Sema: Fix circular validation between memberwise initializer and stored property

Fixes <rdar://problem/42704745>.

Author: slavapestov

lib/Sema/CodeSynthesis.cpp

@@ -1690,6 +1690,25 @@ static void maybeAddMemberwiseDefaultArg(ParamDecl *arg, VarDecl *var,
   arg->setDefaultArgumentKind(DefaultArgumentKind::StoredProperty);
 }
 
+bool swift::isMemberwiseInitialized(VarDecl *var) {
+  // Implicit, computed, and static properties are not initialized.
+  // The exception is lazy properties, which due to batch mode we may or
+  // may not have yet finalized, so they may currently be "stored" or
+  // "computed" in the current AST state.
+  if (var->isImplicit() || var->isStatic())
+    return false;
+
+  if (!var->hasStorage() && !var->getAttrs().hasAttribute<LazyAttr>())
+    return false;
+
+  // Initialized 'let' properties have storage, but don't get an argument
+  // to the memberwise initializer since they already have an initial
+  // value that cannot be overridden.
+  if (var->isLet() && var->getParentInitializer())
+    return false;
+
+  return true;
+}
 /// Create an implicit struct or class constructor.
 ///
 /// \param decl The struct or class for which a constructor will be created.
@@ -1716,23 +1735,10 @@ ConstructorDecl *swift::createImplicitConstructor(TypeChecker &tc,
       auto var = dyn_cast<VarDecl>(member);
       if (!var)
         continue;
-      
-      // Implicit, computed, and static properties are not initialized.
-      // The exception is lazy properties, which due to batch mode we may or
-      // may not have yet finalized, so they may currently be "stored" or
-      // "computed" in the current AST state.
-      if (var->isImplicit() || var->isStatic())
-        continue;
 
-      if (!var->hasStorage() && !var->getAttrs().hasAttribute<LazyAttr>())
+      if (!isMemberwiseInitialized(var))
         continue;
 
-      // Initialized 'let' properties have storage, but don't get an argument
-      // to the memberwise initializer since they already have an initial
-      // value that cannot be overridden.
-      if (var->isLet() && var->getParentInitializer())
-        continue;
-      
       accessLevel = std::min(accessLevel, var->getFormalAccess());
 
       tc.validateDecl(var);
@@ -1765,9 +1771,9 @@ ConstructorDecl *swift::createImplicitConstructor(TypeChecker &tc,
   DeclName name(ctx, DeclBaseName::createConstructor(), paramList);
   auto *ctor =
     new (ctx) ConstructorDecl(name, Loc,
-                                  OTK_None, /*FailabilityLoc=*/SourceLoc(),
-                                  /*Throws=*/false, /*ThrowsLoc=*/SourceLoc(),
-                                  paramList, /*GenericParams=*/nullptr, decl);
+                              OTK_None, /*FailabilityLoc=*/SourceLoc(),
+                              /*Throws=*/false, /*ThrowsLoc=*/SourceLoc(),
+                              paramList, /*GenericParams=*/nullptr, decl);
 
   // Mark implicit.
   ctor->setImplicit();

lib/Sema/CodeSynthesis.h

@@ -69,6 +69,8 @@ enum class ImplicitConstructorKind {
   Memberwise
 };
 
+bool isMemberwiseInitialized(VarDecl *var);
+
 /// Create an implicit struct or class constructor.
 ///
 /// \param decl The struct or class for which a constructor will be created.

lib/Sema/TypeCheckDecl.cpp

@@ -5048,8 +5048,8 @@ void TypeChecker::addImplicitConstructors(NominalTypeDecl *decl) {
     }
   }
 
-  // Bail out if we're validating one of our constructors already; we'll
-  // revisit the issue later.
+  // Bail out if we're validating one of our constructors or stored properties
+  // already; we'll revisit the issue later.
   if (isa<ClassDecl>(decl)) {
     for (auto member : decl->getMembers()) {
       if (auto ctor = dyn_cast<ConstructorDecl>(member)) {
@@ -5060,13 +5060,25 @@ void TypeChecker::addImplicitConstructors(NominalTypeDecl *decl) {
     }
   }
 
+  if (isa<StructDecl>(decl)) {
+    for (auto member : decl->getMembers()) {
+      if (auto var = dyn_cast<VarDecl>(member)) {
+        if (!isMemberwiseInitialized(var))
+          continue;
+
+        validateDecl(var);
+        if (!var->hasValidSignature())
+          return;
+      }
+    }
+  }
+
   decl->setAddedImplicitInitializers();
 
   // Check whether there is a user-declared constructor or an instance
   // variable.
   bool FoundMemberwiseInitializedProperty = false;
   bool SuppressDefaultInitializer = false;
-  bool SuppressMemberwiseInitializer = false;
   bool FoundDesignatedInit = false;
 
   SmallVector<std::pair<ValueDecl *, Type>, 4> declaredInitializers;
@@ -5110,7 +5122,7 @@ void TypeChecker::addImplicitConstructors(NominalTypeDecl *decl) {
       }
 
       if (auto var = dyn_cast<VarDecl>(member)) {
-        if (var->hasStorage() && !var->isStatic() && !var->isInvalid()) {
+        if (isMemberwiseInitialized(var)) {
           // Initialized 'let' properties have storage, but don't get an argument
           // to the memberwise initializer since they already have an initial
           // value that cannot be overridden.
@@ -5165,7 +5177,7 @@ void TypeChecker::addImplicitConstructors(NominalTypeDecl *decl) {
     assert(!structDecl->hasUnreferenceableStorage() &&
            "User-defined structs cannot have unreferenceable storage");
 
-    if (!FoundDesignatedInit && !SuppressMemberwiseInitializer) {
+    if (!FoundDesignatedInit) {
       // For a struct with memberwise initialized properties, we add a
       // memberwise init.
       if (FoundMemberwiseInitializedProperty) {

test/decl/init/Inputs/memberwise-init-multifile-other.swift

@@ -0,0 +1,3 @@
+struct S {
+  var a = S() // expected-error {{'S' cannot be constructed because it has no accessible initializers}}
+}

test/decl/init/memberwise-init-multifile.swift

@@ -0,0 +1,3 @@
+// RUN: %target-swift-frontend -typecheck -verify -primary-file %s %S/Inputs/memberwise-init-multifile-other.swift
+
+func f(_: S) {}