Rollup of 6 pull requests

compiler/rustc_borrowck/src/borrowck_errors.rs

@@ -1,7 +1,9 @@
 #![allow(rustc::diagnostic_outside_of_impl)]
 #![allow(rustc::untranslatable_diagnostic)]
 
+use rustc_errors::Applicability;
 use rustc_errors::{codes::*, struct_span_code_err, Diag, DiagCtxtHandle};
+use rustc_hir as hir;
 use rustc_middle::span_bug;
 use rustc_middle::ty::{self, Ty, TyCtxt};
 use rustc_span::Span;
@@ -382,13 +384,35 @@ impl<'infcx, 'tcx> crate::MirBorrowckCtxt<'_, '_, 'infcx, 'tcx> {
         yield_span: Span,
     ) -> Diag<'infcx> {
         let coroutine_kind = self.body.coroutine.as_ref().unwrap().coroutine_kind;
-        struct_span_code_err!(
+        let mut diag = struct_span_code_err!(
             self.dcx(),
             span,
             E0626,
             "borrow may still be in use when {coroutine_kind:#} yields",
-        )
-        .with_span_label(yield_span, "possible yield occurs here")
+        );
+        diag.span_label(
+            self.infcx.tcx.def_span(self.body.source.def_id()),
+            format!("within this {coroutine_kind:#}"),
+        );
+        diag.span_label(yield_span, "possible yield occurs here");
+        if matches!(coroutine_kind, hir::CoroutineKind::Coroutine(_)) {
+            let hir::Closure { capture_clause, fn_decl_span, .. } = self
+                .infcx
+                .tcx
+                .hir_node_by_def_id(self.body.source.def_id().expect_local())
+                .expect_closure();
+            let span = match capture_clause {
+                rustc_hir::CaptureBy::Value { move_kw } => move_kw.shrink_to_lo(),
+                rustc_hir::CaptureBy::Ref => fn_decl_span.shrink_to_lo(),
+            };
+            diag.span_suggestion_verbose(
+                span,
+                "add `static` to mark this coroutine as unmovable",
+                "static ",
+                Applicability::MaybeIncorrect,
+            );
+        }
+        diag
     }
 
     pub(crate) fn cannot_borrow_across_destructor(&self, borrow_span: Span) -> Diag<'infcx> {

compiler/rustc_error_codes/src/error_codes/E0626.md

@@ -1,4 +1,4 @@
-This error occurs because a borrow in a coroutine persists across a
+This error occurs because a borrow in a movable coroutine persists across a
 yield point.
 
 Erroneous code example:
@@ -15,19 +15,35 @@ let mut b = #[coroutine] || {
 Pin::new(&mut b).resume(());
 ```
 
-At present, it is not permitted to have a yield that occurs while a
-borrow is still in scope. To resolve this error, the borrow must
-either be "contained" to a smaller scope that does not overlap the
-yield or else eliminated in another way. So, for example, we might
-resolve the previous example by removing the borrow and just storing
-the integer by value:
+Coroutines may be either unmarked, or marked with `static`. If it is unmarked,
+then the coroutine is considered "movable". At present, it is not permitted to
+have a yield in a movable coroutine that occurs while a borrow is still in
+scope. To resolve this error, the coroutine may be marked `static`:
+
+```
+# #![feature(coroutines, coroutine_trait, stmt_expr_attributes)]
+# use std::ops::Coroutine;
+# use std::pin::Pin;
+let mut b = #[coroutine] static || { // <-- note the static keyword
+    let a = &String::from("hello, world");
+    yield ();
+    println!("{}", a);
+};
+let mut b = std::pin::pin!(b);
+b.as_mut().resume(());
+```
+
+If the coroutine must remain movable, for example to be used as `Unpin`
+without pinning it on the stack or in an allocation, we can alternatively
+resolve the previous example by removing the borrow and just storing the
+type by value:
 
 ```
 # #![feature(coroutines, coroutine_trait, stmt_expr_attributes)]
 # use std::ops::Coroutine;
 # use std::pin::Pin;
 let mut b = #[coroutine] || {
-    let a = 3;
+    let a = String::from("hello, world");
     yield ();
     println!("{}", a);
 };

compiler/rustc_hir_typeck/src/closure.rs

@@ -18,7 +18,6 @@ use rustc_span::def_id::LocalDefId;
 use rustc_span::Span;
 use rustc_target::spec::abi::Abi;
 use rustc_trait_selection::error_reporting::traits::ArgKind;
-use rustc_trait_selection::error_reporting::traits::InferCtxtExt as _;
 use rustc_trait_selection::traits;
 use rustc_type_ir::ClosureKind;
 use std::iter;
@@ -734,13 +733,14 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             .map(|ty| ArgKind::from_expected_ty(*ty, None))
             .collect();
         let (closure_span, closure_arg_span, found_args) =
-            match self.get_fn_like_arguments(expr_map_node) {
+            match self.err_ctxt().get_fn_like_arguments(expr_map_node) {
                 Some((sp, arg_sp, args)) => (Some(sp), arg_sp, args),
                 None => (None, None, Vec::new()),
             };
         let expected_span =
             expected_sig.cause_span.unwrap_or_else(|| self.tcx.def_span(expr_def_id));
         let guar = self
+            .err_ctxt()
             .report_arg_count_mismatch(
                 expected_span,
                 closure_span,

compiler/rustc_infer/src/infer/mod.rs

@@ -755,18 +755,6 @@ impl<'tcx> InferCtxt<'tcx> {
             .collect()
     }
 
-    // FIXME(-Znext-solver): Get rid of this method, it's never correct. Either that,
-    // or we need to process the obligations.
-    pub fn can_eq_shallow<T>(&self, param_env: ty::ParamEnv<'tcx>, a: T, b: T) -> bool
-    where
-        T: at::ToTrace<'tcx>,
-    {
-        let origin = &ObligationCause::dummy();
-        // We're only answering whether the types could be the same, and with
-        // opaque types, "they can be the same", via registering a hidden type.
-        self.probe(|_| self.at(origin, param_env).eq(DefineOpaqueTypes::Yes, a, b).is_ok())
-    }
-
     #[instrument(skip(self), level = "debug")]
     pub fn sub_regions(
         &self,

compiler/rustc_mir_build/src/check_unsafety.rs

@@ -466,6 +466,24 @@ impl<'a, 'tcx> Visitor<'a, 'tcx> for UnsafetyVisitor<'a, 'tcx> {
                     }
                 }
             }
+            ExprKind::AddressOf { arg, .. } => {
+                if let ExprKind::Scope { value: arg, .. } = self.thir[arg].kind
+                // THIR desugars UNSAFE_STATIC into *UNSAFE_STATIC_REF, where
+                // UNSAFE_STATIC_REF holds the addr of the UNSAFE_STATIC, so: take two steps
+                    && let ExprKind::Deref { arg } = self.thir[arg].kind
+                    // FIXME(workingjubiee): we lack a clear reason to reject ThreadLocalRef here,
+                    // but we also have no conclusive reason to allow it either!
+                    && let ExprKind::StaticRef { .. } = self.thir[arg].kind
+                {
+                    // A raw ref to a place expr, even an "unsafe static", is okay!
+                    // We short-circuit to not recursively traverse this expression.
+                    return;
+                    // note: const_mut_refs enables this code, and it currently remains unsafe:
+                    // static mut BYTE: u8 = 0;
+                    // static mut BYTE_PTR: *mut u8 = unsafe { addr_of_mut!(BYTE) };
+                    // static mut DEREF_BYTE_PTR: *mut u8 = unsafe { addr_of_mut!(*BYTE_PTR) };
+                }
+            }
             ExprKind::Deref { arg } => {
                 if let ExprKind::StaticRef { def_id, .. } | ExprKind::ThreadLocalRef(def_id) =
                     self.thir[arg].kind

compiler/rustc_mir_build/src/thir/cx/expr.rs

@@ -939,9 +939,11 @@ impl<'tcx> Cx<'tcx> {
                 }
             }
 
-            // We encode uses of statics as a `*&STATIC` where the `&STATIC` part is
-            // a constant reference (or constant raw pointer for `static mut`) in MIR
+            // A source Rust `path::to::STATIC` is a place expr like *&ident is.
+            // In THIR, we make them exactly equivalent by inserting the implied *& or *&raw,
+            // but distinguish between &STATIC and &THREAD_LOCAL as they have different semantics
             Res::Def(DefKind::Static { .. }, id) => {
+                // this is &raw for extern static or static mut, and & for other statics
                 let ty = self.tcx.static_ptr_ty(id);
                 let temp_lifetime = self
                     .rvalue_scopes

compiler/rustc_trait_selection/src/error_reporting/infer/note_and_explain.rs

@@ -12,6 +12,7 @@ use rustc_middle::{
 use rustc_span::{def_id::DefId, sym, BytePos, Span, Symbol};
 
 use crate::error_reporting::TypeErrCtxt;
+use crate::infer::InferCtxtExt;
 
 impl<'tcx> TypeErrCtxt<'_, 'tcx> {
     pub fn note_and_explain_type_err(
@@ -821,7 +822,7 @@ fn foo(&self) -> Self::T { String::new() }
                                 tcx.defaultness(item.id.owner_id)
                             {
                                 let assoc_ty = tcx.type_of(item.id.owner_id).instantiate_identity();
-                                if self.infcx.can_eq_shallow(param_env, assoc_ty, found) {
+                                if self.infcx.can_eq(param_env, assoc_ty, found) {
                                     diag.span_label(
                                         item.span,
                                         "associated type defaults can't be assumed inside the \
@@ -844,7 +845,7 @@ fn foo(&self) -> Self::T { String::new() }
                         let assoc_ty = tcx.type_of(item.id.owner_id).instantiate_identity();
                         if let hir::Defaultness::Default { has_value: true } =
                             tcx.defaultness(item.id.owner_id)
-                            && self.infcx.can_eq_shallow(param_env, assoc_ty, found)
+                            && self.infcx.can_eq(param_env, assoc_ty, found)
                         {
                             diag.span_label(
                                 item.span,