[SE-0258] Adjust name for CodingKeys property to drop the '$'.

When synthesizing Codable conformances, the enum case name for a
property with an attached delegate does not have the '$', i.e., it's
the name of the originally-declared property.

Author: DougGregor

lib/Sema/DerivedConformanceCodable.cpp

@@ -136,6 +136,14 @@ static CodableConformanceType varConformsToCodable(TypeChecker &tc,
                                isIUO, proto);
 }
 
+/// Retrieve the variable name for the purposes of encoding/decoding.
+static Identifier getVarNameForCoding(VarDecl *var) {
+  if (auto originalVar = var->getOriginalDelegatedProperty())
+    return originalVar->getName();
+
+  return var->getName();
+}
+
 /// Validates the given CodingKeys enum decl by ensuring its cases are a 1-to-1
 /// match with the stored vars of the given type.
 ///
@@ -162,7 +170,7 @@ static bool validateCodingKeysEnum(DerivedConformance &derived,
     if (varDecl->getAttrs().hasAttribute<LazyAttr>())
       continue;
 
-    properties[varDecl->getName()] = varDecl;
+    properties[getVarNameForCoding(varDecl)] = varDecl;
   }
 
   bool propertiesAreValid = true;
@@ -365,7 +373,8 @@ static EnumDecl *synthesizeCodingKeysEnum(DerivedConformance &derived) {
     switch (conformance) {
       case Conforms:
       {
-        auto *elt = new (C) EnumElementDecl(SourceLoc(), varDecl->getName(),
+        auto *elt = new (C) EnumElementDecl(SourceLoc(),
+                                            getVarNameForCoding(varDecl),
                                             nullptr, SourceLoc(), nullptr,
                                             enumDecl);
         elt->setImplicit();
@@ -518,6 +527,11 @@ lookupVarDeclForCodingKeysCase(DeclContext *conformanceDC,
                                NominalTypeDecl *targetDecl) {
   for (auto decl : targetDecl->lookupDirect(DeclName(elt->getName()))) {
     if (auto *vd = dyn_cast<VarDecl>(decl)) {
+      // If we found a property with an attached delegate, retrieve the
+      // backing property.
+      if (auto backingVar = vd->getPropertyDelegateBackingProperty())
+        vd = backingVar;
+
       if (!vd->isStatic()) {
         // This is the VarDecl we're looking for.
 

test/decl/protocol/special/coding/property_delegate_codable.swift

@@ -0,0 +1,37 @@
+// RUN: %target-typecheck-verify-swift -verify-ignore-unknown
+
+@_propertyDelegate
+struct Wrapper<T: Codable> {
+  var value: T
+}
+
+@_propertyDelegate
+struct WrapperWithInitialValue<T: Codable> {
+  var value: T
+
+  init(initialValue: T) {
+    self.value = initialValue
+  }
+}
+
+extension WrapperWithInitialValue: Codable { }
+
+struct X: Codable {
+  @WrapperWithInitialValue var foo = 17
+
+  // Make sure the generated key is named 'foo', like the original property.
+  private func getFooKey() -> CodingKeys {
+    return .foo
+  }
+}
+
+
+
+// expected-error@+2{{type 'Y' does not conform to protocol 'Encodable'}}
+// expected-error@+1{{type 'Y' does not conform to protocol 'Decodable'}}
+struct Y: Codable {
+  @Wrapper var foo: Int
+  // expected-note@-1{{cannot automatically synthesize 'Encodable' because 'Wrapper<Int>' does not conform to 'Encodable'}}
+  // expected-note@-2{{cannot automatically synthesize 'Decodable' because 'Wrapper<Int>' does not conform to 'Decodable'}}
+  
+}