Auto merge of #111153 - Dylan-DPC:rollup-0pq0hh3, r=Dylan-DPC

Rollup of 11 pull requests

Successful merges:

 - #107978 (Correctly convert an NT path to a Win32 path in `read_link`)
 - #110436 (Support loading version information from xz tarballs)
 - #110791 (Implement negative bounds for internal testing purposes)
 - #110874 (Adjust obligation cause code for `find_and_report_unsatisfied_index_impl`)
 - #110908 (resolve: One more attempt to simplify `module_children`)
 - #110943 (interpret: fail more gracefully on uninit unsized locals)
 - #111062 (Don't bail out early when checking invalid `repr` attr)
 - #111069 (remove pointless `FIXME` in `bootstrap::download`)
 - #111086 (Remove `MemEncoder`)
 - #111097 (Avoid ICEing miri on layout query cycles)
 - #111112 (Add some triagebot notifications for nnethercote.)

Failed merges:

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

Author: bors

Cargo.lock

@@ -297,6 +297,7 @@ dependencies = [
  "sha2",
  "tar",
  "toml",
+ "xz2",
 ]
 
 [[package]]
@@ -2060,9 +2061,9 @@ dependencies = [
 
 [[package]]
 name = "lzma-sys"
-version = "0.1.16"
+version = "0.1.20"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "f24f76ec44a8ac23a31915d6e326bca17ce88da03096f1ff194925dc714dac99"
+checksum = "5fda04ab3764e6cde78b9974eec4f779acaba7c4e84b36eca3cf77c581b85d27"
 dependencies = [
  "cc",
  "libc",
@@ -4059,6 +4060,7 @@ dependencies = [
  "indexmap",
  "rustc_macros",
  "smallvec",
+ "tempfile",
  "thin-vec",
 ]
 
@@ -5658,9 +5660,9 @@ dependencies = [
 
 [[package]]
 name = "xz2"
-version = "0.1.6"
+version = "0.1.7"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "c179869f34fc7c01830d3ce7ea2086bc3a07e0d35289b667d0a8bf910258926c"
+checksum = "388c44dc09d76f1536602ead6d325eb532f5c122f17782bd57fb47baeeb767e2"
 dependencies = [
  "lzma-sys",
 ]

compiler/rustc_ast/src/ast.rs

@@ -287,12 +287,20 @@ pub enum TraitBoundModifier {
     /// No modifiers
     None,
 
+    /// `!Trait`
+    Negative,
+
     /// `?Trait`
     Maybe,
 
     /// `~const Trait`
     MaybeConst,
 
+    /// `~const !Trait`
+    //
+    // This parses but will be rejected during AST validation.
+    MaybeConstNegative,
+
     /// `~const ?Trait`
     //
     // This parses but will be rejected during AST validation.
@@ -2446,6 +2454,16 @@ impl fmt::Debug for ImplPolarity {
     }
 }
 
+#[derive(Copy, Clone, PartialEq, Encodable, Decodable, HashStable_Generic)]
+pub enum BoundPolarity {
+    /// `Type: Trait`
+    Positive,
+    /// `Type: !Trait`
+    Negative(Span),
+    /// `Type: ?Trait`
+    Maybe(Span),
+}
+
 #[derive(Clone, Encodable, Decodable, Debug)]
 pub enum FnRetTy {
     /// Returns type is not specified.

compiler/rustc_ast_lowering/src/lib.rs

@@ -1368,13 +1368,17 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
                         this.arena.alloc_from_iter(bounds.iter().filter_map(|bound| match bound {
                             GenericBound::Trait(
                                 ty,
-                                TraitBoundModifier::None | TraitBoundModifier::MaybeConst,
+                                TraitBoundModifier::None
+                                | TraitBoundModifier::MaybeConst
+                                | TraitBoundModifier::Negative,
                             ) => Some(this.lower_poly_trait_ref(ty, itctx)),
                             // `~const ?Bound` will cause an error during AST validation
                             // anyways, so treat it like `?Bound` as compilation proceeds.
                             GenericBound::Trait(
                                 _,
-                                TraitBoundModifier::Maybe | TraitBoundModifier::MaybeConstMaybe,
+                                TraitBoundModifier::Maybe
+                                | TraitBoundModifier::MaybeConstMaybe
+                                | TraitBoundModifier::MaybeConstNegative,
                             ) => None,
                             GenericBound::Outlives(lifetime) => {
                                 if lifetime_bound.is_none() {
@@ -2421,11 +2425,20 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
             TraitBoundModifier::None => hir::TraitBoundModifier::None,
             TraitBoundModifier::MaybeConst => hir::TraitBoundModifier::MaybeConst,
 
+            TraitBoundModifier::Negative => {
+                if self.tcx.features().negative_bounds {
+                    hir::TraitBoundModifier::Negative
+                } else {
+                    hir::TraitBoundModifier::None
+                }
+            }
+
             // `MaybeConstMaybe` will cause an error during AST validation, but we need to pick a
             // placeholder for compilation to proceed.
             TraitBoundModifier::MaybeConstMaybe | TraitBoundModifier::Maybe => {
                 hir::TraitBoundModifier::Maybe
             }
+            TraitBoundModifier::MaybeConstNegative => hir::TraitBoundModifier::MaybeConst,
         }
     }
 

compiler/rustc_ast_passes/messages.ftl

@@ -206,7 +206,7 @@ ast_passes_tilde_const_disallowed = `~const` is not allowed here
     .closure = closures cannot have `~const` trait bounds
     .function = this function is not `const`, so it cannot have `~const` trait bounds
 
-ast_passes_optional_const_exclusive = `~const` and `?` are mutually exclusive
+ast_passes_optional_const_exclusive = `~const` and `{$modifier}` are mutually exclusive
 
 ast_passes_const_and_async = functions cannot be both `const` and `async`
     .const = `const` because of this
@@ -235,3 +235,9 @@ ast_passes_incompatible_features = `{$f1}` and `{$f2}` are incompatible, using t
     .help = remove one of these features
 
 ast_passes_show_span = {$msg}
+
+ast_passes_negative_bound_not_supported =
+    negative bounds are not supported
+
+ast_passes_constraint_on_negative_bound =
+    associated type constraints not allowed on negative bounds

compiler/rustc_ast_passes/src/ast_validation.rs

@@ -1168,12 +1168,27 @@ impl<'a> Visitor<'a> for AstValidator<'a> {
                     });
                 }
                 (_, TraitBoundModifier::MaybeConstMaybe) => {
-                    self.err_handler().emit_err(errors::OptionalConstExclusive {span: bound.span()});
+                    self.err_handler().emit_err(errors::OptionalConstExclusive {span: bound.span(), modifier: "?" });
+                }
+                (_, TraitBoundModifier::MaybeConstNegative) => {
+                    self.err_handler().emit_err(errors::OptionalConstExclusive {span: bound.span(), modifier: "!" });
                 }
                 _ => {}
             }
         }
 
+        // Negative trait bounds are not allowed to have associated constraints
+        if let GenericBound::Trait(trait_ref, TraitBoundModifier::Negative) = bound
+            && let Some(segment) = trait_ref.trait_ref.path.segments.last()
+            && let Some(ast::GenericArgs::AngleBracketed(args)) = segment.args.as_deref()
+        {
+            for arg in &args.args {
+                if let ast::AngleBracketedArg::Constraint(constraint) = arg {
+                    self.err_handler().emit_err(errors::ConstraintOnNegativeBound { span: constraint.span });
+                }
+            }
+        }
+
         visit::walk_param_bound(self, bound)
     }
 

compiler/rustc_ast_passes/src/errors.rs

@@ -567,6 +567,7 @@ pub enum TildeConstReason {
 pub struct OptionalConstExclusive {
     #[primary_span]
     pub span: Span,
+    pub modifier: &'static str,
 }
 
 #[derive(Diagnostic)]
@@ -693,3 +694,17 @@ pub struct ShowSpan {
     pub span: Span,
     pub msg: &'static str,
 }
+
+#[derive(Diagnostic)]
+#[diag(ast_passes_negative_bound_not_supported)]
+pub struct NegativeBoundUnsupported {
+    #[primary_span]
+    pub span: Span,
+}
+
+#[derive(Diagnostic)]
+#[diag(ast_passes_constraint_on_negative_bound)]
+pub struct ConstraintOnNegativeBound {
+    #[primary_span]
+    pub span: Span,
+}

compiler/rustc_ast_passes/src/feature_gate.rs

@@ -603,6 +603,12 @@ pub fn check_crate(krate: &ast::Crate, sess: &Session) {
     gate_all!(dyn_star, "`dyn*` trait objects are experimental");
     gate_all!(const_closures, "const closures are experimental");
 
+    if !visitor.features.negative_bounds {
+        for &span in spans.get(&sym::negative_bounds).iter().copied().flatten() {
+            sess.emit_err(errors::NegativeBoundUnsupported { span });
+        }
+    }
+
     // All uses of `gate_all!` below this point were added in #65742,
     // and subsequently disabled (with the non-early gating readded).
     // We emit an early future-incompatible warning for these.

compiler/rustc_ast_pretty/src/pprust/state.rs

@@ -1570,12 +1570,19 @@ impl<'a> State<'a> {
                 GenericBound::Trait(tref, modifier) => {
                     match modifier {
                         TraitBoundModifier::None => {}
+                        TraitBoundModifier::Negative => {
+                            self.word("!");
+                        }
                         TraitBoundModifier::Maybe => {
                             self.word("?");
                         }
                         TraitBoundModifier::MaybeConst => {
                             self.word_space("~const");
                         }
+                        TraitBoundModifier::MaybeConstNegative => {
+                            self.word_space("~const");
+                            self.word("!");
+                        }
                         TraitBoundModifier::MaybeConstMaybe => {
                             self.word_space("~const");
                             self.word("?");

compiler/rustc_codegen_ssa/src/lib.rs

@@ -31,14 +31,15 @@ use rustc_middle::dep_graph::WorkProduct;
 use rustc_middle::middle::dependency_format::Dependencies;
 use rustc_middle::middle::exported_symbols::SymbolExportKind;
 use rustc_middle::ty::query::{ExternProviders, Providers};
-use rustc_serialize::opaque::{MemDecoder, MemEncoder};
+use rustc_serialize::opaque::{FileEncoder, MemDecoder};
 use rustc_serialize::{Decodable, Decoder, Encodable, Encoder};
 use rustc_session::config::{CrateType, OutputFilenames, OutputType, RUST_CGU_EXT};
 use rustc_session::cstore::{self, CrateSource};
 use rustc_session::utils::NativeLibKind;
 use rustc_span::symbol::Symbol;
 use rustc_span::DebuggerVisualizerFile;
 use std::collections::BTreeSet;
+use std::io;
 use std::path::{Path, PathBuf};
 
 pub mod back;
@@ -215,8 +216,11 @@ const RLINK_MAGIC: &[u8] = b"rustlink";
 const RUSTC_VERSION: Option<&str> = option_env!("CFG_VERSION");
 
 impl CodegenResults {
-    pub fn serialize_rlink(codegen_results: &CodegenResults) -> Vec<u8> {
-        let mut encoder = MemEncoder::new();
+    pub fn serialize_rlink(
+        rlink_file: &Path,
+        codegen_results: &CodegenResults,
+    ) -> Result<usize, io::Error> {
+        let mut encoder = FileEncoder::new(rlink_file)?;
         encoder.emit_raw_bytes(RLINK_MAGIC);
         // `emit_raw_bytes` is used to make sure that the version representation does not depend on
         // Encoder's inner representation of `u32`.

compiler/rustc_const_eval/src/const_eval/valtrees.rs

@@ -337,7 +337,7 @@ fn valtree_into_mplace<'tcx>(
 
     match ty.kind() {
         ty::FnDef(_, _) => {
-            ecx.write_immediate(Immediate::Uninit, &place.into()).unwrap();
+            // Zero-sized type, nothing to do.
         }
         ty::Bool | ty::Int(_) | ty::Uint(_) | ty::Float(_) | ty::Char => {
             let scalar_int = valtree.unwrap_leaf();