Rollup merge of #110930 - b-naber:normalize-elaborate-drops, r=cjgillot

Don't expect normalization to succeed in elaborate_drops

Fixes https://github.com/rust-lang/rust/issues/110682

This was exposed through the changes in https://github.com/rust-lang/rust/pull/109247, which causes more things to be inlined. Inlining can happen before monomorphization, so we can't expect normalization to succeed. In the elaborate_drops analysis we currently have [this call](https://github.com/rust-lang/rust/blob/033aa092ab23ba14cdad27073c5e37ba0eddb428/compiler/rustc_mir_dataflow/src/elaborate_drops.rs#L278) to `normalize_erasing_regions`, which ICEs when normalization fails. The types are used to infer [whether the type needs a drop](https://github.com/rust-lang/rust/blob/033aa092ab23ba14cdad27073c5e37ba0eddb428/compiler/rustc_mir_dataflow/src/elaborate_drops.rs#L374), where `needs_drop` itself [uses `try_normalize_erasing_regions`](https://github.com/rust-lang/rust/blob/033aa092ab23ba14cdad27073c5e37ba0eddb428/compiler/rustc_middle/src/ty/util.rs#L1121).

~[`instance_mir`](https://doc.rust-lang.org/stable/nightly-rustc/rustc_middle/ty/context/struct.TyCtxt.html#method.instance_mir) isn't explicit about whether it expects the instances corresponding to the `InstanceDef`s to be monomorphized (though I think in all other contexts the function is used post-monomorphization), so the use of `instance_mir` in inlining doesn't necessarily seem wrong to me.~

1 files changed, 26 insertions, 1 deletions

diff --git a/compiler/rustc_mir_transform/src/inline.rs b/compiler/rustc_mir_transform/src/inline.rs
index ece20d8d3e6..12f955d46bd 100644
--- a/compiler/rustc_mir_transform/src/inline.rs
+++ b/compiler/rustc_mir_transform/src/inline.rs
@@ -7,6 +7,7 @@ use rustc_index::Idx;
 use rustc_middle::middle::codegen_fn_attrs::{CodegenFnAttrFlags, CodegenFnAttrs};
 use rustc_middle::mir::visit::*;
 use rustc_middle::mir::*;
+use rustc_middle::ty::TypeVisitableExt;
 use rustc_middle::ty::{self, Instance, InstanceDef, ParamEnv, Ty, TyCtxt};
 use rustc_session::config::OptLevel;
 use rustc_span::{hygiene::ExpnKind, ExpnData, LocalExpnId, Span};
@@ -168,7 +169,7 @@ impl<'tcx> Inliner<'tcx> {
         let callee_attrs = self.tcx.codegen_fn_attrs(callsite.callee.def_id());
         self.check_codegen_attributes(callsite, callee_attrs)?;
         self.check_mir_is_available(caller_body, &callsite.callee)?;
-        let callee_body = self.tcx.instance_mir(callsite.callee.def);
+        let callee_body = try_instance_mir(self.tcx, callsite.callee.def)?;
         self.check_mir_body(callsite, callee_body, callee_attrs)?;
 
         if !self.tcx.consider_optimizing(|| {
@@ -1128,3 +1129,27 @@ impl<'tcx> MutVisitor<'tcx> for Integrator<'_, 'tcx> {
         }
     }
 }
+
+#[instrument(skip(tcx), level = "debug")]
+fn try_instance_mir<'tcx>(
+    tcx: TyCtxt<'tcx>,
+    instance: InstanceDef<'tcx>,
+) -> Result<&'tcx Body<'tcx>, &'static str> {
+    match instance {
+        ty::InstanceDef::DropGlue(_, Some(ty)) => match ty.kind() {
+            ty::Adt(def, substs) => {
+                let fields = def.all_fields();
+                for field in fields {
+                    let field_ty = field.ty(tcx, substs);
+                    if field_ty.has_param() && field_ty.has_projections() {
+                        return Err("cannot build drop shim for polymorphic type");
+                    }
+                }
+
+                Ok(tcx.instance_mir(instance))
+            }
+            _ => Ok(tcx.instance_mir(instance)),
+        },
+        _ => Ok(tcx.instance_mir(instance)),
+    }
+}