Auto merge of #113938 - Mark-Simulacrum:beta-backport, r=Mark-Simulacrum

[beta] backport

This PR backports:

- #113690: allow opaques to be defined by trait queries, again
- #113631: make MCP510 behavior opt-in to avoid conflicts between the CLI and target flavors

It also includes a bump of bootstrap to the released stable.

r? `@Mark-Simulacrum`

compiler/rustc_codegen_ssa/src/back/link.rs

@@ -2970,10 +2970,25 @@ fn add_lld_args(cmd: &mut dyn Linker, sess: &Session, flavor: LinkerFlavor) {
         return;
     }
 
+    let self_contained_linker = sess.opts.cg.link_self_contained.linker();
+
+    // FIXME: some targets default to using `lld`, but users can only override the linker on the CLI
+    // and cannot yet select the precise linker flavor to opt out of that. See for example issue
+    // #113597 for the `thumbv6m-none-eabi` target: a driver is used, and its default linker
+    // conflicts with the target's flavor, causing unexpected arguments being passed.
+    //
+    // Until the new `LinkerFlavor`-like CLI options are stabilized, we only adopt MCP510's behavior
+    // if its dedicated unstable CLI flags are used, to keep the current sub-optimal stable
+    // behavior.
+    let using_mcp510 =
+        self_contained_linker || sess.opts.cg.linker_flavor.is_some_and(|f| f.is_unstable());
+    if !using_mcp510 && !unstable_use_lld {
+        return;
+    }
+
     // 1. Implement the "self-contained" part of this feature by adding rustc distribution
     //    directories to the tool's search path.
-    let self_contained_linker = sess.opts.cg.link_self_contained.linker() || unstable_use_lld;
-    if self_contained_linker {
+    if self_contained_linker || unstable_use_lld {
         for path in sess.get_tools_search_paths(false) {
             cmd.arg({
                 let mut arg = OsString::from("-B");

compiler/rustc_trait_selection/src/infer.rs

@@ -1,5 +1,5 @@
 use crate::traits::query::evaluate_obligation::InferCtxtExt as _;
-use crate::traits::{self, ObligationCtxt};
+use crate::traits::{self, DefiningAnchor, ObligationCtxt};
 
 use rustc_hir::def_id::DefId;
 use rustc_hir::lang_items::LangItem;
@@ -80,7 +80,7 @@ impl<'tcx> InferCtxtExt<'tcx> for InferCtxt<'tcx> {
 
 pub trait InferCtxtBuilderExt<'tcx> {
     fn enter_canonical_trait_query<K, R>(
-        &mut self,
+        self,
         canonical_key: &Canonical<'tcx, K>,
         operation: impl FnOnce(&ObligationCtxt<'_, 'tcx>, K) -> Result<R, NoSolution>,
     ) -> Result<CanonicalQueryResponse<'tcx, R>, NoSolution>
@@ -108,7 +108,7 @@ impl<'tcx> InferCtxtBuilderExt<'tcx> for InferCtxtBuilder<'tcx> {
     /// have `'tcx` be free on this function so that we can talk about
     /// `K: TypeFoldable<TyCtxt<'tcx>>`.)
     fn enter_canonical_trait_query<K, R>(
-        &mut self,
+        self,
         canonical_key: &Canonical<'tcx, K>,
         operation: impl FnOnce(&ObligationCtxt<'_, 'tcx>, K) -> Result<R, NoSolution>,
     ) -> Result<CanonicalQueryResponse<'tcx, R>, NoSolution>
@@ -117,8 +117,9 @@ impl<'tcx> InferCtxtBuilderExt<'tcx> for InferCtxtBuilder<'tcx> {
         R: Debug + TypeFoldable<TyCtxt<'tcx>>,
         Canonical<'tcx, QueryResponse<'tcx, R>>: ArenaAllocatable<'tcx>,
     {
-        let (infcx, key, canonical_inference_vars) =
-            self.build_with_canonical(DUMMY_SP, canonical_key);
+        let (infcx, key, canonical_inference_vars) = self
+            .with_opaque_type_inference(DefiningAnchor::Bubble)
+            .build_with_canonical(DUMMY_SP, canonical_key);
         let ocx = ObligationCtxt::new(&infcx);
         let value = operation(&ocx, key)?;
         ocx.make_canonicalized_query_response(canonical_inference_vars, value)