Sema: Remove ConstraintKind::OneWayEqual

Author: slavapestov

include/swift/Sema/Constraint.h

@@ -150,11 +150,6 @@ enum class ConstraintKind : char {
   /// The key path type is chosen based on the selection of overloads for the
   /// member references along the path.
   KeyPath,
-  /// The first type will be equal to the second type, but only when the
-  /// second type has been fully determined (and mapped down to a concrete
-  /// type). At that point, this constraint will be treated like an `Equal`
-  /// constraint.
-  OneWayEqual,
   /// If there is no contextual info e.g. `_ = { 42 }` default first type
   /// to a second type. This is effectively a `Defaultable` constraint
   /// which one significant difference:
@@ -680,7 +675,6 @@ class Constraint final : public llvm::ilist_node<Constraint>,
     case ConstraintKind::DynamicCallableApplicableFunction:
     case ConstraintKind::BindOverload:
     case ConstraintKind::OptionalObject:
-    case ConstraintKind::OneWayEqual:
     case ConstraintKind::FallbackType:
     case ConstraintKind::UnresolvedMemberChainBase:
     case ConstraintKind::PackElementOf:
@@ -828,7 +822,7 @@ class Constraint final : public llvm::ilist_node<Constraint>,
 
   /// Whether this is a one-way constraint.
   bool isOneWayConstraint() const {
-    return Kind == ConstraintKind::OneWayEqual;
+    return false;
   }
 
   /// Retrieve the overload choice for an overload-binding constraint.

include/swift/Sema/ConstraintSystem.h

@@ -5011,12 +5011,6 @@ class ConstraintSystem {
                                                  TypeMatchOptions flags,
                                                  ConstraintLocatorBuilder locator);
 
-  /// Attempt to simplify a one-way constraint.
-  SolutionKind simplifyOneWayConstraint(ConstraintKind kind,
-                                        Type first, Type second,
-                                        TypeMatchOptions flags,
-                                        ConstraintLocatorBuilder locator);
-
   /// Simplify an equality constraint between result and base types of
   /// an unresolved member chain.
   SolutionKind simplifyUnresolvedMemberChainBaseConstraint(

lib/Sema/CSBindings.cpp

@@ -1949,20 +1949,6 @@ void PotentialBindings::infer(ConstraintSystem &CS,
 
     break;
   }
-
-  case ConstraintKind::OneWayEqual:{
-    // Don't produce any bindings if this type variable is on the left-hand
-    // side of a one-way binding.
-    auto firstType = constraint->getFirstType();
-    if (auto *tv = firstType->getAs<TypeVariableType>()) {
-      if (tv->getImpl().getRepresentative(nullptr) == TypeVar) {
-        DelayedBy.push_back(constraint);
-        break;
-      }
-    }
-
-    break;
-  }
   }
 }
 

lib/Sema/CSSimplify.cpp

@@ -2178,7 +2178,6 @@ ConstraintSystem::matchTupleTypes(TupleType *tuple1, TupleType *tuple2,
   case ConstraintKind::ValueMember:
   case ConstraintKind::ValueWitness:
   case ConstraintKind::BridgingConversion:
-  case ConstraintKind::OneWayEqual:
   case ConstraintKind::FallbackType:
   case ConstraintKind::UnresolvedMemberChainBase:
   case ConstraintKind::PropertyWrapper:
@@ -2549,7 +2548,6 @@ static bool matchFunctionRepresentations(FunctionType::ExtInfo einfo1,
   case ConstraintKind::UnresolvedValueMember:
   case ConstraintKind::ValueMember:
   case ConstraintKind::ValueWitness:
-  case ConstraintKind::OneWayEqual:
   case ConstraintKind::FallbackType:
   case ConstraintKind::UnresolvedMemberChainBase:
   case ConstraintKind::PropertyWrapper:
@@ -3193,7 +3191,6 @@ ConstraintSystem::matchFunctionTypes(FunctionType *func1, FunctionType *func2,
   case ConstraintKind::ValueMember:
   case ConstraintKind::ValueWitness:
   case ConstraintKind::BridgingConversion:
-  case ConstraintKind::OneWayEqual:
   case ConstraintKind::FallbackType:
   case ConstraintKind::UnresolvedMemberChainBase:
   case ConstraintKind::PropertyWrapper:
@@ -7128,7 +7125,6 @@ ConstraintSystem::matchTypes(Type type1, Type type2, ConstraintKind kind,
     case ConstraintKind::UnresolvedValueMember:
     case ConstraintKind::ValueMember:
     case ConstraintKind::ValueWitness:
-    case ConstraintKind::OneWayEqual:
     case ConstraintKind::FallbackType:
     case ConstraintKind::UnresolvedMemberChainBase:
     case ConstraintKind::PropertyWrapper:
@@ -11561,38 +11557,6 @@ ConstraintSystem::simplifyPropertyWrapperConstraint(
   return SolutionKind::Solved;
 }
 
-ConstraintSystem::SolutionKind
-ConstraintSystem::simplifyOneWayConstraint(
-    ConstraintKind kind,
-    Type first, Type second, TypeMatchOptions flags,
-    ConstraintLocatorBuilder locator) {
-  // Determine whether the second type can be fully simplified. Only then
-  // will this constraint be resolved.
-  Type secondSimplified = simplifyType(second);
-  if (secondSimplified->hasTypeVariable()) {
-    if (flags.contains(TMF_GenerateConstraints)) {
-      addUnsolvedConstraint(
-        Constraint::create(*this, kind, first, second,
-                           getConstraintLocator(locator)));
-      return SolutionKind::Solved;
-    }
-
-    return SolutionKind::Unsolved;
-  }
-
-  // Propagate holes through one-way constraints.
-  if (secondSimplified->isPlaceholder()) {
-    recordAnyTypeVarAsPotentialHole(first);
-    return SolutionKind::Solved;
-  }
-
-  // Translate this constraint into an equality or bind-parameter constraint,
-  // as appropriate.
-  ASSERT(kind == ConstraintKind::OneWayEqual);
-  return matchTypes(first, secondSimplified, ConstraintKind::Equal, flags,
-                    locator);
-}
-
 ConstraintSystem::SolutionKind
 ConstraintSystem::simplifyUnresolvedMemberChainBaseConstraint(
     Type first, Type second, TypeMatchOptions flags,
@@ -15724,9 +15688,6 @@ ConstraintSystem::addConstraintImpl(ConstraintKind kind, Type first,
   case ConstraintKind::PropertyWrapper:
     return simplifyPropertyWrapperConstraint(first, second, subflags, locator);
 
-  case ConstraintKind::OneWayEqual:
-    return simplifyOneWayConstraint(kind, first, second, subflags, locator);
-
   case ConstraintKind::UnresolvedMemberChainBase:
     return simplifyUnresolvedMemberChainBaseConstraint(first, second, subflags,
                                                        locator);
@@ -16304,12 +16265,6 @@ ConstraintSystem::simplifyConstraint(const Constraint &constraint) {
     // See {Dis, Con}junctionStep class in CSStep.cpp for solving
     return SolutionKind::Unsolved;
 
-  case ConstraintKind::OneWayEqual:
-    return simplifyOneWayConstraint(
-        constraint.getKind(), constraint.getFirstType(),
-        constraint.getSecondType(),
-        /*flags*/ std::nullopt, constraint.getLocator());
-
   case ConstraintKind::UnresolvedMemberChainBase:
     return simplifyUnresolvedMemberChainBaseConstraint(
         constraint.getFirstType(), constraint.getSecondType(),

lib/Sema/Constraint.cpp

@@ -74,7 +74,6 @@ Constraint::Constraint(ConstraintKind Kind, Type First, Type Second,
   case ConstraintKind::EscapableFunctionOf:
   case ConstraintKind::OpenedExistentialOf:
   case ConstraintKind::OptionalObject:
-  case ConstraintKind::OneWayEqual:
   case ConstraintKind::UnresolvedMemberChainBase:
   case ConstraintKind::PropertyWrapper:
   case ConstraintKind::BindTupleOfFunctionParams:
@@ -162,7 +161,6 @@ Constraint::Constraint(ConstraintKind Kind, Type First, Type Second, Type Third,
   case ConstraintKind::BindOverload:
   case ConstraintKind::Disjunction:
   case ConstraintKind::Conjunction:
-  case ConstraintKind::OneWayEqual:
   case ConstraintKind::FallbackType:
   case ConstraintKind::UnresolvedMemberChainBase:
   case ConstraintKind::PropertyWrapper:
@@ -395,7 +393,6 @@ void Constraint::print(llvm::raw_ostream &Out, SourceManager *sm,
   case ConstraintKind::DynamicTypeOf: Out << " dynamicType type of "; break;
   case ConstraintKind::EscapableFunctionOf: Out << " @escaping type of "; break;
   case ConstraintKind::OpenedExistentialOf: Out << " opened archetype of "; break;
-  case ConstraintKind::OneWayEqual: Out << " one-way bind to "; break;
   case ConstraintKind::FallbackType:
     Out << " can fallback to ";
     break;
@@ -675,7 +672,6 @@ gatherReferencedTypeVars(Constraint *constraint,
   case ConstraintKind::ConformsTo:
   case ConstraintKind::LiteralConformsTo:
   case ConstraintKind::TransitivelyConformsTo:
-  case ConstraintKind::OneWayEqual:
   case ConstraintKind::FallbackType:
   case ConstraintKind::UnresolvedMemberChainBase:
   case ConstraintKind::PropertyWrapper:

lib/Sema/ConstraintSystem.cpp

@@ -1837,39 +1837,6 @@ Type Solution::simplifyTypeForCodeCompletion(Type Ty) const {
     return typeVar;
   });
 
-  // Logic to determine the contextual type inside buildBlock result builders:
-  //
-  // When completing inside a result builder, the result builder
-  //   @ViewBuilder var body: some View {
-  //     Text("Foo")
-  //     #^COMPLETE^#
-  //   }
-  // gets rewritten to
-  //   @ViewBuilder var body: some View {
-  //     let $__builder2: Text
-  //     let $__builder0 = Text("Foo")
-  //     let $__builder1 = #^COMPLETE^#
-  //     $__builder2 = ViewBuilder.buildBlock($__builder0, $__builder1)
-  //     return $__builder2
-  //   }
-  // Inside the constraint system
-  //     let $__builder1 = #^COMPLETE^#
-  // gets type checked without context, so we can't know the contextual type for
-  // the code completion token. But we know that $__builder1 (and thus the type
-  // of #^COMPLETE^#) is used as the second argument to ViewBuilder.buildBlock,
-  // so we can extract the contextual type from that call. To do this, figure
-  // out the type variable that is used for $__builder1 in the buildBlock call.
-  // This type variable is connected to the type variable of $__builder1's
-  // definition by a one-way constraint.
-  if (auto TV = Ty->getAs<TypeVariableType>()) {
-    for (auto constraint : CS.getConstraintGraph()[TV].getConstraints()) {
-      if (constraint->getKind() == ConstraintKind::OneWayEqual &&
-          constraint->getSecondType()->isEqual(TV)) {
-        return simplifyTypeForCodeCompletion(constraint->getFirstType());
-      }
-    }
-  }
-
   // Remove any remaining type variables and placeholders
   Ty = simplifyType(Ty);