Auto merge of #65588 - Centril:rollup-9k55k3t, r=Centril

Rollup of 6 pull requests

Successful merges:

 - #65174 (Fix zero-size uninitialized boxes)
 - #65252 (expand: Simplify expansion of derives)
 - #65485 (Suppress ICE when validators disagree on `LiveDrop`s in presence of `&mut`)
 - #65542 (Refer to "associated functions" instead of "static methods")
 - #65545 (More symbol cleanups)
 - #65576 (Don't add `argc` and `argv` arguments to `main` on WASI.)

Failed merges:

r? @ghost

src/liballoc/boxed.rs

@@ -142,6 +142,9 @@ impl<T> Box<T> {
     #[unstable(feature = "new_uninit", issue = "63291")]
     pub fn new_uninit() -> Box<mem::MaybeUninit<T>> {
         let layout = alloc::Layout::new::<mem::MaybeUninit<T>>();
+        if layout.size() == 0 {
+            return Box(NonNull::dangling().into())
+        }
         let ptr = unsafe {
             Global.alloc(layout)
                 .unwrap_or_else(|_| alloc::handle_alloc_error(layout))
@@ -182,9 +185,16 @@ impl<T> Box<[T]> {
     #[unstable(feature = "new_uninit", issue = "63291")]
     pub fn new_uninit_slice(len: usize) -> Box<[mem::MaybeUninit<T>]> {
         let layout = alloc::Layout::array::<mem::MaybeUninit<T>>(len).unwrap();
-        let ptr = unsafe { alloc::alloc(layout) };
-        let unique = Unique::new(ptr).unwrap_or_else(|| alloc::handle_alloc_error(layout));
-        let slice = unsafe { slice::from_raw_parts_mut(unique.cast().as_ptr(), len) };
+        let ptr = if layout.size() == 0 {
+            NonNull::dangling()
+        } else {
+            unsafe {
+                Global.alloc(layout)
+                    .unwrap_or_else(|_| alloc::handle_alloc_error(layout))
+                    .cast()
+            }
+        };
+        let slice = unsafe { slice::from_raw_parts_mut(ptr.as_ptr(), len) };
         Box(Unique::from(slice))
     }
 }

src/liballoc/tests/boxed.rs

@@ -0,0 +1,18 @@
+use std::ptr::NonNull;
+use std::mem::MaybeUninit;
+
+#[test]
+fn unitialized_zero_size_box() {
+    assert_eq!(
+        &*Box::<()>::new_uninit() as *const _,
+        NonNull::<MaybeUninit<()>>::dangling().as_ptr(),
+    );
+    assert_eq!(
+        Box::<[()]>::new_uninit_slice(4).as_ptr(),
+        NonNull::<MaybeUninit<()>>::dangling().as_ptr(),
+    );
+    assert_eq!(
+        Box::<[String]>::new_uninit_slice(0).as_ptr(),
+        NonNull::<MaybeUninit<String>>::dangling().as_ptr(),
+    );
+}

src/liballoc/tests/lib.rs

@@ -2,6 +2,7 @@
 #![feature(box_syntax)]
 #![feature(drain_filter)]
 #![feature(exact_size_is_empty)]
+#![feature(new_uninit)]
 #![feature(option_flattening)]
 #![feature(pattern)]
 #![feature(trusted_len)]
@@ -14,6 +15,7 @@ use std::collections::hash_map::DefaultHasher;
 
 mod arc;
 mod binary_heap;
+mod boxed;
 mod btree;
 mod cow_str;
 mod fmt;

src/librustc/hir/map/def_collector.rs

@@ -90,7 +90,7 @@ impl<'a> DefCollector<'a> {
         }
     }
 
-    pub fn visit_macro_invoc(&mut self, id: NodeId) {
+    fn visit_macro_invoc(&mut self, id: NodeId) {
         self.definitions.set_invocation_parent(id.placeholder_to_expn_id(), self.parent_def);
     }
 }

src/librustc/hir/map/definitions.rs

@@ -111,7 +111,7 @@ pub struct Definitions {
 /// A unique identifier that we can use to lookup a definition
 /// precisely. It combines the index of the definition's parent (if
 /// any) with a `DisambiguatedDefPathData`.
-#[derive(Clone, PartialEq, Debug, Hash, RustcEncodable, RustcDecodable)]
+#[derive(Clone, PartialEq, Debug, RustcEncodable, RustcDecodable)]
 pub struct DefKey {
     /// The parent path.
     pub parent: Option<DefIndex>,
@@ -162,13 +162,13 @@ impl DefKey {
 /// between them. This introduces some artificial ordering dependency
 /// but means that if you have, e.g., two impls for the same type in
 /// the same module, they do get distinct `DefId`s.
-#[derive(Clone, PartialEq, Debug, Hash, RustcEncodable, RustcDecodable)]
+#[derive(Clone, PartialEq, Debug, RustcEncodable, RustcDecodable)]
 pub struct DisambiguatedDefPathData {
     pub data: DefPathData,
     pub disambiguator: u32
 }
 
-#[derive(Clone, Debug, Hash, RustcEncodable, RustcDecodable)]
+#[derive(Clone, Debug, RustcEncodable, RustcDecodable)]
 pub struct DefPath {
     /// The path leading from the crate root to the item.
     pub data: Vec<DisambiguatedDefPathData>,

src/librustc_codegen_ssa/base.rs

@@ -414,8 +414,11 @@ pub fn maybe_create_entry_wrapper<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(cx: &'
         rust_main_def_id: DefId,
         use_start_lang_item: bool,
     ) {
-        let llfty =
-            cx.type_func(&[cx.type_int(), cx.type_ptr_to(cx.type_i8p())], cx.type_int());
+        let llfty = if cx.sess().target.target.options.main_needs_argc_argv {
+            cx.type_func(&[cx.type_int(), cx.type_ptr_to(cx.type_i8p())], cx.type_int())
+        } else {
+            cx.type_func(&[], cx.type_int())
+        };
 
         let main_ret_ty = cx.tcx().fn_sig(rust_main_def_id).output();
         // Given that `main()` has no arguments,
@@ -445,11 +448,19 @@ pub fn maybe_create_entry_wrapper<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(cx: &'
 
         bx.insert_reference_to_gdb_debug_scripts_section_global();
 
-        // Params from native main() used as args for rust start function
-        let param_argc = bx.get_param(0);
-        let param_argv = bx.get_param(1);
-        let arg_argc = bx.intcast(param_argc, cx.type_isize(), true);
-        let arg_argv = param_argv;
+        let (arg_argc, arg_argv) = if cx.sess().target.target.options.main_needs_argc_argv {
+            // Params from native main() used as args for rust start function
+            let param_argc = bx.get_param(0);
+            let param_argv = bx.get_param(1);
+            let arg_argc = bx.intcast(param_argc, cx.type_isize(), true);
+            let arg_argv = param_argv;
+            (arg_argc, arg_argv)
+        } else {
+            // The Rust start function doesn't need argc and argv, so just pass zeros.
+            let arg_argc = bx.const_int(cx.type_int(), 0);
+            let arg_argv = bx.const_null(cx.type_ptr_to(cx.type_i8p()));
+            (arg_argc, arg_argv)
+        };
 
         let (start_fn, args) = if use_start_lang_item {
             let start_def_id = cx.tcx().require_lang_item(StartFnLangItem, None);

src/librustc_mir/lib.rs

@@ -14,6 +14,7 @@ Rust MIR: a lowered representation of Rust. Also: an experiment!
 #![feature(core_intrinsics)]
 #![feature(const_fn)]
 #![feature(decl_macro)]
+#![feature(drain_filter)]
 #![feature(exhaustive_patterns)]
 #![feature(never_type)]
 #![feature(specialization)]

src/librustc_mir/transform/qualify_consts.rs

@@ -1024,23 +1024,12 @@ impl<'a, 'tcx> Checker<'a, 'tcx> {
             new_errors.dedup();
 
             if self.errors != new_errors {
-                error!("old validator: {:?}", self.errors);
-                error!("new validator: {:?}", new_errors);
-
-                // ICE on nightly if the validators do not emit exactly the same errors.
-                // Users can supress this panic with an unstable compiler flag (hopefully after
-                // filing an issue).
-                let opts = &self.tcx.sess.opts;
-                let trigger_ice = opts.unstable_features.is_nightly_build()
-                    && !opts.debugging_opts.suppress_const_validation_back_compat_ice;
-
-                if trigger_ice {
-                    span_bug!(
-                        body.span,
-                        "{}",
-                        VALIDATOR_MISMATCH_ERR,
-                    );
-                }
+                validator_mismatch(
+                    self.tcx,
+                    body,
+                    std::mem::replace(&mut self.errors, vec![]),
+                    new_errors,
+                );
             }
         }
 
@@ -1870,6 +1859,58 @@ fn args_required_const(tcx: TyCtxt<'_>, def_id: DefId) -> Option<FxHashSet<usize
     Some(ret)
 }
 
+fn validator_mismatch(
+    tcx: TyCtxt<'tcx>,
+    body: &Body<'tcx>,
+    mut old_errors: Vec<(Span, String)>,
+    mut new_errors: Vec<(Span, String)>,
+) {
+    error!("old validator: {:?}", old_errors);
+    error!("new validator: {:?}", new_errors);
+
+    // ICE on nightly if the validators do not emit exactly the same errors.
+    // Users can supress this panic with an unstable compiler flag (hopefully after
+    // filing an issue).
+    let opts = &tcx.sess.opts;
+    let strict_validation_enabled = opts.unstable_features.is_nightly_build()
+        && !opts.debugging_opts.suppress_const_validation_back_compat_ice;
+
+    if !strict_validation_enabled {
+        return;
+    }
+
+    // If this difference would cause a regression from the old to the new or vice versa, trigger
+    // the ICE.
+    if old_errors.is_empty() || new_errors.is_empty() {
+        span_bug!(body.span, "{}", VALIDATOR_MISMATCH_ERR);
+    }
+
+    // HACK: Borrows that would allow mutation are forbidden in const contexts, but they cause the
+    // new validator to be more conservative about when a dropped local has been moved out of.
+    //
+    // Supress the mismatch ICE in cases where the validators disagree only on the number of
+    // `LiveDrop` errors and both observe the same sequence of `MutBorrow`s.
+
+    let is_live_drop = |(_, s): &mut (_, String)| s.starts_with("LiveDrop");
+    let is_mut_borrow = |(_, s): &&(_, String)| s.starts_with("MutBorrow");
+
+    let old_live_drops: Vec<_> = old_errors.drain_filter(is_live_drop).collect();
+    let new_live_drops: Vec<_> = new_errors.drain_filter(is_live_drop).collect();
+
+    let only_live_drops_differ = old_live_drops != new_live_drops && old_errors == new_errors;
+
+    let old_mut_borrows = old_errors.iter().filter(is_mut_borrow);
+    let new_mut_borrows = new_errors.iter().filter(is_mut_borrow);
+
+    let at_least_one_mut_borrow = old_mut_borrows.clone().next().is_some();
+
+    if only_live_drops_differ && at_least_one_mut_borrow && old_mut_borrows.eq(new_mut_borrows) {
+        return;
+    }
+
+    span_bug!(body.span, "{}", VALIDATOR_MISMATCH_ERR);
+}
+
 const VALIDATOR_MISMATCH_ERR: &str =
     r"Disagreement between legacy and dataflow-based const validators.
     After filing an issue, use `-Zsuppress-const-validation-back-compat-ice` to compile your code.";

src/librustc_privacy/lib.rs

@@ -880,11 +880,11 @@ impl Visitor<'tcx> for EmbargoVisitor<'tcx> {
             self.tcx,
             self.tcx.hir().local_def_id(md.hir_id)
         ).unwrap();
-        let mut module_id = self.tcx.hir().as_local_hir_id(macro_module_def_id).unwrap();
-        if !self.tcx.hir().is_hir_id_module(module_id) {
-            // `module_id` doesn't correspond to a `mod`, return early (#63164).
-            return;
-        }
+        let mut module_id = match self.tcx.hir().as_local_hir_id(macro_module_def_id) {
+            Some(module_id) if self.tcx.hir().is_hir_id_module(module_id) => module_id,
+            // `module_id` doesn't correspond to a `mod`, return early (#63164, #65252).
+            _ => return,
+        };
         let level = if md.vis.node.is_pub() { self.get(module_id) } else { None };
         let new_level = self.update(md.hir_id, level);
         if new_level.is_none() {

src/librustc_resolve/build_reduced_graph.rs

@@ -163,25 +163,15 @@ impl<'a> Resolver<'a> {
         Some(ext)
     }
 
-    // FIXME: `extra_placeholders` should be included into the `fragment` as regular placeholders.
     crate fn build_reduced_graph(
         &mut self,
         fragment: &AstFragment,
-        extra_placeholders: &[NodeId],
         parent_scope: ParentScope<'a>,
     ) -> LegacyScope<'a> {
         let mut def_collector = DefCollector::new(&mut self.definitions, parent_scope.expansion);
         fragment.visit_with(&mut def_collector);
-        for placeholder in extra_placeholders {
-            def_collector.visit_macro_invoc(*placeholder);
-        }
-
         let mut visitor = BuildReducedGraphVisitor { r: self, parent_scope };
         fragment.visit_with(&mut visitor);
-        for placeholder in extra_placeholders {
-            visitor.parent_scope.legacy = visitor.visit_invoc(*placeholder);
-        }
-
         visitor.parent_scope.legacy
     }
 
@@ -1064,8 +1054,17 @@ impl<'a, 'b> BuildReducedGraphVisitor<'a, 'b> {
         None
     }
 
+    // Mark the given macro as unused unless its name starts with `_`.
+    // Macro uses will remove items from this set, and the remaining
+    // items will be reported as `unused_macros`.
+    fn insert_unused_macro(&mut self, ident: Ident, node_id: NodeId, span: Span) {
+        if !ident.as_str().starts_with("_") {
+            self.r.unused_macros.insert(node_id, span);
+        }
+    }
+
     fn define_macro(&mut self, item: &ast::Item) -> LegacyScope<'a> {
-        let parent_scope = &self.parent_scope;
+        let parent_scope = self.parent_scope;
         let expansion = parent_scope.expansion;
         let (ext, ident, span, is_legacy) = match &item.kind {
             ItemKind::MacroDef(def) => {
@@ -1105,7 +1104,7 @@ impl<'a, 'b> BuildReducedGraphVisitor<'a, 'b> {
                             (res, vis, span, expansion, IsMacroExport));
             } else {
                 self.r.check_reserved_macro_name(ident, res);
-                self.r.unused_macros.insert(item.id, span);
+                self.insert_unused_macro(ident, item.id, span);
             }
             LegacyScope::Binding(self.r.arenas.alloc_legacy_binding(LegacyBinding {
                 parent_legacy_scope: parent_scope.legacy, binding, ident
@@ -1114,7 +1113,7 @@ impl<'a, 'b> BuildReducedGraphVisitor<'a, 'b> {
             let module = parent_scope.module;
             let vis = self.resolve_visibility(&item.vis);
             if vis != ty::Visibility::Public {
-                self.r.unused_macros.insert(item.id, span);
+                self.insert_unused_macro(ident, item.id, span);
             }
             self.r.define(module, ident, MacroNS, (res, vis, span, expansion));
             self.parent_scope.legacy

src/librustc_resolve/error_codes.rs

@@ -1013,7 +1013,8 @@ fn h1() -> i32 {
 "##,
 
 E0424: r##"
-The `self` keyword was used in a static method.
+The `self` keyword was used inside of an associated function without a "`self`
+receiver" parameter.
 
 Erroneous code example:
 
@@ -1021,25 +1022,33 @@ Erroneous code example:
 struct Foo;
 
 impl Foo {
-    fn bar(self) {}
+    // `bar` is a method, because it has a receiver parameter.
+    fn bar(&self) {}
 
+    // `foo` is not a method, because it has no receiver parameter.
     fn foo() {
-        self.bar(); // error: `self` is not available in a static method.
+        self.bar(); // error: `self` value is a keyword only available in
+                    //        methods with a `self` parameter
     }
 }
 ```
 
-Please check if the method's argument list should have contained `self`,
-`&self`, or `&mut self` (in case you didn't want to create a static
-method), and add it if so. Example:
+The `self` keyword can only be used inside methods, which are associated
+functions (functions defined inside of a `trait` or `impl` block) that have a
+`self` receiver as its first parameter, like `self`, `&self`, `&mut self` or
+`self: &mut Pin<Self>` (this last one is an example of an ["abitrary `self`
+type"](https://github.com/rust-lang/rust/issues/44874)).
+
+Check if the associated function's parameter list should have contained a `self`
+receiver for it to be a method, and add it if so. Example:
 
 ```
 struct Foo;
 
 impl Foo {
-    fn bar(self) {}
+    fn bar(&self) {}
 
-    fn foo(self) {
+    fn foo(self) { // `foo` is now a method.
         self.bar(); // ok!
     }
 }

src/librustc_resolve/late.rs

@@ -345,6 +345,9 @@ struct LateResolutionVisitor<'a, 'b> {
     /// The current self item if inside an ADT (used for better errors).
     current_self_item: Option<NodeId>,
 
+    /// The current enclosing funciton (used for better errors).
+    current_function: Option<Span>,
+
     /// A list of labels as of yet unused. Labels will be removed from this map when
     /// they are used (in a `break` or `continue` statement)
     unused_labels: FxHashMap<NodeId, Span>,
@@ -415,7 +418,8 @@ impl<'a, 'tcx> Visitor<'tcx> for LateResolutionVisitor<'a, '_> {
             }
         }
     }
-    fn visit_fn(&mut self, fn_kind: FnKind<'tcx>, declaration: &'tcx FnDecl, _: Span, _: NodeId) {
+    fn visit_fn(&mut self, fn_kind: FnKind<'tcx>, declaration: &'tcx FnDecl, sp: Span, _: NodeId) {
+        let previous_value = replace(&mut self.current_function, Some(sp));
         debug!("(resolving function) entering function");
         let rib_kind = match fn_kind {
             FnKind::ItemFn(..) => FnItemRibKind,
@@ -441,6 +445,7 @@ impl<'a, 'tcx> Visitor<'tcx> for LateResolutionVisitor<'a, '_> {
                 debug!("(resolving function) leaving function");
             })
         });
+        self.current_function = previous_value;
     }
 
     fn visit_generics(&mut self, generics: &'tcx Generics) {
@@ -546,6 +551,7 @@ impl<'a, 'b> LateResolutionVisitor<'a, '_> {
             current_trait_assoc_types: Vec::new(),
             current_self_type: None,
             current_self_item: None,
+            current_function: None,
             unused_labels: Default::default(),
             current_type_ascription: Vec::new(),
         }

src/librustc_resolve/late/diagnostics.rs

@@ -115,8 +115,10 @@ impl<'a> LateResolutionVisitor<'a, '_> {
         if is_self_type(path, ns) {
             syntax::diagnostic_used!(E0411);
             err.code(DiagnosticId::Error("E0411".into()));
-            err.span_label(span, format!("`Self` is only available in impls, traits, \
-                                          and type definitions"));
+            err.span_label(
+                span,
+                format!("`Self` is only available in impls, traits, and type definitions"),
+            );
             return (err, Vec::new());
         }
         if is_self_value(path, ns) {
@@ -125,17 +127,16 @@ impl<'a> LateResolutionVisitor<'a, '_> {
             syntax::diagnostic_used!(E0424);
             err.code(DiagnosticId::Error("E0424".into()));
             err.span_label(span, match source {
-                PathSource::Pat => {
-                    format!("`self` value is a keyword \
-                             and may not be bound to \
-                             variables or shadowed")
-                }
-                _ => {
-                    format!("`self` value is a keyword \
-                             only available in methods \
-                             with `self` parameter")
-                }
+                PathSource::Pat => format!(
+                    "`self` value is a keyword and may not be bound to variables or shadowed",
+                ),
+                _ => format!(
+                    "`self` value is a keyword only available in methods with a `self` parameter",
+                ),
             });
+            if let Some(span) = &self.current_function {
+                err.span_label(*span, "this function doesn't have a `self` parameter");
+            }
             return (err, Vec::new());
         }
 

src/librustc_resolve/macros.rs

@@ -108,15 +108,11 @@ impl<'a> base::Resolver for Resolver<'a> {
         });
     }
 
-    // FIXME: `extra_placeholders` should be included into the `fragment` as regular placeholders.
-    fn visit_ast_fragment_with_placeholders(
-        &mut self, expansion: ExpnId, fragment: &AstFragment, extra_placeholders: &[NodeId]
-    ) {
+    fn visit_ast_fragment_with_placeholders(&mut self, expansion: ExpnId, fragment: &AstFragment) {
         // Integrate the new AST fragment into all the definition and module structures.
         // We are inside the `expansion` now, but other parent scope components are still the same.
         let parent_scope = ParentScope { expansion, ..self.invocation_parent_scopes[&expansion] };
-        let output_legacy_scope =
-            self.build_reduced_graph(fragment, extra_placeholders, parent_scope);
+        let output_legacy_scope = self.build_reduced_graph(fragment, parent_scope);
         self.output_legacy_scopes.insert(expansion, output_legacy_scope);
 
         parent_scope.module.unexpanded_invocations.borrow_mut().remove(&expansion);

src/librustc_target/spec/mod.rs

@@ -691,6 +691,9 @@ pub struct TargetOptions {
     /// defined in libgcc. If this option is enabled, the target must provide
     /// `eh_unwind_resume` lang item.
     pub custom_unwind_resume: bool,
+    /// Whether the runtime startup code requires the `main` function be passed
+    /// `argc` and `argv` values.
+    pub main_needs_argc_argv: bool,
 
     /// Flag indicating whether ELF TLS (e.g., #[thread_local]) is available for
     /// this target.
@@ -849,6 +852,7 @@ impl Default for TargetOptions {
             link_env_remove: Vec::new(),
             archive_format: "gnu".to_string(),
             custom_unwind_resume: false,
+            main_needs_argc_argv: true,
             allow_asm: true,
             has_elf_tls: false,
             obj_is_bitcode: false,
@@ -1159,6 +1163,7 @@ impl Target {
         key!(archive_format);
         key!(allow_asm, bool);
         key!(custom_unwind_resume, bool);
+        key!(main_needs_argc_argv, bool);
         key!(has_elf_tls, bool);
         key!(obj_is_bitcode, bool);
         key!(no_integrated_as, bool);
@@ -1376,6 +1381,7 @@ impl ToJson for Target {
         target_option_val!(archive_format);
         target_option_val!(allow_asm);
         target_option_val!(custom_unwind_resume);
+        target_option_val!(main_needs_argc_argv);
         target_option_val!(has_elf_tls);
         target_option_val!(obj_is_bitcode);
         target_option_val!(no_integrated_as);

src/librustc_target/spec/wasm32_wasi.rs

@@ -101,6 +101,10 @@ pub fn target() -> Result<Target, String> {
     // without a main function.
     options.crt_static_allows_dylibs = true;
 
+    // WASI's `sys::args::init` function ignores its arguments; instead,
+    // `args::args()` makes the WASI API calls itself.
+    options.main_needs_argc_argv = false;
+
     Ok(Target {
         llvm_target: "wasm32-wasi".to_string(),
         target_endian: "little".to_string(),

src/libsyntax_expand/base.rs

@@ -851,8 +851,7 @@ pub trait Resolver {
     fn next_node_id(&mut self) -> NodeId;
 
     fn resolve_dollar_crates(&mut self);
-    fn visit_ast_fragment_with_placeholders(&mut self, expn_id: ExpnId, fragment: &AstFragment,
-                                            extra_placeholders: &[NodeId]);
+    fn visit_ast_fragment_with_placeholders(&mut self, expn_id: ExpnId, fragment: &AstFragment);
     fn register_builtin_macro(&mut self, ident: ast::Ident, ext: SyntaxExtension);
 
     fn expansion_for_ast_pass(

src/libsyntax_expand/expand.rs

@@ -26,7 +26,6 @@ use errors::{Applicability, FatalError};
 use smallvec::{smallvec, SmallVec};
 use syntax_pos::{Span, DUMMY_SP, FileName};
 
-use rustc_data_structures::fx::FxHashMap;
 use rustc_data_structures::sync::Lrc;
 use std::io::ErrorKind;
 use std::{iter, mem, slice};
@@ -75,6 +74,22 @@ macro_rules! ast_fragments {
         }
 
         impl AstFragment {
+            pub fn add_placeholders(&mut self, placeholders: &[NodeId]) {
+                if placeholders.is_empty() {
+                    return;
+                }
+                match self {
+                    $($(AstFragment::$Kind(ast) => ast.extend(placeholders.iter().flat_map(|id| {
+                        // We are repeating through arguments with `many`, to do that we have to
+                        // mention some macro variable from those arguments even if it's not used.
+                        #[cfg_attr(bootstrap, allow(unused_macros))]
+                        macro _repeating($flat_map_ast_elt) {}
+                        placeholder(AstFragmentKind::$Kind, *id).$make_ast()
+                    })),)?)*
+                    _ => panic!("unexpected AST fragment kind")
+                }
+            }
+
             pub fn make_opt_expr(self) -> Option<P<ast::Expr>> {
                 match self {
                     AstFragment::OptExpr(expr) => expr,
@@ -342,7 +357,6 @@ impl<'a, 'b> MacroExpander<'a, 'b> {
         // Unresolved macros produce dummy outputs as a recovery measure.
         invocations.reverse();
         let mut expanded_fragments = Vec::new();
-        let mut all_derive_placeholders: FxHashMap<ExpnId, Vec<_>> = FxHashMap::default();
         let mut undetermined_invocations = Vec::new();
         let (mut progress, mut force) = (false, !self.monotonic);
         loop {
@@ -420,9 +434,7 @@ impl<'a, 'b> MacroExpander<'a, 'b> {
                         self.cx.resolver.add_derives(invoc.expansion_data.id, SpecialDerives::COPY);
                     }
 
-                    let derive_placeholders =
-                        all_derive_placeholders.entry(invoc.expansion_data.id).or_default();
-                    derive_placeholders.reserve(derives.len());
+                    let mut derive_placeholders = Vec::with_capacity(derives.len());
                     invocations.reserve(derives.len());
                     for path in derives {
                         let expn_id = ExpnId::fresh(None);
@@ -438,7 +450,7 @@ impl<'a, 'b> MacroExpander<'a, 'b> {
                     }
                     let fragment = invoc.fragment_kind
                         .expect_from_annotatables(::std::iter::once(item));
-                    self.collect_invocations(fragment, derive_placeholders)
+                    self.collect_invocations(fragment, &derive_placeholders)
                 }
             };
 
@@ -457,10 +469,8 @@ impl<'a, 'b> MacroExpander<'a, 'b> {
         let mut placeholder_expander = PlaceholderExpander::new(self.cx, self.monotonic);
         while let Some(expanded_fragments) = expanded_fragments.pop() {
             for (expn_id, expanded_fragment) in expanded_fragments.into_iter().rev() {
-                let derive_placeholders =
-                    all_derive_placeholders.remove(&expn_id).unwrap_or_else(Vec::new);
                 placeholder_expander.add(NodeId::placeholder_from_expn_id(expn_id),
-                                         expanded_fragment, derive_placeholders);
+                                         expanded_fragment);
             }
         }
         fragment_with_placeholders.mut_visit_with(&mut placeholder_expander);
@@ -493,13 +503,14 @@ impl<'a, 'b> MacroExpander<'a, 'b> {
                 monotonic: self.monotonic,
             };
             fragment.mut_visit_with(&mut collector);
+            fragment.add_placeholders(extra_placeholders);
             collector.invocations
         };
 
-        // FIXME: Merge `extra_placeholders` into the `fragment` as regular placeholders.
         if self.monotonic {
             self.cx.resolver.visit_ast_fragment_with_placeholders(
-                self.cx.current_expansion.id, &fragment, extra_placeholders);
+                self.cx.current_expansion.id, &fragment
+            );
         }
 
         (fragment, invocations)

src/libsyntax_expand/lib.rs

@@ -1,4 +1,5 @@
 #![feature(crate_visibility_modifier)]
+#![feature(decl_macro)]
 #![feature(proc_macro_diagnostic)]
 #![feature(proc_macro_internals)]
 #![feature(proc_macro_span)]

src/libsyntax_expand/placeholders.rs

@@ -1,7 +1,7 @@
 use crate::base::ExtCtxt;
 use crate::expand::{AstFragment, AstFragmentKind};
 
-use syntax::ast::{self, NodeId};
+use syntax::ast;
 use syntax::source_map::{DUMMY_SP, dummy_spanned};
 use syntax::tokenstream::TokenStream;
 use syntax::mut_visit::*;
@@ -171,17 +171,8 @@ impl<'a, 'b> PlaceholderExpander<'a, 'b> {
         }
     }
 
-    pub fn add(&mut self, id: ast::NodeId, mut fragment: AstFragment, placeholders: Vec<NodeId>) {
+    pub fn add(&mut self, id: ast::NodeId, mut fragment: AstFragment) {
         fragment.mut_visit_with(self);
-        if let AstFragment::Items(mut items) = fragment {
-            for placeholder in placeholders {
-                match self.remove(placeholder) {
-                    AstFragment::Items(derived_items) => items.extend(derived_items),
-                    _ => unreachable!(),
-                }
-            }
-            fragment = AstFragment::Items(items);
-        }
         self.expanded_fragments.insert(id, fragment);
     }
 

src/libsyntax_ext/deriving/clone.rs

@@ -174,14 +174,12 @@ fn cs_clone(name: &str,
             all_fields = af;
             vdata = &variant.data;
         }
-        EnumNonMatchingCollapsed(..) => {
-            cx.span_bug(trait_span,
-                        &format!("non-matching enum variants in \
-                                 `derive({})`",
-                                 name))
-        }
+        EnumNonMatchingCollapsed(..) => cx.span_bug(trait_span, &format!(
+            "non-matching enum variants in `derive({})`",
+            name,
+        )),
         StaticEnum(..) | StaticStruct(..) => {
-            cx.span_bug(trait_span, &format!("static method in `derive({})`", name))
+            cx.span_bug(trait_span, &format!("associated function in `derive({})`", name))
         }
     }
 
@@ -191,12 +189,10 @@ fn cs_clone(name: &str,
                 .map(|field| {
                     let ident = match field.name {
                         Some(i) => i,
-                        None => {
-                            cx.span_bug(trait_span,
-                                        &format!("unnamed field in normal struct in \
-                                                `derive({})`",
-                                                    name))
-                        }
+                        None => cx.span_bug(trait_span, &format!(
+                            "unnamed field in normal struct in `derive({})`",
+                            name,
+                        )),
                     };
                     let call = subcall(cx, field);
                     cx.field_imm(field.span, ident, call)

src/libsyntax_ext/deriving/default.rs

@@ -75,6 +75,6 @@ fn default_substructure(cx: &mut ExtCtxt<'_>,
             // let compilation continue
             DummyResult::raw_expr(trait_span, true)
         }
-        _ => cx.span_bug(trait_span, "Non-static method in `derive(Default)`"),
+        _ => cx.span_bug(trait_span, "method in `derive(Default)`"),
     };
 }

src/libsyntax_ext/deriving/generic/mod.rs

@@ -1055,9 +1055,7 @@ impl<'a> MethodDef<'a> {
                 })
                 .collect()
         } else {
-            cx.span_bug(trait_.span,
-                        "no self arguments to non-static method in generic \
-                         `derive`")
+            cx.span_bug(trait_.span, "no `self` parameter for method in generic `derive`")
         };
 
         // body of the inner most destructuring match

src/libsyntax_pos/symbol.rs

@@ -934,19 +934,19 @@ impl Symbol {
 
 impl fmt::Debug for Symbol {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        fmt::Display::fmt(self, f)
+        self.with(|str| fmt::Debug::fmt(&str, f))
     }
 }
 
 impl fmt::Display for Symbol {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        fmt::Display::fmt(&self.as_str(), f)
+        self.with(|str| fmt::Display::fmt(&str, f))
     }
 }
 
 impl Encodable for Symbol {
     fn encode<S: Encoder>(&self, s: &mut S) -> Result<(), S::Error> {
-        s.emit_str(&self.as_str())
+        self.with(|string| s.emit_str(string))
     }
 }
 
@@ -1106,8 +1106,8 @@ fn with_interner<T, F: FnOnce(&mut Interner) -> T>(f: F) -> T {
 }
 
 /// An alternative to `Symbol` and `InternedString`, useful when the chars
-/// within the symbol need to be accessed. It is best used for temporary
-/// values.
+/// within the symbol need to be accessed. It deliberately has limited
+/// functionality and should only be used for temporary values.
 ///
 /// Because the interner outlives any thread which uses this type, we can
 /// safely treat `string` which points to interner data, as an immortal string,
@@ -1116,7 +1116,7 @@ fn with_interner<T, F: FnOnce(&mut Interner) -> T>(f: F) -> T {
 // FIXME: ensure that the interner outlives any thread which uses
 // `LocalInternedString`, by creating a new thread right after constructing the
 // interner.
-#[derive(Clone, Copy, Eq, PartialOrd, Ord)]
+#[derive(Eq, PartialOrd, Ord)]
 pub struct LocalInternedString {
     string: &'static str,
 }

src/test/rustdoc/macro-in-closure.rs

@@ -0,0 +1,9 @@
+// Regression issue for rustdoc ICE encountered in PR #65252.
+
+#![feature(decl_macro)]
+
+fn main() {
+    || {
+        macro m() {}
+    };
+}

src/test/ui/consts/const-eval/issue-65394.rs

@@ -0,0 +1,13 @@
+// Test for absence of validation mismatch ICE in #65394
+
+#![feature(rustc_attrs)]
+
+#[rustc_mir(borrowck_graphviz_postflow="hello.dot")]
+const _: Vec<i32> = {
+    let mut x = Vec::<i32>::new();
+    let r = &mut x; //~ ERROR references in constants may only refer to immutable values
+    let y = x;
+    y
+};
+
+fn main() {}

src/test/ui/consts/const-eval/issue-65394.stderr

@@ -0,0 +1,11 @@
+error[E0017]: references in constants may only refer to immutable values
+  --> $DIR/issue-65394.rs:8:13
+   |
+LL |     let r = &mut x;
+   |             ^^^^^^ constants require immutable values
+
+[ERROR rustc_mir::transform::qualify_consts] old validator: [($DIR/issue-65394.rs:8:13: 8:19, "MutBorrow(Mut { allow_two_phase_borrow: false })")]
+[ERROR rustc_mir::transform::qualify_consts] new validator: [($DIR/issue-65394.rs:8:13: 8:19, "MutBorrow(Mut { allow_two_phase_borrow: false })"), ($DIR/issue-65394.rs:7:9: 7:14, "LiveDrop")]
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0017`.

src/test/ui/error-codes/E0424.stderr

@@ -1,14 +1,20 @@
 error[E0424]: expected value, found module `self`
   --> $DIR/E0424.rs:7:9
    |
-LL |         self.bar();
-   |         ^^^^ `self` value is a keyword only available in methods with `self` parameter
+LL | /     fn foo() {
+LL | |         self.bar();
+   | |         ^^^^ `self` value is a keyword only available in methods with a `self` parameter
+LL | |     }
+   | |_____- this function doesn't have a `self` parameter
 
 error[E0424]: expected unit struct/variant or constant, found module `self`
   --> $DIR/E0424.rs:12:9
    |
-LL |     let self = "self";
-   |         ^^^^ `self` value is a keyword and may not be bound to variables or shadowed
+LL | / fn main () {
+LL | |     let self = "self";
+   | |         ^^^^ `self` value is a keyword and may not be bound to variables or shadowed
+LL | | }
+   | |_- this function doesn't have a `self` parameter
 
 error: aborting due to 2 previous errors
 

src/test/ui/hygiene/unpretty-debug.stdout

@@ -17,7 +17,7 @@ fn y /* 0#0 */() { }
 /*
 Expansions:
 0: parent: ExpnId(0), call_site_ctxt: #0, kind: Root
-1: parent: ExpnId(0), call_site_ctxt: #0, kind: Macro(Bang, foo)
+1: parent: ExpnId(0), call_site_ctxt: #0, kind: Macro(Bang, "foo")
 
 SyntaxContexts:
 #0: parent: #0, outer_mark: (ExpnId(0), Opaque)

src/test/ui/lint/redundant-semicolon/redundant-semi-proc-macro.stderr

@@ -1,4 +1,4 @@
-TokenStream [Ident { ident: "fn", span: #0 bytes(197..199) }, Ident { ident: "span_preservation", span: #0 bytes(200..217) }, Group { delimiter: Parenthesis, stream: TokenStream [], span: #0 bytes(217..219) }, Group { delimiter: Brace, stream: TokenStream [Ident { ident: "let", span: #0 bytes(227..230) }, Ident { ident: "tst", span: #0 bytes(231..234) }, Punct { ch: '=', spacing: Alone, span: #0 bytes(235..236) }, Literal { lit: Lit { kind: Integer, symbol: 123, suffix: None }, span: Span { lo: BytePos(237), hi: BytePos(240), ctxt: #0 } }, Punct { ch: ';', spacing: Joint, span: #0 bytes(240..241) }, Punct { ch: ';', spacing: Alone, span: #0 bytes(241..242) }, Ident { ident: "match", span: #0 bytes(288..293) }, Ident { ident: "tst", span: #0 bytes(294..297) }, Group { delimiter: Brace, stream: TokenStream [Literal { lit: Lit { kind: Integer, symbol: 123, suffix: None }, span: Span { lo: BytePos(482), hi: BytePos(485), ctxt: #0 } }, Punct { ch: '=', spacing: Joint, span: #0 bytes(486..488) }, Punct { ch: '>', spacing: Alone, span: #0 bytes(486..488) }, Group { delimiter: Parenthesis, stream: TokenStream [], span: #0 bytes(489..491) }, Punct { ch: ',', spacing: Alone, span: #0 bytes(491..492) }, Ident { ident: "_", span: #0 bytes(501..502) }, Punct { ch: '=', spacing: Joint, span: #0 bytes(503..505) }, Punct { ch: '>', spacing: Alone, span: #0 bytes(503..505) }, Group { delimiter: Parenthesis, stream: TokenStream [], span: #0 bytes(506..508) }], span: #0 bytes(298..514) }, Punct { ch: ';', spacing: Joint, span: #0 bytes(514..515) }, Punct { ch: ';', spacing: Joint, span: #0 bytes(515..516) }, Punct { ch: ';', spacing: Alone, span: #0 bytes(516..517) }], span: #0 bytes(221..561) }]
+TokenStream [Ident { ident: "fn", span: #0 bytes(197..199) }, Ident { ident: "span_preservation", span: #0 bytes(200..217) }, Group { delimiter: Parenthesis, stream: TokenStream [], span: #0 bytes(217..219) }, Group { delimiter: Brace, stream: TokenStream [Ident { ident: "let", span: #0 bytes(227..230) }, Ident { ident: "tst", span: #0 bytes(231..234) }, Punct { ch: '=', spacing: Alone, span: #0 bytes(235..236) }, Literal { lit: Lit { kind: Integer, symbol: "123", suffix: None }, span: Span { lo: BytePos(237), hi: BytePos(240), ctxt: #0 } }, Punct { ch: ';', spacing: Joint, span: #0 bytes(240..241) }, Punct { ch: ';', spacing: Alone, span: #0 bytes(241..242) }, Ident { ident: "match", span: #0 bytes(288..293) }, Ident { ident: "tst", span: #0 bytes(294..297) }, Group { delimiter: Brace, stream: TokenStream [Literal { lit: Lit { kind: Integer, symbol: "123", suffix: None }, span: Span { lo: BytePos(482), hi: BytePos(485), ctxt: #0 } }, Punct { ch: '=', spacing: Joint, span: #0 bytes(486..488) }, Punct { ch: '>', spacing: Alone, span: #0 bytes(486..488) }, Group { delimiter: Parenthesis, stream: TokenStream [], span: #0 bytes(489..491) }, Punct { ch: ',', spacing: Alone, span: #0 bytes(491..492) }, Ident { ident: "_", span: #0 bytes(501..502) }, Punct { ch: '=', spacing: Joint, span: #0 bytes(503..505) }, Punct { ch: '>', spacing: Alone, span: #0 bytes(503..505) }, Group { delimiter: Parenthesis, stream: TokenStream [], span: #0 bytes(506..508) }], span: #0 bytes(298..514) }, Punct { ch: ';', spacing: Joint, span: #0 bytes(514..515) }, Punct { ch: ';', spacing: Joint, span: #0 bytes(515..516) }, Punct { ch: ';', spacing: Alone, span: #0 bytes(516..517) }], span: #0 bytes(221..561) }]
 error: unnecessary trailing semicolon
   --> $DIR/redundant-semi-proc-macro.rs:9:19
    |

src/test/ui/resolve/issue-2356.stderr

@@ -61,8 +61,14 @@ LL |         purr();
 error[E0424]: expected value, found module `self`
   --> $DIR/issue-2356.rs:65:8
    |
-LL |     if self.whiskers > 3 {
-   |        ^^^^ `self` value is a keyword only available in methods with `self` parameter
+LL | /   fn meow() {
+LL | |     if self.whiskers > 3 {
+   | |        ^^^^ `self` value is a keyword only available in methods with a `self` parameter
+LL | |
+LL | |         println!("MEOW");
+LL | |     }
+LL | |   }
+   | |___- this function doesn't have a `self` parameter
 
 error[E0425]: cannot find function `grow_older` in this scope
   --> $DIR/issue-2356.rs:72:5
@@ -97,8 +103,12 @@ LL |     purr_louder();
 error[E0424]: expected value, found module `self`
   --> $DIR/issue-2356.rs:92:5
    |
-LL |     self += 1;
-   |     ^^^^ `self` value is a keyword only available in methods with `self` parameter
+LL | / fn main() {
+LL | |     self += 1;
+   | |     ^^^^ `self` value is a keyword only available in methods with a `self` parameter
+LL | |
+LL | | }
+   | |_- this function doesn't have a `self` parameter
 
 error: aborting due to 17 previous errors