[AST] Prefer parent PatternBindingDecl as owner for CustomAttr

If we have a VarDecl, use its parent PatternBindingDecl as the owner
to ensure we can correctly represent pattern bindings that bind multiple
vars.

Author: hamishknight

include/swift/AST/Attr.h

@@ -2322,7 +2322,7 @@ class CustomAttr final : public DeclAttribute {
 
   /// Retrieve the Decl or DeclContext owner for the attribute.
   CustomAttrOwner getOwner() const { return owner; }
-  void setOwner(CustomAttrOwner newOwner) { owner = newOwner; }
+  void setOwner(CustomAttrOwner newOwner);
 
   ASTContext &getASTContext() const;
 

lib/AST/Attr.cpp

@@ -3084,6 +3084,16 @@ CustomAttr *CustomAttr::create(ASTContext &ctx, SourceLoc atLoc, TypeExpr *type,
       CustomAttr(atLoc, range, type, owner, initContext, argList, implicit);
 }
 
+void CustomAttr::setOwner(CustomAttrOwner newOwner) {
+  // Prefer to set the parent PatternBindingDecl as the owner for a VarDecl,
+  // this ensures we can handle PBDs with multiple vars.
+  if (auto *VD = dyn_cast_or_null<VarDecl>(newOwner.getAsDecl())) {
+    if (auto *PBD = VD->getParentPatternBinding())
+      newOwner = PBD;
+  }
+  owner = newOwner;
+}
+
 std::pair<UnqualifiedIdentTypeRepr *, DeclRefTypeRepr *>
 CustomAttr::destructureMacroRef() {
   TypeRepr *typeRepr = getTypeRepr();

lib/AST/NameLookup.cpp

@@ -3976,9 +3976,11 @@ static bool shouldPreferPropertyWrapperOverMacro(CustomAttrOwner owner) {
   // if one exists. This is necessary since we don't properly support peer
   // declarations in local contexts, so want to use a property wrapper if one
   // exists.
-  if (auto *D = dyn_cast_or_null<VarDecl>(owner.getAsDecl())) {
-    if (D->getDeclContext()->isLocalContext())
+  if (auto *D = owner.getAsDecl()) {
+    if ((isa<VarDecl>(D) || isa<PatternBindingDecl>(D)) &&
+        D->getDeclContext()->isLocalContext()) {
       return true;
+    }
   }
   return false;
 }