[CS] Clean up some property wrapper logic

hamishknight · hamishknight · commit 69510b3445dd · 2025-10-26T09:55:49.000Z
These methods can be simplified a bunch since the returned decl is
always the input decl and we can refactor the lambdas to just return
the auxiliary variable and have the type computation in the caller.
diff --git a/include/swift/Sema/ConstraintSystem.h b/include/swift/Sema/ConstraintSystem.h
@@ -3969,21 +3969,18 @@ class ConstraintSystem {
   isRepresentativeFor(TypeVariableType *typeVar,
                       ConstraintLocator::PathElementKind kind) const;
 
-  /// Gets the VarDecl associated with resolvedOverload, and the type of the
-  /// projection if the decl has an associated property wrapper with a projectedValue.
-  std::optional<std::pair<VarDecl *, Type>>
-  getPropertyWrapperProjectionInfo(SelectedOverload resolvedOverload);
+  /// Gets the the type of the projection if the decl has an associated property
+  /// wrapper with a projectedValue.
+  Type getPropertyWrapperProjectionType(SelectedOverload resolvedOverload);
 
-  /// Gets the VarDecl associated with resolvedOverload, and the type of the
-  /// backing storage if the decl has an associated property wrapper.
-  std::optional<std::pair<VarDecl *, Type>>
-  getPropertyWrapperInformation(SelectedOverload resolvedOverload);
+  /// Gets the type of the backing storage if the decl has an associated
+  /// property wrapper.
+  Type getPropertyWrapperBackingType(SelectedOverload resolvedOverload);
 
   /// Gets the VarDecl, and the type of the type property that it wraps if
   /// resolved overload has a decl which is the backing storage for a
   /// property wrapper.
-  std::optional<std::pair<VarDecl *, Type>>
-  getWrappedPropertyInformation(SelectedOverload resolvedOverload);
+  Type getWrappedPropertyType(SelectedOverload resolvedOverload);
 
   /// Merge the equivalence sets of the two type variables.
   ///
diff --git a/lib/Sema/CSSimplify.cpp b/lib/Sema/CSSimplify.cpp
@@ -4825,14 +4825,19 @@ static ConstraintFix *fixPropertyWrapperFailure(
   if (!resolvedOverload)
     return nullptr;
 
+  auto *decl = resolvedOverload->choice.getDeclOrNull();
+  auto *VD = dyn_cast_or_null<VarDecl>(decl);
+  if (!VD)
+    return nullptr;
+
   enum class Fix : uint8_t {
     ProjectedValue,
     PropertyWrapper,
     WrappedValue,
   };
 
-  auto applyFix = [&](Fix fix, VarDecl *decl, Type type) -> ConstraintFix * {
-    if (!decl->hasInterfaceType() || !type)
+  auto applyFix = [&](Fix fix, Type type) -> ConstraintFix * {
+    if (!VD->hasInterfaceType() || !type)
       return nullptr;
 
     if (baseTy->isEqual(type))
@@ -4841,40 +4846,34 @@ static ConstraintFix *fixPropertyWrapperFailure(
     if (baseTy->is<TypeVariableType>() || type->is<TypeVariableType>())
       return nullptr;
 
-    if (!attemptFix(*resolvedOverload, decl, type))
+    if (!attemptFix(*resolvedOverload, VD, type))
       return nullptr;
 
     switch (fix) {
     case Fix::ProjectedValue:
     case Fix::PropertyWrapper:
-      return UsePropertyWrapper::create(cs, decl, fix == Fix::ProjectedValue,
-                                        baseTy, toType.value_or(type),
-                                        locator);
+      return UsePropertyWrapper::create(cs, VD, fix == Fix::ProjectedValue,
+                                        baseTy, toType.value_or(type), locator);
 
     case Fix::WrappedValue:
-      return UseWrappedValue::create(cs, decl, baseTy, toType.value_or(type),
+      return UseWrappedValue::create(cs, VD, baseTy, toType.value_or(type),
                                      locator);
     }
     llvm_unreachable("Unhandled Fix type in switch");
   };
 
-  if (auto projection =
-          cs.getPropertyWrapperProjectionInfo(*resolvedOverload)) {
-    if (auto *fix = applyFix(Fix::ProjectedValue, projection->first,
-                             projection->second))
+  if (auto projectTy = cs.getPropertyWrapperProjectionType(*resolvedOverload)) {
+    if (auto *fix = applyFix(Fix::ProjectedValue, projectTy))
       return fix;
   }
 
-  if (auto wrapper = cs.getPropertyWrapperInformation(*resolvedOverload)) {
-    if (auto *fix =
-            applyFix(Fix::PropertyWrapper, wrapper->first, wrapper->second))
+  if (auto backingTy = cs.getPropertyWrapperBackingType(*resolvedOverload)) {
+    if (auto *fix = applyFix(Fix::PropertyWrapper, backingTy))
       return fix;
   }
 
-  if (auto wrappedProperty =
-          cs.getWrappedPropertyInformation(*resolvedOverload)) {
-    if (auto *fix = applyFix(Fix::WrappedValue, wrappedProperty->first,
-                             wrappedProperty->second))
+  if (auto wrappedTy = cs.getWrappedPropertyType(*resolvedOverload)) {
+    if (auto *fix = applyFix(Fix::WrappedValue, wrappedTy))
       return fix;
   }
 
diff --git a/lib/Sema/ConstraintSystem.cpp b/lib/Sema/ConstraintSystem.cpp
@@ -1244,72 +1244,51 @@ TypeVariableType *ConstraintSystem::isRepresentativeFor(
   return *member;
 }
 
-static std::optional<std::pair<VarDecl *, Type>>
-getPropertyWrapperInformationFromOverload(
-    SelectedOverload resolvedOverload, DeclContext *DC,
-    llvm::function_ref<std::optional<std::pair<VarDecl *, Type>>(VarDecl *)>
-        getInformation) {
-  if (auto *decl =
-          dyn_cast_or_null<VarDecl>(resolvedOverload.choice.getDeclOrNull())) {
-    if (auto declInformation = getInformation(decl)) {
-      Type type;
-      VarDecl *memberDecl;
-      std::tie(memberDecl, type) = *declInformation;
-      if (Type baseType = resolvedOverload.choice.getBaseType()) {
-        type = baseType->getRValueType()->getTypeOfMember(memberDecl, type);
-      }
-      return std::make_pair(decl, type);
-    }
-  }
-  return std::nullopt;
-}
+static Type getPropertyWrapperTypeFromOverload(
+    ConstraintSystem &cs, SelectedOverload resolvedOverload,
+    llvm::function_ref<VarDecl *(VarDecl *)> getWrapperVar) {
+  auto *D = dyn_cast_or_null<VarDecl>(resolvedOverload.choice.getDeclOrNull());
+  if (!D)
+    return Type();
 
-std::optional<std::pair<VarDecl *, Type>>
-ConstraintSystem::getPropertyWrapperProjectionInfo(
-    SelectedOverload resolvedOverload) {
-  return getPropertyWrapperInformationFromOverload(
-      resolvedOverload, DC,
-      [](VarDecl *decl) -> std::optional<std::pair<VarDecl *, Type>> {
-        if (!decl->hasAttachedPropertyWrapper())
-          return std::nullopt;
+  auto *wrapperVar = getWrapperVar(D);
+  if (!wrapperVar)
+    return Type();
 
-        auto projectionVar = decl->getPropertyWrapperProjectionVar();
-        if (!projectionVar)
-          return std::nullopt;
+  // For the backing property we need to query the request to ensure it kicks
+  // type-checking if necessary. Otherwise we can query the interface type.
+  auto ty = wrapperVar == D->getPropertyWrapperBackingProperty()
+                ? D->getPropertyWrapperBackingPropertyType()
+                : wrapperVar->getInterfaceType();
+  if (!ty)
+    return Type();
 
-        return std::make_pair(projectionVar,
-                              projectionVar->getInterfaceType());
-      });
+  // If this is a for a property, substitute the base type.
+  if (auto baseType = resolvedOverload.choice.getBaseType())
+    ty = baseType->getRValueType()->getTypeOfMember(wrapperVar, ty);
+
+  return ty;
 }
 
-std::optional<std::pair<VarDecl *, Type>>
-ConstraintSystem::getPropertyWrapperInformation(
+Type ConstraintSystem::getPropertyWrapperProjectionType(
     SelectedOverload resolvedOverload) {
-  return getPropertyWrapperInformationFromOverload(
-      resolvedOverload, DC,
-      [](VarDecl *decl) -> std::optional<std::pair<VarDecl *, Type>> {
-        if (!decl->hasAttachedPropertyWrapper())
-          return std::nullopt;
-
-        auto backingTy = decl->getPropertyWrapperBackingPropertyType();
-        if (!backingTy)
-          return std::nullopt;
-
-        return std::make_pair(decl, backingTy);
-      });
+  return getPropertyWrapperTypeFromOverload(
+      *this, resolvedOverload,
+      [&](VarDecl *decl) { return decl->getPropertyWrapperProjectionVar(); });
 }
 
-std::optional<std::pair<VarDecl *, Type>>
-ConstraintSystem::getWrappedPropertyInformation(
+Type ConstraintSystem::getPropertyWrapperBackingType(
     SelectedOverload resolvedOverload) {
-  return getPropertyWrapperInformationFromOverload(
-      resolvedOverload, DC,
-      [](VarDecl *decl) -> std::optional<std::pair<VarDecl *, Type>> {
-        if (auto wrapped = decl->getOriginalWrappedProperty())
-          return std::make_pair(decl, wrapped->getInterfaceType());
+  return getPropertyWrapperTypeFromOverload(
+      *this, resolvedOverload,
+      [](VarDecl *decl) { return decl->getPropertyWrapperBackingProperty(); });
+}
 
-        return std::nullopt;
-      });
+Type ConstraintSystem::getWrappedPropertyType(
+    SelectedOverload resolvedOverload) {
+  return getPropertyWrapperTypeFromOverload(
+      *this, resolvedOverload,
+      [](VarDecl *decl) { return decl->getOriginalWrappedProperty(); });
 }
 
 void ConstraintSystem::addOverloadSet(Type boundType,
diff --git a/test/decl/var/property_wrappers.swift b/test/decl/var/property_wrappers.swift
@@ -1346,6 +1346,15 @@ struct MissingPropertyWrapperUnwrap {
   }
 }
 
+_ = {
+  struct S {
+    @WrapperWithInitialValue var x = 0
+    init() {}
+  }
+  func a<T>(_: WrapperWithInitialValue<T>) {}
+  a(S().x) // expected-error {{cannot convert value 'x' of type 'Int' to expected type 'WrapperWithInitialValue<Int>', use wrapper instead}} {{9-9=_}}
+}
+
 struct InvalidPropertyDelegateUse {
   // TODO(diagnostics): We need to a tailored diagnostic for extraneous arguments in property delegate initialization
   @Foo var x: Int = 42 // expected-error@:21 {{extra argument 'wrappedValue' in call}}
