Rollup of 6 pull requests

compiler/rustc_builtin_macros/src/deriving/generic/mod.rs

@@ -181,11 +181,10 @@ use std::{iter, vec};
 use rustc_ast::ptr::P;
 use rustc_ast::{
     self as ast, BindingMode, ByRef, EnumDef, Expr, GenericArg, GenericParamKind, Generics,
-    Mutability, PatKind, TyKind, VariantData,
+    Mutability, PatKind, VariantData,
 };
 use rustc_attr as attr;
 use rustc_expand::base::{Annotatable, ExtCtxt};
-use rustc_session::lint::builtin::BYTE_SLICE_IN_PACKED_STRUCT_WITH_DERIVE;
 use rustc_span::symbol::{kw, sym, Ident, Symbol};
 use rustc_span::{Span, DUMMY_SP};
 use thin_vec::{thin_vec, ThinVec};
@@ -1599,52 +1598,11 @@ impl<'a> TraitDef<'a> {
                         ),
                     );
                     if is_packed {
-                        // In general, fields in packed structs are copied via a
-                        // block, e.g. `&{self.0}`. The two exceptions are `[u8]`
-                        // and `str` fields, which cannot be copied and also never
-                        // cause unaligned references. These exceptions are allowed
-                        // to handle the `FlexZeroSlice` type in the `zerovec`
-                        // crate within `icu4x-0.9.0`.
-                        //
-                        // Once use of `icu4x-0.9.0` has dropped sufficiently, this
-                        // exception should be removed.
-                        let is_simple_path = |ty: &P<ast::Ty>, sym| {
-                            if let TyKind::Path(None, ast::Path { segments, .. }) = &ty.kind
-                                && let [seg] = segments.as_slice()
-                                && seg.ident.name == sym
-                                && seg.args.is_none()
-                            {
-                                true
-                            } else {
-                                false
-                            }
-                        };
-
-                        let exception = if let TyKind::Slice(ty) = &struct_field.ty.kind
-                            && is_simple_path(ty, sym::u8)
-                        {
-                            Some("byte")
-                        } else if is_simple_path(&struct_field.ty, sym::str) {
-                            Some("string")
-                        } else {
-                            None
-                        };
-
-                        if let Some(ty) = exception {
-                            cx.sess.psess.buffer_lint(
-                                BYTE_SLICE_IN_PACKED_STRUCT_WITH_DERIVE,
-                                sp,
-                                ast::CRATE_NODE_ID,
-                                rustc_lint_defs::BuiltinLintDiag::ByteSliceInPackedStructWithDerive {
-                                    ty: ty.to_string(),
-                                },
-                            );
-                        } else {
-                            // Wrap the expression in `{...}`, causing a copy.
-                            field_expr = cx.expr_block(
-                                cx.block(struct_field.span, thin_vec![cx.stmt_expr(field_expr)]),
-                            );
-                        }
+                        // Fields in packed structs are wrapped in a block, e.g. `&{self.0}`,
+                        // causing a copy instead of a (potentially misaligned) reference.
+                        field_expr = cx.expr_block(
+                            cx.block(struct_field.span, thin_vec![cx.stmt_expr(field_expr)]),
+                        );
                     }
                     cx.expr_addr_of(sp, field_expr)
                 })

compiler/rustc_feature/src/removed.rs

@@ -82,6 +82,9 @@ declare_features! (
     /// Allows the use of `#[derive(Anything)]` as sugar for `#[derive_Anything]`.
     (removed, custom_derive, "1.32.0", Some(29644),
      Some("subsumed by `#[proc_macro_derive]`")),
+    /// Allows default type parameters to influence type inference.
+    (removed, default_type_parameter_fallback, "CURRENT_RUSTC_VERSION", Some(27336),
+     Some("never properly implemented; requires significant design work")),
     /// Allows using `#[doc(keyword = "...")]`.
     (removed, doc_keyword, "1.28.0", Some(51315),
      Some("merged into `#![feature(rustdoc_internals)]`")),

compiler/rustc_feature/src/unstable.rs

@@ -431,8 +431,6 @@ declare_features! (
     (unstable, custom_test_frameworks, "1.30.0", Some(50297)),
     /// Allows declarative macros 2.0 (`macro`).
     (unstable, decl_macro, "1.17.0", Some(39412)),
-    /// Allows default type parameters to influence type inference.
-    (unstable, default_type_parameter_fallback, "1.3.0", Some(27336)),
     /// Allows using `#[deprecated_safe]` to deprecate the safeness of a function or trait
     (unstable, deprecated_safe, "1.61.0", Some(94978)),
     /// Allows having using `suggestion` in the `#[deprecated]` attribute.

compiler/rustc_hir_analysis/src/collect/generics_of.rs

@@ -338,8 +338,6 @@ pub(super) fn generics_of(tcx: TyCtxt<'_>, def_id: LocalDefId) -> ty::Generics {
             if default.is_some() {
                 match allow_defaults {
                     Defaults::Allowed => {}
-                    Defaults::FutureCompatDisallowed
-                        if tcx.features().default_type_parameter_fallback => {}
                     Defaults::FutureCompatDisallowed => {
                         tcx.node_span_lint(
                             lint::builtin::INVALID_TYPE_PARAM_DEFAULT,

compiler/rustc_lint/src/lib.rs

@@ -543,7 +543,7 @@ fn register_builtins(store: &mut LintStore) {
     );
     store.register_removed(
         "suspicious_auto_trait_impls",
-        "no longer needed, see #93367 \
+        "no longer needed, see issue #93367 \
          <https://github.com/rust-lang/rust/issues/93367> for more information",
     );
     store.register_removed(
@@ -565,6 +565,11 @@ fn register_builtins(store: &mut LintStore) {
         "box_pointers",
         "it does not detect other kinds of allocations, and existed only for historical reasons",
     );
+    store.register_removed(
+        "byte_slice_in_packed_struct_with_derive",
+        "converted into hard error, see issue #107457 \
+         <https://github.com/rust-lang/rust/issues/107457> for more information",
+    )
 }
 
 fn register_internals(store: &mut LintStore) {

compiler/rustc_lint_defs/src/builtin.rs

@@ -26,7 +26,6 @@ declare_lint_pass! {
         BARE_TRAIT_OBJECTS,
         BINDINGS_WITH_VARIANT_NAME,
         BREAK_WITH_LABEL_AND_LOOP,
-        BYTE_SLICE_IN_PACKED_STRUCT_WITH_DERIVE,
         CENUM_IMPL_DROP_CAST,
         COHERENCE_LEAK_CHECK,
         CONFLICTING_REPR_HINTS,
@@ -1267,7 +1266,7 @@ declare_lint! {
     Deny,
     "type parameter default erroneously allowed in invalid location",
     @future_incompatible = FutureIncompatibleInfo {
-        reason: FutureIncompatibilityReason::FutureReleaseErrorDontReportInDeps,
+        reason: FutureIncompatibilityReason::FutureReleaseErrorReportInDeps,
         reference: "issue #36887 <https://github.com/rust-lang/rust/issues/36887>",
     };
 }
@@ -4315,39 +4314,6 @@ declare_lint! {
     report_in_external_macro
 }
 
-declare_lint! {
-    /// The `byte_slice_in_packed_struct_with_derive` lint detects cases where a byte slice field
-    /// (`[u8]`) or string slice field (`str`) is used in a `packed` struct that derives one or
-    /// more built-in traits.
-    ///
-    /// ### Example
-    ///
-    /// ```rust
-    /// #[repr(packed)]
-    /// #[derive(Hash)]
-    /// struct FlexZeroSlice {
-    ///     width: u8,
-    ///     data: [u8],
-    /// }
-    /// ```
-    ///
-    /// {{produces}}
-    ///
-    /// ### Explanation
-    ///
-    /// This was previously accepted but is being phased out, because fields in packed structs are
-    /// now required to implement `Copy` for `derive` to work. Byte slices and string slices are a
-    /// temporary exception because certain crates depended on them.
-    pub BYTE_SLICE_IN_PACKED_STRUCT_WITH_DERIVE,
-    Warn,
-    "`[u8]` or `str` used in a packed struct with `derive`",
-    @future_incompatible = FutureIncompatibleInfo {
-        reason: FutureIncompatibilityReason::FutureReleaseErrorReportInDeps,
-        reference: "issue #107457 <https://github.com/rust-lang/rust/issues/107457>",
-    };
-    report_in_external_macro
-}
-
 declare_lint! {
     /// The `invalid_macro_export_arguments` lint detects cases where `#[macro_export]` is being used with invalid arguments.
     ///

compiler/rustc_passes/src/check_attr.rs

@@ -116,130 +116,130 @@ impl<'tcx> CheckAttrVisitor<'tcx> {
         let attrs = self.tcx.hir().attrs(hir_id);
         for attr in attrs {
             match attr.path().as_slice() {
-                [sym::diagnostic, sym::do_not_recommend] => {
+                [sym::diagnostic, sym::do_not_recommend, ..] => {
                     self.check_do_not_recommend(attr.span, hir_id, target)
                 }
-                [sym::diagnostic, sym::on_unimplemented] => {
+                [sym::diagnostic, sym::on_unimplemented, ..] => {
                     self.check_diagnostic_on_unimplemented(attr.span, hir_id, target)
                 }
-                [sym::inline] => self.check_inline(hir_id, attr, span, target),
-                [sym::coverage] => self.check_coverage(attr, span, target),
-                [sym::optimize] => self.check_optimize(hir_id, attr, target),
-                [sym::non_exhaustive] => self.check_non_exhaustive(hir_id, attr, span, target),
-                [sym::marker] => self.check_marker(hir_id, attr, span, target),
-                [sym::target_feature] => {
+                [sym::inline, ..] => self.check_inline(hir_id, attr, span, target),
+                [sym::coverage, ..] => self.check_coverage(attr, span, target),
+                [sym::optimize, ..] => self.check_optimize(hir_id, attr, target),
+                [sym::non_exhaustive, ..] => self.check_non_exhaustive(hir_id, attr, span, target),
+                [sym::marker, ..] => self.check_marker(hir_id, attr, span, target),
+                [sym::target_feature, ..] => {
                     self.check_target_feature(hir_id, attr, span, target, attrs)
                 }
-                [sym::thread_local] => self.check_thread_local(attr, span, target),
-                [sym::track_caller] => {
+                [sym::thread_local, ..] => self.check_thread_local(attr, span, target),
+                [sym::track_caller, ..] => {
                     self.check_track_caller(hir_id, attr.span, attrs, span, target)
                 }
-                [sym::doc] => self.check_doc_attrs(
+                [sym::doc, ..] => self.check_doc_attrs(
                     attr,
                     hir_id,
                     target,
                     &mut specified_inline,
                     &mut doc_aliases,
                 ),
-                [sym::no_link] => self.check_no_link(hir_id, attr, span, target),
-                [sym::export_name] => self.check_export_name(hir_id, attr, span, target),
-                [sym::rustc_layout_scalar_valid_range_start]
-                | [sym::rustc_layout_scalar_valid_range_end] => {
+                [sym::no_link, ..] => self.check_no_link(hir_id, attr, span, target),
+                [sym::export_name, ..] => self.check_export_name(hir_id, attr, span, target),
+                [sym::rustc_layout_scalar_valid_range_start, ..]
+                | [sym::rustc_layout_scalar_valid_range_end, ..] => {
                     self.check_rustc_layout_scalar_valid_range(attr, span, target)
                 }
-                [sym::allow_internal_unstable] => {
+                [sym::allow_internal_unstable, ..] => {
                     self.check_allow_internal_unstable(hir_id, attr, span, target, attrs)
                 }
-                [sym::debugger_visualizer] => self.check_debugger_visualizer(attr, target),
-                [sym::rustc_allow_const_fn_unstable] => {
+                [sym::debugger_visualizer, ..] => self.check_debugger_visualizer(attr, target),
+                [sym::rustc_allow_const_fn_unstable, ..] => {
                     self.check_rustc_allow_const_fn_unstable(hir_id, attr, span, target)
                 }
-                [sym::rustc_std_internal_symbol] => {
+                [sym::rustc_std_internal_symbol, ..] => {
                     self.check_rustc_std_internal_symbol(attr, span, target)
                 }
-                [sym::naked] => self.check_naked(hir_id, attr, span, target, attrs),
-                [sym::rustc_never_returns_null_ptr] => {
+                [sym::naked, ..] => self.check_naked(hir_id, attr, span, target, attrs),
+                [sym::rustc_never_returns_null_ptr, ..] => {
                     self.check_applied_to_fn_or_method(hir_id, attr, span, target)
                 }
-                [sym::rustc_legacy_const_generics] => {
+                [sym::rustc_legacy_const_generics, ..] => {
                     self.check_rustc_legacy_const_generics(hir_id, attr, span, target, item)
                 }
-                [sym::rustc_lint_query_instability] => {
+                [sym::rustc_lint_query_instability, ..] => {
                     self.check_rustc_lint_query_instability(hir_id, attr, span, target)
                 }
-                [sym::rustc_lint_diagnostics] => {
+                [sym::rustc_lint_diagnostics, ..] => {
                     self.check_rustc_lint_diagnostics(hir_id, attr, span, target)
                 }
-                [sym::rustc_lint_opt_ty] => self.check_rustc_lint_opt_ty(attr, span, target),
-                [sym::rustc_lint_opt_deny_field_access] => {
+                [sym::rustc_lint_opt_ty, ..] => self.check_rustc_lint_opt_ty(attr, span, target),
+                [sym::rustc_lint_opt_deny_field_access, ..] => {
                     self.check_rustc_lint_opt_deny_field_access(attr, span, target)
                 }
-                [sym::rustc_clean]
-                | [sym::rustc_dirty]
-                | [sym::rustc_if_this_changed]
-                | [sym::rustc_then_this_would_need] => self.check_rustc_dirty_clean(attr),
-                [sym::rustc_coinductive]
-                | [sym::rustc_must_implement_one_of]
-                | [sym::rustc_deny_explicit_impl]
-                | [sym::const_trait] => self.check_must_be_applied_to_trait(attr, span, target),
-                [sym::cmse_nonsecure_entry] => {
+                [sym::rustc_clean, ..]
+                | [sym::rustc_dirty, ..]
+                | [sym::rustc_if_this_changed, ..]
+                | [sym::rustc_then_this_would_need, ..] => self.check_rustc_dirty_clean(attr),
+                [sym::rustc_coinductive, ..]
+                | [sym::rustc_must_implement_one_of, ..]
+                | [sym::rustc_deny_explicit_impl, ..]
+                | [sym::const_trait, ..] => self.check_must_be_applied_to_trait(attr, span, target),
+                [sym::cmse_nonsecure_entry, ..] => {
                     self.check_cmse_nonsecure_entry(hir_id, attr, span, target)
                 }
-                [sym::collapse_debuginfo] => self.check_collapse_debuginfo(attr, span, target),
-                [sym::must_not_suspend] => self.check_must_not_suspend(attr, span, target),
-                [sym::must_use] => self.check_must_use(hir_id, attr, target),
-                [sym::rustc_pass_by_value] => self.check_pass_by_value(attr, span, target),
-                [sym::rustc_allow_incoherent_impl] => {
+                [sym::collapse_debuginfo, ..] => self.check_collapse_debuginfo(attr, span, target),
+                [sym::must_not_suspend, ..] => self.check_must_not_suspend(attr, span, target),
+                [sym::must_use, ..] => self.check_must_use(hir_id, attr, target),
+                [sym::rustc_pass_by_value, ..] => self.check_pass_by_value(attr, span, target),
+                [sym::rustc_allow_incoherent_impl, ..] => {
                     self.check_allow_incoherent_impl(attr, span, target)
                 }
-                [sym::rustc_has_incoherent_inherent_impls] => {
+                [sym::rustc_has_incoherent_inherent_impls, ..] => {
                     self.check_has_incoherent_inherent_impls(attr, span, target)
                 }
-                [sym::ffi_pure] => self.check_ffi_pure(attr.span, attrs, target),
-                [sym::ffi_const] => self.check_ffi_const(attr.span, target),
-                [sym::rustc_const_unstable]
-                | [sym::rustc_const_stable]
-                | [sym::unstable]
-                | [sym::stable]
-                | [sym::rustc_allowed_through_unstable_modules]
-                | [sym::rustc_promotable] => self.check_stability_promotable(attr, target),
-                [sym::link_ordinal] => self.check_link_ordinal(attr, span, target),
-                [sym::rustc_confusables] => self.check_confusables(attr, target),
-                [sym::rustc_safe_intrinsic] => {
+                [sym::ffi_pure, ..] => self.check_ffi_pure(attr.span, attrs, target),
+                [sym::ffi_const, ..] => self.check_ffi_const(attr.span, target),
+                [sym::rustc_const_unstable, ..]
+                | [sym::rustc_const_stable, ..]
+                | [sym::unstable, ..]
+                | [sym::stable, ..]
+                | [sym::rustc_allowed_through_unstable_modules, ..]
+                | [sym::rustc_promotable, ..] => self.check_stability_promotable(attr, target),
+                [sym::link_ordinal, ..] => self.check_link_ordinal(attr, span, target),
+                [sym::rustc_confusables, ..] => self.check_confusables(attr, target),
+                [sym::rustc_safe_intrinsic, ..] => {
                     self.check_rustc_safe_intrinsic(hir_id, attr, span, target)
                 }
-                [sym::cold] => self.check_cold(hir_id, attr, span, target),
-                [sym::link] => self.check_link(hir_id, attr, span, target),
-                [sym::link_name] => self.check_link_name(hir_id, attr, span, target),
-                [sym::link_section] => self.check_link_section(hir_id, attr, span, target),
-                [sym::no_mangle] => self.check_no_mangle(hir_id, attr, span, target),
-                [sym::deprecated] => self.check_deprecated(hir_id, attr, span, target),
-                [sym::macro_use] | [sym::macro_escape] => {
+                [sym::cold, ..] => self.check_cold(hir_id, attr, span, target),
+                [sym::link, ..] => self.check_link(hir_id, attr, span, target),
+                [sym::link_name, ..] => self.check_link_name(hir_id, attr, span, target),
+                [sym::link_section, ..] => self.check_link_section(hir_id, attr, span, target),
+                [sym::no_mangle, ..] => self.check_no_mangle(hir_id, attr, span, target),
+                [sym::deprecated, ..] => self.check_deprecated(hir_id, attr, span, target),
+                [sym::macro_use, ..] | [sym::macro_escape, ..] => {
                     self.check_macro_use(hir_id, attr, target)
                 }
-                [sym::path] => self.check_generic_attr(hir_id, attr, target, Target::Mod),
-                [sym::macro_export] => self.check_macro_export(hir_id, attr, target),
-                [sym::ignore] | [sym::should_panic] => {
+                [sym::path, ..] => self.check_generic_attr(hir_id, attr, target, Target::Mod),
+                [sym::macro_export, ..] => self.check_macro_export(hir_id, attr, target),
+                [sym::ignore, ..] | [sym::should_panic, ..] => {
                     self.check_generic_attr(hir_id, attr, target, Target::Fn)
                 }
-                [sym::automatically_derived] => {
+                [sym::automatically_derived, ..] => {
                     self.check_generic_attr(hir_id, attr, target, Target::Impl)
                 }
-                [sym::no_implicit_prelude] => {
+                [sym::no_implicit_prelude, ..] => {
                     self.check_generic_attr(hir_id, attr, target, Target::Mod)
                 }
-                [sym::rustc_object_lifetime_default] => self.check_object_lifetime_default(hir_id),
-                [sym::proc_macro] => {
+                [sym::rustc_object_lifetime_default, ..] => self.check_object_lifetime_default(hir_id),
+                [sym::proc_macro, ..] => {
                     self.check_proc_macro(hir_id, target, ProcMacroKind::FunctionLike)
                 }
-                [sym::proc_macro_attribute] => {
+                [sym::proc_macro_attribute, ..] => {
                     self.check_proc_macro(hir_id, target, ProcMacroKind::Attribute);
                 }
-                [sym::proc_macro_derive] => {
+                [sym::proc_macro_derive, ..] => {
                     self.check_generic_attr(hir_id, attr, target, Target::Fn);
                     self.check_proc_macro(hir_id, target, ProcMacroKind::Derive)
                 }
-                [sym::coroutine] => {
+                [sym::coroutine, ..] => {
                     self.check_coroutine(attr, target);
                 }
                 [
@@ -273,14 +273,16 @@ impl<'tcx> CheckAttrVisitor<'tcx> {
                     | sym::default_lib_allocator
                     | sym::start
                     | sym::custom_mir,
+                    ..
                 ] => {}
                 [name, ..] => {
                     match BUILTIN_ATTRIBUTE_MAP.get(name) {
                         // checked below
                         Some(BuiltinAttribute { type_: AttributeType::CrateLevel, .. }) => {}
                         Some(_) => {
-                            // FIXME: differentiate between unstable and internal attributes just like we do with features instead
-                            // of just accepting `rustc_` attributes by name. That should allow trimming the above list, too.
+                            // FIXME: differentiate between unstable and internal attributes just
+                            // like we do with features instead of just accepting `rustc_`
+                            // attributes by name. That should allow trimming the above list, too.
                             if !name.as_str().starts_with("rustc_") {
                                 span_bug!(
                                     attr.span,

config.example.toml

@@ -472,7 +472,8 @@
 # This is mostly useful for tools; if you have changes to `compiler/` or `library/` they will be ignored.
 #
 # Set this to "if-unchanged" to only download if the compiler and standard library have not been modified.
-# Set this to `true` to download unconditionally (useful if e.g. you are only changing doc-comments).
+# Set this to `true` to download unconditionally. This is useful if you are working on tools, doc-comments,
+# or library (you will be able to build the standard library without needing to build the compiler).
 #download-rustc = false
 
 # Number of codegen units to use for each compiler invocation. A value of 0

src/bootstrap/src/core/build_steps/compile.rs

@@ -26,7 +26,8 @@ use crate::core::builder::{
 use crate::core::config::{DebuginfoLevel, LlvmLibunwind, RustcLto, TargetSelection};
 use crate::utils::exec::command;
 use crate::utils::helpers::{
-    exe, get_clang_cl_resource_dir, is_debug_info, is_dylib, symlink_dir, t, up_to_date,
+    self, exe, get_clang_cl_resource_dir, get_closest_merge_base_commit, is_debug_info, is_dylib,
+    symlink_dir, t, up_to_date,
 };
 use crate::{CLang, Compiler, DependencyType, GitRepo, Mode, LLVM_TOOLS};
 
@@ -114,21 +115,43 @@ impl Step for Std {
     const DEFAULT: bool = true;
 
     fn should_run(run: ShouldRun<'_>) -> ShouldRun<'_> {
-        // When downloading stage1, the standard library has already been copied to the sysroot, so
-        // there's no need to rebuild it.
-        let builder = run.builder;
-        run.crate_or_deps("sysroot")
-            .path("library")
-            .lazy_default_condition(Box::new(|| !builder.download_rustc()))
+        run.crate_or_deps("sysroot").path("library")
     }
 
     fn make_run(run: RunConfig<'_>) {
         let crates = std_crates_for_run_make(&run);
+        let builder = run.builder;
+
+        // Force compilation of the standard library from source if the `library` is modified. This allows
+        // library team to compile the standard library without needing to compile the compiler with
+        // the `rust.download-rustc=true` option.
+        let force_recompile =
+            if builder.rust_info().is_managed_git_subrepository() && builder.download_rustc() {
+                let closest_merge_commit = get_closest_merge_base_commit(
+                    Some(&builder.src),
+                    &builder.config.git_config(),
+                    &builder.config.stage0_metadata.config.git_merge_commit_email,
+                    &[],
+                )
+                .unwrap();
+
+                // Check if `library` has changes (returns false otherwise)
+                !t!(helpers::git(Some(&builder.src))
+                    .args(["diff-index", "--quiet", &closest_merge_commit])
+                    .arg("--")
+                    .arg(builder.src.join("library"))
+                    .as_command_mut()
+                    .status())
+                .success()
+            } else {
+                false
+            };
+
         run.builder.ensure(Std {
             compiler: run.builder.compiler(run.builder.top_stage, run.build_triple()),
             target: run.target,
             crates,
-            force_recompile: false,
+            force_recompile,
             extra_rust_args: &[],
             is_for_mir_opt_tests: false,
         });

tests/codegen/issues/issue-122600-ptr-discriminant-update.rs

@@ -0,0 +1,19 @@
+//@ compile-flags: -O
+//@ min-llvm-version: 19
+
+#![crate_type = "lib"]
+
+pub enum State {
+    A([u8; 753]),
+    B([u8; 753]),
+}
+
+// CHECK-LABEL: @update
+#[no_mangle]
+pub unsafe fn update(s: *mut State) {
+    // CHECK-NEXT: start:
+    // CHECK-NEXT: store i8
+    // CHECK-NEXT: ret
+    let State::A(v) = s.read() else { std::hint::unreachable_unchecked() };
+    s.write(State::B(v));
+}

tests/ui/attributes/check-builtin-attr-ice.rs

@@ -0,0 +1,58 @@
+//! Regression test for #128622.
+//!
+//! PR #128581 introduced an assertion that all builtin attributes are actually checked via
+//! `CheckAttrVisitor` and aren't accidentally usable on completely unrelated HIR nodes.
+//! Unfortunately, the check had correctness problems.
+//!
+//! The match on attribute path segments looked like
+//!
+//! ```rs,ignore
+//! [sym::should_panic] => /* check is implemented */
+//! match BUILTIN_ATTRIBUTE_MAP.get(name) {
+//!     // checked below
+//!     Some(BuiltinAttribute { type_: AttributeType::CrateLevel, .. }) => {}
+//!     Some(_) => {
+//!         if !name.as_str().starts_with("rustc_") {
+//!             span_bug!(
+//!                 attr.span,
+//!                 "builtin attribute {name:?} not handled by `CheckAttrVisitor`"
+//!             )
+//!         }
+//!     }
+//!     None => (),
+//! }
+//! ```
+//!
+//! However, it failed to account for edge cases such as an attribute whose:
+//!
+//! 1. path segments *starts* with a builtin attribute such as `should_panic`
+//! 2. which does not start with `rustc_`, and
+//! 3. is also an `AttributeType::Normal` attribute upon registration with the builtin attribute map
+//!
+//! These conditions when all satisfied cause the span bug to be issued for e.g.
+//! `#[should_panic::skip]` because the `[sym::should_panic]` arm is not matched (since it's
+//! `[sym::should_panic, sym::skip]`).
+//!
+//! This test checks that the span bug is not fired for such cases.
+//!
+//! issue: rust-lang/rust#128622
+
+// Notably, `should_panic` is a `AttributeType::Normal` attribute that is checked separately.
+
+struct Foo {
+    #[should_panic::skip]
+    //~^ ERROR failed to resolve
+    pub field: u8,
+
+    #[should_panic::a::b::c]
+    //~^ ERROR failed to resolve
+    pub field2: u8,
+}
+
+fn foo() {}
+
+fn main() {
+    #[deny::skip]
+    //~^ ERROR failed to resolve
+    foo();
+}

tests/ui/attributes/check-builtin-attr-ice.stderr

@@ -0,0 +1,21 @@
+error[E0433]: failed to resolve: use of undeclared crate or module `should_panic`
+  --> $DIR/check-builtin-attr-ice.rs:43:7
+   |
+LL |     #[should_panic::skip]
+   |       ^^^^^^^^^^^^ use of undeclared crate or module `should_panic`
+
+error[E0433]: failed to resolve: use of undeclared crate or module `should_panic`
+  --> $DIR/check-builtin-attr-ice.rs:47:7
+   |
+LL |     #[should_panic::a::b::c]
+   |       ^^^^^^^^^^^^ use of undeclared crate or module `should_panic`
+
+error[E0433]: failed to resolve: use of undeclared crate or module `deny`
+  --> $DIR/check-builtin-attr-ice.rs:55:7
+   |
+LL |     #[deny::skip]
+   |       ^^^^ use of undeclared crate or module `deny`
+
+error: aborting due to 3 previous errors
+
+For more information about this error, try `rustc --explain E0433`.

tests/ui/derives/deriving-with-repr-packed.rs

@@ -22,25 +22,22 @@ struct Y(usize);
 struct X(Y);
 //~^ ERROR cannot move out of `self` which is behind a shared reference
 
-// This is currently allowed, but will be phased out at some point. From
-// `zerovec` within icu4x-0.9.0.
 #[derive(Debug)]
 #[repr(packed)]
 struct FlexZeroSlice {
     width: u8,
     data: [u8],
-    //~^ WARNING byte slice in a packed struct that derives a built-in trait
-    //~^^ this was previously accepted
+    //~^ ERROR cannot move
+    //~| ERROR cannot move
 }
 
-// Again, currently allowed, but will be phased out.
 #[derive(Debug)]
 #[repr(packed)]
 struct WithStr {
     width: u8,
     data: str,
-    //~^ WARNING string slice in a packed struct that derives a built-in trait
-    //~^^ this was previously accepted
+    //~^ ERROR cannot move
+    //~| ERROR cannot move
 }
 
 fn main() {}

tests/ui/derives/deriving-with-repr-packed.stderr

@@ -1,32 +1,3 @@
-warning: byte slice in a packed struct that derives a built-in trait
-  --> $DIR/deriving-with-repr-packed.rs:31:5
-   |
-LL | #[derive(Debug)]
-   |          ----- in this derive macro expansion
-...
-LL |     data: [u8],
-   |     ^^^^^^^^^^
-   |
-   = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
-   = note: for more information, see issue #107457 <https://github.com/rust-lang/rust/issues/107457>
-   = help: consider implementing the trait by hand, or remove the `packed` attribute
-   = note: `#[warn(byte_slice_in_packed_struct_with_derive)]` on by default
-   = note: this warning originates in the derive macro `Debug` (in Nightly builds, run with -Z macro-backtrace for more info)
-
-warning: string slice in a packed struct that derives a built-in trait
-  --> $DIR/deriving-with-repr-packed.rs:41:5
-   |
-LL | #[derive(Debug)]
-   |          ----- in this derive macro expansion
-...
-LL |     data: str,
-   |     ^^^^^^^^^
-   |
-   = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
-   = note: for more information, see issue #107457 <https://github.com/rust-lang/rust/issues/107457>
-   = help: consider implementing the trait by hand, or remove the `packed` attribute
-   = note: this warning originates in the derive macro `Debug` (in Nightly builds, run with -Z macro-backtrace for more info)
-
 error[E0507]: cannot move out of `self` which is behind a shared reference
   --> $DIR/deriving-with-repr-packed.rs:22:10
    |
@@ -47,38 +18,43 @@ LL | struct X(Y);
    = note: `#[derive(Debug)]` triggers a move because taking references to the fields of a packed struct is undefined behaviour
    = note: this error originates in the derive macro `Debug` (in Nightly builds, run with -Z macro-backtrace for more info)
 
-error: aborting due to 1 previous error; 2 warnings emitted
+error[E0161]: cannot move a value of type `[u8]`
+  --> $DIR/deriving-with-repr-packed.rs:29:5
+   |
+LL |     data: [u8],
+   |     ^^^^^^^^^^ the size of `[u8]` cannot be statically determined
 
-For more information about this error, try `rustc --explain E0507`.
-Future incompatibility report: Future breakage diagnostic:
-warning: byte slice in a packed struct that derives a built-in trait
-  --> $DIR/deriving-with-repr-packed.rs:31:5
+error[E0507]: cannot move out of `self.data` which is behind a shared reference
+  --> $DIR/deriving-with-repr-packed.rs:29:5
    |
 LL | #[derive(Debug)]
    |          ----- in this derive macro expansion
 ...
 LL |     data: [u8],
-   |     ^^^^^^^^^^
+   |     ^^^^^^^^^^ move occurs because `self.data` has type `[u8]`, which does not implement the `Copy` trait
+   |
+   = note: `#[derive(Debug)]` triggers a move because taking references to the fields of a packed struct is undefined behaviour
+   = note: this error originates in the derive macro `Debug` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+error[E0161]: cannot move a value of type `str`
+  --> $DIR/deriving-with-repr-packed.rs:38:5
    |
-   = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
-   = note: for more information, see issue #107457 <https://github.com/rust-lang/rust/issues/107457>
-   = help: consider implementing the trait by hand, or remove the `packed` attribute
-   = note: `#[warn(byte_slice_in_packed_struct_with_derive)]` on by default
-   = note: this warning originates in the derive macro `Debug` (in Nightly builds, run with -Z macro-backtrace for more info)
+LL |     data: str,
+   |     ^^^^^^^^^ the size of `str` cannot be statically determined
 
-Future breakage diagnostic:
-warning: string slice in a packed struct that derives a built-in trait
-  --> $DIR/deriving-with-repr-packed.rs:41:5
+error[E0507]: cannot move out of `self.data` which is behind a shared reference
+  --> $DIR/deriving-with-repr-packed.rs:38:5
    |
 LL | #[derive(Debug)]
    |          ----- in this derive macro expansion
 ...
 LL |     data: str,
-   |     ^^^^^^^^^
+   |     ^^^^^^^^^ move occurs because `self.data` has type `str`, which does not implement the `Copy` trait
    |
-   = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
-   = note: for more information, see issue #107457 <https://github.com/rust-lang/rust/issues/107457>
-   = help: consider implementing the trait by hand, or remove the `packed` attribute
-   = note: `#[warn(byte_slice_in_packed_struct_with_derive)]` on by default
-   = note: this warning originates in the derive macro `Debug` (in Nightly builds, run with -Z macro-backtrace for more info)
+   = note: `#[derive(Debug)]` triggers a move because taking references to the fields of a packed struct is undefined behaviour
+   = note: this error originates in the derive macro `Debug` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+error: aborting due to 5 previous errors
 
+Some errors have detailed explanations: E0161, E0507.
+For more information about an error, try `rustc --explain E0161`.

tests/ui/deriving/deriving-all-codegen.rs

@@ -73,16 +73,6 @@ impl Copy for PackedManualCopy {}
 #[derive(Debug, Hash, PartialEq, Eq, PartialOrd, Ord)]
 struct Unsized([u32]);
 
-// A packed struct with an unsized `[u8]` field. This is currently allowed, but
-// causes a warning and will be phased out at some point.
-#[derive(Debug, Hash)]
-#[repr(packed)]
-struct PackedUnsizedU8([u8]);
-//~^ WARNING byte slice in a packed struct that derives a built-in trait
-//~^^ WARNING byte slice in a packed struct that derives a built-in trait
-//~^^^ this was previously accepted
-//~^^^^ this was previously accepted
-
 trait Trait {
     type A;
 }

tests/ui/deriving/deriving-all-codegen.stdout

@@ -516,26 +516,6 @@ impl ::core::cmp::Ord for Unsized {
     }
 }
 
-// A packed struct with an unsized `[u8]` field. This is currently allowed, but
-// causes a warning and will be phased out at some point.
-#[repr(packed)]
-struct PackedUnsizedU8([u8]);
-#[automatically_derived]
-impl ::core::fmt::Debug for PackedUnsizedU8 {
-    #[inline]
-    fn fmt(&self, f: &mut ::core::fmt::Formatter) -> ::core::fmt::Result {
-        ::core::fmt::Formatter::debug_tuple_field1_finish(f,
-            "PackedUnsizedU8", &&self.0)
-    }
-}
-#[automatically_derived]
-impl ::core::hash::Hash for PackedUnsizedU8 {
-    #[inline]
-    fn hash<__H: ::core::hash::Hasher>(&self, state: &mut __H) -> () {
-        ::core::hash::Hash::hash(&self.0, state)
-    }
-}
-
 trait Trait {
     type A;
 }

tests/ui/impl-trait/where-allowed.stderr

@@ -433,3 +433,25 @@ error: aborting due to 50 previous errors
 
 Some errors have detailed explanations: E0053, E0118, E0283, E0562, E0599, E0658, E0666.
 For more information about an error, try `rustc --explain E0053`.
+Future incompatibility report: Future breakage diagnostic:
+error: defaults for type parameters are only allowed in `struct`, `enum`, `type`, or `trait` definitions
+  --> $DIR/where-allowed.rs:239:7
+   |
+LL | impl <T = impl Debug> T {}
+   |       ^^^^^^^^^^^^^^
+   |
+   = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
+   = note: for more information, see issue #36887 <https://github.com/rust-lang/rust/issues/36887>
+   = note: `#[deny(invalid_type_param_default)]` on by default
+
+Future breakage diagnostic:
+error: defaults for type parameters are only allowed in `struct`, `enum`, `type`, or `trait` definitions
+  --> $DIR/where-allowed.rs:246:36
+   |
+LL | fn in_method_generic_param_default<T = impl Debug>(_: T) {}
+   |                                    ^^^^^^^^^^^^^^
+   |
+   = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
+   = note: for more information, see issue #36887 <https://github.com/rust-lang/rust/issues/36887>
+   = note: `#[deny(invalid_type_param_default)]` on by default
+

tests/ui/issues/issue-26812.rs

@@ -1,6 +1,6 @@
-#![feature(default_type_parameter_fallback)]
-
 fn avg<T=T::Item>(_: T) {}
 //~^ ERROR generic parameters with a default cannot use forward declared identifiers
+//~| ERROR defaults for type parameters
+//~| WARN previously accepted
 
 fn main() {}

tests/ui/issues/issue-26812.stderr

@@ -1,9 +1,30 @@
 error[E0128]: generic parameters with a default cannot use forward declared identifiers
-  --> $DIR/issue-26812.rs:3:10
+  --> $DIR/issue-26812.rs:1:10
    |
 LL | fn avg<T=T::Item>(_: T) {}
    |          ^^^^^^^ defaulted generic parameters cannot be forward declared
 
-error: aborting due to 1 previous error
+error: defaults for type parameters are only allowed in `struct`, `enum`, `type`, or `trait` definitions
+  --> $DIR/issue-26812.rs:1:8
+   |
+LL | fn avg<T=T::Item>(_: T) {}
+   |        ^^^^^^^^^
+   |
+   = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
+   = note: for more information, see issue #36887 <https://github.com/rust-lang/rust/issues/36887>
+   = note: `#[deny(invalid_type_param_default)]` on by default
+
+error: aborting due to 2 previous errors
 
 For more information about this error, try `rustc --explain E0128`.
+Future incompatibility report: Future breakage diagnostic:
+error: defaults for type parameters are only allowed in `struct`, `enum`, `type`, or `trait` definitions
+  --> $DIR/issue-26812.rs:1:8
+   |
+LL | fn avg<T=T::Item>(_: T) {}
+   |        ^^^^^^^^^
+   |
+   = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
+   = note: for more information, see issue #36887 <https://github.com/rust-lang/rust/issues/36887>
+   = note: `#[deny(invalid_type_param_default)]` on by default
+

tests/ui/lifetimes/unusual-rib-combinations.stderr

@@ -72,3 +72,14 @@ error: aborting due to 8 previous errors
 
 Some errors have detailed explanations: E0106, E0214, E0308, E0770.
 For more information about an error, try `rustc --explain E0106`.
+Future incompatibility report: Future breakage diagnostic:
+error: defaults for type parameters are only allowed in `struct`, `enum`, `type`, or `trait` definitions
+  --> $DIR/unusual-rib-combinations.rs:15:6
+   |
+LL | fn c<T = u8()>() {}
+   |      ^^^^^^^^
+   |
+   = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
+   = note: for more information, see issue #36887 <https://github.com/rust-lang/rust/issues/36887>
+   = note: `#[deny(invalid_type_param_default)]` on by default
+

tests/ui/type-inference/unbounded-type-param-in-fn-with-assoc-type.stderr

@@ -12,3 +12,13 @@ LL |     foo::<T, U>();
 error: aborting due to 1 previous error
 
 For more information about this error, try `rustc --explain E0282`.
+Future incompatibility report: Future breakage diagnostic:
+warning: defaults for type parameters are only allowed in `struct`, `enum`, `type`, or `trait` definitions
+  --> $DIR/unbounded-type-param-in-fn-with-assoc-type.rs:3:11
+   |
+LL | fn foo<T, U = u64>() -> (T, U) {
+   |           ^^^^^^^
+   |
+   = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
+   = note: for more information, see issue #36887 <https://github.com/rust-lang/rust/issues/36887>
+

tests/ui/type/default_type_parameter_in_fn_or_impl.stderr

@@ -0,0 +1,43 @@
+error: defaults for type parameters are only allowed in `struct`, `enum`, `type`, or `trait` definitions
+  --> $DIR/default_type_parameter_in_fn_or_impl.rs:3:8
+   |
+LL | fn avg<T=i32>(_: T) {}
+   |        ^^^^^
+   |
+   = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
+   = note: for more information, see issue #36887 <https://github.com/rust-lang/rust/issues/36887>
+   = note: `#[deny(invalid_type_param_default)]` on by default
+
+error: defaults for type parameters are only allowed in `struct`, `enum`, `type`, or `trait` definitions
+  --> $DIR/default_type_parameter_in_fn_or_impl.rs:8:6
+   |
+LL | impl<T=i32> S<T> {}
+   |      ^^^^^
+   |
+   = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
+   = note: for more information, see issue #36887 <https://github.com/rust-lang/rust/issues/36887>
+
+error: aborting due to 2 previous errors
+
+Future incompatibility report: Future breakage diagnostic:
+error: defaults for type parameters are only allowed in `struct`, `enum`, `type`, or `trait` definitions
+  --> $DIR/default_type_parameter_in_fn_or_impl.rs:3:8
+   |
+LL | fn avg<T=i32>(_: T) {}
+   |        ^^^^^
+   |
+   = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
+   = note: for more information, see issue #36887 <https://github.com/rust-lang/rust/issues/36887>
+   = note: `#[deny(invalid_type_param_default)]` on by default
+
+Future breakage diagnostic:
+error: defaults for type parameters are only allowed in `struct`, `enum`, `type`, or `trait` definitions
+  --> $DIR/default_type_parameter_in_fn_or_impl.rs:8:6
+   |
+LL | impl<T=i32> S<T> {}
+   |      ^^^^^
+   |
+   = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
+   = note: for more information, see issue #36887 <https://github.com/rust-lang/rust/issues/36887>
+   = note: `#[deny(invalid_type_param_default)]` on by default
+