[CodeSynthesis] Teach AreAllStoredPropertiesDefaultInitableRequest about init accessors

If stored property is covered by one or more init accessor property,
it's default initializable when at least one of the init accessor
properties has default value.

Author: xedin

lib/Sema/CodeSynthesis.cpp

@@ -845,6 +845,10 @@ bool AreAllStoredPropertiesDefaultInitableRequest::evaluate(
     Evaluator &evaluator, NominalTypeDecl *decl) const {
   assert(!hasClangImplementation(decl));
 
+  std::multimap<VarDecl *, VarDecl *> initializedViaInitAccessor;
+  decl->collectPropertiesInitializableByInitAccessors(
+      initializedViaInitAccessor);
+
   for (auto member : decl->getImplementationContext()->getMembers()) {
     // If a stored property lacks an initial value and if there is no way to
     // synthesize an initial value (e.g. for an optional) then we suppress
@@ -859,12 +863,24 @@ bool AreAllStoredPropertiesDefaultInitableRequest::evaluate(
         bool HasStorage = false;
         bool CheckDefaultInitializer = true;
         pbd->getPattern(idx)->forEachVariable(
-            [&HasStorage, &CheckDefaultInitializer](VarDecl *VD) {
+            [&HasStorage, &CheckDefaultInitializer,
+             &initializedViaInitAccessor](VarDecl *VD) {
               // If one of the bound variables is @NSManaged, go ahead no matter
               // what.
               if (VD->getAttrs().hasAttribute<NSManagedAttr>())
                 CheckDefaultInitializer = false;
 
+              // If this property is covered by one or more init accessor(s)
+              // check whether at least one of them is initializable.
+              auto initAccessorProperties =
+                  llvm::make_range(initializedViaInitAccessor.equal_range(VD));
+              if (llvm::any_of(initAccessorProperties, [&](const auto &entry) {
+                    auto *property =
+                        entry.second->getParentPatternBinding();
+                    return property->isInitialized(0);
+                  }))
+                return;
+
               if (VD->hasStorageOrWrapsStorage())
                 HasStorage = true;
             });

test/Interpreter/init_accessors.swift

@@ -678,6 +678,27 @@ func test_properties_with_inits() {
   }
 
   _ = TestAssign(x1: S(x: 0), x2: S(x: -3), y: 2)
+
+  class TestDefault : CustomStringConvertible {
+    var _a: Int
+
+    var a: Int = 42 {
+      @storageRestrictions(initializes: _a)
+      init {
+        _a = newValue
+      }
+
+      get { _a }
+    }
+
+    var b: String = "<<default>>"
+
+    var description: String {
+      "TestDefault(a: \(a), b: \(b))"
+    }
+  }
+
+  print("test-init-expr-3: \(TestDefault())")
 }
 
 test_properties_with_inits()
@@ -687,3 +708,4 @@ test_properties_with_inits()
 // CHECK-NEXT: TestAssign in x.init: self.x = S(x: 42)
 // CHECK-NEXT: TestAssign in x.init: self.x = S(x: 0)
 // CHECK-NEXT: TestAssign: self.x = S(x: -3)
+// CHECK-NEXT: test-init-expr-3: TestDefault(a: 42, b: <<default>>)

test/SILOptimizer/init_accessor_raw_sil_lowering.swift

@@ -233,4 +233,34 @@ func test_default_inits() {
     // CHECK: function_ref variable initialization expression of y in Test3 #1 in test_default_inits()
     // CHECK-NOT: function_ref variable initialization expression of _y in Test3 #1 in test_default_inits()
   }
+
+  class Test4 {
+    var _x: Int
+
+    var x: Int = 42 {
+      @storageRestrictions(initializes: _x)
+      init {
+        _x = newValue
+      }
+      get { _x }
+    }
+
+    var _y: String
+
+    var y: String = "" {
+      @storageRestrictions(initializes: _y)
+      init {
+        _y = newValue
+      }
+      get { _y }
+    }
+
+    // CHECK-LABEL: sil private [ossa] @$s23assign_or_init_lowering18test_default_initsyyF5Test4L_CADycfc : $@convention(method) (@owned Test4) -> @owned Test4
+    // CHECK: [[X_DEFAULT:%.*]] = function_ref @$s23assign_or_init_lowering18test_default_initsyyF5Test4L_C1xSivpfi : $@convention(thin) () -> Int
+    // CHECK-NEXT: [[X_VALUE:%.*]] = apply [[X_DEFAULT]]() : $@convention(thin) () -> Int
+    // CHECK: assign_or_init [init] self %0 : $Test4, value [[X_VALUE]] : $Int, init {{.*}} : $@convention(thin) (Int) -> @out Int, set undef : $@convention(thin) (Int) -> @out Int
+    // CHECK: [[Y_DEFAULT:%.*]] = function_ref @$s23assign_or_init_lowering18test_default_initsyyF5Test4L_C1ySSvpfi : $@convention(thin) () -> @owned String
+    // CHECK-NEXT: [[Y_VALUE:%.*]] = apply [[Y_DEFAULT]]() : $@convention(thin) () -> @owned String
+    // CHECK: assign_or_init [init] self %0 : $Test4, value [[Y_VALUE]] : $String, init {{.*}} : $@convention(thin) (@owned String) -> @out String, set undef : $@convention(thin) (@owned String) -> @out String
+  }
 }