Auto merge of #88556 - m-ou-se:rollup-q636wyd, r=m-ou-se

Rollup of 9 pull requests

Successful merges:

 - #86376 (Emit specific warning to clarify that `#[no_mangle]` should not be applied on foreign statics or functions)
 - #88040 (BTree: remove Ord bound from new)
 - #88053 (Fix the flock fallback implementation)
 - #88350 (add support for clobbering xer, cr, and cr[0-7] for asm! on OpenPower/PowerPC)
 - #88410 (Remove bolding on associated constants)
 - #88525 (fix(rustc_typeck): produce better errors for dyn auto trait)
 - #88542 (Use the return value of readdir_r() instead of errno)
 - #88548 (Stabilize `Iterator::intersperse()`)
 - #88551 (Stabilize `UnsafeCell::raw_get()`)

Failed merges:

r? `@ghost`
`@rustbot` modify labels: rollup

Author: bors

compiler/rustc_codegen_llvm/src/asm.rs

@@ -616,6 +616,10 @@ fn reg_to_llvm(reg: InlineAsmRegOrRegClass, layout: Option<&TyAndLayout<'tcx>>)
             InlineAsmRegClass::PowerPC(PowerPCInlineAsmRegClass::reg) => "r",
             InlineAsmRegClass::PowerPC(PowerPCInlineAsmRegClass::reg_nonzero) => "b",
             InlineAsmRegClass::PowerPC(PowerPCInlineAsmRegClass::freg) => "f",
+            InlineAsmRegClass::PowerPC(PowerPCInlineAsmRegClass::cr)
+            | InlineAsmRegClass::PowerPC(PowerPCInlineAsmRegClass::xer) => {
+                unreachable!("clobber-only")
+            }
             InlineAsmRegClass::RiscV(RiscVInlineAsmRegClass::reg) => "r",
             InlineAsmRegClass::RiscV(RiscVInlineAsmRegClass::freg) => "f",
             InlineAsmRegClass::RiscV(RiscVInlineAsmRegClass::vreg) => {
@@ -755,6 +759,10 @@ fn dummy_output_type(cx: &CodegenCx<'ll, 'tcx>, reg: InlineAsmRegClass) -> &'ll
         InlineAsmRegClass::PowerPC(PowerPCInlineAsmRegClass::reg) => cx.type_i32(),
         InlineAsmRegClass::PowerPC(PowerPCInlineAsmRegClass::reg_nonzero) => cx.type_i32(),
         InlineAsmRegClass::PowerPC(PowerPCInlineAsmRegClass::freg) => cx.type_f64(),
+        InlineAsmRegClass::PowerPC(PowerPCInlineAsmRegClass::cr)
+        | InlineAsmRegClass::PowerPC(PowerPCInlineAsmRegClass::xer) => {
+            unreachable!("clobber-only")
+        }
         InlineAsmRegClass::RiscV(RiscVInlineAsmRegClass::reg) => cx.type_i32(),
         InlineAsmRegClass::RiscV(RiscVInlineAsmRegClass::freg) => cx.type_f32(),
         InlineAsmRegClass::RiscV(RiscVInlineAsmRegClass::vreg) => {

compiler/rustc_data_structures/src/flock.rs

@@ -222,6 +222,10 @@ cfg_if! {
                 let msg = "file locks not supported on this platform";
                 Err(io::Error::new(io::ErrorKind::Other, msg))
             }
+
+            pub fn error_unsupported(_err: &io::Error) -> bool {
+                true
+            }
         }
     }
 }

compiler/rustc_error_codes/src/error_codes.rs

@@ -480,6 +480,7 @@ E0781: include_str!("./error_codes/E0781.md"),
 E0782: include_str!("./error_codes/E0782.md"),
 E0783: include_str!("./error_codes/E0783.md"),
 E0784: include_str!("./error_codes/E0784.md"),
+E0785: include_str!("./error_codes/E0785.md"),
 ;
 //  E0006, // merged with E0005
 //  E0008, // cannot bind by-move into a pattern guard

compiler/rustc_error_codes/src/error_codes/E0785.md

@@ -0,0 +1,30 @@
+An inherent `impl` was written on a dyn auto trait.
+
+Erroneous code example:
+
+```compile_fail,E0785
+#![feature(auto_traits)]
+
+auto trait AutoTrait {}
+
+impl dyn AutoTrait {}
+```
+
+Dyn objects allow any number of auto traits, plus at most one non-auto trait.
+The non-auto trait becomes the "principal trait".
+
+When checking if an impl on a dyn trait is coherent, the principal trait is
+normally the only one considered. Since the erroneous code has no principal
+trait, it cannot be implemented at all.
+
+Working example:
+
+```
+#![feature(auto_traits)]
+
+trait PrincipalTrait {}
+
+auto trait AutoTrait {}
+
+impl dyn PrincipalTrait + AutoTrait + Send {}
+```

compiler/rustc_passes/src/check_attr.rs

@@ -1331,6 +1331,36 @@ impl CheckAttrVisitor<'tcx> {
             Target::Field | Target::Arm | Target::MacroDef => {
                 self.inline_attr_str_error_with_macro_def(hir_id, attr, "no_mangle");
             }
+            // FIXME: #[no_mangle] was previously allowed on non-functions/statics, this should be an error
+            // The error should specify that the item that is wrong is specifically a *foreign* fn/static
+            // otherwise the error seems odd
+            Target::ForeignFn | Target::ForeignStatic => {
+                let foreign_item_kind = match target {
+                    Target::ForeignFn => "function",
+                    Target::ForeignStatic => "static",
+                    _ => unreachable!(),
+                };
+                self.tcx.struct_span_lint_hir(UNUSED_ATTRIBUTES, hir_id, attr.span, |lint| {
+                    lint.build(&format!(
+                        "`#[no_mangle]` has no effect on a foreign {}",
+                        foreign_item_kind
+                    ))
+                    .warn(
+                        "this was previously accepted by the compiler but is \
+                            being phased out; it will become a hard error in \
+                            a future release!",
+                    )
+                    .span_label(*span, format!("foreign {}", foreign_item_kind))
+                    .note("symbol names in extern blocks are not mangled")
+                    .span_suggestion(
+                        attr.span,
+                        "remove this attribute",
+                        String::new(),
+                        Applicability::MachineApplicable,
+                    )
+                    .emit();
+                });
+            }
             _ => {
                 // FIXME: #[no_mangle] was previously allowed on non-functions/statics and some
                 // crates used this, so only emit a warning.

compiler/rustc_span/src/symbol.rs

@@ -479,6 +479,7 @@ symbols! {
         core_panic_macro,
         cosf32,
         cosf64,
+        cr,
         crate_id,
         crate_in_paths,
         crate_local,
@@ -1418,6 +1419,7 @@ symbols! {
         wreg,
         write_bytes,
         x87_reg,
+        xer,
         xmm_reg,
         ymm_reg,
         zmm_reg,

compiler/rustc_target/src/asm/mod.rs

@@ -355,7 +355,7 @@ impl InlineAsmReg {
             Self::Arm(r) => r.overlapping_regs(|r| cb(Self::Arm(r))),
             Self::AArch64(_) => cb(self),
             Self::RiscV(_) => cb(self),
-            Self::PowerPC(_) => cb(self),
+            Self::PowerPC(r) => r.overlapping_regs(|r| cb(Self::PowerPC(r))),
             Self::Hexagon(r) => r.overlapping_regs(|r| cb(Self::Hexagon(r))),
             Self::Mips(_) => cb(self),
             Self::S390x(_) => cb(self),

compiler/rustc_target/src/asm/powerpc.rs

@@ -7,6 +7,8 @@ def_reg_class! {
         reg,
         reg_nonzero,
         freg,
+        cr,
+        xer,
     }
 }
 
@@ -44,6 +46,7 @@ impl PowerPCInlineAsmRegClass {
                 }
             }
             Self::freg => types! { _: F32, F64; },
+            Self::cr | Self::xer => &[],
         }
     }
 }
@@ -108,6 +111,16 @@ def_regs! {
         f29: freg = ["f29", "fr29"],
         f30: freg = ["f30", "fr30"],
         f31: freg = ["f31", "fr31"],
+        cr: cr = ["cr"],
+        cr0: cr = ["cr0"],
+        cr1: cr = ["cr1"],
+        cr2: cr = ["cr2"],
+        cr3: cr = ["cr3"],
+        cr4: cr = ["cr4"],
+        cr5: cr = ["cr5"],
+        cr6: cr = ["cr6"],
+        cr7: cr = ["cr7"],
+        xer: xer = ["xer"],
         #error = ["r1", "1", "sp"] =>
             "the stack pointer cannot be used as an operand for inline asm",
         #error = ["r2", "2"] =>
@@ -136,17 +149,55 @@ impl PowerPCInlineAsmReg {
         _arch: InlineAsmArch,
         _modifier: Option<char>,
     ) -> fmt::Result {
+        macro_rules! do_emit {
+            (
+                $($(($reg:ident, $value:literal)),*;)*
+            ) => {
+                out.write_str(match self {
+                    $($(Self::$reg => $value,)*)*
+                })
+            };
+        }
         // Strip off the leading prefix.
-        if self as u32 <= Self::r28 as u32 {
-            let index = self as u32 - Self::r28 as u32;
-            write!(out, "{}", index)
-        } else if self as u32 >= Self::f0 as u32 && self as u32 <= Self::f31 as u32 {
-            let index = self as u32 - Self::f31 as u32;
-            write!(out, "{}", index)
-        } else {
-            unreachable!()
+        do_emit! {
+            (r0, "0"), (r3, "3"), (r4, "4"), (r5, "5"), (r6, "6"), (r7, "7");
+            (r8, "8"), (r9, "9"), (r10, "10"), (r11, "11"), (r12, "12"), (r14, "14"), (r15, "15");
+            (r16, "16"), (r17, "17"), (r18, "18"), (r19, "19"), (r20, "20"), (r21, "21"), (r22, "22"), (r23, "23");
+            (r24, "24"), (r25, "25"), (r26, "26"), (r27, "27"), (r28, "28");
+            (f0, "0"), (f1, "1"), (f2, "2"), (f3, "3"), (f4, "4"), (f5, "5"), (f6, "6"), (f7, "7");
+            (f8, "8"), (f9, "9"), (f10, "10"), (f11, "11"), (f12, "12"), (f13, "13"), (f14, "14"), (f15, "15");
+            (f16, "16"), (f17, "17"), (f18, "18"), (f19, "19"), (f20, "20"), (f21, "21"), (f22, "22"), (f23, "23");
+            (f24, "24"), (f25, "25"), (f26, "26"), (f27, "27"), (f28, "28"), (f29, "29"), (f30, "30"), (f31, "31");
+            (cr, "cr");
+            (cr0, "0"), (cr1, "1"), (cr2, "2"), (cr3, "3"), (cr4, "4"), (cr5, "5"), (cr6, "6"), (cr7, "7");
+            (xer, "xer");
         }
     }
 
-    pub fn overlapping_regs(self, mut _cb: impl FnMut(PowerPCInlineAsmReg)) {}
+    pub fn overlapping_regs(self, mut cb: impl FnMut(PowerPCInlineAsmReg)) {
+        macro_rules! reg_conflicts {
+            (
+                $(
+                    $full:ident : $($field:ident)*
+                ),*;
+            ) => {
+                match self {
+                    $(
+                        Self::$full => {
+                            cb(Self::$full);
+                            $(cb(Self::$field);)*
+                        }
+                        $(Self::$field)|* => {
+                            cb(Self::$full);
+                            cb(self);
+                        }
+                    )*
+                    r => cb(r),
+                }
+            };
+        }
+        reg_conflicts! {
+            cr : cr0 cr1 cr2 cr3 cr4 cr5 cr6 cr7;
+        }
+    }
 }

compiler/rustc_typeck/src/coherence/inherent_impls.rs

@@ -60,6 +60,17 @@ impl ItemLikeVisitor<'v> for InherentCollect<'tcx> {
             ty::Dynamic(ref data, ..) if data.principal_def_id().is_some() => {
                 self.check_def_id(item, data.principal_def_id().unwrap());
             }
+            ty::Dynamic(..) => {
+                struct_span_err!(
+                    self.tcx.sess,
+                    ty.span,
+                    E0785,
+                    "cannot define inherent `impl` for a dyn auto trait"
+                )
+                .span_label(ty.span, "impl requires at least one non-auto trait")
+                .note("define and implement a new trait or type instead")
+                .emit();
+            }
             ty::Bool => {
                 self.check_primitive_impl(
                     item.def_id,

library/alloc/src/collections/btree/map.rs

@@ -233,9 +233,7 @@ impl<K: Clone, V: Clone> Clone for BTreeMap<K, V> {
         }
 
         if self.is_empty() {
-            // Ideally we'd call `BTreeMap::new` here, but that has the `K:
-            // Ord` constraint, which this method lacks.
-            BTreeMap { root: None, length: 0 }
+            BTreeMap::new()
         } else {
             clone_subtree(self.root.as_ref().unwrap().reborrow()) // unwrap succeeds because not empty
         }
@@ -499,10 +497,7 @@ impl<K, V> BTreeMap<K, V> {
     /// ```
     #[stable(feature = "rust1", since = "1.0.0")]
     #[rustc_const_unstable(feature = "const_btree_new", issue = "71835")]
-    pub const fn new() -> BTreeMap<K, V>
-    where
-        K: Ord,
-    {
+    pub const fn new() -> BTreeMap<K, V> {
         BTreeMap { root: None, length: 0 }
     }
 
@@ -522,7 +517,7 @@ impl<K, V> BTreeMap<K, V> {
     /// ```
     #[stable(feature = "rust1", since = "1.0.0")]
     pub fn clear(&mut self) {
-        *self = BTreeMap { root: None, length: 0 };
+        *self = BTreeMap::new();
     }
 
     /// Returns a reference to the value corresponding to the key.
@@ -1957,7 +1952,7 @@ impl<K: Hash, V: Hash> Hash for BTreeMap<K, V> {
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
-impl<K: Ord, V> Default for BTreeMap<K, V> {
+impl<K, V> Default for BTreeMap<K, V> {
     /// Creates an empty `BTreeMap`.
     fn default() -> BTreeMap<K, V> {
         BTreeMap::new()