[Property Wrappers] Add a VarDecl helper method for visiting synthesized

property wrapper vars.

Author: hborla

include/swift/AST/Decl.h

@@ -5202,6 +5202,14 @@ class VarDecl : public AbstractStorageDecl {
   /// property wrapper with a \c projectedValue .
   VarDecl *getPropertyWrapperProjectionVar() const;
 
+  /// Visit all auxiliary declarations to this VarDecl.
+  ///
+  /// An auxiliary declaration is a declaration synthesized by the compiler to support
+  /// this VarDecl, such as synthesized property wrapper variables.
+  ///
+  /// \note this function only visits auxiliary decls that are not part of the AST.
+  void visitAuxiliaryDecls(llvm::function_ref<void(VarDecl *)>) const;
+
   /// Retrieve the backing storage property for a lazy property.
   VarDecl *getLazyStorageProperty() const;
 

lib/AST/Decl.cpp

@@ -5956,6 +5956,17 @@ VarDecl *VarDecl::getPropertyWrapperProjectionVar() const {
   return getPropertyWrapperBackingPropertyInfo().projectionVar;
 }
 
+void VarDecl::visitAuxiliaryDecls(llvm::function_ref<void(VarDecl *)> visit) const {
+  if (!getDeclContext()->isLocalContext())
+    return;
+
+  if (auto *backingVar = getPropertyWrapperBackingProperty())
+    visit(backingVar);
+
+  if (auto *projectionVar = getPropertyWrapperProjectionVar())
+    visit(projectionVar);
+}
+
 VarDecl *VarDecl::getLazyStorageProperty() const {
   auto &ctx = getASTContext();
   auto mutableThis = const_cast<VarDecl *>(this);

lib/SILGen/SILGenDecl.cpp

@@ -1195,13 +1195,6 @@ void SILGenFunction::emitPatternBinding(PatternBindingDecl *PBD,
 }
 
 void SILGenFunction::visitPatternBindingDecl(PatternBindingDecl *PBD) {
-  // Visit (local) property wrapper backing var first
-  auto *singleVar = PBD->getSingleVar();
-  if (singleVar && singleVar->hasAttachedPropertyWrapper() &&
-      singleVar->getDeclContext()->isLocalContext()) {
-    auto *backingVar = singleVar->getPropertyWrapperBackingProperty();
-    visitPatternBindingDecl(backingVar->getParentPatternBinding());
-  }
 
   // Allocate the variables and build up an Initialization over their
   // allocated storage.
@@ -1213,17 +1206,17 @@ void SILGenFunction::visitPatternBindingDecl(PatternBindingDecl *PBD) {
 void SILGenFunction::visitVarDecl(VarDecl *D) {
   // We handle emitting the variable storage when we see the pattern binding.
 
-  // Visit property wrapper synthesized accessors first.
-  if (D->hasAttachedPropertyWrapper() && D->getDeclContext()->isLocalContext()) {
-    auto wrapperInfo = D->getPropertyWrapperBackingPropertyInfo();
-    if (!wrapperInfo)
-      return;
-
+  // Emit the property wrapper backing initializer if necessary.
+  auto wrapperInfo = D->getPropertyWrapperBackingPropertyInfo();
+  if (wrapperInfo && wrapperInfo.initializeFromOriginal)
     SGM.emitPropertyWrapperBackingInitializer(D);
-    visit(wrapperInfo.backingVar);
-    if (wrapperInfo.projectionVar)
-      visit(wrapperInfo.projectionVar);
-  }
+
+  D->visitAuxiliaryDecls([&](VarDecl *var) {
+    if (auto *patternBinding = var->getParentPatternBinding())
+      visitPatternBindingDecl(patternBinding);
+
+    visit(var);
+  });
 
   // Emit the variable's accessors.
   D->visitEmittedAccessors([&](AccessorDecl *accessor) {

lib/Sema/TypeCheckDeclPrimary.cpp

@@ -1418,16 +1418,10 @@ class DeclChecker : public DeclVisitor<DeclChecker> {
     (void) VD->getPropertyWrapperBackingProperty();
     (void) VD->getImplInfo();
 
-    if (VD->hasAttachedPropertyWrapper() && VD->getDeclContext()->isLocalContext()) {
-      // If this is a local wrapped variable, visit the synthesized
-      // storage and projection first
-      auto wrapperInfo = VD->getPropertyWrapperBackingPropertyInfo();
-      assert(wrapperInfo);
-
-      visitBoundVariable(wrapperInfo.backingVar);
-      if (wrapperInfo.projectionVar)
-        visitBoundVariable(wrapperInfo.projectionVar);
-    }
+    // Visit auxiliary decls first
+    VD->visitAuxiliaryDecls([&](VarDecl *var) {
+      this->visitBoundVariable(var);
+    });
 
     // Add the '@_hasStorage' attribute if this property is stored.
     if (VD->hasStorage() && !VD->getAttrs().hasAttribute<HasStorageAttr>())