From 3394616e6fe3f8d1c4e10b61d8de427f860e5703 Mon Sep 17 00:00:00 2001
From: Dan Zheng <danielzheng@google.com>
Date: Fri, 14 Jun 2019 16:50:26 -0700
Subject: [PATCH 1/2] [Sema] Always create memberwise init when deriving
 `AdditiveArithmetic`.

Previously, during `AdditiveArithmetic` derived conformances, memberwise
initializers were synthesized only when synthesizing `static var zero`.
This led to a crash for types that specified `static var zero` but not
other requirements.

Resolves TF-579.
---
 .../DerivedConformanceAdditiveArithmetic.cpp  | 26 ++++++++++++-------
 test/Sema/struct_additive_arithmetic.swift    |  7 +++++
 2 files changed, 23 insertions(+), 10 deletions(-)

diff --git a/lib/Sema/DerivedConformanceAdditiveArithmetic.cpp b/lib/Sema/DerivedConformanceAdditiveArithmetic.cpp
index e5d38c28d892c..bdb730f2a03ef 100644
--- a/lib/Sema/DerivedConformanceAdditiveArithmetic.cpp
+++ b/lib/Sema/DerivedConformanceAdditiveArithmetic.cpp
@@ -61,6 +61,20 @@ static ValueDecl *getProtocolRequirement(ProtocolDecl *proto, Identifier name) {
   return lookup.front();
 }
 
+// Get the effective memberwise initializer of the given nominal type, or create
+// it if it does not exist.
+static ConstructorDecl *getOrCreateEffectiveMemberwiseInitializer(
+      TypeChecker &TC, NominalTypeDecl *nominal) {
+  auto &C = nominal->getASTContext();
+  if (auto *initDecl = nominal->getEffectiveMemberwiseInitializer())
+    return initDecl;
+  auto *initDecl = createImplicitConstructor(
+      TC, nominal, ImplicitConstructorKind::Memberwise);
+  nominal->addMember(initDecl);
+  C.addSynthesizedDecl(initDecl);
+  return initDecl;
+}
+
 // Return true if given nominal type has a `let` stored with an initial value.
 static bool hasLetStoredPropertyWithInitialValue(NominalTypeDecl *nominal) {
   return llvm::any_of(nominal->getStoredProperties(), [&](VarDecl *v) {
@@ -302,16 +316,6 @@ static ValueDecl *deriveAdditiveArithmetic_zero(DerivedConformance &derived) {
   auto &TC = derived.TC;
   auto &C = TC.Context;
 
-  // The implicit memberwise constructor must be explicitly created so that it
-  // can called when synthesizing the `zero` property getter. Normally, the
-  // memberwise constructor is synthesized during SILGen, which is too late.
-  if (!nominal->getEffectiveMemberwiseInitializer()) {
-    auto *initDecl = createImplicitConstructor(
-        TC, nominal, ImplicitConstructorKind::Memberwise);
-    nominal->addMember(initDecl);
-    C.addSynthesizedDecl(initDecl);
-  }
-
   auto returnInterfaceTy = nominal->getDeclaredInterfaceType();
   auto returnTy = parentDC->mapTypeIntoContext(returnInterfaceTy);
 
@@ -338,6 +342,8 @@ DerivedConformance::deriveAdditiveArithmetic(ValueDecl *requirement) {
   // Diagnose conformances in disallowed contexts.
   if (checkAndDiagnoseDisallowedContext(requirement))
     return nullptr;
+  // Create memberwise initializer for nominal type if it doesn't already exist.
+  getOrCreateEffectiveMemberwiseInitializer(TC, Nominal);
   if (requirement->getBaseName() == TC.Context.getIdentifier("+"))
     return deriveMathOperator(*this, Add);
   if (requirement->getBaseName() == TC.Context.getIdentifier("-"))
diff --git a/test/Sema/struct_additive_arithmetic.swift b/test/Sema/struct_additive_arithmetic.swift
index 31ff16727734a..cdc8bd0a494dc 100644
--- a/test/Sema/struct_additive_arithmetic.swift
+++ b/test/Sema/struct_additive_arithmetic.swift
@@ -91,6 +91,13 @@ struct NoMemberwiseInitializer<T : AdditiveArithmetic> : AdditiveArithmetic {
   var value: T
   init(randomLabel value: T) { self.value = value }
 }
+struct NoMemberwiseInitializerCustomZero: AdditiveArithmetic {
+  var x: Float
+  static var zero: Self { return NoMemberwiseInitializerCustomZero(0) }
+  init(_ x: Float) {
+    self.x = x
+  }
+}
 struct NoMemberwiseInitializerExtended<T> {
   var value: T
   init(_ value: T) {

From 6d1a4464925e166c0b7e4bd73b3fc2144b56e9b4 Mon Sep 17 00:00:00 2001
From: Dan Zheng <danielzheng@google.com>
Date: Fri, 14 Jun 2019 17:13:31 -0700
Subject: [PATCH 2/2] Address review feedback.

Co-Authored-By: Richard Wei <rxwei@google.com>
---
 lib/Sema/DerivedConformanceAdditiveArithmetic.cpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/lib/Sema/DerivedConformanceAdditiveArithmetic.cpp b/lib/Sema/DerivedConformanceAdditiveArithmetic.cpp
index bdb730f2a03ef..6974aca531492 100644
--- a/lib/Sema/DerivedConformanceAdditiveArithmetic.cpp
+++ b/lib/Sema/DerivedConformanceAdditiveArithmetic.cpp
@@ -64,7 +64,7 @@ static ValueDecl *getProtocolRequirement(ProtocolDecl *proto, Identifier name) {
 // Get the effective memberwise initializer of the given nominal type, or create
 // it if it does not exist.
 static ConstructorDecl *getOrCreateEffectiveMemberwiseInitializer(
-      TypeChecker &TC, NominalTypeDecl *nominal) {
+    TypeChecker &TC, NominalTypeDecl *nominal) {
   auto &C = nominal->getASTContext();
   if (auto *initDecl = nominal->getEffectiveMemberwiseInitializer())
     return initDecl;