as they must always be defined by the compiler.
+fn fn_maybe_err(tcx: TyCtxt<'_>, sp: Span, abi: Abi) {
+    if let Abi::RustIntrinsic | Abi::PlatformIntrinsic = abi {
+        tcx.sess.span_err(sp, "intrinsic must be in `extern \"rust-intrinsic\" { ... }` block");
+    }
+}
+
 pub fn check_item_type<'tcx>(tcx: TyCtxt<'tcx>, it: &'tcx hir::Item) {
     debug!(
         "check_item_type(it.hir_id={}, it.name={})",
@@ -1475,9 +1485,17 @@ pub fn check_item_type<'tcx>(tcx: TyCtxt<'tcx>, it: &'tcx hir::Item) {
                 check_on_unimplemented(tcx, trait_def_id, it);
             }
         }
-        hir::ItemKind::Trait(..) => {
+        hir::ItemKind::Trait(_, _, _, _, ref items) => {
             let def_id = tcx.hir().local_def_id(it.hir_id);
             check_on_unimplemented(tcx, def_id, it);
+
+            for item in items.iter() {
+                let item = tcx.hir().trait_item(item.id);
+                if let hir::TraitItemKind::Method(sig, _) = &item.node {
+                    let abi = sig.header.abi;
+                    fn_maybe_err(tcx, item.ident.span, abi);
+                }
+            }
         }
         hir::ItemKind::Struct(..) => {
             check_struct(tcx, it.hir_id, it.span);

src/libsyntax/ext/expand.rs

@@ -26,7 +26,7 @@ use syntax_pos::{Span, DUMMY_SP, FileName};
 use rustc_data_structures::fx::FxHashMap;
 use rustc_data_structures::sync::Lrc;
 use std::io::ErrorKind;
-use std::{iter, mem};
+use std::{iter, mem, slice};
 use std::ops::DerefMut;
 use std::rc::Rc;
 use std::path::PathBuf;
@@ -1019,7 +1019,7 @@ impl<'a, 'b> InvocationCollector<'a, 'b> {
     fn check_attributes(&mut self, attrs: &[ast::Attribute]) {
         let features = self.cx.ecfg.features.unwrap();
         for attr in attrs.iter() {
-            self.check_attribute_inner(attr, features);
+            feature_gate::check_attribute(attr, self.cx.parse_sess, features);
 
             // macros are expanded before any lint passes so this warning has to be hardcoded
             if attr.path == sym::derive {
@@ -1029,15 +1029,6 @@ impl<'a, 'b> InvocationCollector<'a, 'b> {
             }
         }
     }
-
-    fn check_attribute(&mut self, at: &ast::Attribute) {
-        let features = self.cx.ecfg.features.unwrap();
-        self.check_attribute_inner(at, features);
-    }
-
-    fn check_attribute_inner(&mut self, at: &ast::Attribute, features: &Features) {
-        feature_gate::check_attribute(at, self.cx.parse_sess, features);
-    }
 }
 
 impl<'a, 'b> MutVisitor for InvocationCollector<'a, 'b> {
@@ -1445,7 +1436,7 @@ impl<'a, 'b> MutVisitor for InvocationCollector<'a, 'b> {
 
                 if let Some(file) = it.value_str() {
                     let err_count = self.cx.parse_sess.span_diagnostic.err_count();
-                    self.check_attribute(&at);
+                    self.check_attributes(slice::from_ref(at));
                     if self.cx.parse_sess.span_diagnostic.err_count() > err_count {
                         // avoid loading the file if they haven't enabled the feature
                         return noop_visit_attribute(at, self);

src/libsyntax/feature_gate/builtin_attrs.rs

@@ -79,6 +79,7 @@ pub enum AttributeType {
     CrateLevel,
 }
 
+#[derive(Clone, Copy)]
 pub enum AttributeGate {
     /// Is gated by a given feature gate, reason
     /// and function to check if enabled