Auto merge of #68189 - jonas-schievink:beta-next, r=Mark-Simulacrum

[Beta] Backports

I did not include #67134 and #67289 since they seem to be on beta already.

* Fix up Command Debug output when arg0 is specified. #67219
* Do not ICE on unnamed future #67289
* Don't suppress move errors for union fields #67314
* Reenable static linking of libstdc++ on windows-gnu #67410
* Use the correct type for static qualifs #67621
* Treat extern statics just like statics in the "const pointer to static" representation #67630
* Do not ICE on lifetime error involving closures #67687

src/bootstrap/compile.rs

@@ -563,7 +563,7 @@ pub fn rustc_cargo_env(builder: &Builder<'_>, cargo: &mut Cargo, target: Interne
         // not for MSVC or macOS
         if builder.config.llvm_static_stdcpp &&
            !target.contains("freebsd") &&
-           !target.contains("windows") &&
+           !target.contains("msvc") &&
            !target.contains("apple") {
             let file = compiler_file(builder,
                                      builder.cxx(target).unwrap(),

src/librustc/ty/util.rs

@@ -692,8 +692,6 @@ impl<'tcx> TyCtxt<'tcx> {
 
         if self.is_mutable_static(def_id) {
             self.mk_mut_ptr(static_ty)
-        } else if self.is_foreign_item(def_id) {
-            self.mk_imm_ptr(static_ty)
         } else {
             self.mk_imm_ref(self.lifetimes.re_erased, static_ty)
         }

src/librustc_mir/borrow_check/diagnostics/conflict_errors.rs

@@ -951,9 +951,27 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
                 err.span_label(
                     drop_span,
                     format!(
-                        "...but `{}` will be dropped here, when the function `{}` returns",
+                        "...but `{}` will be dropped here, when the {} returns",
                         name,
-                        self.infcx.tcx.hir().name(fn_hir_id),
+                        self.infcx
+                            .tcx
+                            .hir()
+                            .opt_name(fn_hir_id)
+                            .map(|name| format!("function `{}`", name))
+                            .unwrap_or_else(|| {
+                                match &self
+                                    .infcx
+                                    .tcx
+                                    .typeck_tables_of(self.mir_def_id)
+                                    .node_type(fn_hir_id)
+                                    .kind
+                                {
+                                    ty::Closure(..) => "enclosing closure",
+                                    ty::Generator(..) => "enclosing generator",
+                                    kind => bug!("expected closure or generator, found {:?}", kind),
+                                }
+                                .to_string()
+                            })
                     ),
                 );
 

src/librustc_mir/dataflow/move_paths/builder.rs

@@ -103,6 +103,13 @@ impl<'b, 'a, 'tcx> Gatherer<'b, 'a, 'tcx> {
             }
         };
 
+        // The move path index of the first union that we find. Once this is
+        // some we stop creating child move paths, since moves from unions
+        // move the whole thing.
+        // We continue looking for other move errors though so that moving
+        // from `*(u.f: &_)` isn't allowed.
+        let mut union_path = None;
+
         for (i, elem) in place.projection.iter().enumerate() {
             let proj_base = &place.projection[..i];
             let body = self.builder.body;
@@ -127,9 +134,8 @@ impl<'b, 'a, 'tcx> Gatherer<'b, 'a, 'tcx> {
                         InteriorOfTypeWithDestructor { container_ty: place_ty },
                     ));
                 }
-                // move out of union - always move the entire union
                 ty::Adt(adt, _) if adt.is_union() => {
-                    return Err(MoveError::UnionMove { path: base });
+                    union_path.get_or_insert(base);
                 }
                 ty::Slice(_) => {
                     return Err(MoveError::cannot_move_out_of(
@@ -155,15 +161,22 @@ impl<'b, 'a, 'tcx> Gatherer<'b, 'a, 'tcx> {
                 _ => {}
             };
 
-            base = self.add_move_path(base, elem, |tcx| {
-                Place {
-                    base: place.base.clone(),
-                    projection: tcx.intern_place_elems(&place.projection[..i+1]),
-                }
-            });
+            if union_path.is_none() {
+                base = self.add_move_path(base, elem, |tcx| {
+                    Place {
+                        base: place.base.clone(),
+                        projection: tcx.intern_place_elems(&place.projection[..i+1]),
+                    }
+                });
+            }
         }
 
-        Ok(base)
+        if let Some(base) = union_path {
+            // Move out of union - always move the entire union.
+            Err(MoveError::UnionMove { path: base })
+        } else {
+            Ok(base)
+        }
     }
 
     fn add_move_path(

src/librustc_mir/transform/check_consts/qualifs.rs

@@ -2,7 +2,6 @@
 
 use rustc::mir::*;
 use rustc::ty::{self, Ty};
-use rustc::hir::def_id::DefId;
 use syntax_pos::DUMMY_SP;
 
 use super::Item as ConstCx;
@@ -33,12 +32,6 @@ pub trait Qualif {
     /// of the type.
     fn in_any_value_of_ty(_cx: &ConstCx<'_, 'tcx>, _ty: Ty<'tcx>) -> bool;
 
-    fn in_static(cx: &ConstCx<'_, 'tcx>, def_id: DefId) -> bool {
-        // `mir_const_qualif` does return the qualifs in the final value of a `static`, so we could
-        // use value-based qualification here, but we shouldn't do this without a good reason.
-        Self::in_any_value_of_ty(cx, cx.tcx.type_of(def_id))
-    }
-
     fn in_projection_structurally(
         cx: &ConstCx<'_, 'tcx>,
         per_local: &impl Fn(Local) -> bool,
@@ -108,8 +101,14 @@ pub trait Qualif {
             Operand::Move(ref place) => Self::in_place(cx, per_local, place.as_ref()),
 
             Operand::Constant(ref constant) => {
-                if let Some(static_) = constant.check_static_ptr(cx.tcx) {
-                    Self::in_static(cx, static_)
+                if constant.check_static_ptr(cx.tcx).is_some() {
+                    // `mir_const_qualif` does return the qualifs in the final value of a `static`,
+                    // so we could use value-based qualification here, but we shouldn't do this
+                    // without a good reason.
+                    //
+                    // Note: this uses `constant.literal.ty` which is a reference or pointer to the
+                    // type of the actual `static` item.
+                    Self::in_any_value_of_ty(cx, constant.literal.ty)
                 } else if let ty::ConstKind::Unevaluated(def_id, _) = constant.literal.val {
                     // Don't peek inside trait associated constants.
                     if cx.tcx.trait_of_item(def_id).is_some() {

src/libstd/sys/unix/process/process_common.rs

@@ -375,8 +375,12 @@ impl ChildStdio {
 
 impl fmt::Debug for Command {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        write!(f, "{:?}", self.program)?;
-        for arg in &self.args {
+        if self.program != self.args[0] {
+            write!(f, "[{:?}] ", self.program)?;
+        }
+        write!(f, "{:?}", self.args[0])?;
+
+        for arg in &self.args[1..] {
             write!(f, " {:?}", arg)?;
         }
         Ok(())

src/test/mir-opt/const-promotion-extern-static.rs

@@ -0,0 +1,71 @@
+extern "C" {
+    static X: i32;
+}
+
+static Y: i32 = 42;
+
+static mut BAR: *const &'static i32 = [&Y].as_ptr();
+
+static mut FOO: *const &'static i32 = [unsafe { &X }].as_ptr();
+
+fn main() {}
+
+// END RUST SOURCE
+// START rustc.FOO.PromoteTemps.before.mir
+// bb0: {
+// ...
+//     _5 = const Scalar(AllocId(1).0x0) : &i32;
+//     _4 = &(*_5);
+//     _3 = [move _4];
+//     _2 = &_3;
+//     _1 = move _2 as &[&'static i32] (Pointer(Unsize));
+//     _0 = const core::slice::<impl [&'static i32]>::as_ptr(move _1) -> [return: bb2, unwind: bb1];
+// }
+// ...
+// bb2: {
+//     StorageDead(_5);
+//     StorageDead(_3);
+//     return;
+// }
+// END rustc.FOO.PromoteTemps.before.mir
+// START rustc.BAR.PromoteTemps.before.mir
+// bb0: {
+// ...
+//     _5 = const Scalar(AllocId(0).0x0) : &i32;
+//     _4 = &(*_5);
+//     _3 = [move _4];
+//     _2 = &_3;
+//     _1 = move _2 as &[&'static i32] (Pointer(Unsize));
+//     _0 = const core::slice::<impl [&'static i32]>::as_ptr(move _1) -> [return: bb2, unwind: bb1];
+// }
+// ...
+// bb2: {
+//     StorageDead(_5);
+//     StorageDead(_3);
+//     return;
+// }
+// END rustc.BAR.PromoteTemps.before.mir
+// START rustc.BAR.PromoteTemps.after.mir
+// bb0: {
+// ...
+//     _2 = &(promoted[0]: [&'static i32; 1]);
+//     _1 = move _2 as &[&'static i32] (Pointer(Unsize));
+//     _0 = const core::slice::<impl [&'static i32]>::as_ptr(move _1) -> [return: bb2, unwind: bb1];
+// }
+// ...
+// bb2: {
+//     return;
+// }
+// END rustc.BAR.PromoteTemps.after.mir
+// START rustc.FOO.PromoteTemps.after.mir
+// bb0: {
+// ...
+//     _2 = &(promoted[0]: [&'static i32; 1]);
+//     _1 = move _2 as &[&'static i32] (Pointer(Unsize));
+//     _0 = const core::slice::<impl [&'static i32]>::as_ptr(move _1) -> [return: bb2, unwind: bb1];
+// }
+// ...
+// bb2: {
+//     return;
+// }
+// END rustc.FOO.PromoteTemps.after.mir

src/test/ui/borrowck/move-from-union-field-issue-66500.rs

@@ -0,0 +1,30 @@
+// Moving from a reference/raw pointer should be an error, even when they're
+// the field of a union.
+
+#![feature(untagged_unions)]
+
+union Pointers {
+    a: &'static String,
+    b: &'static mut String,
+    c: *const String,
+    d: *mut String,
+}
+
+unsafe fn move_ref(u: Pointers) -> String {
+    *u.a
+    //~^ ERROR cannot move out of `*u.a`
+}
+unsafe fn move_ref_mut(u: Pointers) -> String {
+    *u.b
+    //~^ ERROR cannot move out of `*u.b`
+}
+unsafe fn move_ptr(u: Pointers) -> String {
+    *u.c
+    //~^ ERROR cannot move out of `*u.c`
+}
+unsafe fn move_ptr_mut(u: Pointers) -> String {
+    *u.d
+    //~^ ERROR cannot move out of `*u.d`
+}
+
+fn main() {}

src/test/ui/borrowck/move-from-union-field-issue-66500.stderr

@@ -0,0 +1,27 @@
+error[E0507]: cannot move out of `*u.a` which is behind a shared reference
+  --> $DIR/move-from-union-field-issue-66500.rs:14:5
+   |
+LL |     *u.a
+   |     ^^^^ move occurs because `*u.a` has type `std::string::String`, which does not implement the `Copy` trait
+
+error[E0507]: cannot move out of `*u.b` which is behind a mutable reference
+  --> $DIR/move-from-union-field-issue-66500.rs:18:5
+   |
+LL |     *u.b
+   |     ^^^^ move occurs because `*u.b` has type `std::string::String`, which does not implement the `Copy` trait
+
+error[E0507]: cannot move out of `*u.c` which is behind a raw pointer
+  --> $DIR/move-from-union-field-issue-66500.rs:22:5
+   |
+LL |     *u.c
+   |     ^^^^ move occurs because `*u.c` has type `std::string::String`, which does not implement the `Copy` trait
+
+error[E0507]: cannot move out of `*u.d` which is behind a raw pointer
+  --> $DIR/move-from-union-field-issue-66500.rs:26:5
+   |
+LL |     *u.d
+   |     ^^^^ move occurs because `*u.d` has type `std::string::String`, which does not implement the `Copy` trait
+
+error: aborting due to 4 previous errors
+
+For more information about this error, try `rustc --explain E0507`.

src/test/ui/command/command-argv0-debug.rs

@@ -0,0 +1,24 @@
+// run-pass
+
+// ignore-windows - this is a unix-specific test
+// ignore-cloudabi no processes
+// ignore-emscripten no processes
+// ignore-sgx no processes
+#![feature(process_set_argv0)]
+
+use std::os::unix::process::CommandExt;
+use std::process::Command;
+
+fn main() {
+    let mut command = Command::new("some-boring-name");
+
+    assert_eq!(format!("{:?}", command), r#""some-boring-name""#);
+
+    command.args(&["1", "2", "3"]);
+
+    assert_eq!(format!("{:?}", command), r#""some-boring-name" "1" "2" "3""#);
+
+    command.arg0("exciting-name");
+
+    assert_eq!(format!("{:?}", command), r#"["some-boring-name"] "exciting-name" "1" "2" "3""#);
+}

src/test/ui/consts/const-eval/promote-static.rs

@@ -0,0 +1,14 @@
+// regression test for #67609.
+
+// check-pass
+
+static NONE: Option<String> = None;
+
+static NONE_REF_REF: &&Option<String> = {
+    let x = &&NONE;
+    x
+};
+
+fn main() {
+    println!("{:?}", NONE_REF_REF);
+}

src/test/ui/lifetimes/unnamed-closure-doesnt-life-long-enough-issue-67634.rs

@@ -0,0 +1,3 @@
+fn main() {
+    [0].iter().flat_map(|a| [0].iter().map(|_| &a)); //~ ERROR `a` does not live long enough
+}

src/test/ui/lifetimes/unnamed-closure-doesnt-life-long-enough-issue-67634.stderr

@@ -0,0 +1,15 @@
+error[E0597]: `a` does not live long enough
+  --> $DIR/unnamed-closure-doesnt-life-long-enough-issue-67634.rs:2:49
+   |
+LL |     [0].iter().flat_map(|a| [0].iter().map(|_| &a));
+   |                                             -   ^- ...but `a` will be dropped here, when the enclosing closure returns
+   |                                             |   |
+   |                                             |   `a` would have to be valid for `'_`...
+   |                                             has type `&i32`
+   |
+   = note: functions cannot return a borrow to data owned within the function's scope, functions can only return borrows to data passed as arguments
+   = note: to learn more, visit <https://doc.rust-lang.org/book/ch04-02-references-and-borrowing.html#dangling-references>
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0597`.