Perform Sync check on static items in wf-check instead of during const checks

compiler/rustc_const_eval/src/transform/check_consts/check.rs

@@ -1,8 +1,8 @@
 //! The `Visitor` responsible for actually checking a `mir::Body` for invalid operations.
 
 use rustc_errors::{Applicability, Diagnostic, ErrorReported};
+use rustc_hir as hir;
 use rustc_hir::def_id::DefId;
-use rustc_hir::{self as hir, HirId, LangItem};
 use rustc_index::bit_set::BitSet;
 use rustc_infer::infer::TyCtxtInferExt;
 use rustc_infer::traits::{ImplSource, Obligation, ObligationCause};
@@ -14,8 +14,7 @@ use rustc_middle::ty::{self, adjustment::PointerCast, Instance, InstanceDef, Ty,
 use rustc_middle::ty::{Binder, TraitPredicate, TraitRef};
 use rustc_mir_dataflow::{self, Analysis};
 use rustc_span::{sym, Span, Symbol};
-use rustc_trait_selection::traits::error_reporting::InferCtxtExt;
-use rustc_trait_selection::traits::{self, SelectionContext, TraitEngine};
+use rustc_trait_selection::traits::SelectionContext;
 
 use std::mem;
 use std::ops::Deref;
@@ -255,16 +254,6 @@ impl Checker<'mir, 'tcx> {
             self.visit_body(&body);
         }
 
-        // Ensure that the end result is `Sync` in a non-thread local `static`.
-        let should_check_for_sync = self.const_kind()
-            == hir::ConstContext::Static(hir::Mutability::Not)
-            && !tcx.is_thread_local_static(def_id.to_def_id());
-
-        if should_check_for_sync {
-            let hir_id = tcx.hir().local_def_id_to_hir_id(def_id);
-            check_return_ty_is_sync(tcx, &body, hir_id);
-        }
-
         // If we got through const-checking without emitting any "primary" errors, emit any
         // "secondary" errors if they occurred.
         let secondary_errors = mem::take(&mut self.secondary_errors);
@@ -1054,20 +1043,6 @@ impl Visitor<'tcx> for Checker<'mir, 'tcx> {
     }
 }
 
-fn check_return_ty_is_sync(tcx: TyCtxt<'tcx>, body: &Body<'tcx>, hir_id: HirId) {
-    let ty = body.return_ty();
-    tcx.infer_ctxt().enter(|infcx| {
-        let cause = traits::ObligationCause::new(body.span, hir_id, traits::SharedStatic);
-        let mut fulfillment_cx = traits::FulfillmentContext::new();
-        let sync_def_id = tcx.require_lang_item(LangItem::Sync, Some(body.span));
-        fulfillment_cx.register_bound(&infcx, ty::ParamEnv::empty(), ty, sync_def_id, cause);
-        let errors = fulfillment_cx.select_all_or_error(&infcx);
-        if !errors.is_empty() {
-            infcx.report_fulfillment_errors(&errors, None, false);
-        }
-    });
-}
-
 fn place_as_reborrow(
     tcx: TyCtxt<'tcx>,
     body: &Body<'tcx>,

compiler/rustc_typeck/src/check/wfcheck.rs

@@ -1060,6 +1060,20 @@ fn check_item_type(tcx: TyCtxt<'_>, item_id: LocalDefId, ty_span: Span, allow_fo
             );
         }
 
+        // Ensure that the end result is `Sync` in a non-thread local `static`.
+        let should_check_for_sync = tcx.static_mutability(item_id.to_def_id())
+            == Some(hir::Mutability::Not)
+            && !tcx.is_foreign_item(item_id.to_def_id())
+            && !tcx.is_thread_local_static(item_id.to_def_id());
+
+        if should_check_for_sync {
+            fcx.register_bound(
+                item_ty,
+                tcx.require_lang_item(LangItem::Sync, Some(ty_span)),
+                traits::ObligationCause::new(ty_span, fcx.body_id, traits::SharedStatic),
+            );
+        }
+
         // No implied bounds in a const, etc.
         FxHashSet::default()
     });

src/test/ui/consts/const-cast-different-types.rs

@@ -1,6 +1,6 @@
-static a: &'static str = "foo";
-static b: *const u8 = a as *const u8; //~ ERROR casting
-static c: *const u8 = &a as *const u8; //~ ERROR casting
+const a: &str = "foo";
+const b: *const u8 = a as *const u8; //~ ERROR casting
+const c: *const u8 = &a as *const u8; //~ ERROR casting
 
 fn main() {
 }

src/test/ui/consts/const-cast-different-types.stderr

@@ -1,14 +1,14 @@
 error[E0606]: casting `&'static str` as `*const u8` is invalid
-  --> $DIR/const-cast-different-types.rs:2:23
+  --> $DIR/const-cast-different-types.rs:2:22
    |
-LL | static b: *const u8 = a as *const u8;
-   |                       ^^^^^^^^^^^^^^
+LL | const b: *const u8 = a as *const u8;
+   |                      ^^^^^^^^^^^^^^
 
 error[E0606]: casting `&&'static str` as `*const u8` is invalid
-  --> $DIR/const-cast-different-types.rs:3:23
+  --> $DIR/const-cast-different-types.rs:3:22
    |
-LL | static c: *const u8 = &a as *const u8;
-   |                       ^^^^^^^^^^^^^^^
+LL | const c: *const u8 = &a as *const u8;
+   |                      ^^^^^^^^^^^^^^^
 
 error: aborting due to 2 previous errors
 

src/test/ui/consts/const-cast-wrong-type.rs

@@ -1,5 +1,5 @@
-static a: [u8; 3] = ['h' as u8, 'i' as u8, 0 as u8];
-static b: *const i8 = &a as *const i8; //~ ERROR mismatched types
+const a: [u8; 3] = ['h' as u8, 'i' as u8, 0 as u8];
+const b: *const i8 = &a as *const i8; //~ ERROR mismatched types
 
 fn main() {
 }

src/test/ui/consts/const-cast-wrong-type.stderr

@@ -1,8 +1,8 @@
 error[E0308]: mismatched types
-  --> $DIR/const-cast-wrong-type.rs:2:23
+  --> $DIR/const-cast-wrong-type.rs:2:22
    |
-LL | static b: *const i8 = &a as *const i8;
-   |                       ^^^^^^^^^^^^^^^ expected `u8`, found `i8`
+LL | const b: *const i8 = &a as *const i8;
+   |                      ^^^^^^^^^^^^^^^ expected `u8`, found `i8`
 
 error: aborting due to previous error
 

src/test/ui/impl-trait/issues/issue-86201.rs

@@ -2,9 +2,9 @@
 #![feature(type_alias_impl_trait)]
 
 type FunType = impl Fn<()>;
-//~^ could not find defining uses
+//~^ ERROR could not find defining uses
 static STATIC_FN: FunType = some_fn;
-//~^ mismatched types
+//~^ ERROR mismatched types
 
 fn some_fn() {}
 

src/test/ui/issues/issue-16538.mir.stderr

@@ -1,27 +1,26 @@
 error[E0015]: calls in statics are limited to constant functions, tuple structs and tuple variants
-  --> $DIR/issue-16538.rs:14:27
+  --> $DIR/issue-16538.rs:15:23
    |
-LL | static foo: *const Y::X = Y::foo(Y::x as *const Y::X);
-   |                           ^^^^^^^^^^^^^^^^^^^^^^^^^^^
+LL | static foo: &Y::X = &*Y::foo(Y::x as *const Y::X);
+   |                       ^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
-error[E0277]: `*const usize` cannot be shared between threads safely
-  --> $DIR/issue-16538.rs:14:1
+error[E0133]: use of extern static is unsafe and requires unsafe function or block
+  --> $DIR/issue-16538.rs:15:30
    |
-LL | static foo: *const Y::X = Y::foo(Y::x as *const Y::X);
-   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ `*const usize` cannot be shared between threads safely
+LL | static foo: &Y::X = &*Y::foo(Y::x as *const Y::X);
+   |                              ^^^^ use of extern static
    |
-   = help: the trait `Sync` is not implemented for `*const usize`
-   = note: shared static variables must have a type that implements `Sync`
+   = note: extern statics are not controlled by the Rust type system: invalid data, aliasing violations or data races will cause undefined behavior
 
-error[E0133]: use of extern static is unsafe and requires unsafe function or block
-  --> $DIR/issue-16538.rs:14:34
+error[E0133]: dereference of raw pointer is unsafe and requires unsafe function or block
+  --> $DIR/issue-16538.rs:15:21
    |
-LL | static foo: *const Y::X = Y::foo(Y::x as *const Y::X);
-   |                                  ^^^^ use of extern static
+LL | static foo: &Y::X = &*Y::foo(Y::x as *const Y::X);
+   |                     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ dereference of raw pointer
    |
-   = note: extern statics are not controlled by the Rust type system: invalid data, aliasing violations or data races will cause undefined behavior
+   = note: raw pointers may be null, dangling or unaligned; they can violate aliasing rules and cause data races: all of these are undefined behavior
 
 error: aborting due to 3 previous errors
 
-Some errors have detailed explanations: E0015, E0133, E0277.
+Some errors have detailed explanations: E0015, E0133.
 For more information about an error, try `rustc --explain E0015`.

src/test/ui/issues/issue-16538.rs

@@ -1,6 +1,7 @@
 // revisions: mir thir
 // [thir]compile-flags: -Z thir-unsafeck
 
+#![feature(const_raw_ptr_deref)]
 mod Y {
     pub type X = usize;
     extern "C" {
@@ -11,8 +12,8 @@ mod Y {
     }
 }
 
-static foo: *const Y::X = Y::foo(Y::x as *const Y::X);
-//~^ ERROR `*const usize` cannot be shared between threads safely [E0277]
+static foo: &Y::X = &*Y::foo(Y::x as *const Y::X);
+//~^ ERROR dereference of raw pointer
 //~| ERROR E0015
 //~| ERROR use of extern static is unsafe and requires
 

src/test/ui/issues/issue-16538.thir.stderr

@@ -1,27 +1,26 @@
+error[E0133]: dereference of raw pointer is unsafe and requires unsafe function or block
+  --> $DIR/issue-16538.rs:15:22
+   |
+LL | static foo: &Y::X = &*Y::foo(Y::x as *const Y::X);
+   |                      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ dereference of raw pointer
+   |
+   = note: raw pointers may be null, dangling or unaligned; they can violate aliasing rules and cause data races: all of these are undefined behavior
+
 error[E0133]: use of extern static is unsafe and requires unsafe function or block
-  --> $DIR/issue-16538.rs:14:34
+  --> $DIR/issue-16538.rs:15:30
    |
-LL | static foo: *const Y::X = Y::foo(Y::x as *const Y::X);
-   |                                  ^^^^ use of extern static
+LL | static foo: &Y::X = &*Y::foo(Y::x as *const Y::X);
+   |                              ^^^^ use of extern static
    |
    = note: extern statics are not controlled by the Rust type system: invalid data, aliasing violations or data races will cause undefined behavior
 
 error[E0015]: calls in statics are limited to constant functions, tuple structs and tuple variants
-  --> $DIR/issue-16538.rs:14:27
-   |
-LL | static foo: *const Y::X = Y::foo(Y::x as *const Y::X);
-   |                           ^^^^^^^^^^^^^^^^^^^^^^^^^^^
-
-error[E0277]: `*const usize` cannot be shared between threads safely
-  --> $DIR/issue-16538.rs:14:1
-   |
-LL | static foo: *const Y::X = Y::foo(Y::x as *const Y::X);
-   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ `*const usize` cannot be shared between threads safely
+  --> $DIR/issue-16538.rs:15:23
    |
-   = help: the trait `Sync` is not implemented for `*const usize`
-   = note: shared static variables must have a type that implements `Sync`
+LL | static foo: &Y::X = &*Y::foo(Y::x as *const Y::X);
+   |                       ^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: aborting due to 3 previous errors
 
-Some errors have detailed explanations: E0015, E0133, E0277.
+Some errors have detailed explanations: E0015, E0133.
 For more information about an error, try `rustc --explain E0015`.

src/test/ui/issues/issue-17718-static-sync.stderr

@@ -1,8 +1,8 @@
 error[E0277]: `Foo` cannot be shared between threads safely
-  --> $DIR/issue-17718-static-sync.rs:9:1
+  --> $DIR/issue-17718-static-sync.rs:9:13
    |
 LL | static BAR: Foo = Foo;
-   | ^^^^^^^^^^^^^^^^^^^^^^ `Foo` cannot be shared between threads safely
+   |             ^^^ `Foo` cannot be shared between threads safely
    |
    = help: the trait `Sync` is not implemented for `Foo`
    = note: shared static variables must have a type that implements `Sync`

src/test/ui/issues/issue-24446.rs

@@ -1,6 +1,7 @@
 fn main() {
     static foo: dyn Fn() -> u32 = || -> u32 {
         //~^ ERROR the size for values of type
+        //~| ERROR cannot be shared between threads safely
         0
     };
 }

src/test/ui/issues/issue-24446.stderr

@@ -6,6 +6,15 @@ LL |     static foo: dyn Fn() -> u32 = || -> u32 {
    |
    = help: the trait `Sized` is not implemented for `(dyn Fn() -> u32 + 'static)`
 
-error: aborting due to previous error
+error[E0277]: `(dyn Fn() -> u32 + 'static)` cannot be shared between threads safely
+  --> $DIR/issue-24446.rs:2:17
+   |
+LL |     static foo: dyn Fn() -> u32 = || -> u32 {
+   |                 ^^^^^^^^^^^^^^^ `(dyn Fn() -> u32 + 'static)` cannot be shared between threads safely
+   |
+   = help: the trait `Sync` is not implemented for `(dyn Fn() -> u32 + 'static)`
+   = note: shared static variables must have a type that implements `Sync`
+
+error: aborting due to 2 previous errors
 
 For more information about this error, try `rustc --explain E0277`.

src/test/ui/issues/issue-5216.rs

@@ -1,10 +1,10 @@
 fn f() { }
-struct S(Box<dyn FnMut()>);
+struct S(Box<dyn FnMut() + Sync>);
 pub static C: S = S(f); //~ ERROR mismatched types
 
 
 fn g() { }
-type T = Box<dyn FnMut()>;
+type T = Box<dyn FnMut() + Sync>;
 pub static D: T = g; //~ ERROR mismatched types
 
 fn main() {}

src/test/ui/issues/issue-5216.stderr

@@ -4,7 +4,7 @@ error[E0308]: mismatched types
 LL | pub static C: S = S(f);
    |                     ^ expected struct `Box`, found fn item
    |
-   = note: expected struct `Box<(dyn FnMut() + 'static)>`
+   = note: expected struct `Box<(dyn FnMut() + Sync + 'static)>`
              found fn item `fn() {f}`
 
 error[E0308]: mismatched types
@@ -13,7 +13,7 @@ error[E0308]: mismatched types
 LL | pub static D: T = g;
    |                   ^ expected struct `Box`, found fn item
    |
-   = note: expected struct `Box<(dyn FnMut() + 'static)>`
+   = note: expected struct `Box<(dyn FnMut() + Sync + 'static)>`
              found fn item `fn() {g}`
 
 error: aborting due to 2 previous errors

src/test/ui/issues/issue-7364.rs

@@ -4,7 +4,6 @@ use std::cell::RefCell;
 
 // Regression test for issue 7364
 static boxed: Box<RefCell<isize>> = box RefCell::new(0);
-//~^ ERROR allocations are not allowed in statics
-//~| ERROR `RefCell<isize>` cannot be shared between threads safely [E0277]
+//~^ ERROR `RefCell<isize>` cannot be shared between threads safely [E0277]
 
 fn main() { }

src/test/ui/issues/issue-7364.stderr

@@ -1,21 +1,14 @@
-error[E0010]: allocations are not allowed in statics
-  --> $DIR/issue-7364.rs:6:37
-   |
-LL | static boxed: Box<RefCell<isize>> = box RefCell::new(0);
-   |                                     ^^^^^^^^^^^^^^^^^^^ allocation not allowed in statics
-
 error[E0277]: `RefCell<isize>` cannot be shared between threads safely
-  --> $DIR/issue-7364.rs:6:1
+  --> $DIR/issue-7364.rs:6:15
    |
 LL | static boxed: Box<RefCell<isize>> = box RefCell::new(0);
-   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ `RefCell<isize>` cannot be shared between threads safely
+   |               ^^^^^^^^^^^^^^^^^^^ `RefCell<isize>` cannot be shared between threads safely
    |
    = help: the trait `Sync` is not implemented for `RefCell<isize>`
    = note: required because of the requirements on the impl of `Sync` for `Unique<RefCell<isize>>`
    = note: required because it appears within the type `Box<RefCell<isize>>`
    = note: shared static variables must have a type that implements `Sync`
 
-error: aborting due to 2 previous errors
+error: aborting due to previous error
 
-Some errors have detailed explanations: E0010, E0277.
-For more information about an error, try `rustc --explain E0010`.
+For more information about this error, try `rustc --explain E0277`.