Add newtype for first input type

compiler/rustc_hir_analysis/src/coherence/orphan.rs

@@ -1,14 +1,13 @@
 //! Orphan checker: every impl either implements a trait defined in this
 //! crate or pertains to a type defined in this crate.
 
+use crate::errors;
 use rustc_errors::ErrorGuaranteed;
 use rustc_hir as hir;
 use rustc_middle::ty::{self, AliasKind, Ty, TyCtxt, TypeVisitableExt};
 use rustc_span::def_id::LocalDefId;
 use rustc_span::Span;
-use rustc_trait_selection::traits;
+use rustc_trait_selection::traits::{self, IsFirstInputType};
-
-use crate::errors;
 
 #[instrument(skip(tcx), level = "debug")]
 pub(crate) fn orphan_check_impl(
@@ -288,7 +287,7 @@ fn emit_orphan_check_error<'tcx>(
                 (Vec::new(), Vec::new(), Vec::new(), Vec::new(), Vec::new());
             let mut sugg = None;
             for &(mut ty, is_target_ty) in &tys {
-                let span = if is_target_ty {
+                let span = if matches!(is_target_ty, IsFirstInputType::Yes) {
                     // Point at `D<A>` in `impl<A, B> for C<B> in D<A>`
                     self_ty_span
                 } else {
@@ -321,7 +320,8 @@ fn emit_orphan_check_error<'tcx>(
                     }
                 }
 
-                let is_foreign = !trait_ref.def_id.is_local() && !is_target_ty;
+                let is_foreign =
+                    !trait_ref.def_id.is_local() && matches!(is_target_ty, IsFirstInputType::No);
 
                 match &ty.kind() {
                     ty::Slice(_) => {

compiler/rustc_trait_selection/src/traits/coherence.rs

@@ -598,9 +598,24 @@ pub fn trait_ref_is_local_or_fundamental<'tcx>(
     trait_ref.def_id.krate == LOCAL_CRATE || tcx.has_attr(trait_ref.def_id, sym::fundamental)
 }
 
+#[derive(Debug, Copy, Clone)]
+pub enum IsFirstInputType {
+    No,
+    Yes,
+}
+
+impl From<bool> for IsFirstInputType {
+    fn from(b: bool) -> IsFirstInputType {
+        match b {
+            false => IsFirstInputType::No,
+            true => IsFirstInputType::Yes,
+        }
+    }
+}
+
 #[derive(Debug)]
 pub enum OrphanCheckErr<'tcx> {
-    NonLocalInputType(Vec<(Ty<'tcx>, bool /* Is this the first input type? */)>),
+    NonLocalInputType(Vec<(Ty<'tcx>, IsFirstInputType)>),
     UncoveredTy(Ty<'tcx>, Option<Ty<'tcx>>),
 }
 
@@ -751,7 +766,7 @@ struct OrphanChecker<'tcx, F> {
     /// Ignore orphan check failures and exclusively search for the first
     /// local type.
     search_first_local_ty: bool,
-    non_local_tys: Vec<(Ty<'tcx>, bool)>,
+    non_local_tys: Vec<(Ty<'tcx>, IsFirstInputType)>,
 }
 
 impl<'tcx, F, E> OrphanChecker<'tcx, F>
@@ -769,7 +784,7 @@ where
     }
 
     fn found_non_local_ty(&mut self, t: Ty<'tcx>) -> ControlFlow<OrphanCheckEarlyExit<'tcx, E>> {
-        self.non_local_tys.push((t, self.in_self_ty));
+        self.non_local_tys.push((t, self.in_self_ty.into()));
         ControlFlow::Continue(())
     }
 

compiler/rustc_trait_selection/src/traits/mod.rs

@@ -42,7 +42,7 @@ use std::fmt::Debug;
 use std::ops::ControlFlow;
 
 pub use self::coherence::{add_placeholder_note, orphan_check, overlapping_impls};
-pub use self::coherence::{OrphanCheckErr, OverlapResult};
+pub use self::coherence::{IsFirstInputType, OrphanCheckErr, OverlapResult};
 pub use self::engine::{ObligationCtxt, TraitEngineExt};
 pub use self::fulfill::{FulfillmentContext, PendingPredicateObligation};
 pub use self::normalize::NormalizeExt;