Auto merge of #131869 - matthiaskrgr:rollup-xrkz174, r=matthiaskrgr

Rollup of 5 pull requests

Successful merges:

 - #131654 (Various fixes for Xous)
 - #131743 (rustc_metadata: minor tidying)
 - #131823 (Bump libc to 0.2.161)
 - #131850 (Missing parenthesis)
 - #131857 (Allow dropping dyn principal)

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

6 files changed, 62 insertions, 47 deletions

diff --git a/compiler/rustc_codegen_cranelift/src/unsize.rs b/compiler/rustc_codegen_cranelift/src/unsize.rs
index 5c297ebfadb..336934354e1 100644
--- a/compiler/rustc_codegen_cranelift/src/unsize.rs
+++ b/compiler/rustc_codegen_cranelift/src/unsize.rs
@@ -34,7 +34,9 @@ pub(crate) fn unsized_info<'tcx>(
         {
             let old_info =
                 old_info.expect("unsized_info: missing old info for trait upcasting coercion");
-            if data_a.principal_def_id() == data_b.principal_def_id() {
+            let b_principal_def_id = data_b.principal_def_id();
+            if data_a.principal_def_id() == b_principal_def_id || b_principal_def_id.is_none() {
+                // A NOP cast that doesn't actually change anything, should be allowed even with invalid vtables.
                 debug_assert!(
                     validate_trivial_unsize(fx.tcx, data_a, data_b),
                     "NOP unsize vtable changed principal trait ref: {data_a} -> {data_b}"
diff --git a/compiler/rustc_codegen_ssa/src/base.rs b/compiler/rustc_codegen_ssa/src/base.rs
index d91c0f0790d..f3d9a7d37e6 100644
--- a/compiler/rustc_codegen_ssa/src/base.rs
+++ b/compiler/rustc_codegen_ssa/src/base.rs
@@ -147,7 +147,7 @@ pub fn validate_trivial_unsize<'tcx>(
                 infcx.leak_check(universe, None).is_ok()
             })
         }
-        (None, None) => true,
+        (_, None) => true,
         _ => false,
     }
 }
@@ -175,7 +175,8 @@ fn unsized_info<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(
         {
             let old_info =
                 old_info.expect("unsized_info: missing old info for trait upcasting coercion");
-            if data_a.principal_def_id() == data_b.principal_def_id() {
+            let b_principal_def_id = data_b.principal_def_id();
+            if data_a.principal_def_id() == b_principal_def_id || b_principal_def_id.is_none() {
                 // Codegen takes advantage of the additional assumption, where if the
                 // principal trait def id of what's being casted doesn't change,
                 // then we don't need to adjust the vtable at all. This
diff --git a/compiler/rustc_metadata/src/locator.rs b/compiler/rustc_metadata/src/locator.rs
index 99c673b021a..a4a69ae9514 100644
--- a/compiler/rustc_metadata/src/locator.rs
+++ b/compiler/rustc_metadata/src/locator.rs
@@ -499,8 +499,11 @@ impl<'a> CrateLocator<'a> {
         dylibs: FxIndexMap<PathBuf, PathKind>,
     ) -> Result<Option<(Svh, Library)>, CrateError> {
         let mut slot = None;
-        // Order here matters, rmeta should come first. See comment in
-        // `extract_one` below.
+        // Order here matters, rmeta should come first.
+        //
+        // Make sure there's at most one rlib and at most one dylib.
+        //
+        // See comment in `extract_one` below.
         let source = CrateSource {
             rmeta: self.extract_one(rmetas, CrateFlavor::Rmeta, &mut slot)?,
             rlib: self.extract_one(rlibs, CrateFlavor::Rlib, &mut slot)?,
@@ -706,54 +709,58 @@ impl<'a> CrateLocator<'a> {
         let mut rmetas = FxIndexMap::default();
         let mut dylibs = FxIndexMap::default();
         for loc in &self.exact_paths {
-            if !loc.canonicalized().exists() {
-                return Err(CrateError::ExternLocationNotExist(
-                    self.crate_name,
-                    loc.original().clone(),
-                ));
+            let loc_canon = loc.canonicalized();
+            let loc_orig = loc.original();
+            if !loc_canon.exists() {
+                return Err(CrateError::ExternLocationNotExist(self.crate_name, loc_orig.clone()));
             }
-            if !loc.original().is_file() {
-                return Err(CrateError::ExternLocationNotFile(
-                    self.crate_name,
-                    loc.original().clone(),
-                ));
+            if !loc_orig.is_file() {
+                return Err(CrateError::ExternLocationNotFile(self.crate_name, loc_orig.clone()));
             }
-            let Some(file) = loc.original().file_name().and_then(|s| s.to_str()) else {
-                return Err(CrateError::ExternLocationNotFile(
-                    self.crate_name,
-                    loc.original().clone(),
-                ));
+            // Note to take care and match against the non-canonicalized name:
+            // some systems save build artifacts into content-addressed stores
+            // that do not preserve extensions, and then link to them using
+            // e.g. symbolic links. If we canonicalize too early, we resolve
+            // the symlink, the file type is lost and we might treat rlibs and
+            // rmetas as dylibs.
+            let Some(file) = loc_orig.file_name().and_then(|s| s.to_str()) else {
+                return Err(CrateError::ExternLocationNotFile(self.crate_name, loc_orig.clone()));
             };
-
-            if file.starts_with("lib") && (file.ends_with(".rlib") || file.ends_with(".rmeta"))
-                || file.starts_with(self.target.dll_prefix.as_ref())
-                    && file.ends_with(self.target.dll_suffix.as_ref())
-            {
-                // Make sure there's at most one rlib and at most one dylib.
-                // Note to take care and match against the non-canonicalized name:
-                // some systems save build artifacts into content-addressed stores
-                // that do not preserve extensions, and then link to them using
-                // e.g. symbolic links. If we canonicalize too early, we resolve
-                // the symlink, the file type is lost and we might treat rlibs and
-                // rmetas as dylibs.
-                let loc_canon = loc.canonicalized().clone();
-                let loc = loc.original();
-                if loc.file_name().unwrap().to_str().unwrap().ends_with(".rlib") {
-                    rlibs.insert(loc_canon, PathKind::ExternFlag);
-                } else if loc.file_name().unwrap().to_str().unwrap().ends_with(".rmeta") {
-                    rmetas.insert(loc_canon, PathKind::ExternFlag);
-                } else {
-                    dylibs.insert(loc_canon, PathKind::ExternFlag);
+            // FnMut cannot return reference to captured value, so references
+            // must be taken outside the closure.
+            let rlibs = &mut rlibs;
+            let rmetas = &mut rmetas;
+            let dylibs = &mut dylibs;
+            let type_via_filename = (|| {
+                if file.starts_with("lib") {
+                    if file.ends_with(".rlib") {
+                        return Some(rlibs);
+                    }
+                    if file.ends_with(".rmeta") {
+                        return Some(rmetas);
+                    }
+                }
+                let dll_prefix = self.target.dll_prefix.as_ref();
+                let dll_suffix = self.target.dll_suffix.as_ref();
+                if file.starts_with(dll_prefix) && file.ends_with(dll_suffix) {
+                    return Some(dylibs);
+                }
+                None
+            })();
+            match type_via_filename {
+                Some(type_via_filename) => {
+                    type_via_filename.insert(loc_canon.clone(), PathKind::ExternFlag);
+                }
+                None => {
+                    self.crate_rejections
+                        .via_filename
+                        .push(CrateMismatch { path: loc_orig.clone(), got: String::new() });
                 }
-            } else {
-                self.crate_rejections
-                    .via_filename
-                    .push(CrateMismatch { path: loc.original().clone(), got: String::new() });
             }
         }
 
         // Extract the dylib/rlib/rmeta triple.
-        Ok(self.extract_lib(rlibs, rmetas, dylibs)?.map(|(_, lib)| lib))
+        self.extract_lib(rlibs, rmetas, dylibs).map(|opt| opt.map(|(_, lib)| lib))
     }
 
     pub(crate) fn into_error(self, root: Option<CratePaths>) -> CrateError {
diff --git a/compiler/rustc_next_trait_solver/src/solve/trait_goals.rs b/compiler/rustc_next_trait_solver/src/solve/trait_goals.rs
index 5828b2ecf34..2cbed0bceb2 100644
--- a/compiler/rustc_next_trait_solver/src/solve/trait_goals.rs
+++ b/compiler/rustc_next_trait_solver/src/solve/trait_goals.rs
@@ -785,7 +785,8 @@ where
         let mut responses = vec![];
         // If the principal def ids match (or are both none), then we're not doing
         // trait upcasting. We're just removing auto traits (or shortening the lifetime).
-        if a_data.principal_def_id() == b_data.principal_def_id() {
+        let b_principal_def_id = b_data.principal_def_id();
+        if a_data.principal_def_id() == b_principal_def_id || b_principal_def_id.is_none() {
             responses.extend(self.consider_builtin_upcast_to_principal(
                 goal,
                 CandidateSource::BuiltinImpl(BuiltinImplSource::Misc),
diff --git a/compiler/rustc_trait_selection/src/traits/select/candidate_assembly.rs b/compiler/rustc_trait_selection/src/traits/select/candidate_assembly.rs
index 52048ca79f9..aa313a526c1 100644
--- a/compiler/rustc_trait_selection/src/traits/select/candidate_assembly.rs
+++ b/compiler/rustc_trait_selection/src/traits/select/candidate_assembly.rs
@@ -1018,7 +1018,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
                 // #2 (region bounds).
                 let principal_def_id_a = a_data.principal_def_id();
                 let principal_def_id_b = b_data.principal_def_id();
-                if principal_def_id_a == principal_def_id_b {
+                if principal_def_id_a == principal_def_id_b || principal_def_id_b.is_none() {
                     // We may upcast to auto traits that are either explicitly listed in
                     // the object type's bounds, or implied by the principal trait ref's
                     // supertraits.
diff --git a/compiler/rustc_trait_selection/src/traits/select/confirmation.rs b/compiler/rustc_trait_selection/src/traits/select/confirmation.rs
index cc5c7532b50..0ba3b4e6e55 100644
--- a/compiler/rustc_trait_selection/src/traits/select/confirmation.rs
+++ b/compiler/rustc_trait_selection/src/traits/select/confirmation.rs
@@ -1153,6 +1153,10 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
                 // We already checked the compatibility of auto traits within `assemble_candidates_for_unsizing`.
                 let iter = data_a
                     .principal()
+                    .filter(|_| {
+                        // optionally drop the principal, if we're unsizing to no principal
+                        data_b.principal().is_some()
+                    })
                     .map(|b| b.map_bound(ty::ExistentialPredicate::Trait))
                     .into_iter()
                     .chain(