Finish all todos

Author: tiif

compiler/rustc_trait_selection/src/error_reporting/traits/fulfillment_errors.rs

@@ -639,11 +639,6 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
                         }
                     }
 
-                    ty::PredicateKind::Clause(ty::ClauseKind::UnstableFeature(symbol)) => {
-                        // TODO: write a test that can trigger this path.
-                        span_bug!(span, "unstable feature {:?} not enabled", symbol);
-                    }
-
                     // Errors for `ConstEvaluatable` predicates show up as
                     // `SelectionError::ConstEvalFailure`,
                     // not `Unimplemented`.
@@ -654,6 +649,8 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
                     | ty::PredicateKind::ConstEquate { .. }
                     // Ambiguous predicates should never error
                     | ty::PredicateKind::Ambiguous
+                    // We never return Err when proving UnstableFeature goal.
+                    | ty::PredicateKind::Clause(ty::ClauseKind::UnstableFeature{ .. })
                     | ty::PredicateKind::NormalizesTo { .. }
                     | ty::PredicateKind::AliasRelate { .. }
                     | ty::PredicateKind::Clause(ty::ClauseKind::ConstArgHasType { .. }) => {

compiler/rustc_type_ir/src/flags.rs

@@ -401,7 +401,6 @@ impl<I: Interner> FlagComputation<I> {
                 self.add_const(expected);
                 self.add_const(found);
             }
-            ty::PredicateKind::Ambiguous => {}
             ty::PredicateKind::NormalizesTo(ty::NormalizesTo { alias, term }) => {
                 self.add_alias_term(alias);
                 self.add_term(term);
@@ -410,7 +409,8 @@ impl<I: Interner> FlagComputation<I> {
                 self.add_term(t1);
                 self.add_term(t2);
             }
-            ty::PredicateKind::Clause(ty::ClauseKind::UnstableFeature(_)) => todo!(),
+            ty::PredicateKind::Clause(ty::ClauseKind::UnstableFeature(_)) 
+            | ty::PredicateKind::Ambiguous => {},
         }
     }
 

src/librustdoc/clean/mod.rs

@@ -397,9 +397,9 @@ pub(crate) fn clean_predicate<'tcx>(
         ty::ClauseKind::ConstEvaluatable(..)
         | ty::ClauseKind::WellFormed(..)
         | ty::ClauseKind::ConstArgHasType(..)
+        | ty::ClauseKind::UnstableFeature(..)
         // FIXME(const_trait_impl): We can probably use this `HostEffect` pred to render `~const`.
         | ty::ClauseKind::HostEffect(_) => None,
-        ty::ClauseKind::UnstableFeature(_) => todo!(),
     }
 }