rust-bors · Oct 16, 2026 · Sep 23, 2026 · Sep 28, 2026 · Sep 28, 2026 · Sep 28, 2026
diff --git a/compiler/rustc_ast_lowering/src/delegation/resolution.rs b/compiler/rustc_ast_lowering/src/delegation/resolution.rs
@@ -484,16 +484,22 @@ impl<'tcx> DelegationResolver<'_, 'tcx> {
                 }
             }
 
-            mapping.map_return = SelfFinder::contains_self(sig.output());
-
-            let arguments_to_map = sig
-                .inputs()
-                .iter()
-                .enumerate()
-                .skip(1) // Already checked above.
-                .filter_map(|(idx, &param)| SelfFinder::contains_self(param).then_some(idx));
+            // Heuristic: don't do wrapping if there is no target expression.
+            if delegation.body.is_some() {
+                let arguments_to_map = sig
+                    .inputs()
+                    .iter()
+                    .enumerate()
+                    .skip(1) // Already checked above.
+                    .filter_map(|(idx, &param)| SelfFinder::contains_self(param).then_some(idx));
+
+                mapping.arguments_to_map.extend(arguments_to_map);
+            }
 
-            mapping.arguments_to_map.extend(arguments_to_map);
+            // Even if there is no target expression an output should be mapped,
+            // this is the case for functions without receiver which return `Self`
+            // for example.
+            mapping.map_return = SelfFinder::contains_self(sig.output());
         }
 
         // We can't yet map more than one argument if there are definitions inside.
@@ -513,11 +519,6 @@ impl<'tcx> DelegationResolver<'_, 'tcx> {
         parent: LocalDefId,
         span: Span,
     ) -> bool {
-        // Heuristic: don't do wrapping if there is no target expression.
-        if delegation.body.is_none() {
-            return false;
-        }
-
         let tcx = self.tcx();
 
         // Apply wrapping for delegations inside

diff --git a/compiler/rustc_hir_analysis/src/check/compare_impl_item.rs b/compiler/rustc_hir_analysis/src/check/compare_impl_item.rs
@@ -2141,7 +2141,16 @@ fn compare_const_generic_param_types<'tcx>(
         iter::zip(const_params_of(impl_item.def_id), const_params_of(trait_item.def_id));
 
     for (param_impl, param_trait) in param_iter {
-        let param_impl_ty_span = tcx.ty_span(param_impl.def_id.expect_local());
+        // If `impl_item` comes from RPITIT:
+        // <https://rustc-dev-guide.rust-lang.org/return-position-impl-trait-in-trait.html>
+        // then expecting a `LocalDefId` for `param_impl` is fraught: the synthetic
+        // associated type reuses the trait's generic parameters, which may be nonlocal.
+        // Use the impl item's span instead.
+        let param_impl_ty_span = if impl_item.is_impl_trait_in_trait() {
+            tcx.def_span(impl_item.def_id)
+        } else {
+            tcx.ty_span(param_impl.def_id.expect_local())
+        };
 
         let cause = ObligationCause::new(
             param_impl_ty_span,

diff --git a/library/std/src/io/stdio.rs b/library/std/src/io/stdio.rs
@@ -594,9 +594,8 @@ impl fmt::Debug for StdinLock<'_> {
 ///
 /// ### Note: Windows Portability Considerations
 ///
-/// When operating in a console, the Windows implementation of this stream does not support
-/// non-UTF-8 byte sequences. Attempting to write bytes that are not valid UTF-8 will return
-/// an error.
+/// When operating in a console, the Windows implementation of this stream decodes bytes
+/// as UTF-8, replacing malformed sequences with the Unicode replacement character (U+FFFD).
 ///
 /// In a process with a detached console, such as one using
 /// `#![windows_subsystem = "windows"]`, or in a child process spawned from such a process,
@@ -627,9 +626,8 @@ pub struct Stdout {
 ///
 /// ### Note: Windows Portability Considerations
 ///
-/// When operating in a console, the Windows implementation of this stream does not support
-/// non-UTF-8 byte sequences. Attempting to write bytes that are not valid UTF-8 will return
-/// an error.
+/// When operating in a console, the Windows implementation of this stream decodes bytes
+/// as UTF-8, replacing malformed sequences with the Unicode replacement character (U+FFFD).
 ///
 /// In a process with a detached console, such as one using
 /// `#![windows_subsystem = "windows"]`, or in a child process spawned from such a process,
@@ -659,9 +657,8 @@ static STDOUT: OnceLock<ReentrantLock<RefCell<LineWriter<StdoutRaw>>>> = OnceLoc
 ///
 /// ### Note: Windows Portability Considerations
 ///
-/// When operating in a console, the Windows implementation of this stream does not support
-/// non-UTF-8 byte sequences. Attempting to write bytes that are not valid UTF-8 will return
-/// an error.
+/// When operating in a console, the Windows implementation of this stream decodes bytes
+/// as UTF-8, replacing malformed sequences with the Unicode replacement character (U+FFFD).
 ///
 /// In a process with a detached console, such as one using
 /// `#![windows_subsystem = "windows"]`, or in a child process spawned from such a process,
@@ -882,9 +879,8 @@ impl fmt::Debug for StdoutLock<'_> {
 ///
 /// ### Note: Windows Portability Considerations
 ///
-/// When operating in a console, the Windows implementation of this stream does not support
-/// non-UTF-8 byte sequences. Attempting to write bytes that are not valid UTF-8 will return
-/// an error.
+/// When operating in a console, the Windows implementation of this stream decodes bytes
+/// as UTF-8, replacing malformed sequences with the Unicode replacement character (U+FFFD).
 ///
 /// In a process with a detached console, such as one using
 /// `#![windows_subsystem = "windows"]`, or in a child process spawned from such a process,
@@ -903,9 +899,8 @@ pub struct Stderr {
 ///
 /// ### Note: Windows Portability Considerations
 ///
-/// When operating in a console, the Windows implementation of this stream does not support
-/// non-UTF-8 byte sequences. Attempting to write bytes that are not valid UTF-8 will return
-/// an error.
+/// When operating in a console, the Windows implementation of this stream decodes bytes
+/// as UTF-8, replacing malformed sequences with the Unicode replacement character (U+FFFD).
 ///
 /// In a process with a detached console, such as one using
 /// `#![windows_subsystem = "windows"]`, or in a child process spawned from such a process,
@@ -924,9 +919,8 @@ pub struct StderrLock<'a> {
 ///
 /// ### Note: Windows Portability Considerations
 ///
-/// When operating in a console, the Windows implementation of this stream does not support
-/// non-UTF-8 byte sequences. Attempting to write bytes that are not valid UTF-8 will return
-/// an error.
+/// When operating in a console, the Windows implementation of this stream decodes bytes
+/// as UTF-8, replacing malformed sequences with the Unicode replacement character (U+FFFD).
 ///
 /// In a process with a detached console, such as one using
 /// `#![windows_subsystem = "windows"]`, or in a child process spawned from such a process,

diff --git a/library/std/src/sys/io/is_terminal/windows.rs b/library/std/src/sys/io/is_terminal/windows.rs
@@ -1,5 +1,4 @@
 use crate::ffi::c_void;
-use crate::mem::MaybeUninit;
 use crate::os::windows::io::{AsHandle, AsRawHandle, BorrowedHandle};
 use crate::sys::c;
 
@@ -27,6 +26,7 @@ fn handle_is_console(handle: BorrowedHandle<'_>) -> bool {
             }
         }
         _ => unsafe {
+            use crate::mem::MaybeUninit;
             // `GetConsoleMode` incurs a remote RPC round-trip (= bad), so it's best avoided.
             // `NtQueryVolumeInformationFile` lets us test the handle directly.
             // The required `FILE_DEVICE_CONSOLE` type was introduced in Windows 8.

diff --git a/library/std/src/sys/pal/windows/c.rs b/library/std/src/sys/pal/windows/c.rs
@@ -20,7 +20,9 @@ pub type WCHAR = u16;
 
 pub const INVALID_HANDLE_VALUE: HANDLE = ::core::ptr::without_provenance_mut(-1i32 as _);
 
+#[cfg(not(target_vendor = "win7"))]
 pub const FILE_DEVICE_NAMED_PIPE: u32 = 0x00000011;
+#[cfg(not(target_vendor = "win7"))]
 pub const FILE_DEVICE_CONSOLE: u32 = 0x00000050;
 
 // https://learn.microsoft.com/en-us/cpp/c-runtime-library/exit-success-exit-failure?view=msvc-170
@@ -147,12 +149,6 @@ pub const HANDLE_FLAG_INHERIT: u32 = cu(windows_sys::HANDLE_FLAG_INHERIT);
 pub const STACK_SIZE_PARAM_IS_A_RESERVATION: u32 =
     cu(windows_sys::STACK_SIZE_PARAM_IS_A_RESERVATION);
 
-// dwFlags -- WideCharToMultiByte
-pub const WC_ERR_INVALID_CHARS: u32 = cu(windows_sys::WC_ERR_INVALID_CHARS);
-
-// dwFlags -- MultiByteToWideChar
-pub const MB_ERR_INVALID_CHARS: u32 = cu(windows_sys::MB_ERR_INVALID_CHARS);
-
 // dwFlags -- CreateWaitableTimerExW
 pub const CREATE_WAITABLE_TIMER_HIGH_RESOLUTION: u32 =
     cu(windows_sys::CREATE_WAITABLE_TIMER_HIGH_RESOLUTION);

diff --git a/library/std/src/sys/pal/windows/c/bindings.txt b/library/std/src/sys/pal/windows/c/bindings.txt
@@ -2284,7 +2284,6 @@ MAX_PATH
 MAXIMUM_REPARSE_DATA_BUFFER_SIZE
 MaximumFileInfoByHandleClass
 MB_COMPOSITE
-MB_ERR_INVALID_CHARS
 MB_PRECOMPOSED
 MB_USEGLYPHCHARS
 MOVEFILE_COPY_ALLOWED
@@ -2500,7 +2499,6 @@ WakeAllConditionVariable
 WakeByAddressAll
 WakeByAddressSingle
 WakeConditionVariable
-WC_ERR_INVALID_CHARS
 WideCharToMultiByte
 WIN32_FIND_DATAW
 WRITE_DAC

diff --git a/library/std/src/sys/pal/windows/c/windows_sys.rs b/library/std/src/sys/pal/windows/c/windows_sys.rs
@@ -2985,7 +2985,6 @@ pub struct M128A {
 pub const MAXIMUM_REPARSE_DATA_BUFFER_SIZE: i32 = 16384;
 pub const MAX_PATH: i32 = 260;
 pub const MB_COMPOSITE: i32 = 2;
-pub const MB_ERR_INVALID_CHARS: i32 = 8;
 pub const MB_PRECOMPOSED: i32 = 1;
 pub const MB_USEGLYPHCHARS: i32 = 4;
 pub const MOVEFILE_COPY_ALLOWED: i32 = 2;
@@ -3351,7 +3350,6 @@ pub const WAIT_FAILED: u32 = 4294967295;
 pub const WAIT_IO_COMPLETION: i32 = 192;
 pub const WAIT_OBJECT_0: i32 = 0;
 pub const WAIT_TIMEOUT: i32 = 258;
-pub const WC_ERR_INVALID_CHARS: i32 = 128;
 #[repr(C)]
 #[derive(Clone, Copy)]
 pub struct WIN32_FIND_DATAW {