Auto merge of #102297 - fee1-dead-contrib:rollup-2np0cre, r=fee1-dead

Rollup of 5 pull requests

Successful merges:

 - #102143 (Recover from struct nested in struct)
 - #102178 (bootstrap: the backtrace feature is stable, no need to allow it any more)
 - #102197 (Stabilize const `BTree{Map,Set}::new`)
 - #102267 (Don't set RUSTC in the bootstrap build script)
 - #102270 (Remove benches from `rustc_middle`)

Failed merges:

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

14 files changed, 60 insertions, 108 deletions

diff --git a/compiler/rustc_hir/src/lib.rs b/compiler/rustc_hir/src/lib.rs
index 946da9265ba..556ff1cc48e 100644
--- a/compiler/rustc_hir/src/lib.rs
+++ b/compiler/rustc_hir/src/lib.rs
@@ -4,7 +4,7 @@
 
 #![feature(associated_type_defaults)]
 #![feature(closure_track_caller)]
-#![feature(const_btree_new)]
+#![feature(const_btree_len)]
 #![cfg_attr(bootstrap, feature(let_else))]
 #![feature(once_cell)]
 #![feature(min_specialization)]
diff --git a/compiler/rustc_middle/benches/lib.rs b/compiler/rustc_middle/benches/lib.rs
deleted file mode 100644
index 237751bcbd7..00000000000
--- a/compiler/rustc_middle/benches/lib.rs
+++ /dev/null
@@ -1,54 +0,0 @@
-#![feature(test)]
-
-extern crate test;
-
-use test::Bencher;
-
-// Static/dynamic method dispatch
-
-struct Struct {
-    field: isize,
-}
-
-trait Trait {
-    fn method(&self) -> isize;
-}
-
-impl Trait for Struct {
-    fn method(&self) -> isize {
-        self.field
-    }
-}
-
-#[bench]
-fn trait_vtable_method_call(b: &mut Bencher) {
-    let s = Struct { field: 10 };
-    let t = &s as &dyn Trait;
-    b.iter(|| t.method());
-}
-
-#[bench]
-fn trait_static_method_call(b: &mut Bencher) {
-    let s = Struct { field: 10 };
-    b.iter(|| s.method());
-}
-
-// Overhead of various match forms
-
-#[bench]
-fn option_some(b: &mut Bencher) {
-    let x = Some(10);
-    b.iter(|| match x {
-        Some(y) => y,
-        None => 11,
-    });
-}
-
-#[bench]
-fn vec_pattern(b: &mut Bencher) {
-    let x = [1, 2, 3, 4, 5, 6];
-    b.iter(|| match x {
-        [1, 2, 3, ..] => 10,
-        _ => 11,
-    });
-}
diff --git a/compiler/rustc_parse/src/parser/item.rs b/compiler/rustc_parse/src/parser/item.rs
index e55b5ce71cd..e385ac44113 100644
--- a/compiler/rustc_parse/src/parser/item.rs
+++ b/compiler/rustc_parse/src/parser/item.rs
@@ -1715,6 +1715,7 @@ impl<'a> Parser<'a> {
     fn parse_field_ident(&mut self, adt_ty: &str, lo: Span) -> PResult<'a, Ident> {
         let (ident, is_raw) = self.ident_or_err()?;
         if !is_raw && ident.is_reserved() {
+            let snapshot = self.create_snapshot_for_diagnostic();
             let err = if self.check_fn_front_matter(false) {
                 let inherited_vis = Visibility {
                     span: rustc_span::DUMMY_SP,
@@ -1735,6 +1736,22 @@ impl<'a> Parser<'a> {
                 err.help("unlike in C++, Java, and C#, functions are declared in `impl` blocks");
                 err.help("see https://doc.rust-lang.org/book/ch05-03-method-syntax.html for more information");
                 err
+            } else if self.eat_keyword(kw::Struct) {
+                match self.parse_item_struct() {
+                    Ok((ident, _)) => {
+                        let mut err = self.struct_span_err(
+                            lo.with_hi(ident.span.hi()),
+                            &format!("structs are not allowed in {adt_ty} definitions"),
+                        );
+                        err.help("consider creating a new `struct` definition instead of nesting");
+                        err
+                    }
+                    Err(err) => {
+                        err.cancel();
+                        self.restore_snapshot(snapshot);
+                        self.expected_ident_found()
+                    }
+                }
             } else {
                 self.expected_ident_found()
             };
diff --git a/library/alloc/src/collections/btree/map.rs b/library/alloc/src/collections/btree/map.rs
index cacbd54b6c2..3018d1c9125 100644
--- a/library/alloc/src/collections/btree/map.rs
+++ b/library/alloc/src/collections/btree/map.rs
@@ -580,7 +580,7 @@ impl<K, V> BTreeMap<K, V> {
     /// map.insert(1, "a");
     /// ```
     #[stable(feature = "rust1", since = "1.0.0")]
-    #[rustc_const_unstable(feature = "const_btree_new", issue = "71835")]
+    #[rustc_const_stable(feature = "const_btree_new", since = "CURRENT_RUSTC_VERSION")]
     #[must_use]
     pub const fn new() -> BTreeMap<K, V> {
         BTreeMap { root: None, length: 0, alloc: ManuallyDrop::new(Global), _marker: PhantomData }
@@ -2392,7 +2392,7 @@ impl<K, V, A: Allocator + Clone> BTreeMap<K, V, A> {
     /// ```
     #[must_use]
     #[stable(feature = "rust1", since = "1.0.0")]
-    #[rustc_const_unstable(feature = "const_btree_new", issue = "71835")]
+    #[rustc_const_unstable(feature = "const_btree_len", issue = "71835")]
     pub const fn len(&self) -> usize {
         self.length
     }
@@ -2413,7 +2413,7 @@ impl<K, V, A: Allocator + Clone> BTreeMap<K, V, A> {
     /// ```
     #[must_use]
     #[stable(feature = "rust1", since = "1.0.0")]
-    #[rustc_const_unstable(feature = "const_btree_new", issue = "71835")]
+    #[rustc_const_unstable(feature = "const_btree_len", issue = "71835")]
     pub const fn is_empty(&self) -> bool {
         self.len() == 0
     }
diff --git a/library/alloc/src/collections/btree/set.rs b/library/alloc/src/collections/btree/set.rs
index 2cfc0807409..3caaf521240 100644
--- a/library/alloc/src/collections/btree/set.rs
+++ b/library/alloc/src/collections/btree/set.rs
@@ -343,7 +343,7 @@ impl<T> BTreeSet<T> {
     /// let mut set: BTreeSet<i32> = BTreeSet::new();
     /// ```
     #[stable(feature = "rust1", since = "1.0.0")]
-    #[rustc_const_unstable(feature = "const_btree_new", issue = "71835")]
+    #[rustc_const_stable(feature = "const_btree_new", since = "CURRENT_RUSTC_VERSION")]
     #[must_use]
     pub const fn new() -> BTreeSet<T> {
         BTreeSet { map: BTreeMap::new() }
@@ -1174,7 +1174,7 @@ impl<T, A: Allocator + Clone> BTreeSet<T, A> {
     /// ```
     #[must_use]
     #[stable(feature = "rust1", since = "1.0.0")]
-    #[rustc_const_unstable(feature = "const_btree_new", issue = "71835")]
+    #[rustc_const_unstable(feature = "const_btree_len", issue = "71835")]
     pub const fn len(&self) -> usize {
         self.map.len()
     }
@@ -1193,7 +1193,7 @@ impl<T, A: Allocator + Clone> BTreeSet<T, A> {
     /// ```
     #[must_use]
     #[stable(feature = "rust1", since = "1.0.0")]
-    #[rustc_const_unstable(feature = "const_btree_new", issue = "71835")]
+    #[rustc_const_unstable(feature = "const_btree_len", issue = "71835")]
     pub const fn is_empty(&self) -> bool {
         self.len() == 0
     }
diff --git a/library/alloc/src/lib.rs b/library/alloc/src/lib.rs
index cadc2f5ad77..de58f22daae 100644
--- a/library/alloc/src/lib.rs
+++ b/library/alloc/src/lib.rs
@@ -99,7 +99,7 @@
 #![feature(coerce_unsized)]
 #![cfg_attr(not(no_global_oom_handling), feature(const_alloc_error))]
 #![feature(const_box)]
-#![cfg_attr(not(no_global_oom_handling), feature(const_btree_new))]
+#![cfg_attr(not(no_global_oom_handling), feature(const_btree_len))]
 #![feature(const_cow_is_borrowed)]
 #![feature(const_convert)]
 #![feature(const_size_of_val)]
diff --git a/library/alloc/tests/lib.rs b/library/alloc/tests/lib.rs
index 490c0d8f76c..55aced5106c 100644
--- a/library/alloc/tests/lib.rs
+++ b/library/alloc/tests/lib.rs
@@ -32,7 +32,7 @@
 #![feature(slice_group_by)]
 #![feature(slice_partition_dedup)]
 #![feature(string_remove_matches)]
-#![feature(const_btree_new)]
+#![feature(const_btree_len)]
 #![feature(const_default_impls)]
 #![feature(const_trait_impl)]
 #![feature(const_str_from_utf8)]
diff --git a/src/bootstrap/build.rs b/src/bootstrap/build.rs
index ab34d5c1e55..cd1f418028c 100644
--- a/src/bootstrap/build.rs
+++ b/src/bootstrap/build.rs
@@ -1,43 +1,7 @@
-use env::consts::{EXE_EXTENSION, EXE_SUFFIX};
 use std::env;
-use std::ffi::OsString;
-use std::path::PathBuf;
-
-/// Given an executable called `name`, return the filename for the
-/// executable for a particular target.
-pub fn exe(name: &PathBuf) -> PathBuf {
-    if EXE_EXTENSION != "" && name.extension() != Some(EXE_EXTENSION.as_ref()) {
-        let mut name: OsString = name.clone().into();
-        name.push(EXE_SUFFIX);
-        name.into()
-    } else {
-        name.clone()
-    }
-}
 
 fn main() {
     let host = env::var("HOST").unwrap();
     println!("cargo:rerun-if-changed=build.rs");
-    println!("cargo:rerun-if-env-changed=RUSTC");
     println!("cargo:rustc-env=BUILD_TRIPLE={}", host);
-
-    // This may not be a canonicalized path.
-    let mut rustc = PathBuf::from(env::var_os("RUSTC").unwrap());
-
-    if rustc.is_relative() {
-        println!("cargo:rerun-if-env-changed=PATH");
-        for dir in env::split_paths(&env::var_os("PATH").unwrap_or_default()) {
-            let absolute = dir.join(&exe(&rustc));
-            if absolute.exists() {
-                rustc = absolute;
-                break;
-            }
-        }
-    }
-    assert!(rustc.is_absolute());
-
-    // FIXME: if the path is not utf-8, this is going to break. Unfortunately
-    // Cargo doesn't have a way for us to specify non-utf-8 paths easily, so
-    // we'll need to invent some encoding scheme if this becomes a problem.
-    println!("cargo:rustc-env=RUSTC={}", rustc.to_str().unwrap());
 }
diff --git a/src/bootstrap/builder.rs b/src/bootstrap/builder.rs
index c33b7fc7cd6..415774d7255 100644
--- a/src/bootstrap/builder.rs
+++ b/src/bootstrap/builder.rs
@@ -1557,13 +1557,12 @@ impl<'a> Builder<'a> {
         match mode {
             Mode::ToolBootstrap => {
                 // Restrict the allowed features to those passed by rustbuild, so we don't depend on nightly accidentally.
-                // HACK: because anyhow does feature detection in build.rs, we need to allow the backtrace feature too.
-                rustflags.arg("-Zallow-features=binary-dep-depinfo,backtrace");
+                rustflags.arg("-Zallow-features=binary-dep-depinfo");
             }
             Mode::ToolStd => {
                 // Right now this is just compiletest and a few other tools that build on stable.
                 // Allow them to use `feature(test)`, but nothing else.
-                rustflags.arg("-Zallow-features=binary-dep-depinfo,test,backtrace,proc_macro_internals,proc_macro_diagnostic,proc_macro_span");
+                rustflags.arg("-Zallow-features=binary-dep-depinfo,test,proc_macro_internals,proc_macro_diagnostic,proc_macro_span");
             }
             Mode::Std | Mode::Rustc | Mode::Codegen | Mode::ToolRustc => {}
         }
diff --git a/src/test/ui/consts/issue-88071.rs b/src/test/ui/consts/issue-88071.rs
index 1c38c43e6c0..f58cdb5945e 100644
--- a/src/test/ui/consts/issue-88071.rs
+++ b/src/test/ui/consts/issue-88071.rs
@@ -2,8 +2,6 @@
 //
 // regression test for #88071
 
-#![feature(const_btree_new)]
-
 use std::collections::BTreeMap;
 
 pub struct CustomMap<K, V>(BTreeMap<K, V>);
diff --git a/src/test/ui/parser/issues/issue-101540.rs b/src/test/ui/parser/issues/issue-101540.rs
new file mode 100644
index 00000000000..328ec6f906b
--- /dev/null
+++ b/src/test/ui/parser/issues/issue-101540.rs
@@ -0,0 +1,7 @@
+struct S1 {
+    struct S2 {
+    //~^ ERROR structs are not allowed in struct definitions
+    }
+}
+
+fn main() {}
diff --git a/src/test/ui/parser/issues/issue-101540.stderr b/src/test/ui/parser/issues/issue-101540.stderr
new file mode 100644
index 00000000000..53c7c9590e6
--- /dev/null
+++ b/src/test/ui/parser/issues/issue-101540.stderr
@@ -0,0 +1,10 @@
+error: structs are not allowed in struct definitions
+  --> $DIR/issue-101540.rs:2:5
+   |
+LL |     struct S2 {
+   |     ^^^^^^^^^
+   |
+   = help: consider creating a new `struct` definition instead of nesting
+
+error: aborting due to previous error
+
diff --git a/src/tools/clippy/clippy_utils/src/qualify_min_const_fn.rs b/src/tools/clippy/clippy_utils/src/qualify_min_const_fn.rs
index 405f0228683..f7ce7191772 100644
--- a/src/tools/clippy/clippy_utils/src/qualify_min_const_fn.rs
+++ b/src/tools/clippy/clippy_utils/src/qualify_min_const_fn.rs
@@ -367,10 +367,21 @@ fn is_const_fn(tcx: TyCtxt<'_>, def_id: DefId, msrv: Option<RustcVersion>) -> bo
                 // Checking MSRV is manually necessary because `rustc` has no such concept. This entire
                 // function could be removed if `rustc` provided a MSRV-aware version of `is_const_fn`.
                 // as a part of an unimplemented MSRV check https://github.com/rust-lang/rust/issues/65262.
+
+                // HACK(nilstrieb): CURRENT_RUSTC_VERSION can return versions like 1.66.0-dev. `rustc-semver` doesn't accept
+                //                  the `-dev` version number so we have to strip it off.
+                let short_version = since
+                    .as_str()
+                    .split('-')
+                    .next()
+                    .expect("rustc_attr::StabilityLevel::Stable::since` is empty");
+
+                let since = rustc_span::Symbol::intern(short_version);
+
                 crate::meets_msrv(
                     msrv,
                     RustcVersion::parse(since.as_str())
-                        .expect("`rustc_attr::StabilityLevel::Stable::since` is ill-formatted"),
+                        .unwrap_or_else(|err| panic!("`rustc_attr::StabilityLevel::Stable::since` is ill-formatted: `{since}`, {err:?}")),
                 )
             } else {
                 // Unstable const fn with the feature enabled.
diff --git a/src/tools/clippy/tests/ui/crashes/ice-7126.rs b/src/tools/clippy/tests/ui/crashes/ice-7126.rs
index ca563ba0978..b2dc2248b55 100644
--- a/src/tools/clippy/tests/ui/crashes/ice-7126.rs
+++ b/src/tools/clippy/tests/ui/crashes/ice-7126.rs
@@ -1,13 +1,13 @@
 // This test requires a feature gated const fn and will stop working in the future.
 
-#![feature(const_btree_new)]
+#![feature(const_btree_len)]
 
 use std::collections::BTreeMap;
 
-struct Foo(BTreeMap<i32, i32>);
+struct Foo(usize);
 impl Foo {
     fn new() -> Self {
-        Self(BTreeMap::new())
+        Self(BTreeMap::len(&BTreeMap::<u8, u8>::new()))
     }
 }