Taint the type of ill-formed (unsized) statics

compiler/rustc_hir_analysis/src/check/check.rs

@@ -767,7 +767,8 @@ pub(crate) fn check_item_type(tcx: TyCtxt<'_>, def_id: LocalDefId) -> Result<(),
                 DefKind::Static { .. } => {
                     check_static_inhabited(tcx, def_id);
                     check_static_linkage(tcx, def_id);
-                    res = res.and(wfcheck::check_static_item(tcx, def_id));
+                    let ty = tcx.type_of(def_id).instantiate_identity();
+                    res = res.and(wfcheck::check_static_item(tcx, def_id, ty, true));
                 }
                 DefKind::Const => res = res.and(wfcheck::check_const_item(tcx, def_id)),
                 _ => unreachable!(),

compiler/rustc_hir_analysis/src/check/wfcheck.rs

@@ -1180,12 +1180,13 @@ fn check_item_fn(
 }
 
 #[instrument(level = "debug", skip(tcx))]
-pub(super) fn check_static_item(
-    tcx: TyCtxt<'_>,
+pub(crate) fn check_static_item<'tcx>(
+    tcx: TyCtxt<'tcx>,
     item_id: LocalDefId,
+    ty: Ty<'tcx>,
+    should_check_for_sync: bool,
 ) -> Result<(), ErrorGuaranteed> {
     enter_wf_checking_ctxt(tcx, item_id, |wfcx| {
-        let ty = tcx.type_of(item_id).instantiate_identity();
         let span = tcx.ty_span(item_id);
         let item_ty = wfcx.deeply_normalize(span, Some(WellFormedLoc::Ty(item_id)), ty);
 
@@ -1212,9 +1213,9 @@ pub(super) fn check_static_item(
         }
 
         // 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)
+        let should_check_for_sync = should_check_for_sync
             && !is_foreign_item
+            && tcx.static_mutability(item_id.to_def_id()) == Some(hir::Mutability::Not)
             && !tcx.is_thread_local_static(item_id.to_def_id());
 
         if should_check_for_sync {

compiler/rustc_hir_analysis/src/collect/type_of.rs

@@ -14,6 +14,7 @@ use rustc_middle::{bug, span_bug};
 use rustc_span::{DUMMY_SP, Ident, Span};
 
 use super::{HirPlaceholderCollector, ItemCtxt, bad_placeholder};
+use crate::check::wfcheck::check_static_item;
 use crate::errors::TypeofReservedKeywordUsed;
 use crate::hir_ty_lowering::HirTyLowerer;
 
@@ -217,7 +218,13 @@ pub(super) fn type_of(tcx: TyCtxt<'_>, def_id: LocalDefId) -> ty::EarlyBinder<'_
                         "static variable",
                     )
                 } else {
-                    icx.lower_ty(ty)
+                    let ty = icx.lower_ty(ty);
+                    // MIR relies on references to statics being scalars.
+                    // Verify that here to avoid ill-formed MIR.
+                    match check_static_item(tcx, def_id, ty, false) {
+                        Ok(()) => ty,
+                        Err(guar) => Ty::new_error(tcx, guar),
+                    }
                 }
             }
             ItemKind::Const(ident, _, ty, body_id) => {
@@ -275,7 +282,15 @@ pub(super) fn type_of(tcx: TyCtxt<'_>, def_id: LocalDefId) -> ty::EarlyBinder<'_
                 let args = ty::GenericArgs::identity_for_item(tcx, def_id);
                 Ty::new_fn_def(tcx, def_id.to_def_id(), args)
             }
-            ForeignItemKind::Static(t, _, _) => icx.lower_ty(t),
+            ForeignItemKind::Static(ty, _, _) => {
+                let ty = icx.lower_ty(ty);
+                // MIR relies on references to statics being scalars.
+                // Verify that here to avoid ill-formed MIR.
+                match check_static_item(tcx, def_id, ty, false) {
+                    Ok(()) => ty,
+                    Err(guar) => Ty::new_error(tcx, guar),
+                }
+            }
             ForeignItemKind::Type => Ty::new_foreign(tcx, def_id.to_def_id()),
         },
 

tests/ui/consts/const-unsized.rs

@@ -10,14 +10,10 @@ const CONST_FOO: str = *"foo";
 
 static STATIC_1: dyn Debug + Sync = *(&1 as &(dyn Debug + Sync));
 //~^ ERROR the size for values of type
-//~| ERROR cannot move out of a shared reference
 
 static STATIC_BAR: str = *"bar";
 //~^ ERROR the size for values of type
-//~| ERROR cannot move out of a shared reference
 
 fn main() {
     println!("{:?} {:?} {:?} {:?}", &CONST_0, &CONST_FOO, &STATIC_1, &STATIC_BAR);
-    //~^ ERROR: cannot move a value of type `str`
-    //~| ERROR: cannot move a value of type `dyn Debug + Sync`
 }

tests/ui/consts/const-unsized.stderr

@@ -26,7 +26,7 @@ LL | static STATIC_1: dyn Debug + Sync = *(&1 as &(dyn Debug + Sync));
    = note: statics and constants must have a statically known size
 
 error[E0277]: the size for values of type `str` cannot be known at compilation time
-  --> $DIR/const-unsized.rs:15:1
+  --> $DIR/const-unsized.rs:14:1
    |
 LL | static STATIC_BAR: str = *"bar";
    | ^^^^^^^^^^^^^^^^^^^^^^ doesn't have a size known at compile-time
@@ -46,31 +46,7 @@ error[E0507]: cannot move out of a shared reference
 LL | const CONST_FOO: str = *"foo";
    |                        ^^^^^^ move occurs because value has type `str`, which does not implement the `Copy` trait
 
-error[E0507]: cannot move out of a shared reference
-  --> $DIR/const-unsized.rs:11:37
-   |
-LL | static STATIC_1: dyn Debug + Sync = *(&1 as &(dyn Debug + Sync));
-   |                                     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ move occurs because value has type `dyn Debug + Sync`, which does not implement the `Copy` trait
-
-error[E0507]: cannot move out of a shared reference
-  --> $DIR/const-unsized.rs:15:26
-   |
-LL | static STATIC_BAR: str = *"bar";
-   |                          ^^^^^^ move occurs because value has type `str`, which does not implement the `Copy` trait
-
-error[E0161]: cannot move a value of type `dyn Debug + Sync`
-  --> $DIR/const-unsized.rs:20:38
-   |
-LL |     println!("{:?} {:?} {:?} {:?}", &CONST_0, &CONST_FOO, &STATIC_1, &STATIC_BAR);
-   |                                      ^^^^^^^ the size of `dyn Debug + Sync` cannot be statically determined
-
-error[E0161]: cannot move a value of type `str`
-  --> $DIR/const-unsized.rs:20:48
-   |
-LL |     println!("{:?} {:?} {:?} {:?}", &CONST_0, &CONST_FOO, &STATIC_1, &STATIC_BAR);
-   |                                                ^^^^^^^^^ the size of `str` cannot be statically determined
-
-error: aborting due to 10 previous errors
+error: aborting due to 6 previous errors
 
-Some errors have detailed explanations: E0161, E0277, E0507.
-For more information about an error, try `rustc --explain E0161`.
+Some errors have detailed explanations: E0277, E0507.
+For more information about an error, try `rustc --explain E0277`.

tests/ui/coroutine/layout-error.rs

@@ -17,6 +17,7 @@ impl<F: Future> Task<F> {
 }
 
 pub type F = impl Future;
+
 #[define_opaque(F)]
 fn foo()
 where

tests/ui/coroutine/layout-error.stderr

@@ -1,5 +1,5 @@
 error[E0425]: cannot find value `Foo` in this scope
-  --> $DIR/layout-error.rs:26:17
+  --> $DIR/layout-error.rs:27:17
    |
 LL |         let a = Foo;
    |                 ^^^ not found in this scope

tests/ui/dyn-compatibility/taint-const-eval.rs

@@ -6,6 +6,5 @@ trait Qux {
 
 static FOO: &(dyn Qux + Sync) = "desc";
 //~^ ERROR the trait `Qux` is not dyn compatible
-//~| ERROR the trait `Qux` is not dyn compatible
 
 fn main() {}

tests/ui/dyn-compatibility/taint-const-eval.stderr

@@ -21,30 +21,6 @@ help: alternatively, consider constraining `bar` so it does not apply to trait o
 LL |     fn bar() where Self: Sized;
    |              +++++++++++++++++
 
-error[E0038]: the trait `Qux` is not dyn compatible
-  --> $DIR/taint-const-eval.rs:7:15
-   |
-LL | static FOO: &(dyn Qux + Sync) = "desc";
-   |               ^^^^^^^^^^^^^^ `Qux` is not dyn compatible
-   |
-note: for a trait to be dyn compatible it needs to allow building a vtable
-      for more information, visit <https://doc.rust-lang.org/reference/items/traits.html#dyn-compatibility>
-  --> $DIR/taint-const-eval.rs:4:8
-   |
-LL | trait Qux {
-   |       --- this trait is not dyn compatible...
-LL |     fn bar();
-   |        ^^^ ...because associated function `bar` has no `self` parameter
-   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
-help: consider turning `bar` into a method by giving it a `&self` argument
-   |
-LL |     fn bar(&self);
-   |            +++++
-help: alternatively, consider constraining `bar` so it does not apply to trait objects
-   |
-LL |     fn bar() where Self: Sized;
-   |              +++++++++++++++++
-
-error: aborting due to 2 previous errors
+error: aborting due to 1 previous error
 
 For more information about this error, try `rustc --explain E0038`.

tests/ui/extern/issue-36122-accessing-externed-dst.rs

@@ -3,5 +3,4 @@ fn main() {
         static symbol: [usize]; //~ ERROR: the size for values of type
     }
     println!("{}", symbol[0]);
-    //~^ ERROR: extern static is unsafe
 }

tests/ui/extern/issue-36122-accessing-externed-dst.stderr

@@ -7,15 +7,6 @@ LL |         static symbol: [usize];
    = help: the trait `Sized` is not implemented for `[usize]`
    = note: statics and constants must have a statically known size
 
-error[E0133]: use of extern static is unsafe and requires unsafe function or block
-  --> $DIR/issue-36122-accessing-externed-dst.rs:5:20
-   |
-LL |     println!("{}", symbol[0]);
-   |                    ^^^^^^ 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: aborting due to 2 previous errors
+error: aborting due to 1 previous error
 
-Some errors have detailed explanations: E0133, E0277.
-For more information about an error, try `rustc --explain E0133`.
+For more information about this error, try `rustc --explain E0277`.

tests/ui/layout/issue-84108.rs

@@ -14,5 +14,3 @@ const BAR: (&Path, [u8], usize) = ("hello", [], 42);
 
 static BAZ: ([u8], usize) = ([], 0);
 //~^ ERROR the size for values of type `[u8]` cannot be known at compilation time
-//~| ERROR the size for values of type `[u8]` cannot be known at compilation time
-//~| ERROR mismatched types

tests/ui/layout/issue-84108.stderr

@@ -57,26 +57,7 @@ LL | const BAR: (&Path, [u8], usize) = ("hello", [], 42);
    = note: expected slice `[u8]`
               found array `[_; 0]`
 
-error[E0277]: the size for values of type `[u8]` cannot be known at compilation time
-  --> $DIR/issue-84108.rs:15:13
-   |
-LL | static BAZ: ([u8], usize) = ([], 0);
-   |             ^^^^^^^^^^^^^ doesn't have a size known at compile-time
-   |
-   = help: the trait `Sized` is not implemented for `[u8]`
-   = note: only the last element of a tuple may have a dynamically sized type
-   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
-
-error[E0308]: mismatched types
-  --> $DIR/issue-84108.rs:15:30
-   |
-LL | static BAZ: ([u8], usize) = ([], 0);
-   |                              ^^ expected `[u8]`, found `[_; 0]`
-   |
-   = note: expected slice `[u8]`
-              found array `[_; 0]`
-
-error: aborting due to 8 previous errors
+error: aborting due to 6 previous errors
 
 Some errors have detailed explanations: E0277, E0308, E0412.
 For more information about an error, try `rustc --explain E0277`.

tests/ui/mir/static-by-value-dyn.rs

@@ -0,0 +1,14 @@
+//! Regression test for #121176
+//! KnownPanicsLint used to assert ABI compatibility in the interpreter,
+//! which ICEs with unsized statics.
+//@ needs-rustc-debug-assertions
+
+use std::fmt::Debug;
+
+static STATIC_1: dyn Debug + Sync = *();
+//~^ ERROR the size for values of type `(dyn Debug + Sync + 'static)` cannot be known
+//~| ERROR type `()` cannot be dereferenced
+
+fn main() {
+    println!("{:?}", &STATIC_1);
+}

tests/ui/mir/static-by-value-dyn.stderr

@@ -0,0 +1,19 @@
+error[E0277]: the size for values of type `(dyn Debug + Sync + 'static)` cannot be known at compilation time
+  --> $DIR/static-by-value-dyn.rs:8:1
+   |
+LL | static STATIC_1: dyn Debug + Sync = *();
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ doesn't have a size known at compile-time
+   |
+   = help: the trait `Sized` is not implemented for `(dyn Debug + Sync + 'static)`
+   = note: statics and constants must have a statically known size
+
+error[E0614]: type `()` cannot be dereferenced
+  --> $DIR/static-by-value-dyn.rs:8:37
+   |
+LL | static STATIC_1: dyn Debug + Sync = *();
+   |                                     ^^^ can't be dereferenced
+
+error: aborting due to 2 previous errors
+
+Some errors have detailed explanations: E0277, E0614.
+For more information about an error, try `rustc --explain E0277`.

tests/ui/mir/static-by-value-slice.rs

@@ -0,0 +1,10 @@
+//! Regression test for #140332
+//! KnownPanicsLint used to assert ABI compatibility in the interpreter,
+//! which ICEs with unsized statics.
+
+static mut S: [i8] = ["Some thing"; 1];
+//~^ ERROR the size for values of type `[i8]` cannot be known
+
+fn main() {
+    assert_eq!(S, [0; 1]);
+}

tests/ui/mir/static-by-value-slice.stderr

@@ -0,0 +1,12 @@
+error[E0277]: the size for values of type `[i8]` cannot be known at compilation time
+  --> $DIR/static-by-value-slice.rs:5:1
+   |
+LL | static mut S: [i8] = ["Some thing"; 1];
+   | ^^^^^^^^^^^^^^^^^^ doesn't have a size known at compile-time
+   |
+   = help: the trait `Sized` is not implemented for `[i8]`
+   = note: statics and constants must have a statically known size
+
+error: aborting due to 1 previous error
+
+For more information about this error, try `rustc --explain E0277`.

tests/ui/mir/static-by-value-str.rs

@@ -0,0 +1,15 @@
+//! Regression test for #139872
+//! KnownPanicsLint used to assert ABI compatibility in the interpreter,
+//! which ICEs with unsized statics.
+
+enum E {
+    V16(u16),
+    V32(u32),
+}
+
+static C: (E, u16, str) = (E::V16(0xDEAD), 0x600D, 0xBAD);
+//~^ ERROR the size for values of type `str` cannot be known
+
+pub fn main() {
+    let (_, n, _) = C;
+}

tests/ui/mir/static-by-value-str.stderr

@@ -0,0 +1,13 @@
+error[E0277]: the size for values of type `str` cannot be known at compilation time
+  --> $DIR/static-by-value-str.rs:10:1
+   |
+LL | static C: (E, u16, str) = (E::V16(0xDEAD), 0x600D, 0xBAD);
+   | ^^^^^^^^^^^^^^^^^^^^^^^ doesn't have a size known at compile-time
+   |
+   = help: within `(E, u16, str)`, the trait `Sized` is not implemented for `str`
+   = note: required because it appears within the type `(E, u16, str)`
+   = note: statics and constants must have a statically known size
+
+error: aborting due to 1 previous error
+
+For more information about this error, try `rustc --explain E0277`.

tests/ui/mir/unsized-extern-static.rs

@@ -0,0 +1,13 @@
+//! Regression test for #129109
+//! MIR building used to produce erroneous constants when referring to statics of unsized type.
+//@ compile-flags: -Zmir-enable-passes=+GVN -Zvalidate-mir
+
+extern "C" {
+    pub static mut symbol: [i8];
+    //~^ ERROR the size for values of type `[i8]`
+}
+
+fn main() {
+    println!("C", unsafe { &symbol });
+    //~^ ERROR argument never used
+}