Rollup merge of #123464 - fmease:rn-has-proj-to-has-aliases, r=compiler-errors

Cleanup: Rename `HAS_PROJECTIONS` to `HAS_ALIASES` etc.

The name of the bitflag `HAS_PROJECTIONS` and of its corresponding method `has_projections` is quite historical dating back to a time when projections were the only kind of alias type.

I think it's time to update it to clear up any potential confusion for newcomers and to reduce unnecessary friction during contributor onboarding.

r? types

12 files changed, 21 insertions, 17 deletions

diff --git a/compiler/rustc_hir_typeck/src/fn_ctxt/_impl.rs b/compiler/rustc_hir_typeck/src/fn_ctxt/_impl.rs
index 8d4d0833eef..85d04f7d1c4 100644
--- a/compiler/rustc_hir_typeck/src/fn_ctxt/_impl.rs
+++ b/compiler/rustc_hir_typeck/src/fn_ctxt/_impl.rs
@@ -461,7 +461,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
     where
         T: TypeVisitable<TyCtxt<'tcx>>,
     {
-        t.has_free_regions() || t.has_projections() || t.has_infer_types()
+        t.has_free_regions() || t.has_aliases() || t.has_infer_types()
     }
 
     pub fn node_ty(&self, id: hir::HirId) -> Ty<'tcx> {
diff --git a/compiler/rustc_middle/src/ty/normalize_erasing_regions.rs b/compiler/rustc_middle/src/ty/normalize_erasing_regions.rs
index d4c8f5900f9..58543674460 100644
--- a/compiler/rustc_middle/src/ty/normalize_erasing_regions.rs
+++ b/compiler/rustc_middle/src/ty/normalize_erasing_regions.rs
@@ -49,7 +49,7 @@ impl<'tcx> TyCtxt<'tcx> {
         let value = self.erase_regions(value);
         debug!(?value);
 
-        if !value.has_projections() {
+        if !value.has_aliases() {
             value
         } else {
             value.fold_with(&mut NormalizeAfterErasingRegionsFolder { tcx: self, param_env })
@@ -81,7 +81,7 @@ impl<'tcx> TyCtxt<'tcx> {
         let value = self.erase_regions(value);
         debug!(?value);
 
-        if !value.has_projections() {
+        if !value.has_aliases() {
             Ok(value)
         } else {
             let mut folder = TryNormalizeAfterErasingRegionsFolder::new(self, param_env);
diff --git a/compiler/rustc_mir_transform/src/inline.rs b/compiler/rustc_mir_transform/src/inline.rs
index ab9fa165a20..60513a674af 100644
--- a/compiler/rustc_mir_transform/src/inline.rs
+++ b/compiler/rustc_mir_transform/src/inline.rs
@@ -1077,7 +1077,7 @@ fn try_instance_mir<'tcx>(
         let fields = def.all_fields();
         for field in fields {
             let field_ty = field.ty(tcx, args);
-            if field_ty.has_param() && field_ty.has_projections() {
+            if field_ty.has_param() && field_ty.has_aliases() {
                 return Err("cannot build drop shim for polymorphic type");
             }
         }
diff --git a/compiler/rustc_trait_selection/src/solve/normalize.rs b/compiler/rustc_trait_selection/src/solve/normalize.rs
index b1c03e82cab..5b45e1a34e4 100644
--- a/compiler/rustc_trait_selection/src/solve/normalize.rs
+++ b/compiler/rustc_trait_selection/src/solve/normalize.rs
@@ -177,7 +177,7 @@ impl<'tcx> FallibleTypeFolder<TyCtxt<'tcx>> for NormalizationFolder<'_, 'tcx> {
     fn try_fold_ty(&mut self, ty: Ty<'tcx>) -> Result<Ty<'tcx>, Self::Error> {
         let infcx = self.at.infcx;
         debug_assert_eq!(ty, infcx.shallow_resolve(ty));
-        if !ty.has_projections() {
+        if !ty.has_aliases() {
             return Ok(ty);
         }
 
@@ -204,7 +204,7 @@ impl<'tcx> FallibleTypeFolder<TyCtxt<'tcx>> for NormalizationFolder<'_, 'tcx> {
     fn try_fold_const(&mut self, ct: ty::Const<'tcx>) -> Result<ty::Const<'tcx>, Self::Error> {
         let infcx = self.at.infcx;
         debug_assert_eq!(ct, infcx.shallow_resolve(ct));
-        if !ct.has_projections() {
+        if !ct.has_aliases() {
             return Ok(ct);
         }
 
diff --git a/compiler/rustc_trait_selection/src/traits/fulfill.rs b/compiler/rustc_trait_selection/src/traits/fulfill.rs
index 88ac9d4dbe5..a04a3bc6ebe 100644
--- a/compiler/rustc_trait_selection/src/traits/fulfill.rs
+++ b/compiler/rustc_trait_selection/src/traits/fulfill.rs
@@ -311,7 +311,7 @@ impl<'a, 'tcx> ObligationProcessor for FulfillProcessor<'a, 'tcx> {
 
         let infcx = self.selcx.infcx;
 
-        if obligation.predicate.has_projections() {
+        if obligation.predicate.has_aliases() {
             let mut obligations = Vec::new();
             let predicate = normalize_with_depth_to(
                 &mut self.selcx,
diff --git a/compiler/rustc_trait_selection/src/traits/normalize.rs b/compiler/rustc_trait_selection/src/traits/normalize.rs
index 15bfffef3ce..b4969926f64 100644
--- a/compiler/rustc_trait_selection/src/traits/normalize.rs
+++ b/compiler/rustc_trait_selection/src/traits/normalize.rs
@@ -101,6 +101,8 @@ pub(super) fn needs_normalization<'tcx, T: TypeVisitable<TyCtxt<'tcx>>>(
     value: &T,
     reveal: Reveal,
 ) -> bool {
+    // This mirrors `ty::TypeFlags::HAS_ALIASES` except that we take `Reveal` into account.
+
     let mut flags = ty::TypeFlags::HAS_TY_PROJECTION
         | ty::TypeFlags::HAS_TY_WEAK
         | ty::TypeFlags::HAS_TY_INHERENT
diff --git a/compiler/rustc_trait_selection/src/traits/project.rs b/compiler/rustc_trait_selection/src/traits/project.rs
index 9d744d9a032..9246a41a2bc 100644
--- a/compiler/rustc_trait_selection/src/traits/project.rs
+++ b/compiler/rustc_trait_selection/src/traits/project.rs
@@ -431,7 +431,7 @@ pub(super) fn opt_normalize_projection_type<'a, 'b, 'tcx>(
 
             let projected_term = selcx.infcx.resolve_vars_if_possible(projected_term);
 
-            let mut result = if projected_term.has_projections() {
+            let mut result = if projected_term.has_aliases() {
                 let normalized_ty = normalize_with_depth_to(
                     selcx,
                     param_env,
@@ -595,7 +595,7 @@ pub fn normalize_inherent_projection<'a, 'b, 'tcx>(
     let ty = tcx.type_of(alias_ty.def_id).instantiate(tcx, args);
 
     let mut ty = selcx.infcx.resolve_vars_if_possible(ty);
-    if ty.has_projections() {
+    if ty.has_aliases() {
         ty = normalize_with_depth_to(selcx, param_env, cause.clone(), depth + 1, ty, obligations);
     }
 
diff --git a/compiler/rustc_trait_selection/src/traits/query/type_op/normalize.rs b/compiler/rustc_trait_selection/src/traits/query/type_op/normalize.rs
index 3b33f6e6144..279d96dec72 100644
--- a/compiler/rustc_trait_selection/src/traits/query/type_op/normalize.rs
+++ b/compiler/rustc_trait_selection/src/traits/query/type_op/normalize.rs
@@ -15,7 +15,7 @@ where
     type QueryResponse = T;
 
     fn try_fast_path(_tcx: TyCtxt<'tcx>, key: &ParamEnvAnd<'tcx, Self>) -> Option<T> {
-        if !key.value.value.has_projections() { Some(key.value.value) } else { None }
+        if !key.value.value.has_aliases() { Some(key.value.value) } else { None }
     }
 
     fn perform_query(
diff --git a/compiler/rustc_trait_selection/src/traits/select/mod.rs b/compiler/rustc_trait_selection/src/traits/select/mod.rs
index 8fb8d21ac90..aa4ab9c7ee9 100644
--- a/compiler/rustc_trait_selection/src/traits/select/mod.rs
+++ b/compiler/rustc_trait_selection/src/traits/select/mod.rs
@@ -1060,7 +1060,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
             // so we will try to normalize the obligation and evaluate again.
             // we will replace it with new solver in the future.
             if EvaluationResult::EvaluatedToErr == result
-                && fresh_trait_pred.has_projections()
+                && fresh_trait_pred.has_aliases()
                 && fresh_trait_pred.is_global()
             {
                 let mut nested_obligations = Vec::new();
diff --git a/compiler/rustc_ty_utils/src/layout.rs b/compiler/rustc_ty_utils/src/layout.rs
index 4ecb0ea7cd9..509727cdeab 100644
--- a/compiler/rustc_ty_utils/src/layout.rs
+++ b/compiler/rustc_ty_utils/src/layout.rs
@@ -241,9 +241,9 @@ fn layout_of_uncached<'tcx>(
 
         // Arrays and slices.
         ty::Array(element, mut count) => {
-            if count.has_projections() {
+            if count.has_aliases() {
                 count = tcx.normalize_erasing_regions(param_env, count);
-                if count.has_projections() {
+                if count.has_aliases() {
                     return Err(error(cx, LayoutError::Unknown(ty)));
                 }
             }
diff --git a/compiler/rustc_type_ir/src/flags.rs b/compiler/rustc_type_ir/src/flags.rs
index cd199222d90..997b410f819 100644
--- a/compiler/rustc_type_ir/src/flags.rs
+++ b/compiler/rustc_type_ir/src/flags.rs
@@ -78,8 +78,10 @@ bitflags! {
         /// Does this have `ConstKind::Unevaluated`?
         const HAS_CT_PROJECTION           = 1 << 14;
 
-        /// Could this type be normalized further?
-        const HAS_PROJECTION              = TypeFlags::HAS_TY_PROJECTION.bits()
+        /// Does this have `Alias` or `ConstKind::Unevaluated`?
+        ///
+        /// Rephrased, could this term be normalized further?
+        const HAS_ALIASES              = TypeFlags::HAS_TY_PROJECTION.bits()
                                           | TypeFlags::HAS_TY_WEAK.bits()
                                           | TypeFlags::HAS_TY_OPAQUE.bits()
                                           | TypeFlags::HAS_TY_INHERENT.bits()
diff --git a/compiler/rustc_type_ir/src/visit.rs b/compiler/rustc_type_ir/src/visit.rs
index 839e75dba4c..d6a3f9f0749 100644
--- a/compiler/rustc_type_ir/src/visit.rs
+++ b/compiler/rustc_type_ir/src/visit.rs
@@ -223,8 +223,8 @@ pub trait TypeVisitableExt<I: Interner>: TypeVisitable<I> {
         self.has_vars_bound_at_or_above(ty::INNERMOST)
     }
 
-    fn has_projections(&self) -> bool {
-        self.has_type_flags(TypeFlags::HAS_PROJECTION)
+    fn has_aliases(&self) -> bool {
+        self.has_type_flags(TypeFlags::HAS_ALIASES)
     }
 
     fn has_inherent_projections(&self) -> bool {