Auto merge of #110662 - bryangarza:safe-transmute-reference-types, r=compiler-errors

Safe Transmute: Enable handling references

This patch enables support for references in Safe Transmute, by generating nested obligations during trait selection. Specifically, when we call `confirm_transmutability_candidate(...)`, we now recursively traverse the `rustc_transmute::Answer` tree and create obligations for all the `Answer` variants, some of which include multiple nested `Answer`s.

1 files changed, 3 insertions, 5 deletions

diff --git a/compiler/rustc_trait_selection/src/solve/eval_ctxt.rs b/compiler/rustc_trait_selection/src/solve/eval_ctxt.rs
index e01187bcd3c..a8a0e1ebfb4 100644
--- a/compiler/rustc_trait_selection/src/solve/eval_ctxt.rs
+++ b/compiler/rustc_trait_selection/src/solve/eval_ctxt.rs
@@ -709,6 +709,7 @@ impl<'tcx> EvalCtxt<'_, 'tcx> {
         scope: Ty<'tcx>,
         assume: rustc_transmute::Assume,
     ) -> Result<Certainty, NoSolution> {
+        use rustc_transmute::Answer;
         // FIXME(transmutability): This really should be returning nested goals for `Answer::If*`
         match rustc_transmute::TransmuteTypeEnv::new(self.infcx).is_transmutable(
             ObligationCause::dummy(),
@@ -716,11 +717,8 @@ impl<'tcx> EvalCtxt<'_, 'tcx> {
             scope,
             assume,
         ) {
-            rustc_transmute::Answer::Yes => Ok(Certainty::Yes),
-            rustc_transmute::Answer::No(_)
-            | rustc_transmute::Answer::IfTransmutable { .. }
-            | rustc_transmute::Answer::IfAll(_)
-            | rustc_transmute::Answer::IfAny(_) => Err(NoSolution),
+            Answer::Yes => Ok(Certainty::Yes),
+            Answer::No(_) | Answer::If(_) => Err(NoSolution),
         }
     }