mv utility methods into separate module

compiler/rustc_const_eval/src/interpret/eval_context.rs

@@ -23,7 +23,7 @@ use super::{
     MemPlaceMeta, Memory, MemoryKind, Operand, Place, PlaceTy, PointerArithmetic, Provenance,
     Scalar, StackPopJump,
 };
-use crate::transform::validate;
+use crate::util;
 
 pub struct InterpCx<'mir, 'tcx, M: Machine<'mir, 'tcx>> {
     /// Stores the `Machine` instance.
@@ -355,7 +355,7 @@ pub(super) fn mir_assign_valid_types<'tcx>(
     // all normal lifetimes are erased, higher-ranked types with their
     // late-bound lifetimes are still around and can lead to type
     // differences.
-    if validate::is_subtype(tcx, param_env, src.ty, dest.ty) {
+    if util::is_subtype(tcx, param_env, src.ty, dest.ty) {
         // Make sure the layout is equal, too -- just to be safe. Miri really
         // needs layout equality. For performance reason we skip this check when
         // the types are equal. Equal types *can* have different layouts when

compiler/rustc_const_eval/src/transform/validate.rs

@@ -2,8 +2,6 @@
 
 use rustc_data_structures::fx::FxHashSet;
 use rustc_index::bit_set::BitSet;
-use rustc_infer::infer::{DefiningAnchor, TyCtxtInferExt};
-use rustc_infer::traits::ObligationCause;
 use rustc_middle::mir::interpret::Scalar;
 use rustc_middle::mir::visit::NonUseContext::VarDebugInfo;
 use rustc_middle::mir::visit::{PlaceContext, Visitor};
@@ -18,7 +16,6 @@ use rustc_mir_dataflow::impls::MaybeStorageLive;
 use rustc_mir_dataflow::storage::always_storage_live_locals;
 use rustc_mir_dataflow::{Analysis, ResultsCursor};
 use rustc_target::abi::{Size, VariantIdx};
-use rustc_trait_selection::traits::ObligationCtxt;
 
 #[derive(Copy, Clone, Debug)]
 enum EdgeKind {
@@ -71,55 +68,6 @@ impl<'tcx> MirPass<'tcx> for Validator {
     }
 }
 
-/// Returns whether the two types are equal up to subtyping.
-///
-/// This is used in case we don't know the expected subtyping direction
-/// and still want to check whether anything is broken.
-pub fn is_equal_up_to_subtyping<'tcx>(
-    tcx: TyCtxt<'tcx>,
-    param_env: ParamEnv<'tcx>,
-    src: Ty<'tcx>,
-    dest: Ty<'tcx>,
-) -> bool {
-    // Fast path.
-    if src == dest {
-        return true;
-    }
-
-    // Check for subtyping in either direction.
-    is_subtype(tcx, param_env, src, dest) || is_subtype(tcx, param_env, dest, src)
-}
-
-pub fn is_subtype<'tcx>(
-    tcx: TyCtxt<'tcx>,
-    param_env: ParamEnv<'tcx>,
-    src: Ty<'tcx>,
-    dest: Ty<'tcx>,
-) -> bool {
-    if src == dest {
-        return true;
-    }
-
-    let mut builder =
-        tcx.infer_ctxt().ignoring_regions().with_opaque_type_inference(DefiningAnchor::Bubble);
-    let infcx = builder.build();
-    let ocx = ObligationCtxt::new(&infcx);
-    let cause = ObligationCause::dummy();
-    let src = ocx.normalize(cause.clone(), param_env, src);
-    let dest = ocx.normalize(cause.clone(), param_env, dest);
-    let Ok(infer_ok) = infcx.at(&cause, param_env).sub(src, dest) else {
-        return false;
-    };
-    let () = ocx.register_infer_ok_obligations(infer_ok);
-    let errors = ocx.select_all_or_error();
-    // With `Reveal::All`, opaque types get normalized away, with `Reveal::UserFacing`
-    // we would get unification errors because we're unable to look into opaque types,
-    // even if they're constrained in our current function.
-    //
-    // It seems very unlikely that this hides any bugs.
-    let _ = infcx.inner.borrow_mut().opaque_type_storage.take_opaque_types();
-    errors.is_empty()
-}
 struct TypeChecker<'a, 'tcx> {
     when: &'a str,
     body: &'a Body<'tcx>,
@@ -195,7 +143,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
             return true;
         }
 
-        is_subtype(self.tcx, self.param_env, src, dest)
+        crate::util::is_subtype(self.tcx, self.param_env, src, dest)
     }
 }
 

compiler/rustc_const_eval/src/util/compare_types.rs

@@ -0,0 +1,60 @@
+//! Routines to check for relations between fully inferred types.
+//!
+//! FIXME: Move this to a more general place. The utility of this extends to
+//! other areas of the compiler as well.
+
+use rustc_infer::infer::{DefiningAnchor, TyCtxtInferExt};
+use rustc_infer::traits::ObligationCause;
+use rustc_middle::ty::{ParamEnv, Ty, TyCtxt};
+use rustc_trait_selection::traits::ObligationCtxt;
+
+/// Returns whether the two types are equal up to subtyping.
+///
+/// This is used in case we don't know the expected subtyping direction
+/// and still want to check whether anything is broken.
+pub fn is_equal_up_to_subtyping<'tcx>(
+    tcx: TyCtxt<'tcx>,
+    param_env: ParamEnv<'tcx>,
+    src: Ty<'tcx>,
+    dest: Ty<'tcx>,
+) -> bool {
+    // Fast path.
+    if src == dest {
+        return true;
+    }
+
+    // Check for subtyping in either direction.
+    is_subtype(tcx, param_env, src, dest) || is_subtype(tcx, param_env, dest, src)
+}
+
+/// Returns whether `src` is a subtype of `dest`, i.e. `src <: dest`.
+pub fn is_subtype<'tcx>(
+    tcx: TyCtxt<'tcx>,
+    param_env: ParamEnv<'tcx>,
+    src: Ty<'tcx>,
+    dest: Ty<'tcx>,
+) -> bool {
+    if src == dest {
+        return true;
+    }
+
+    let mut builder =
+        tcx.infer_ctxt().ignoring_regions().with_opaque_type_inference(DefiningAnchor::Bubble);
+    let infcx = builder.build();
+    let ocx = ObligationCtxt::new(&infcx);
+    let cause = ObligationCause::dummy();
+    let src = ocx.normalize(cause.clone(), param_env, src);
+    let dest = ocx.normalize(cause.clone(), param_env, dest);
+    let Ok(infer_ok) = infcx.at(&cause, param_env).sub(src, dest) else {
+        return false;
+    };
+    let () = ocx.register_infer_ok_obligations(infer_ok);
+    let errors = ocx.select_all_or_error();
+    // With `Reveal::All`, opaque types get normalized away, with `Reveal::UserFacing`
+    // we would get unification errors because we're unable to look into opaque types,
+    // even if they're constrained in our current function.
+    //
+    // It seems very unlikely that this hides any bugs.
+    let _ = infcx.inner.borrow_mut().opaque_type_storage.take_opaque_types();
+    errors.is_empty()
+}

compiler/rustc_const_eval/src/util/mod.rs

@@ -2,6 +2,7 @@ pub mod aggregate;
 mod alignment;
 mod call_kind;
 pub mod collect_writes;
+mod compare_types;
 mod find_self_call;
 mod might_permit_raw_init;
 mod type_name;
@@ -9,6 +10,7 @@ mod type_name;
 pub use self::aggregate::expand_aggregate;
 pub use self::alignment::is_disaligned;
 pub use self::call_kind::{call_kind, CallDesugaringKind, CallKind};
+pub use self::compare_types::{is_equal_up_to_subtyping, is_subtype};
 pub use self::find_self_call::find_self_call;
 pub use self::might_permit_raw_init::might_permit_raw_init;
 pub use self::type_name::type_name;

compiler/rustc_infer/src/infer/nll_relate/mod.rs

@@ -557,11 +557,8 @@ where
 
         debug!(?self.ambient_variance);
         // In a bivariant context this always succeeds.
-        let r = if self.ambient_variance == ty::Variance::Bivariant {
+        let r =
-            a
+            if self.ambient_variance == ty::Variance::Bivariant { a } else { self.relate(a, b)? };
-        } else {
-            self.relate(a, b)?
-        };
 
         self.ambient_variance = old_ambient_variance;
 

compiler/rustc_mir_transform/src/inline.rs

@@ -14,7 +14,7 @@ use rustc_target::abi::VariantIdx;
 use rustc_target::spec::abi::Abi;
 
 use crate::simplify::{remove_dead_blocks, CfgSimplifier};
-use crate::validate;
+use crate::util;
 use crate::MirPass;
 use std::iter;
 use std::ops::{Range, RangeFrom};
@@ -180,7 +180,7 @@ impl<'tcx> Inliner<'tcx> {
         let TerminatorKind::Call { args, destination, .. } = &terminator.kind else { bug!() };
         let destination_ty = destination.ty(&caller_body.local_decls, self.tcx).ty;
         let output_type = callee_body.return_ty();
-        if !validate::is_subtype(self.tcx, self.param_env, output_type, destination_ty) {
+        if !util::is_subtype(self.tcx, self.param_env, output_type, destination_ty) {
             trace!(?output_type, ?destination_ty);
             return Err("failed to normalize return type");
         }
@@ -200,7 +200,7 @@ impl<'tcx> Inliner<'tcx> {
                 arg_tuple_tys.iter().zip(callee_body.args_iter().skip(skipped_args))
             {
                 let input_type = callee_body.local_decls[input].ty;
-                if !validate::is_subtype(self.tcx, self.param_env, input_type, arg_ty) {
+                if !util::is_subtype(self.tcx, self.param_env, input_type, arg_ty) {
                     trace!(?arg_ty, ?input_type);
                     return Err("failed to normalize tuple argument type");
                 }
@@ -209,7 +209,7 @@ impl<'tcx> Inliner<'tcx> {
             for (arg, input) in args.iter().zip(callee_body.args_iter()) {
                 let input_type = callee_body.local_decls[input].ty;
                 let arg_ty = arg.ty(&caller_body.local_decls, self.tcx);
-                if !validate::is_subtype(self.tcx, self.param_env, input_type, arg_ty) {
+                if !util::is_subtype(self.tcx, self.param_env, input_type, arg_ty) {
                     trace!(?arg_ty, ?input_type);
                     return Err("failed to normalize argument type");
                 }
@@ -847,7 +847,7 @@ impl<'tcx> Visitor<'tcx> for CostChecker<'_, 'tcx> {
             let parent = Place { local, projection: self.tcx.intern_place_elems(proj_base) };
             let parent_ty = parent.ty(&self.callee_body.local_decls, self.tcx);
             let check_equal = |this: &mut Self, f_ty| {
-                if !validate::is_equal_up_to_subtyping(this.tcx, this.param_env, ty, f_ty) {
+                if !util::is_equal_up_to_subtyping(this.tcx, this.param_env, ty, f_ty) {
                     trace!(?ty, ?f_ty);
                     this.validation = Err("failed to normalize projection type");
                     return;