diff --git a/RELEASES.md b/RELEASES.md
index 1a77c33b9957d..83eb49a3fe64c 100644
--- a/RELEASES.md
+++ b/RELEASES.md
@@ -45,83 +45,83 @@ Libraries
 Stabilized APIs
 ---------------
 
-- [`Vec::extract_if`](https://doc.rust-lang.org/nightly/std/vec/struct.Vec.html#method.extract_if)
-- [`vec::ExtractIf`](https://doc.rust-lang.org/nightly/std/vec/struct.ExtractIf.html)
-- [`LinkedList::extract_if`](https://doc.rust-lang.org/nightly/std/collections/struct.LinkedList.html#method.extract_if)
-- [`linked_list::ExtractIf`](https://doc.rust-lang.org/nightly/std/collections/linked_list/struct.ExtractIf.html)
-- [`<[T]>::split_off`](https://doc.rust-lang.org/nightly/std/primitive.slice.html#method.split_off)
-- [`<[T]>::split_off_mut`](https://doc.rust-lang.org/nightly/std/primitive.slice.html#method.split_off_mut)
-- [`<[T]>::split_off_first`](https://doc.rust-lang.org/nightly/std/primitive.slice.html#method.split_off_first)
-- [`<[T]>::split_off_first_mut`](https://doc.rust-lang.org/nightly/std/primitive.slice.html#method.split_off_first_mut)
-- [`<[T]>::split_off_last`](https://doc.rust-lang.org/nightly/std/primitive.slice.html#method.split_off_last)
-- [`<[T]>::split_off_last_mut`](https://doc.rust-lang.org/nightly/std/primitive.slice.html#method.split_off_last_mut)
+- [`Vec::extract_if`](https://doc.rust-lang.org/stable/std/vec/struct.Vec.html#method.extract_if)
+- [`vec::ExtractIf`](https://doc.rust-lang.org/stable/std/vec/struct.ExtractIf.html)
+- [`LinkedList::extract_if`](https://doc.rust-lang.org/stable/std/collections/struct.LinkedList.html#method.extract_if)
+- [`linked_list::ExtractIf`](https://doc.rust-lang.org/stable/std/collections/linked_list/struct.ExtractIf.html)
+- [`<[T]>::split_off`](https://doc.rust-lang.org/stable/std/primitive.slice.html#method.split_off)
+- [`<[T]>::split_off_mut`](https://doc.rust-lang.org/stable/std/primitive.slice.html#method.split_off_mut)
+- [`<[T]>::split_off_first`](https://doc.rust-lang.org/stable/std/primitive.slice.html#method.split_off_first)
+- [`<[T]>::split_off_first_mut`](https://doc.rust-lang.org/stable/std/primitive.slice.html#method.split_off_first_mut)
+- [`<[T]>::split_off_last`](https://doc.rust-lang.org/stable/std/primitive.slice.html#method.split_off_last)
+- [`<[T]>::split_off_last_mut`](https://doc.rust-lang.org/stable/std/primitive.slice.html#method.split_off_last_mut)
 - [`String::extend_from_within`](https://doc.rust-lang.org/stable/alloc/string/struct.String.html#method.extend_from_within)
-- [`os_str::Display`](https://doc.rust-lang.org/nightly/std/ffi/os_str/struct.Display.html)
-- [`OsString::display`](https://doc.rust-lang.org/nightly/std/ffi/struct.OsString.html#method.display)
-- [`OsStr::display`](https://doc.rust-lang.org/nightly/std/ffi/struct.OsStr.html#method.display)
-- [`io::pipe`](https://doc.rust-lang.org/nightly/std/io/fn.pipe.html)
-- [`io::PipeReader`](https://doc.rust-lang.org/nightly/std/io/struct.PipeReader.html)
-- [`io::PipeWriter`](https://doc.rust-lang.org/nightly/std/io/struct.PipeWriter.html)
-- [`impl From<PipeReader> for OwnedHandle`](https://doc.rust-lang.org/nightly/std/os/windows/io/struct.OwnedHandle.html#impl-From%3CPipeReader%3E-for-OwnedHandle)
-- [`impl From<PipeWriter> for OwnedHandle`](https://doc.rust-lang.org/nightly/std/os/windows/io/struct.OwnedHandle.html#impl-From%3CPipeWriter%3E-for-OwnedHandle)
-- [`impl From<PipeReader> for Stdio`](https://doc.rust-lang.org/nightly/std/process/struct.Stdio.html)
-- [`impl From<PipeWriter> for Stdio`](https://doc.rust-lang.org/nightly/std/process/struct.Stdio.html#impl-From%3CPipeWriter%3E-for-Stdio)
-- [`impl From<PipeReader> for OwnedFd`](https://doc.rust-lang.org/nightly/std/os/fd/struct.OwnedFd.html#impl-From%3CPipeReader%3E-for-OwnedFd)
-- [`impl From<PipeWriter> for OwnedFd`](https://doc.rust-lang.org/nightly/std/os/fd/struct.OwnedFd.html#impl-From%3CPipeWriter%3E-for-OwnedFd)
-- [`Box<MaybeUninit<T>>::write`](https://doc.rust-lang.org/nightly/std/boxed/struct.Box.html#method.write)
-- [`impl TryFrom<Vec<u8>> for String`](https://doc.rust-lang.org/nightly/std/string/struct.String.html#impl-TryFrom%3CVec%3Cu8%3E%3E-for-String)
-
-These APIs are now stable in const contexts:
-
-- [`<*const T>::offset_from_unsigned`](https://doc.rust-lang.org/nightly/std/primitive.pointer.html#method.offset_from_unsigned)
-- [`<*const T>::byte_offset_from_unsigned`](https://doc.rust-lang.org/nightly/std/primitive.pointer.html#method.byte_offset_from_unsigned)
-- [`<*mut T>::offset_from_unsigned`](https://doc.rust-lang.org/nightly/std/primitive.pointer.html#method.offset_from_unsigned-1)
-- [`<*mut T>::byte_offset_from_unsigned`](https://doc.rust-lang.org/nightly/std/primitive.pointer.html#method.byte_offset_from_unsigned-1)
-- [`NonNull::offset_from_unsigned`](https://doc.rust-lang.org/nightly/std/ptr/struct.NonNull.html#method.offset_from_unsigned)
-- [`NonNull::byte_offset_from_unsigned`](https://doc.rust-lang.org/nightly/std/ptr/struct.NonNull.html#method.byte_offset_from_unsigned)
-- [`<uN>::cast_signed`](https://doc.rust-lang.org/nightly/std/primitive.usize.html#method.cast_signed)
-- [`NonZero::<uN>::cast_signed`](https://doc.rust-lang.org/nightly/std/num/struct.NonZero.html#method.cast_signed-5).
-- [`<iN>::cast_signed`](https://doc.rust-lang.org/nightly/std/primitive.isize.html#method.cast_signed).
-- [`NonZero::<iN>::cast_unsigned`](https://doc.rust-lang.org/nightly/std/num/struct.NonZero.html#method.cast_unsigned-5).
-- [`<uN>::is_multiple_of`](https://doc.rust-lang.org/nightly/std/primitive.usize.html#method.is_multiple_of)
-- [`<uN>::unbounded_shl`](https://doc.rust-lang.org/nightly/std/primitive.usize.html#method.unbounded_shl)
-- [`<uN>::unbounded_shr`](https://doc.rust-lang.org/nightly/std/primitive.usize.html#method.unbounded_shr)
-- [`<iN>::unbounded_shl`](https://doc.rust-lang.org/nightly/std/primitive.isize.html#method.unbounded_shl)
-- [`<iN>::unbounded_shr`](https://doc.rust-lang.org/nightly/std/primitive.isize.html#method.unbounded_shr)
-- [`<str>::from_utf8`](https://doc.rust-lang.org/nightly/std/primitive.str.html#method.from_utf8)
-- [`<str>::from_utf8_mut`](https://doc.rust-lang.org/nightly/std/primitive.str.html#method.from_utf8_mut)
-- [`<str>::from_utf8_unchecked`](https://doc.rust-lang.org/nightly/std/primitive.str.html#method.from_utf8_unchecked)
-- [`<str>::from_utf8_unchecked_mut`](https://doc.rust-lang.org/nightly/std/primitive.str.html#method.from_utf8_unchecked_mut)
-- [`core::str::from_utf8_mut`](https://doc.rust-lang.org/nightly/std/str/fn.from_utf8_mut.html)
-- [`<[T]>::copy_from_slice`](https://doc.rust-lang.org/nightly/std/primitive.slice.html#method.copy_from_slice)
-- [`SocketAddr::set_ip`](https://doc.rust-lang.org/nightly/std/net/enum.SocketAddr.html#method.set_ip)
-- [`SocketAddr::set_port`](https://doc.rust-lang.org/nightly/std/net/enum.SocketAddr.html#method.set_port),
-- [`SocketAddrV4::set_ip`](https://doc.rust-lang.org/nightly/std/net/struct.SocketAddrV4.html#method.set_ip)
-- [`SocketAddrV4::set_port`](https://doc.rust-lang.org/nightly/std/net/struct.SocketAddrV4.html#method.set_port),
-- [`SocketAddrV6::set_ip`](https://doc.rust-lang.org/nightly/std/net/struct.SocketAddrV6.html#method.set_ip)
-- [`SocketAddrV6::set_port`](https://doc.rust-lang.org/nightly/std/net/struct.SocketAddrV6.html#method.set_port)
-- [`SocketAddrV6::set_flowinfo`](https://doc.rust-lang.org/nightly/std/net/struct.SocketAddrV6.html#method.set_flowinfo)
-- [`SocketAddrV6::set_scope_id`](https://doc.rust-lang.org/nightly/std/net/struct.SocketAddrV6.html#method.set_scope_id)
-- [`char::is_digit`](https://doc.rust-lang.org/nightly/std/primitive.char.html#method.is_digit)
-- [`char::is_whitespace`](https://doc.rust-lang.org/nightly/std/primitive.char.html#method.is_whitespace)
-- [`<iN>::midpoint`](https://doc.rust-lang.org/std/primitive.isize.html#method.midpoint)
-- [`<[[T; N]]>::as_flattened`](https://doc.rust-lang.org/nightly/std/primitive.slice.html#method.as_flattened)
-- [`<[[T; N]]>::as_flattened_mut`](https://doc.rust-lang.org/nightly/std/primitive.slice.html#method.as_flattened_mut) 
-- [`String::into_bytes`](https://doc.rust-lang.org/nightly/std/string/struct.String.html#method.into_bytes)
-- [`String::as_str`](https://doc.rust-lang.org/nightly/std/string/struct.String.html#method.as_str)
-- [`String::capacity`](https://doc.rust-lang.org/nightly/std/string/struct.String.html#method.capacity)
-- [`String::as_bytes`](https://doc.rust-lang.org/nightly/std/string/struct.String.html#method.as_bytes)
-- [`String::len`](https://doc.rust-lang.org/nightly/std/string/struct.String.html#method.len)
-- [`String::is_empty`](https://doc.rust-lang.org/nightly/std/string/struct.String.html#method.is_empty)
-- [`String::as_mut_str`](https://doc.rust-lang.org/nightly/std/string/struct.String.html#method.as_mut_str)
-- [`String::as_mut_vec`](https://doc.rust-lang.org/nightly/std/string/struct.String.html#method.as_mut_vec)
-- [`Vec::as_ptr`](https://doc.rust-lang.org/nightly/std/vec/struct.Vec.html#method.as_ptr)
-- [`Vec::as_slice`](https://doc.rust-lang.org/nightly/std/vec/struct.Vec.html#method.as_slice)
-- [`Vec::capacity`](https://doc.rust-lang.org/nightly/std/vec/struct.Vec.html#method.capacity)
-- [`Vec::len`](https://doc.rust-lang.org/nightly/std/vec/struct.Vec.html#method.len)
-- [`Vec::is_empty`](https://doc.rust-lang.org/nightly/std/vec/struct.Vec.html#method.is_empty)
-- [`Vec::as_mut_slice`](https://doc.rust-lang.org/nightly/std/vec/struct.Vec.html#method.as_mut_slice)
-- [`Vec::as_mut_ptr`](https://doc.rust-lang.org/nightly/std/vec/struct.Vec.html#method.as_mut_ptr)
+- [`os_str::Display`](https://doc.rust-lang.org/stable/std/ffi/os_str/struct.Display.html)
+- [`OsString::display`](https://doc.rust-lang.org/stable/std/ffi/struct.OsString.html#method.display)
+- [`OsStr::display`](https://doc.rust-lang.org/stable/std/ffi/struct.OsStr.html#method.display)
+- [`io::pipe`](https://doc.rust-lang.org/stable/std/io/fn.pipe.html)
+- [`io::PipeReader`](https://doc.rust-lang.org/stable/std/io/struct.PipeReader.html)
+- [`io::PipeWriter`](https://doc.rust-lang.org/stable/std/io/struct.PipeWriter.html)
+- [`impl From<PipeReader> for OwnedHandle`](https://doc.rust-lang.org/stable/std/os/windows/io/struct.OwnedHandle.html#impl-From%3CPipeReader%3E-for-OwnedHandle)
+- [`impl From<PipeWriter> for OwnedHandle`](https://doc.rust-lang.org/stable/std/os/windows/io/struct.OwnedHandle.html#impl-From%3CPipeWriter%3E-for-OwnedHandle)
+- [`impl From<PipeReader> for Stdio`](https://doc.rust-lang.org/stable/std/process/struct.Stdio.html)
+- [`impl From<PipeWriter> for Stdio`](https://doc.rust-lang.org/stable/std/process/struct.Stdio.html#impl-From%3CPipeWriter%3E-for-Stdio)
+- [`impl From<PipeReader> for OwnedFd`](https://doc.rust-lang.org/stable/std/os/fd/struct.OwnedFd.html#impl-From%3CPipeReader%3E-for-OwnedFd)
+- [`impl From<PipeWriter> for OwnedFd`](https://doc.rust-lang.org/stable/std/os/fd/struct.OwnedFd.html#impl-From%3CPipeWriter%3E-for-OwnedFd)
+- [`Box<MaybeUninit<T>>::write`](https://doc.rust-lang.org/stable/std/boxed/struct.Box.html#method.write)
+- [`impl TryFrom<Vec<u8>> for String`](https://doc.rust-lang.org/stable/std/string/struct.String.html#impl-TryFrom%3CVec%3Cu8%3E%3E-for-String)
+- [`<*const T>::offset_from_unsigned`](https://doc.rust-lang.org/stable/std/primitive.pointer.html#method.offset_from_unsigned)
+- [`<*const T>::byte_offset_from_unsigned`](https://doc.rust-lang.org/stable/std/primitive.pointer.html#method.byte_offset_from_unsigned)
+- [`<*mut T>::offset_from_unsigned`](https://doc.rust-lang.org/stable/std/primitive.pointer.html#method.offset_from_unsigned-1)
+- [`<*mut T>::byte_offset_from_unsigned`](https://doc.rust-lang.org/stable/std/primitive.pointer.html#method.byte_offset_from_unsigned-1)
+- [`NonNull::offset_from_unsigned`](https://doc.rust-lang.org/stable/std/ptr/struct.NonNull.html#method.offset_from_unsigned)
+- [`NonNull::byte_offset_from_unsigned`](https://doc.rust-lang.org/stable/std/ptr/struct.NonNull.html#method.byte_offset_from_unsigned)
+- [`<uN>::cast_signed`](https://doc.rust-lang.org/stable/std/primitive.usize.html#method.cast_signed)
+- [`NonZero::<uN>::cast_signed`](https://doc.rust-lang.org/stable/std/num/struct.NonZero.html#method.cast_signed-5).
+- [`<iN>::cast_unsigned`](https://doc.rust-lang.org/stable/std/primitive.isize.html#method.cast_unsigned).
+- [`NonZero::<iN>::cast_unsigned`](https://doc.rust-lang.org/stable/std/num/struct.NonZero.html#method.cast_unsigned-5).
+- [`<uN>::is_multiple_of`](https://doc.rust-lang.org/stable/std/primitive.usize.html#method.is_multiple_of)
+- [`<uN>::unbounded_shl`](https://doc.rust-lang.org/stable/std/primitive.usize.html#method.unbounded_shl)
+- [`<uN>::unbounded_shr`](https://doc.rust-lang.org/stable/std/primitive.usize.html#method.unbounded_shr)
+- [`<iN>::unbounded_shl`](https://doc.rust-lang.org/stable/std/primitive.isize.html#method.unbounded_shl)
+- [`<iN>::unbounded_shr`](https://doc.rust-lang.org/stable/std/primitive.isize.html#method.unbounded_shr)
+- [`<iN>::midpoint`](https://doc.rust-lang.org/stable/std/primitive.isize.html#method.midpoint)
+- [`<str>::from_utf8`](https://doc.rust-lang.org/stable/std/primitive.str.html#method.from_utf8)
+- [`<str>::from_utf8_mut`](https://doc.rust-lang.org/stable/std/primitive.str.html#method.from_utf8_mut)
+- [`<str>::from_utf8_unchecked`](https://doc.rust-lang.org/stable/std/primitive.str.html#method.from_utf8_unchecked)
+- [`<str>::from_utf8_unchecked_mut`](https://doc.rust-lang.org/stable/std/primitive.str.html#method.from_utf8_unchecked_mut)
+
+These previously stable APIs are now stable in const contexts:
+
+- [`core::str::from_utf8_mut`](https://doc.rust-lang.org/stable/std/str/fn.from_utf8_mut.html)
+- [`<[T]>::copy_from_slice`](https://doc.rust-lang.org/stable/std/primitive.slice.html#method.copy_from_slice)
+- [`SocketAddr::set_ip`](https://doc.rust-lang.org/stable/std/net/enum.SocketAddr.html#method.set_ip)
+- [`SocketAddr::set_port`](https://doc.rust-lang.org/stable/std/net/enum.SocketAddr.html#method.set_port),
+- [`SocketAddrV4::set_ip`](https://doc.rust-lang.org/stable/std/net/struct.SocketAddrV4.html#method.set_ip)
+- [`SocketAddrV4::set_port`](https://doc.rust-lang.org/stable/std/net/struct.SocketAddrV4.html#method.set_port),
+- [`SocketAddrV6::set_ip`](https://doc.rust-lang.org/stable/std/net/struct.SocketAddrV6.html#method.set_ip)
+- [`SocketAddrV6::set_port`](https://doc.rust-lang.org/stable/std/net/struct.SocketAddrV6.html#method.set_port)
+- [`SocketAddrV6::set_flowinfo`](https://doc.rust-lang.org/stable/std/net/struct.SocketAddrV6.html#method.set_flowinfo)
+- [`SocketAddrV6::set_scope_id`](https://doc.rust-lang.org/stable/std/net/struct.SocketAddrV6.html#method.set_scope_id)
+- [`char::is_digit`](https://doc.rust-lang.org/stable/std/primitive.char.html#method.is_digit)
+- [`char::is_whitespace`](https://doc.rust-lang.org/stable/std/primitive.char.html#method.is_whitespace)
+- [`<[[T; N]]>::as_flattened`](https://doc.rust-lang.org/stable/std/primitive.slice.html#method.as_flattened)
+- [`<[[T; N]]>::as_flattened_mut`](https://doc.rust-lang.org/stable/std/primitive.slice.html#method.as_flattened_mut) 
+- [`String::into_bytes`](https://doc.rust-lang.org/stable/std/string/struct.String.html#method.into_bytes)
+- [`String::as_str`](https://doc.rust-lang.org/stable/std/string/struct.String.html#method.as_str)
+- [`String::capacity`](https://doc.rust-lang.org/stable/std/string/struct.String.html#method.capacity)
+- [`String::as_bytes`](https://doc.rust-lang.org/stable/std/string/struct.String.html#method.as_bytes)
+- [`String::len`](https://doc.rust-lang.org/stable/std/string/struct.String.html#method.len)
+- [`String::is_empty`](https://doc.rust-lang.org/stable/std/string/struct.String.html#method.is_empty)
+- [`String::as_mut_str`](https://doc.rust-lang.org/stable/std/string/struct.String.html#method.as_mut_str)
+- [`String::as_mut_vec`](https://doc.rust-lang.org/stable/std/string/struct.String.html#method.as_mut_vec)
+- [`Vec::as_ptr`](https://doc.rust-lang.org/stable/std/vec/struct.Vec.html#method.as_ptr)
+- [`Vec::as_slice`](https://doc.rust-lang.org/stable/std/vec/struct.Vec.html#method.as_slice)
+- [`Vec::capacity`](https://doc.rust-lang.org/stable/std/vec/struct.Vec.html#method.capacity)
+- [`Vec::len`](https://doc.rust-lang.org/stable/std/vec/struct.Vec.html#method.len)
+- [`Vec::is_empty`](https://doc.rust-lang.org/stable/std/vec/struct.Vec.html#method.is_empty)
+- [`Vec::as_mut_slice`](https://doc.rust-lang.org/stable/std/vec/struct.Vec.html#method.as_mut_slice)
+- [`Vec::as_mut_ptr`](https://doc.rust-lang.org/stable/std/vec/struct.Vec.html#method.as_mut_ptr)
 
 <a id="1.87.0-Cargo"></a>
 
diff --git a/compiler/rustc_parse/messages.ftl b/compiler/rustc_parse/messages.ftl
index 3d7e0fcc30869..f88c15785d336 100644
--- a/compiler/rustc_parse/messages.ftl
+++ b/compiler/rustc_parse/messages.ftl
@@ -690,8 +690,8 @@ parse_nul_in_c_str = null characters in C string literals are not supported
 
 parse_or_in_let_chain = `||` operators are not supported in let chain conditions
 
-parse_or_pattern_not_allowed_in_fn_parameters = top-level or-patterns are not allowed in function parameters
-parse_or_pattern_not_allowed_in_let_binding = top-level or-patterns are not allowed in `let` bindings
+parse_or_pattern_not_allowed_in_fn_parameters = function parameters require top-level or-patterns in parentheses
+parse_or_pattern_not_allowed_in_let_binding = `let` bindings require top-level or-patterns in parentheses
 parse_out_of_range_hex_escape = out of range hex escape
     .label = must be a character in the range [\x00-\x7f]
 
diff --git a/src/doc/edition-guide b/src/doc/edition-guide
index 467f45637b73e..1b1bb49babd65 160000
--- a/src/doc/edition-guide
+++ b/src/doc/edition-guide
@@ -1 +1 @@
-Subproject commit 467f45637b73ec6aa70fb36bc3054bb50b8967ea
+Subproject commit 1b1bb49babd65c732468cfa515b0c009bd1d26bc
diff --git a/src/librustdoc/config.rs b/src/librustdoc/config.rs
index 4ef73ff48edb5..f93aa8ffd0de9 100644
--- a/src/librustdoc/config.rs
+++ b/src/librustdoc/config.rs
@@ -174,7 +174,7 @@ pub(crate) struct Options {
     pub(crate) expanded_args: Vec<String>,
 
     /// Arguments to be used when compiling doctests.
-    pub(crate) doctest_compilation_args: Vec<String>,
+    pub(crate) doctest_build_args: Vec<String>,
 }
 
 impl fmt::Debug for Options {
@@ -802,7 +802,7 @@ impl Options {
         let scrape_examples_options = ScrapeExamplesOptions::new(matches, dcx);
         let with_examples = matches.opt_strs("with-examples");
         let call_locations = crate::scrape_examples::load_call_locations(with_examples, dcx);
-        let doctest_compilation_args = matches.opt_strs("doctest-compilation-args");
+        let doctest_build_args = matches.opt_strs("doctest-build-arg");
 
         let unstable_features =
             rustc_feature::UnstableFeatures::from_environment(crate_name.as_deref());
@@ -851,7 +851,7 @@ impl Options {
             scrape_examples_options,
             unstable_features,
             expanded_args: args,
-            doctest_compilation_args,
+            doctest_build_args,
         };
         let render_options = RenderOptions {
             output,
diff --git a/src/librustdoc/doctest.rs b/src/librustdoc/doctest.rs
index 0cdf2f92a8917..ef70b8621857a 100644
--- a/src/librustdoc/doctest.rs
+++ b/src/librustdoc/doctest.rs
@@ -51,46 +51,6 @@ pub(crate) struct GlobalTestOptions {
     pub(crate) args_file: PathBuf,
 }
 
-/// Function used to split command line arguments just like a shell would.
-fn split_args(args: &str) -> Vec<String> {
-    let mut out = Vec::new();
-    let mut iter = args.chars();
-    let mut current = String::new();
-
-    while let Some(c) = iter.next() {
-        if c == '\\' {
-            if let Some(c) = iter.next() {
-                // If it's escaped, even a quote or a whitespace will be ignored.
-                current.push(c);
-            }
-        } else if c == '"' || c == '\'' {
-            while let Some(new_c) = iter.next() {
-                if new_c == c {
-                    break;
-                } else if new_c == '\\' {
-                    if let Some(c) = iter.next() {
-                        // If it's escaped, even a quote will be ignored.
-                        current.push(c);
-                    }
-                } else {
-                    current.push(new_c);
-                }
-            }
-        } else if " \n\t\r".contains(c) {
-            if !current.is_empty() {
-                out.push(current.clone());
-                current.clear();
-            }
-        } else {
-            current.push(c);
-        }
-    }
-    if !current.is_empty() {
-        out.push(current);
-    }
-    out
-}
-
 pub(crate) fn generate_args_file(file_path: &Path, options: &RustdocOptions) -> Result<(), String> {
     let mut file = File::create(file_path)
         .map_err(|error| format!("failed to create args file: {error:?}"))?;
@@ -119,9 +79,7 @@ pub(crate) fn generate_args_file(file_path: &Path, options: &RustdocOptions) ->
         content.push(format!("-Z{unstable_option_str}"));
     }
 
-    for compilation_args in &options.doctest_compilation_args {
-        content.extend(split_args(compilation_args));
-    }
+    content.extend(options.doctest_build_args.clone());
 
     let content = content.join("\n");
 
diff --git a/src/librustdoc/doctest/tests.rs b/src/librustdoc/doctest/tests.rs
index 49add73e9d64b..618c2041b43c9 100644
--- a/src/librustdoc/doctest/tests.rs
+++ b/src/librustdoc/doctest/tests.rs
@@ -381,28 +381,6 @@ fn main() {
     assert_eq!((output, len), (expected, 1));
 }
 
-#[test]
-fn check_split_args() {
-    fn compare(input: &str, expected: &[&str]) {
-        let output = super::split_args(input);
-        let expected = expected.iter().map(|s| s.to_string()).collect::<Vec<_>>();
-        assert_eq!(expected, output, "test failed for {input:?}");
-    }
-
-    compare("'a' \"b\"c", &["a", "bc"]);
-    compare("'a' \"b \"c d", &["a", "b c", "d"]);
-    compare("'a' \"b\\\"c\"", &["a", "b\"c"]);
-    compare("'a\"'", &["a\""]);
-    compare("\"a'\"", &["a'"]);
-    compare("\\ a", &[" a"]);
-    compare("\\\\", &["\\"]);
-    compare("a'", &["a"]);
-    compare("a          ", &["a"]);
-    compare("a          b", &["a", "b"]);
-    compare("a\n\t \rb", &["a", "b"]);
-    compare("a\n\t1 \rb", &["a", "1", "b"]);
-}
-
 #[test]
 fn comment_in_attrs() {
     // If there is an inline code comment after attributes, we need to ensure that
diff --git a/src/librustdoc/lib.rs b/src/librustdoc/lib.rs
index bca40b8117bdb..b4210e7b51819 100644
--- a/src/librustdoc/lib.rs
+++ b/src/librustdoc/lib.rs
@@ -73,9 +73,11 @@ extern crate tikv_jemalloc_sys as jemalloc_sys;
 
 use std::env::{self, VarError};
 use std::io::{self, IsTerminal};
+use std::path::Path;
 use std::process;
 
 use rustc_errors::DiagCtxtHandle;
+use rustc_hir::def_id::LOCAL_CRATE;
 use rustc_interface::interface;
 use rustc_middle::ty::TyCtxt;
 use rustc_session::config::{ErrorOutputType, RustcOptGroup, make_crate_type_option};
@@ -654,9 +656,9 @@ fn opts() -> Vec<RustcOptGroup> {
             Unstable,
             Multi,
             "",
-            "doctest-compilation-args",
-            "",
-            "add arguments to be used when compiling doctests",
+            "doctest-build-arg",
+            "One argument (of possibly many) to be used when compiling doctests",
+            "ARG",
         ),
         opt(
             Unstable,
@@ -904,6 +906,10 @@ fn main_args(early_dcx: &mut EarlyDiagCtxt, at_args: &[String]) {
                 rustc_interface::passes::write_dep_info(tcx);
             }
 
+            if let Some(metrics_dir) = &sess.opts.unstable_opts.metrics_dir {
+                dump_feature_usage_metrics(tcx, metrics_dir);
+            }
+
             if run_check {
                 // Since we're in "check" mode, no need to generate anything beyond this point.
                 return;
@@ -923,3 +929,16 @@ fn main_args(early_dcx: &mut EarlyDiagCtxt, at_args: &[String]) {
         })
     })
 }
+
+fn dump_feature_usage_metrics(tcxt: TyCtxt<'_>, metrics_dir: &Path) {
+    let hash = tcxt.crate_hash(LOCAL_CRATE);
+    let crate_name = tcxt.crate_name(LOCAL_CRATE);
+    let metrics_file_name = format!("unstable_feature_usage_metrics-{crate_name}-{hash}.json");
+    let metrics_path = metrics_dir.join(metrics_file_name);
+    if let Err(error) = tcxt.features().dump_feature_usage_metrics(metrics_path) {
+        // FIXME(yaahc): once metrics can be enabled by default we will want "failure to emit
+        // default metrics" to only produce a warning when metrics are enabled by default and emit
+        // an error only when the user manually enables metrics
+        tcxt.dcx().err(format!("cannot emit feature usage metrics: {error}"));
+    }
+}
diff --git a/src/tools/run-make-support/src/command.rs b/src/tools/run-make-support/src/command.rs
index 70a72bd1abebe..b46ddd1d3154b 100644
--- a/src/tools/run-make-support/src/command.rs
+++ b/src/tools/run-make-support/src/command.rs
@@ -63,6 +63,12 @@ impl Command {
         }
     }
 
+    // Internal-only.
+    pub(crate) fn into_raw_command(mut self) -> std::process::Command {
+        self.drop_bomb.defuse();
+        self.cmd
+    }
+
     /// Specify a stdin input buffer. This is a convenience helper,
     pub fn stdin_buf<I: AsRef<[u8]>>(&mut self, input: I) -> &mut Self {
         self.stdin_buf = Some(input.as_ref().to_vec().into_boxed_slice());
diff --git a/src/tools/run-make-support/src/external_deps/rustdoc.rs b/src/tools/run-make-support/src/external_deps/rustdoc.rs
index 433a57cd9fa65..7040fb667cfcc 100644
--- a/src/tools/run-make-support/src/external_deps/rustdoc.rs
+++ b/src/tools/run-make-support/src/external_deps/rustdoc.rs
@@ -5,7 +5,7 @@ use crate::command::Command;
 use crate::env::env_var;
 use crate::util::set_host_compiler_dylib_path;
 
-/// Construct a new `rustdoc` invocation.
+/// Construct a new `rustdoc` invocation. This will configure the host compiler runtime libs.
 #[track_caller]
 pub fn rustdoc() -> Rustdoc {
     Rustdoc::new()
@@ -28,7 +28,7 @@ fn setup_common() -> Command {
 }
 
 impl Rustdoc {
-    /// Construct a bare `rustdoc` invocation.
+    /// Construct a bare `rustdoc` invocation. This will configure the host compiler runtime libs.
     #[track_caller]
     pub fn new() -> Self {
         let cmd = setup_common();
diff --git a/src/tools/run-make-support/src/macros.rs b/src/tools/run-make-support/src/macros.rs
index 94955aefe57aa..9d5cc4e5876df 100644
--- a/src/tools/run-make-support/src/macros.rs
+++ b/src/tools/run-make-support/src/macros.rs
@@ -28,6 +28,18 @@
 macro_rules! impl_common_helpers {
     ($wrapper: ident) => {
         impl $wrapper {
+            /// In very rare circumstances, you may need a e.g. `bare_rustc()` or `bare_rustdoc()`
+            /// with host runtime libs configured, but want the underlying raw
+            /// [`std::process::Command`] (e.g. for manipulating pipes or whatever). This function
+            /// will consume the command wrapper and extract the underlying
+            /// [`std::process::Command`].
+            ///
+            /// Caution: this will mean that you can no longer use the convenience methods on the
+            /// command wrapper. Use as a last resort.
+            pub fn into_raw_command(self) -> ::std::process::Command {
+                self.cmd.into_raw_command()
+            }
+
             /// Specify an environment variable.
             pub fn env<K, V>(&mut self, key: K, value: V) -> &mut Self
             where
diff --git a/tests/run-make/broken-pipe-no-ice/rmake.rs b/tests/run-make/broken-pipe-no-ice/rmake.rs
index 0521b3950207d..b0a28b6c899da 100644
--- a/tests/run-make/broken-pipe-no-ice/rmake.rs
+++ b/tests/run-make/broken-pipe-no-ice/rmake.rs
@@ -14,7 +14,7 @@
 use std::io::Read;
 use std::process::{Command, Stdio};
 
-use run_make_support::env_var;
+use run_make_support::{bare_rustc, rustdoc};
 
 #[derive(Debug, PartialEq)]
 enum Binary {
@@ -67,11 +67,13 @@ fn check_broken_pipe_handled_gracefully(bin: Binary, mut cmd: Command) {
 }
 
 fn main() {
-    let mut rustc = Command::new(env_var("RUSTC"));
+    let mut rustc = bare_rustc();
     rustc.arg("--print=sysroot");
+    let rustc = rustc.into_raw_command();
     check_broken_pipe_handled_gracefully(Binary::Rustc, rustc);
 
-    let mut rustdoc = Command::new(env_var("RUSTDOC"));
+    let mut rustdoc = rustdoc();
     rustdoc.arg("--version");
+    let rustdoc = rustdoc.into_raw_command();
     check_broken_pipe_handled_gracefully(Binary::Rustdoc, rustdoc);
 }
diff --git a/tests/run-make/rustdoc-default-output/output-default.stdout b/tests/run-make/rustdoc-default-output/output-default.stdout
index 78ca8c863ebab..506f135ff8e72 100644
--- a/tests/run-make/rustdoc-default-output/output-default.stdout
+++ b/tests/run-make/rustdoc-default-output/output-default.stdout
@@ -188,8 +188,9 @@ Options:
                         from provided path. Only use with --merge=finalize
         --html-no-source 
                         Disable HTML source code pages generation
-        --doctest-compilation-args add arguments to be used when compiling doctests
-                        
+        --doctest-build-arg ARG
+                        One argument (of possibly many) to be used when
+                        compiling doctests
         --disable-minification 
                         disable the minification of CSS/JS files
                         (perma-unstable, do not use with cached files)
diff --git a/tests/rustdoc-ui/doctest/rustflags-multiple-args.rs b/tests/rustdoc-ui/doctest/rustflags-multiple-args.rs
index 8d8c60ede5856..88e2e0cf01977 100644
--- a/tests/rustdoc-ui/doctest/rustflags-multiple-args.rs
+++ b/tests/rustdoc-ui/doctest/rustflags-multiple-args.rs
@@ -1,9 +1,8 @@
-// This test checks that the test behave when `--doctest-compilation-args` is passed
-// multiple times.
+// This test checks that the test behave when `--doctest-build-arg` is passed multiple times.
 
 //@ check-pass
-//@ compile-flags: --test -Zunstable-options --doctest-compilation-args=--cfg=testcase_must_be_present
-//@ compile-flags: --doctest-compilation-args=--cfg=another
+//@ compile-flags: --test -Zunstable-options --doctest-build-arg=--cfg=testcase_must_be_present
+//@ compile-flags: --doctest-build-arg=--cfg=another
 //@ normalize-stdout: "tests/rustdoc-ui/doctest" -> "$$DIR"
 //@ normalize-stdout: "finished in \d+\.\d+s" -> "finished in $$TIME"
 
diff --git a/tests/rustdoc-ui/doctest/rustflags-multiple-args.stdout b/tests/rustdoc-ui/doctest/rustflags-multiple-args.stdout
index 0e8a9e1efcf6f..f6b8ad6afabba 100644
--- a/tests/rustdoc-ui/doctest/rustflags-multiple-args.stdout
+++ b/tests/rustdoc-ui/doctest/rustflags-multiple-args.stdout
@@ -1,6 +1,6 @@
 
 running 1 test
-test $DIR/rustflags-multiple-args.rs - Bar (line 10) ... ok
+test $DIR/rustflags-multiple-args.rs - Bar (line 9) ... ok
 
 test result: ok. 1 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out; finished in $TIME
 
diff --git a/tests/rustdoc-ui/doctest/rustflags.rs b/tests/rustdoc-ui/doctest/rustflags.rs
index 9f1e6017ea15f..f030158cdaa49 100644
--- a/tests/rustdoc-ui/doctest/rustflags.rs
+++ b/tests/rustdoc-ui/doctest/rustflags.rs
@@ -1,5 +1,5 @@
 //@ check-pass
-//@ compile-flags: --test -Zunstable-options --doctest-compilation-args=--cfg=testcase_must_be_present
+//@ compile-flags: --test -Zunstable-options --doctest-build-arg=--cfg=testcase_must_be_present
 //@ normalize-stdout: "tests/rustdoc-ui/doctest" -> "$$DIR"
 //@ normalize-stdout: "finished in \d+\.\d+s" -> "finished in $$TIME"
 
diff --git a/tests/ui/or-patterns/fn-param-wrap-parens.fixed b/tests/ui/or-patterns/fn-param-wrap-parens.fixed
index fbf60069c7d42..608f826390da6 100644
--- a/tests/ui/or-patterns/fn-param-wrap-parens.fixed
+++ b/tests/ui/or-patterns/fn-param-wrap-parens.fixed
@@ -10,4 +10,4 @@ enum E { A, B }
 use E::*;
 
 #[cfg(false)]
-fn fun1((A | B): E) {} //~ ERROR top-level or-patterns are not allowed
+fn fun1((A | B): E) {} //~ ERROR function parameters require top-level or-patterns in parentheses
diff --git a/tests/ui/or-patterns/fn-param-wrap-parens.rs b/tests/ui/or-patterns/fn-param-wrap-parens.rs
index d796f998e97c7..d6fe7e9bf5860 100644
--- a/tests/ui/or-patterns/fn-param-wrap-parens.rs
+++ b/tests/ui/or-patterns/fn-param-wrap-parens.rs
@@ -10,4 +10,4 @@ enum E { A, B }
 use E::*;
 
 #[cfg(false)]
-fn fun1(A | B: E) {} //~ ERROR top-level or-patterns are not allowed
+fn fun1(A | B: E) {} //~ ERROR function parameters require top-level or-patterns in parentheses
diff --git a/tests/ui/or-patterns/fn-param-wrap-parens.stderr b/tests/ui/or-patterns/fn-param-wrap-parens.stderr
index da2832ef1ae41..e0307b44e8386 100644
--- a/tests/ui/or-patterns/fn-param-wrap-parens.stderr
+++ b/tests/ui/or-patterns/fn-param-wrap-parens.stderr
@@ -1,4 +1,4 @@
-error: top-level or-patterns are not allowed in function parameters
+error: function parameters require top-level or-patterns in parentheses
   --> $DIR/fn-param-wrap-parens.rs:13:9
    |
 LL | fn fun1(A | B: E) {}
diff --git a/tests/ui/or-patterns/nested-undelimited-precedence.rs b/tests/ui/or-patterns/nested-undelimited-precedence.rs
index 047836203575f..73f72cb3f8616 100644
--- a/tests/ui/or-patterns/nested-undelimited-precedence.rs
+++ b/tests/ui/or-patterns/nested-undelimited-precedence.rs
@@ -17,7 +17,7 @@ fn foo() {
     let b @ (A | B): E = A;
 
     let b @ A | B: E = A; //~ERROR `b` is not bound in all patterns
-    //~^ ERROR top-level or-patterns are not allowed
+    //~^ ERROR `let` bindings require top-level or-patterns in parentheses
 }
 
 enum F {
@@ -32,13 +32,13 @@ fn bar() {
     let (A(x) | B(x)): F = A(3);
 
     let &A(_) | B(_): F = A(3); //~ERROR mismatched types
-    //~^ ERROR top-level or-patterns are not allowed
+    //~^ ERROR `let` bindings require top-level or-patterns in parentheses
     let &&A(_) | B(_): F = A(3); //~ERROR mismatched types
-    //~^ ERROR top-level or-patterns are not allowed
+    //~^ ERROR `let` bindings require top-level or-patterns in parentheses
     let &mut A(_) | B(_): F = A(3); //~ERROR mismatched types
-    //~^ ERROR top-level or-patterns are not allowed
+    //~^ ERROR `let` bindings require top-level or-patterns in parentheses
     let &&mut A(_) | B(_): F = A(3); //~ERROR mismatched types
-    //~^ ERROR top-level or-patterns are not allowed
+    //~^ ERROR `let` bindings require top-level or-patterns in parentheses
 }
 
 fn main() {}
diff --git a/tests/ui/or-patterns/nested-undelimited-precedence.stderr b/tests/ui/or-patterns/nested-undelimited-precedence.stderr
index f16d83ecaea93..0835ca1929f15 100644
--- a/tests/ui/or-patterns/nested-undelimited-precedence.stderr
+++ b/tests/ui/or-patterns/nested-undelimited-precedence.stderr
@@ -1,4 +1,4 @@
-error: top-level or-patterns are not allowed in `let` bindings
+error: `let` bindings require top-level or-patterns in parentheses
   --> $DIR/nested-undelimited-precedence.rs:19:9
    |
 LL |     let b @ A | B: E = A;
@@ -9,7 +9,7 @@ help: wrap the pattern in parentheses
 LL |     let (b @ A | B): E = A;
    |         +         +
 
-error: top-level or-patterns are not allowed in `let` bindings
+error: `let` bindings require top-level or-patterns in parentheses
   --> $DIR/nested-undelimited-precedence.rs:34:9
    |
 LL |     let &A(_) | B(_): F = A(3);
@@ -20,7 +20,7 @@ help: wrap the pattern in parentheses
 LL |     let (&A(_) | B(_)): F = A(3);
    |         +            +
 
-error: top-level or-patterns are not allowed in `let` bindings
+error: `let` bindings require top-level or-patterns in parentheses
   --> $DIR/nested-undelimited-precedence.rs:36:9
    |
 LL |     let &&A(_) | B(_): F = A(3);
@@ -31,7 +31,7 @@ help: wrap the pattern in parentheses
 LL |     let (&&A(_) | B(_)): F = A(3);
    |         +             +
 
-error: top-level or-patterns are not allowed in `let` bindings
+error: `let` bindings require top-level or-patterns in parentheses
   --> $DIR/nested-undelimited-precedence.rs:38:9
    |
 LL |     let &mut A(_) | B(_): F = A(3);
@@ -42,7 +42,7 @@ help: wrap the pattern in parentheses
 LL |     let (&mut A(_) | B(_)): F = A(3);
    |         +                +
 
-error: top-level or-patterns are not allowed in `let` bindings
+error: `let` bindings require top-level or-patterns in parentheses
   --> $DIR/nested-undelimited-precedence.rs:40:9
    |
 LL |     let &&mut A(_) | B(_): F = A(3);
diff --git a/tests/ui/or-patterns/or-patterns-syntactic-fail.rs b/tests/ui/or-patterns/or-patterns-syntactic-fail.rs
index 23dbb57cbcf0f..bc4babe709b70 100644
--- a/tests/ui/or-patterns/or-patterns-syntactic-fail.rs
+++ b/tests/ui/or-patterns/or-patterns-syntactic-fail.rs
@@ -16,18 +16,18 @@ fn no_top_level_or_patterns() {
 fn no_top_level_or_patterns_2() {
     // ...and for now neither do we allow or-patterns at the top level of functions.
     fn fun1(A | B: E) {}
-    //~^ ERROR top-level or-patterns are not allowed
+    //~^ ERROR function parameters require top-level or-patterns in parentheses
 
     fn fun2(| A | B: E) {}
-    //~^ ERROR top-level or-patterns are not allowed
+    //~^ ERROR function parameters require top-level or-patterns in parentheses
 
     // We don't allow top-level or-patterns before type annotation in let-statements because we
     // want to reserve this syntactic space for possible future type ascription.
     let A | B: E = A;
-    //~^ ERROR top-level or-patterns are not allowed
+    //~^ ERROR `let` bindings require top-level or-patterns in parentheses
 
     let | A | B: E = A;
-    //~^ ERROR top-level or-patterns are not allowed
+    //~^ ERROR `let` bindings require top-level or-patterns in parentheses
 
     let (A | B): E = A; // ok -- wrapped in parens
 }
diff --git a/tests/ui/or-patterns/or-patterns-syntactic-fail.stderr b/tests/ui/or-patterns/or-patterns-syntactic-fail.stderr
index 74e4ceab80e88..f6b7d427bd60e 100644
--- a/tests/ui/or-patterns/or-patterns-syntactic-fail.stderr
+++ b/tests/ui/or-patterns/or-patterns-syntactic-fail.stderr
@@ -11,7 +11,7 @@ help: you might have meant to open the body of the closure
 LL |     let _ = |A | { B: E| ();
    |                  +
 
-error: top-level or-patterns are not allowed in function parameters
+error: function parameters require top-level or-patterns in parentheses
   --> $DIR/or-patterns-syntactic-fail.rs:18:13
    |
 LL |     fn fun1(A | B: E) {}
@@ -22,7 +22,7 @@ help: wrap the pattern in parentheses
 LL |     fn fun1((A | B): E) {}
    |             +     +
 
-error: top-level or-patterns are not allowed in function parameters
+error: function parameters require top-level or-patterns in parentheses
   --> $DIR/or-patterns-syntactic-fail.rs:21:13
    |
 LL |     fn fun2(| A | B: E) {}
@@ -33,7 +33,7 @@ help: wrap the pattern in parentheses
 LL |     fn fun2((| A | B): E) {}
    |             +       +
 
-error: top-level or-patterns are not allowed in `let` bindings
+error: `let` bindings require top-level or-patterns in parentheses
   --> $DIR/or-patterns-syntactic-fail.rs:26:9
    |
 LL |     let A | B: E = A;
@@ -44,7 +44,7 @@ help: wrap the pattern in parentheses
 LL |     let (A | B): E = A;
    |         +     +
 
-error: top-level or-patterns are not allowed in `let` bindings
+error: `let` bindings require top-level or-patterns in parentheses
   --> $DIR/or-patterns-syntactic-fail.rs:29:9
    |
 LL |     let | A | B: E = A;
diff --git a/tests/ui/or-patterns/remove-leading-vert.fixed b/tests/ui/or-patterns/remove-leading-vert.fixed
index 136ca5765b7e2..2851b8f18c54a 100644
--- a/tests/ui/or-patterns/remove-leading-vert.fixed
+++ b/tests/ui/or-patterns/remove-leading-vert.fixed
@@ -8,7 +8,7 @@ fn main() {}
 
 #[cfg(false)]
 fn leading() {
-    fn fun1(  A: E) {} //~ ERROR top-level or-patterns are not allowed
+    fn fun1(  A: E) {} //~ ERROR function parameters require top-level or-patterns in parentheses
     fn fun2(  A: E) {} //~ ERROR unexpected `||` before function parameter
     let ( | A): E;
     let ( | A): (E); //~ ERROR unexpected token `||` in pattern
diff --git a/tests/ui/or-patterns/remove-leading-vert.rs b/tests/ui/or-patterns/remove-leading-vert.rs
index d9e9c9fe4d2f8..1e1dbfbc6e665 100644
--- a/tests/ui/or-patterns/remove-leading-vert.rs
+++ b/tests/ui/or-patterns/remove-leading-vert.rs
@@ -8,7 +8,7 @@ fn main() {}
 
 #[cfg(false)]
 fn leading() {
-    fn fun1( | A: E) {} //~ ERROR top-level or-patterns are not allowed
+    fn fun1( | A: E) {} //~ ERROR function parameters require top-level or-patterns in parentheses
     fn fun2( || A: E) {} //~ ERROR unexpected `||` before function parameter
     let ( | A): E;
     let ( || A): (E); //~ ERROR unexpected token `||` in pattern
diff --git a/tests/ui/or-patterns/remove-leading-vert.stderr b/tests/ui/or-patterns/remove-leading-vert.stderr
index b92fcb89a404e..0323c64f04231 100644
--- a/tests/ui/or-patterns/remove-leading-vert.stderr
+++ b/tests/ui/or-patterns/remove-leading-vert.stderr
@@ -1,4 +1,4 @@
-error: top-level or-patterns are not allowed in function parameters
+error: function parameters require top-level or-patterns in parentheses
   --> $DIR/remove-leading-vert.rs:11:14
    |
 LL |     fn fun1( | A: E) {}
diff --git a/tests/ui/rfcs/rfc-0000-never_patterns/parse.rs b/tests/ui/rfcs/rfc-0000-never_patterns/parse.rs
index 566bb07164640..e004e6612107a 100644
--- a/tests/ui/rfcs/rfc-0000-never_patterns/parse.rs
+++ b/tests/ui/rfcs/rfc-0000-never_patterns/parse.rs
@@ -65,7 +65,7 @@ fn parse(x: Void) {
     let res: Result<bool, Void> = Ok(false);
     let Ok(_) = res;
     let Ok(_) | Err(!) = &res; // Disallowed; see #82048.
-    //~^ ERROR top-level or-patterns are not allowed in `let` bindings
+    //~^ ERROR `let` bindings require top-level or-patterns in parentheses
     let (Ok(_) | Err(!)) = &res;
     let (Ok(_) | Err(&!)) = res.as_ref();
 
diff --git a/tests/ui/rfcs/rfc-0000-never_patterns/parse.stderr b/tests/ui/rfcs/rfc-0000-never_patterns/parse.stderr
index 05980510f1cde..320e157f71724 100644
--- a/tests/ui/rfcs/rfc-0000-never_patterns/parse.stderr
+++ b/tests/ui/rfcs/rfc-0000-never_patterns/parse.stderr
@@ -26,7 +26,7 @@ error: expected one of `,`, `=>`, `if`, `|`, or `}`, found `<=`
 LL |         Some(!) <=
    |                 ^^ expected one of `,`, `=>`, `if`, `|`, or `}`
 
-error: top-level or-patterns are not allowed in `let` bindings
+error: `let` bindings require top-level or-patterns in parentheses
   --> $DIR/parse.rs:67:9
    |
 LL |     let Ok(_) | Err(!) = &res; // Disallowed; see #82048.
diff --git a/tests/ui/traits/const-traits/const-trait-impl-parameter-mismatch.rs b/tests/ui/traits/const-traits/const-trait-impl-parameter-mismatch.rs
new file mode 100644
index 0000000000000..f90ff91aff4bb
--- /dev/null
+++ b/tests/ui/traits/const-traits/const-trait-impl-parameter-mismatch.rs
@@ -0,0 +1,32 @@
+// This test demonstrates an ICE that may occur when we try to resolve the instance
+// of a impl that has different generics than the trait it's implementing. This ensures
+// we first check that the args are compatible before resolving the body, just like
+// we do in projection before substituting a GAT.
+//
+// Regression test for issue #125877.
+
+//@ compile-flags: -Znext-solver
+
+#![feature(const_trait_impl, effects)]
+//~^ ERROR feature has been removed
+
+#[const_trait]
+trait Main {
+    fn compute<T: ~const Aux>() -> u32;
+}
+
+impl const Main for () {
+    fn compute<'x>() -> u32 {
+        //~^ ERROR associated function `compute` has 0 type parameters but its trait declaration has 1 type parameter
+        0
+    }
+}
+
+#[const_trait]
+trait Aux {}
+
+impl const Aux for () {}
+
+fn main() {
+    const _: u32 = <()>::compute::<()>();
+}
diff --git a/tests/ui/traits/const-traits/const-trait-impl-parameter-mismatch.stderr b/tests/ui/traits/const-traits/const-trait-impl-parameter-mismatch.stderr
new file mode 100644
index 0000000000000..d45c4cba1f8b5
--- /dev/null
+++ b/tests/ui/traits/const-traits/const-trait-impl-parameter-mismatch.stderr
@@ -0,0 +1,21 @@
+error[E0557]: feature has been removed
+  --> $DIR/const-trait-impl-parameter-mismatch.rs:10:30
+   |
+LL | #![feature(const_trait_impl, effects)]
+   |                              ^^^^^^^ feature has been removed
+   |
+   = note: removed, redundant with `#![feature(const_trait_impl)]`
+
+error[E0049]: associated function `compute` has 0 type parameters but its trait declaration has 1 type parameter
+  --> $DIR/const-trait-impl-parameter-mismatch.rs:19:16
+   |
+LL |     fn compute<T: ~const Aux>() -> u32;
+   |                - expected 1 type parameter
+...
+LL |     fn compute<'x>() -> u32 {
+   |                ^^ found 0 type parameters
+
+error: aborting due to 2 previous errors
+
+Some errors have detailed explanations: E0049, E0557.
+For more information about an error, try `rustc --explain E0049`.