[ConstraintSystem] NFC: Remove obsolete ValueWitness constraint

xedin · xedin · commit 7c082c425921 · 2022-05-20T14:28:01.000-07:00
diff --git a/include/swift/Sema/Constraint.h b/include/swift/Sema/Constraint.h
@@ -137,11 +137,6 @@ enum class ConstraintKind : char {
   /// name, and the type of that member, when referenced as a value, is the
   /// second type.
   UnresolvedValueMember,
-  /// The first type conforms to the protocol in which the member requirement
-  /// resides. Once the conformance is resolved, the value witness will be
-  /// determined, and the type of that witness, when referenced as a value,
-  /// will be bound to the second type.
-  ValueWitness,
   /// The first type can be defaulted to the second (which currently
   /// cannot be dependent).  This is more like a type property than a
   /// relational constraint.
@@ -409,18 +404,11 @@ class Constraint final : public llvm::ilist_node<Constraint>,
       /// The type of the member.
       Type Second;
 
-      union {
-        /// If non-null, the name of a member of the first type is that
-        /// being related to the second type.
-        ///
-        /// Used for ValueMember an UnresolvedValueMember constraints.
-        DeclNameRef Name;
-
-        /// If non-null, the member being referenced.
-        ///
-        /// Used for ValueWitness constraints.
-        ValueDecl *Ref;
-      } Member;
+      /// If non-null, the name of a member of the first type is that
+      /// being related to the second type.
+      ///
+      /// Used for ValueMember an UnresolvedValueMember constraints.
+      DeclNameRef Name;
 
       /// The DC in which the use appears.
       DeclContext *UseDC;
@@ -535,12 +523,6 @@ class Constraint final : public llvm::ilist_node<Constraint>,
                                   FunctionRefKind functionRefKind,
                                   ConstraintLocator *locator);
 
-  /// Create a new value witness constraint.
-  static Constraint *createValueWitness(
-      ConstraintSystem &cs, ConstraintKind kind, Type first, Type second,
-      ValueDecl *requirement, DeclContext *useDC,
-      FunctionRefKind functionRefKind, ConstraintLocator *locator);
-
   /// Create an overload-binding constraint.
   static Constraint *createBindOverload(ConstraintSystem &cs, Type type, 
                                         OverloadChoice choice, 
@@ -688,7 +670,6 @@ class Constraint final : public llvm::ilist_node<Constraint>,
 
     case ConstraintKind::ValueMember:
     case ConstraintKind::UnresolvedValueMember:
-    case ConstraintKind::ValueWitness:
     case ConstraintKind::PropertyWrapper:
       return ConstraintClassification::Member;
 
@@ -728,7 +709,6 @@ class Constraint final : public llvm::ilist_node<Constraint>,
 
     case ConstraintKind::ValueMember:
     case ConstraintKind::UnresolvedValueMember:
-    case ConstraintKind::ValueWitness:
       return Member.First;
 
     case ConstraintKind::SyntacticElement:
@@ -750,7 +730,6 @@ class Constraint final : public llvm::ilist_node<Constraint>,
 
     case ConstraintKind::ValueMember:
     case ConstraintKind::UnresolvedValueMember:
-    case ConstraintKind::ValueWitness:
       return Member.Second;
 
     default:
@@ -776,20 +755,13 @@ class Constraint final : public llvm::ilist_node<Constraint>,
   DeclNameRef getMember() const {
     assert(Kind == ConstraintKind::ValueMember ||
            Kind == ConstraintKind::UnresolvedValueMember);
-    return Member.Member.Name;
-  }
-
-  /// Retrieve the requirement being referenced by a value witness constraint.
-  ValueDecl *getRequirement() const {
-    assert(Kind == ConstraintKind::ValueWitness);
-    return Member.Member.Ref;
+    return Member.Name;
   }
 
   /// Determine the kind of function reference we have for a member reference.
   FunctionRefKind getFunctionRefKind() const {
     if (Kind == ConstraintKind::ValueMember ||
-        Kind == ConstraintKind::UnresolvedValueMember ||
-        Kind == ConstraintKind::ValueWitness)
+        Kind == ConstraintKind::UnresolvedValueMember)
       return static_cast<FunctionRefKind>(TheFunctionRefKind);
 
     // Conservative answer: drop all of the labels.
@@ -849,8 +821,7 @@ class Constraint final : public llvm::ilist_node<Constraint>,
   /// Retrieve the DC in which the member was used.
   DeclContext *getMemberUseDC() const {
     assert(Kind == ConstraintKind::ValueMember ||
-           Kind == ConstraintKind::UnresolvedValueMember ||
-           Kind == ConstraintKind::ValueWitness);
+           Kind == ConstraintKind::UnresolvedValueMember);
     return Member.UseDC;
   }
 
diff --git a/include/swift/Sema/ConstraintSystem.h b/include/swift/Sema/ConstraintSystem.h
@@ -4050,26 +4050,6 @@ class ConstraintSystem {
     }
   }
 
-  /// Add a value witness constraint to the constraint system.
-  void addValueWitnessConstraint(
-      Type baseTy, ValueDecl *requirement, Type memberTy, DeclContext *useDC,
-      FunctionRefKind functionRefKind, ConstraintLocatorBuilder locator) {
-    assert(baseTy);
-    assert(memberTy);
-    assert(requirement);
-    assert(useDC);
-    switch (simplifyValueWitnessConstraint(
-        ConstraintKind::ValueWitness, baseTy, requirement, memberTy, useDC,
-        functionRefKind, TMF_GenerateConstraints, locator)) {
-    case SolutionKind::Unsolved:
-      llvm_unreachable("Unsolved result when generating constraints!");
-
-    case SolutionKind::Solved:
-    case SolutionKind::Error:
-      break;
-    }
-  }
-
   /// Add an explicit conversion constraint (e.g., \c 'x as T').
   ///
   /// \param fromType The type of the expression being converted.
diff --git a/lib/Sema/CSBindings.cpp b/lib/Sema/CSBindings.cpp
@@ -1467,7 +1467,6 @@ void PotentialBindings::infer(Constraint *constraint) {
 
   case ConstraintKind::ValueMember:
   case ConstraintKind::UnresolvedValueMember:
-  case ConstraintKind::ValueWitness:
   case ConstraintKind::PropertyWrapper: {
     // If current type variable represents a member type of some reference,
     // it would be bound once member is resolved either to a actual member
diff --git a/lib/Sema/CSSimplify.cpp b/lib/Sema/CSSimplify.cpp
@@ -2182,7 +2182,6 @@ ConstraintSystem::matchTupleTypes(TupleType *tuple1, TupleType *tuple2,
   case ConstraintKind::SelfObjectOfProtocol:
   case ConstraintKind::UnresolvedValueMember:
   case ConstraintKind::ValueMember:
-  case ConstraintKind::ValueWitness:
   case ConstraintKind::BridgingConversion:
   case ConstraintKind::OneWayEqual:
   case ConstraintKind::OneWayBindParam:
@@ -2346,7 +2345,6 @@ static bool matchFunctionRepresentations(FunctionType::ExtInfo einfo1,
   case ConstraintKind::SelfObjectOfProtocol:
   case ConstraintKind::UnresolvedValueMember:
   case ConstraintKind::ValueMember:
-  case ConstraintKind::ValueWitness:
   case ConstraintKind::OneWayEqual:
   case ConstraintKind::OneWayBindParam:
   case ConstraintKind::DefaultClosureType:
@@ -2793,7 +2791,6 @@ ConstraintSystem::matchFunctionTypes(FunctionType *func1, FunctionType *func2,
   case ConstraintKind::SelfObjectOfProtocol:
   case ConstraintKind::UnresolvedValueMember:
   case ConstraintKind::ValueMember:
-  case ConstraintKind::ValueWitness:
   case ConstraintKind::BridgingConversion:
   case ConstraintKind::OneWayEqual:
   case ConstraintKind::OneWayBindParam:
@@ -6031,7 +6028,6 @@ ConstraintSystem::matchTypes(Type type1, Type type2, ConstraintKind kind,
     case ConstraintKind::SelfObjectOfProtocol:
     case ConstraintKind::UnresolvedValueMember:
     case ConstraintKind::ValueMember:
-    case ConstraintKind::ValueWitness:
     case ConstraintKind::OneWayEqual:
     case ConstraintKind::OneWayBindParam:
     case ConstraintKind::DefaultClosureType:
@@ -9125,8 +9121,7 @@ ConstraintSystem::SolutionKind ConstraintSystem::simplifyMemberConstraint(
         markMemberTypeAsPotentialHole(memberTy);
         return SolutionKind::Solved;
       }
-    } else if ((kind == ConstraintKind::ValueMember ||
-                kind == ConstraintKind::ValueWitness) &&
+    } else if (kind == ConstraintKind::ValueMember &&
                baseObjTy->getMetatypeInstanceType()->isPlaceholder()) {
       // If base type is a "hole" there is no reason to record any
       // more "member not found" fixes for chained member references.
@@ -9548,67 +9543,6 @@ ConstraintSystem::SolutionKind ConstraintSystem::simplifyMemberConstraint(
   return SolutionKind::Error;
 }
 
-ConstraintSystem::SolutionKind
-ConstraintSystem::simplifyValueWitnessConstraint(
-    ConstraintKind kind, Type baseType, ValueDecl *requirement, Type memberType,
-    DeclContext *useDC, FunctionRefKind functionRefKind,
-    TypeMatchOptions flags, ConstraintLocatorBuilder locator) {
-  // We'd need to record original base type because it might be a type
-  // variable representing another missing member.
-  auto origBaseType = baseType;
-
-  auto formUnsolved = [&] {
-    // If requested, generate a constraint.
-    if (flags.contains(TMF_GenerateConstraints)) {
-      auto *witnessConstraint = Constraint::createValueWitness(
-          *this, kind, origBaseType, memberType, requirement, useDC,
-          functionRefKind, getConstraintLocator(locator));
-
-      addUnsolvedConstraint(witnessConstraint);
-      return SolutionKind::Solved;
-    }
-
-    return SolutionKind::Unsolved;
-  };
-
-  // Resolve the base type, if we can. If we can't resolve the base type,
-  // then we can't solve this constraint.
-  Type baseObjectType = getFixedTypeRecursive(
-      baseType, flags, /*wantRValue=*/true);
-  if (baseObjectType->isTypeVariableOrMember()) {
-    return formUnsolved();
-  }
-
-  // Check conformance to the protocol. If it doesn't conform, this constraint
-  // fails. Don't attempt to fix it.
-  // FIXME: Look in the constraint system to see if we've resolved the
-  // conformance already?
-  auto proto = requirement->getDeclContext()->getSelfProtocolDecl();
-  assert(proto && "Value witness constraint for a non-requirement");
-  auto conformance = useDC->getParentModule()->lookupConformance(
-      baseObjectType, proto);
-  if (!conformance) {
-    // The conformance failed, so mark the member type as a "hole". We cannot
-    // do anything further here.
-    if (!shouldAttemptFixes())
-      return SolutionKind::Error;
-
-    recordAnyTypeVarAsPotentialHole(memberType);
-
-    return SolutionKind::Solved;
-  }
-
-  // Reference the requirement.
-  Type resolvedBaseType = simplifyType(baseType, flags);
-  if (resolvedBaseType->isTypeVariableOrMember())
-    return formUnsolved();
-
-  auto choice = OverloadChoice(resolvedBaseType, requirement, functionRefKind);
-  resolveOverload(getConstraintLocator(locator), memberType, choice,
-                  useDC);
-  return SolutionKind::Solved;
-}
-
 ConstraintSystem::SolutionKind ConstraintSystem::simplifyDefaultableConstraint(
     Type first, Type second, TypeMatchOptions flags,
     ConstraintLocatorBuilder locator) {
@@ -13221,7 +13155,6 @@ ConstraintSystem::addConstraintImpl(ConstraintKind kind, Type first,
 
   case ConstraintKind::ValueMember:
   case ConstraintKind::UnresolvedValueMember:
-  case ConstraintKind::ValueWitness:
   case ConstraintKind::BindOverload:
   case ConstraintKind::Disjunction:
   case ConstraintKind::Conjunction:
@@ -13712,16 +13645,6 @@ ConstraintSystem::simplifyConstraint(const Constraint &constraint) {
                                     /*outerAlternatives=*/{},
                                     /*flags*/ None, constraint.getLocator());
 
-  case ConstraintKind::ValueWitness:
-    return simplifyValueWitnessConstraint(constraint.getKind(),
-                                          constraint.getFirstType(),
-                                          constraint.getRequirement(),
-                                          constraint.getSecondType(),
-                                          constraint.getMemberUseDC(),
-                                          constraint.getFunctionRefKind(),
-                                          /*flags*/ None,
-                                          constraint.getLocator());
-
   case ConstraintKind::Defaultable:
     return simplifyDefaultableConstraint(constraint.getFirstType(),
                                          constraint.getSecondType(),
diff --git a/lib/Sema/Constraint.cpp b/lib/Sema/Constraint.cpp
@@ -90,7 +90,6 @@ Constraint::Constraint(ConstraintKind Kind, Type First, Type Second,
 
   case ConstraintKind::ValueMember:
   case ConstraintKind::UnresolvedValueMember:
-  case ConstraintKind::ValueWitness:
     llvm_unreachable("Wrong constructor for member constraint");
 
   case ConstraintKind::Defaultable:
@@ -150,7 +149,6 @@ Constraint::Constraint(ConstraintKind Kind, Type First, Type Second, Type Third,
   case ConstraintKind::ApplicableFunction:
   case ConstraintKind::DynamicCallableApplicableFunction:
   case ConstraintKind::ValueMember:
-  case ConstraintKind::ValueWitness:
   case ConstraintKind::UnresolvedValueMember:
   case ConstraintKind::Defaultable:
   case ConstraintKind::BindOverload:
@@ -197,28 +195,6 @@ Constraint::Constraint(ConstraintKind kind, Type first, Type second,
   std::copy(typeVars.begin(), typeVars.end(), getTypeVariablesBuffer().begin());
 }
 
-Constraint::Constraint(ConstraintKind kind, Type first, Type second,
-                       ValueDecl *requirement, DeclContext *useDC,
-                       FunctionRefKind functionRefKind,
-                       ConstraintLocator *locator,
-                       SmallPtrSetImpl<TypeVariableType *> &typeVars)
-    : Kind(kind), HasRestriction(false), IsActive(false), IsDisabled(false),
-      IsDisabledForPerformance(false), RememberChoice(false), IsFavored(false),
-      IsIsolated(false), NumTypeVariables(typeVars.size()), Locator(locator) {
-  Member.First = first;
-  Member.Second = second;
-  Member.Member.Ref = requirement;
-  Member.UseDC = useDC;
-  TheFunctionRefKind = static_cast<unsigned>(functionRefKind);
-
-  assert(kind == ConstraintKind::ValueWitness);
-  assert(getFunctionRefKind() == functionRefKind);
-  assert(requirement && "Value witness constraint has no requirement");
-  assert(useDC && "Member constraint has no use DC");
-
-  std::copy(typeVars.begin(), typeVars.end(), getTypeVariablesBuffer().begin());
-}
-
 Constraint::Constraint(Type type, OverloadChoice choice, DeclContext *useDC,
                        ConstraintFix *fix, ConstraintLocator *locator,
                        SmallPtrSetImpl<TypeVariableType *> &typeVars)
@@ -324,11 +300,6 @@ Constraint *Constraint::clone(ConstraintSystem &cs) const {
                         getMember(), getMemberUseDC(), getFunctionRefKind(),
                         getLocator());
 
-  case ConstraintKind::ValueWitness:
-    return createValueWitness(
-        cs, getKind(), getFirstType(), getSecondType(), getRequirement(),
-        getMemberUseDC(), getFunctionRefKind(), getLocator());
-
   case ConstraintKind::Disjunction:
     return createDisjunction(
         cs, getNestedConstraints(), getLocator(),
@@ -509,14 +480,6 @@ void Constraint::print(llvm::raw_ostream &Out, SourceManager *sm) const {
     Out << "[(implicit) ." << getMember() << ": value] == ";
     break;
 
-  case ConstraintKind::ValueWitness: {
-    auto requirement = getRequirement();
-    auto selfNominal = requirement->getDeclContext()->getSelfNominalTypeDecl();
-    Out << "[." << selfNominal->getName() << "::" << requirement->getName()
-        << ": witness] == ";
-    break;
-  }
-
   case ConstraintKind::Defaultable:
     Out << " can default to ";
     break;
@@ -672,7 +635,6 @@ gatherReferencedTypeVars(Constraint *constraint,
   case ConstraintKind::Subtype:
   case ConstraintKind::UnresolvedValueMember:
   case ConstraintKind::ValueMember:
-  case ConstraintKind::ValueWitness:
   case ConstraintKind::DynamicTypeOf:
   case ConstraintKind::EscapableFunctionOf:
   case ConstraintKind::OpenedExistentialOf:
@@ -818,26 +780,6 @@ Constraint *Constraint::createMember(ConstraintSystem &cs, ConstraintKind kind,
                               functionRefKind, locator, typeVars);
 }
 
-Constraint *Constraint::createValueWitness(
-    ConstraintSystem &cs, ConstraintKind kind, Type first, Type second,
-    ValueDecl *requirement, DeclContext *useDC,
-    FunctionRefKind functionRefKind, ConstraintLocator *locator) {
-  assert(kind == ConstraintKind::ValueWitness);
-
-  // Collect type variables.
-  SmallPtrSet<TypeVariableType *, 4> typeVars;
-  if (first->hasTypeVariable())
-    first->getTypeVariables(typeVars);
-  if (second->hasTypeVariable())
-    second->getTypeVariables(typeVars);
-
-  // Create the constraint.
-  unsigned size = totalSizeToAlloc<TypeVariableType*>(typeVars.size());
-  void *mem = cs.getAllocator().Allocate(size, alignof(Constraint));
-  return new (mem) Constraint(kind, first, second, requirement, useDC,
-                              functionRefKind, locator, typeVars);
-}
-
 Constraint *Constraint::createBindOverload(ConstraintSystem &cs, Type type, 
                                            OverloadChoice choice, 
                                            DeclContext *useDC,
