[NameLookup] Teach unqualified lookup to resolve backing property wrapper

and projected value references

Author: hborla

include/swift/AST/NameLookup.h

@@ -225,6 +225,8 @@ enum class UnqualifiedLookupFlags {
   /// This lookup should include results from outside the innermost scope with
   /// results.
   IncludeOuterResults   = 1 << 4,
+  /// Includes property wrapper name lookup results
+  IncludePropertyWrapperResults = 1 << 5,
 };
 
 using UnqualifiedLookupOptions = OptionSet<UnqualifiedLookupFlags>;

lib/AST/UnqualifiedLookup.cpp

@@ -22,6 +22,7 @@
 #include "swift/AST/ModuleNameLookup.h"
 #include "swift/AST/NameLookup.h"
 #include "swift/AST/NameLookupRequests.h"
+#include "swift/AST/PropertyWrappers.h"
 #include "swift/Basic/Debug.h"
 #include "swift/Basic/STLExtras.h"
 #include "swift/Basic/SourceManager.h"
@@ -602,8 +603,28 @@ bool ASTScopeDeclConsumerForUnqualifiedLookup::consume(
       }
     }
 
-    if (!value->getName().matchesRef(factory.Name.getFullName()))
-      continue;
+    auto fullName = factory.Name.getFullName();
+    if (!value->getName().matchesRef(fullName)) {
+      if (!factory.options.contains(UnqualifiedLookupFlags::IncludePropertyWrapperResults))
+        continue;
+
+      auto *varDecl = dyn_cast<VarDecl>(value);
+      if (!varDecl || !varDecl->hasAttachedPropertyWrapper())
+        continue;
+
+      auto wrapperInfo = varDecl->getPropertyWrapperBackingPropertyInfo();
+      if (!wrapperInfo)
+        continue;
+
+      if (wrapperInfo.backingVar->ValueDecl::getName().matchesRef(fullName)) {
+        value = wrapperInfo.backingVar;
+      } else if (wrapperInfo.projectionVar &&
+                 wrapperInfo.projectionVar->ValueDecl::getName().matchesRef(fullName)) {
+        value = wrapperInfo.projectionVar;
+      } else {
+        continue;
+      }
+    }
 
     // In order to preserve the behavior of the existing context-based lookup,
     // which finds all results for non-local variables at the top level instead

lib/Sema/TypeCheckConstraints.cpp

@@ -538,6 +538,10 @@ Expr *TypeChecker::resolveDeclRefExpr(UnresolvedDeclRefExpr *UDRE,
   //       name/module qualifier to access top-level name.
   lookupOptions |= NameLookupFlags::IncludeOuterResults;
 
+  // Include property wrapper results in case we have a reference to a backing
+  // property wrapper or projected value
+  lookupOptions |= NameLookupFlags::IncludePropertyWrapperResults;
+
   if (Loc.isInvalid())
     DC = DC->getModuleScopeContext();
 

lib/Sema/TypeCheckNameLookup.cpp

@@ -211,6 +211,8 @@ convertToUnqualifiedLookupOptions(NameLookupOptions options) {
     newOptions |= UnqualifiedLookupFlags::IgnoreAccessControl;
   if (options.contains(NameLookupFlags::IncludeOuterResults))
     newOptions |= UnqualifiedLookupFlags::IncludeOuterResults;
+  if (options.contains(NameLookupFlags::IncludePropertyWrapperResults))
+    newOptions |= UnqualifiedLookupFlags::IncludePropertyWrapperResults;
 
   return newOptions;
 }

lib/Sema/TypeChecker.h

@@ -192,6 +192,8 @@ enum class NameLookupFlags {
   /// Whether to include results from outside the innermost scope that has a
   /// result.
   IncludeOuterResults = 1 << 1,
+  /// Whether to consider property wrapper names
+  IncludePropertyWrapperResults = 1 << 2,
 };
 
 /// A set of options that control name lookup.