[Typechecker] Add an hasObservers() convenience method and simplify some code

Author: theblixguy

include/swift/AST/Decl.h

@@ -4707,6 +4707,13 @@ class AbstractStorageDecl : public ValueDecl {
   /// Does this storage require a 'modify' accessor in its opaque-accessors set?
   bool requiresOpaqueModifyCoroutine() const;
 
+  /// Does this storage have any explicit observers (willSet or didSet) attached
+  /// to it?
+  bool hasObservers() const {
+    return getParsedAccessor(AccessorKind::WillSet) ||
+           getParsedAccessor(AccessorKind::DidSet);
+  }
+
   SourceRange getBracesRange() const {
     if (auto info = Accessors.getPointer())
       return info->getBracesRange();

lib/Sema/TypeCheckDeclOverride.cpp

@@ -1568,8 +1568,7 @@ static bool checkSingleOverride(ValueDecl *override, ValueDecl *base) {
     // Make sure that the overriding property doesn't have storage.
     if ((overrideASD->hasStorage() ||
          overrideASD->getAttrs().hasAttribute<LazyAttr>()) &&
-        !(overrideASD->getParsedAccessor(AccessorKind::WillSet) ||
-          overrideASD->getParsedAccessor(AccessorKind::DidSet))) {
+        !overrideASD->hasObservers()) {
       bool downgradeToWarning = false;
       if (!ctx.isSwiftVersionAtLeast(5) &&
           overrideASD->getAttrs().hasAttribute<LazyAttr>()) {

lib/Sema/TypeCheckStorage.cpp

@@ -760,11 +760,6 @@ static Expr *buildStorageReference(AccessorDecl *accessor,
     auto var = dyn_cast<VarDecl>(decl);
     if (!var)
       return None;
-    bool hasObservers = var->getParsedAccessor(AccessorKind::WillSet) ||
-                        var->getParsedAccessor(AccessorKind::DidSet);
-    if (accessor->isCoroutine() && hasObservers) {
-      return None;
-    }
     auto mut = var->getPropertyWrapperMutability();
     if (!mut)
       return None;
@@ -1536,8 +1531,7 @@ synthesizeSetterBody(AccessorDecl *setter, ASTContext &ctx) {
     }
 
     if (var->hasAttachedPropertyWrapper()) {
-      if (var->getParsedAccessor(AccessorKind::WillSet) ||
-          var->getParsedAccessor(AccessorKind::DidSet)) {
+      if (var->hasObservers()) {
         return synthesizeObservedSetterBody(setter, TargetImpl::Wrapper, ctx);
       }
 
@@ -1589,20 +1583,19 @@ synthesizeCoroutineAccessorBody(AccessorDecl *accessor, ASTContext &ctx) {
                    ? TargetImpl::Ordinary
                    : TargetImpl::Implementation);
 
-  bool hasObservers = storage->getParsedAccessor(AccessorKind::DidSet) ||
-                      storage->getParsedAccessor(AccessorKind::WillSet);
-
   // If this is a variable with an attached property wrapper, then
   // the accessors need to yield the wrappedValue or projectedValue.
-  if (auto var = dyn_cast<VarDecl>(storage)) {
-    if (var->hasAttachedPropertyWrapper() && !hasObservers) {
-      target = TargetImpl::Wrapper;
-    }
+  if (storage->getReadImpl() == ReadImplKind::Read ||
+      storageReadWriteImpl == ReadWriteImplKind::Modify) {
+    if (auto var = dyn_cast<VarDecl>(storage)) {
+      if (var->hasAttachedPropertyWrapper()) {
+        target = TargetImpl::Wrapper;
+      }
 
-    if (var->getOriginalWrappedProperty(
-            PropertyWrapperSynthesizedPropertyKind::StorageWrapper) &&
-        !hasObservers) {
-      target = TargetImpl::WrapperStorage;
+      if (var->getOriginalWrappedProperty(
+              PropertyWrapperSynthesizedPropertyKind::StorageWrapper)) {
+        target = TargetImpl::WrapperStorage;
+      }
     }
   }
 
@@ -2052,8 +2045,7 @@ IsAccessorTransparentRequest::evaluate(Evaluator &evaluator,
       // FIXME: This should be folded into the WriteImplKind below.
       if (auto var = dyn_cast<VarDecl>(storage)) {
         if (var->hasAttachedPropertyWrapper()) {
-          if (var->getParsedAccessor(AccessorKind::DidSet) ||
-              var->getParsedAccessor(AccessorKind::WillSet))
+          if (var->hasObservers())
             return false;
 
           break;
@@ -2590,16 +2582,13 @@ static void finishPropertyWrapperImplInfo(VarDecl *var,
     }
   }
 
-  bool hasObservers = var->getParsedAccessor(AccessorKind::DidSet) ||
-                      var->getParsedAccessor(AccessorKind::WillSet);
-
   if (wrapperSetterIsUsable) {
-    if (hasObservers) {
+    if (var->hasObservers()) {
       info = StorageImplInfo::getMutableComputed();
-    } else {
-      info = StorageImplInfo(ReadImplKind::Get, WriteImplKind::Set,
-                             ReadWriteImplKind::Modify);
+      return;
     }
+    info = StorageImplInfo(ReadImplKind::Get, WriteImplKind::Set,
+                           ReadWriteImplKind::Modify);
   } else {
     info = StorageImplInfo::getImmutableComputed();
   }

tools/SourceKit/lib/SwiftLang/SwiftEditor.cpp

@@ -1190,8 +1190,7 @@ static bool inferIsSettableSyntactically(const AbstractStorageDecl *D) {
   }
   if (D->hasParsedAccessors()) {
     return D->getParsedAccessor(AccessorKind::Set) != nullptr ||
-           D->getParsedAccessor(AccessorKind::WillSet) != nullptr ||
-           D->getParsedAccessor(AccessorKind::DidSet) != nullptr;
+           D->hasObservers();
   } else {
     return true;
   }