Clean up TypeVariableType::Implementation::mustBeMaterializable(), etc

Author: slavapestov

lib/Sema/CSGen.cpp

@@ -1605,6 +1605,7 @@ namespace {
               CS.getConstraintLocator(expr,
                                       ConstraintLocator::ApplyArgument),
               (TVO_CanBindToLValue |
+               TVO_CanBindToInOut |
                TVO_PrefersSubtypeBinding));
           CS.addConstraint(
               ConstraintKind::FunctionInput, methodTy, argTy,

lib/Sema/CSSimplify.cpp

@@ -1579,6 +1579,12 @@ ConstraintSystem::matchTypesBindTypeVar(
   // If the left-hand type variable cannot bind to an lvalue,
   // but we still have an lvalue, fail.
   if (!typeVar->getImpl().canBindToLValue() && type->hasLValueType()) {
+      return getTypeMatchFailure(locator);
+  }
+
+  // If the left-hand type variable cannot bind to an inout,
+  // but we still have an inout, fail.
+  if (!typeVar->getImpl().canBindToInOut() && type->is<InOutType>()) {
     return getTypeMatchFailure(locator);
   }
 
@@ -1600,15 +1606,6 @@ ConstraintSystem::matchTypesBindTypeVar(
     }
   }
 
-  // Check whether the type variable must be bound to a materializable
-  // type.
-  if (typeVar->getImpl().mustBeMaterializable()) {
-    if (!type->isMaterializable())
-      return getTypeMatchFailure(locator);
-
-    setMustBeMaterializableRecursive(type);
-  }
-
   // Okay. Bind below.
 
   // A constraint that binds any pointer to a void pointer is
@@ -1620,6 +1617,16 @@ ConstraintSystem::matchTypesBindTypeVar(
     return getTypeMatchSuccess();
   }
 
+  if (!typeVar->getImpl().canBindToLValue()) {
+    // When binding a fixed type to a type variable that cannot contain
+    // lvalues, any type variables within the fixed type cannot contain
+    // lvalues either.
+    type.visit([&](Type t) {
+      if (auto *tvt = dyn_cast<TypeVariableType>(t.getPointer()))
+        typeVar->getImpl().setCannotBindToLValue(getSavedBindings());
+    });
+  }
+
   assignFixedType(typeVar, type);
 
   return getTypeMatchSuccess();
@@ -2660,6 +2667,7 @@ ConstraintSystem::simplifyConstructionConstraint(
     auto argType = createTypeVariable(
         getConstraintLocator(locator, ConstraintLocator::ApplyArgument),
         (TVO_CanBindToLValue |
+         TVO_CanBindToInOut |
          TVO_PrefersSubtypeBinding));
     addConstraint(ConstraintKind::FunctionInput, memberType, argType, locator);
   }

lib/Sema/ConstraintGraph.cpp

@@ -698,7 +698,7 @@ bool ConstraintGraph::contractEdges() {
           auto type = binding.BindingType;
           isNotContractable = type.findIf([&](Type nestedType) -> bool {
             if (auto tv = nestedType->getAs<TypeVariableType>()) {
-              if (!tv->getImpl().mustBeMaterializable())
+              if (tv->getImpl().canBindToInOut())
                 return true;
             }
 

lib/Sema/ConstraintSystem.cpp

@@ -201,23 +201,6 @@ void ConstraintSystem::assignFixedType(TypeVariableType *typeVar, Type type,
   addTypeVariableConstraintsToWorkList(typeVar);
 }
 
-void ConstraintSystem::setMustBeMaterializableRecursive(Type type)
-{
-  assert(type->isMaterializable() &&
-         "argument to setMustBeMaterializableRecursive may not be inherently "
-         "non-materializable");
-  type = getFixedTypeRecursive(type, /*wantRValue=*/false);
-  type = type->lookThroughAllOptionalTypes();
-
-  if (auto typeVar = type->getAs<TypeVariableType>()) {
-    typeVar->getImpl().setMustBeMaterializable(getSavedBindings());
-  } else if (auto *tupleTy = type->getAs<TupleType>()) {
-    for (auto elt : tupleTy->getElementTypes()) {
-      setMustBeMaterializableRecursive(elt);
-    }
-  }
-}
-
 void ConstraintSystem::addTypeVariableConstraintsToWorkList(
        TypeVariableType *typeVar) {
   // Gather the constraints affected by a change to this type variable.

lib/Sema/ConstraintSystem.h

@@ -232,11 +232,6 @@ class TypeVariableType::Implementation {
     return getRawOptions() & TVO_PrefersSubtypeBinding;
   }
 
-  bool mustBeMaterializable() const {
-    return !(getRawOptions() & TVO_CanBindToInOut) &&
-           !(getRawOptions() & TVO_CanBindToLValue);
-  }
-
   /// Retrieve the corresponding node in the constraint graph.
   constraints::ConstraintGraphNode *getGraphNode() const { return GraphNode; }
 
@@ -343,10 +338,16 @@ class TypeVariableType::Implementation {
     if (record)
       otherRep->getImpl().recordBinding(*record);
     otherRep->getImpl().ParentOrFixed = getTypeVariable();
-    if (!mustBeMaterializable() && otherRep->getImpl().mustBeMaterializable()) {
+
+    if (canBindToLValue() && !otherRep->getImpl().canBindToLValue()) {
       if (record)
         recordBinding(*record);
       getTypeVariable()->Bits.TypeVariableType.Options &= ~TVO_CanBindToLValue;
+    }
+
+    if (canBindToInOut() && !otherRep->getImpl().canBindToInOut()) {
+      if (record)
+        recordBinding(*record);
       getTypeVariable()->Bits.TypeVariableType.Options &= ~TVO_CanBindToInOut;
     }
   }
@@ -380,15 +381,13 @@ class TypeVariableType::Implementation {
     rep->getImpl().ParentOrFixed = type.getPointer();
   }
 
-  void setMustBeMaterializable(constraints::SavedTypeVariableBindings *record) {
+  void setCannotBindToLValue(constraints::SavedTypeVariableBindings *record) {
     auto rep = getRepresentative(record);
-    if (!rep->getImpl().mustBeMaterializable()) {
+    if (rep->getImpl().canBindToLValue()) {
       if (record)
         rep->getImpl().recordBinding(*record);
       rep->getImpl().getTypeVariable()->Bits.TypeVariableType.Options
         &= ~TVO_CanBindToLValue;
-      rep->getImpl().getTypeVariable()->Bits.TypeVariableType.Options
-        &= ~TVO_CanBindToInOut;
     }
   }
 
@@ -2083,11 +2082,6 @@ class ConstraintSystem {
   void assignFixedType(TypeVariableType *typeVar, Type type,
                        bool updateState = true);
 
-  /// \brief Set the TVO_MustBeMaterializable bit on all type variables
-  /// necessary to ensure that the type in question is materializable in a
-  /// viable solution.
-  void setMustBeMaterializableRecursive(Type type);
-  
   /// Determine if the type in question is an Array<T> and, if so, provide the
   /// element type of the array.
   static Optional<Type> isArrayType(Type type);