Use TypeVisitor::BreakTy in UnresolvedTypeFinder

compiler/rustc_infer/src/infer/mod.rs

@@ -1,5 +1,3 @@
-//! See the Book for more information.
-
 pub use self::freshen::TypeFreshener;
 pub use self::LateBoundRegionConversionTime::*;
 pub use self::RegionVariableOrigin::*;
@@ -1334,9 +1332,7 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
     where
         T: TypeFoldable<'tcx>,
     {
-        let mut r = resolve::UnresolvedTypeFinder::new(self);
+        value.visit_with(&mut resolve::UnresolvedTypeFinder::new(self)).break_value()
-        value.visit_with(&mut r);
-        r.first_unresolved
     }
 
     pub fn probe_const_var(

compiler/rustc_infer/src/infer/resolve.rs

@@ -111,18 +111,16 @@ impl<'a, 'tcx> TypeFolder<'tcx> for OpportunisticRegionResolver<'a, 'tcx> {
 /// involve some hashing and so forth).
 pub struct UnresolvedTypeFinder<'a, 'tcx> {
     infcx: &'a InferCtxt<'a, 'tcx>,
-
-    /// Used to find the type parameter name and location for error reporting.
-    pub first_unresolved: Option<(Ty<'tcx>, Option<Span>)>,
 }
 
 impl<'a, 'tcx> UnresolvedTypeFinder<'a, 'tcx> {
     pub fn new(infcx: &'a InferCtxt<'a, 'tcx>) -> Self {
-        UnresolvedTypeFinder { infcx, first_unresolved: None }
+        UnresolvedTypeFinder { infcx }
     }
 }
 
 impl<'a, 'tcx> TypeVisitor<'tcx> for UnresolvedTypeFinder<'a, 'tcx> {
+    type BreakTy = (Ty<'tcx>, Option<Span>);
     fn visit_ty(&mut self, t: Ty<'tcx>) -> ControlFlow<Self::BreakTy> {
         let t = self.infcx.shallow_resolve(t);
         if t.has_infer_types() {
@@ -144,8 +142,7 @@ impl<'a, 'tcx> TypeVisitor<'tcx> for UnresolvedTypeFinder<'a, 'tcx> {
                 } else {
                     None
                 };
-                self.first_unresolved = Some((t, ty_var_span));
+                ControlFlow::Break((t, ty_var_span))
-                ControlFlow::BREAK
             } else {
                 // Otherwise, visit its contents.
                 t.super_visit_with(self)