Sema: Synthesize materializeForSet for lazy properties

Fixes <rdar://problem/25707968>.

Author: slavapestov

lib/SILGen/SILGenLValue.cpp

@@ -830,8 +830,8 @@ namespace {
 
       // If the declaration is dynamically dispatched through a class,
       // we have to use materializeForSet.
-      if (isa<ClassDecl>(decl->getDeclContext())) {
-        if (decl->isFinal())
+      if (auto *classDecl = dyn_cast<ClassDecl>(decl->getDeclContext())) {
+        if (decl->isFinal() || classDecl->isFinal())
           return false;
 
         return true;

lib/Sema/CodeSynthesis.cpp

@@ -1576,6 +1576,8 @@ void TypeChecker::completeLazyVarImplementation(VarDecl *VD) {
          "variable not validated yet");
   assert(!VD->isStatic() && "Static vars are already lazy on their own");
 
+  maybeAddMaterializeForSet(VD, *this);
+
   // Create the storage property as an optional of VD's type.
   SmallString<64> NameBuf = VD->getName().str();
   NameBuf += ".storage";

test/SILGen/materializeForSet.swift

@@ -459,9 +459,49 @@ struct TuxedoPanda : Panda { }
 // CHECK: }
 
 
+// Test for materializeForSet vs lazy properties of structs.
+
+struct LazyStructProperty {
+  lazy var cat: Int = 5
+}
+
+// CHECK-LABEL: sil hidden @_TF17materializeForSet31inoutAccessOfLazyStructPropertyFT1lRVS_18LazyStructProperty_T_
+// CHECK:   function_ref @_TFV17materializeForSet18LazyStructPropertyg3catSi
+// CHECK:   function_ref @_TFV17materializeForSet18LazyStructPropertys3catSi
+func inoutAccessOfLazyStructProperty(l: inout LazyStructProperty) {
+  increment(&l.cat)
+}
+
+// Test for materializeForSet vs lazy properties of classes.
+
+// CHECK-LABEL: sil hidden [transparent] @_TFC17materializeForSet17LazyClassPropertym3catSi
+
+class LazyClassProperty {
+  lazy var cat: Int = 5
+}
+
+// CHECK-LABEL: sil hidden @_TF17materializeForSet30inoutAccessOfLazyClassPropertyFT1lRCS_17LazyClassProperty_T_
+// CHECK:    class_method {{.*}} : $LazyClassProperty, #LazyClassProperty.cat!materializeForSet.1
+func inoutAccessOfLazyClassProperty(l: inout LazyClassProperty) {
+  increment(&l.cat)
+}
+
+// Test for materializeForSet vs lazy properties of final classes.
+
+final class LazyFinalClassProperty {
+  lazy var cat: Int = 5
+}
+
+// CHECK-LABEL: sil hidden @_TF17materializeForSet35inoutAccessOfLazyFinalClassPropertyFT1lRCS_22LazyFinalClassProperty_T_
+// CHECK:    function_ref @_TFC17materializeForSet22LazyFinalClassPropertyg3catSi
+// CHECK:    function_ref @_TFC17materializeForSet22LazyFinalClassPropertys3catSi
+func inoutAccessOfLazyFinalClassProperty(l: inout LazyFinalClassProperty) {
+  increment(&l.cat)
+}
+
+
 // CHECK-LABEL: sil_witness_table hidden Bill: Totalled module materializeForSet {
 // CHECK:   method #Totalled.total!getter.1: @_TTWV17materializeForSet4BillS_8TotalledS_FS1_g5totalSi
 // CHECK:   method #Totalled.total!setter.1: @_TTWV17materializeForSet4BillS_8TotalledS_FS1_s5totalSi
 // CHECK:   method #Totalled.total!materializeForSet.1: @_TTWV17materializeForSet4BillS_8TotalledS_FS1_m5totalSi
 // CHECK: }
-

test/multifile/synthesized-accessors/one-module-internal/library.swift

@@ -24,3 +24,7 @@ final class Beer {
     set { }
   }
 }
+
+class LazyCat {
+  lazy var purrs: Int = 10
+}

test/multifile/synthesized-accessors/one-module-internal/main.swift

@@ -19,5 +19,11 @@ protocol Beverage {
 
 extension Beer : Beverage {}
 
+protocol PurrExtractor {
+  var purrs: Int { get set }
+}
+
+extension LazyCat : PurrExtractor {}
+
 // Dummy statement
 _ = ()

test/multifile/synthesized-accessors/one-module-public/library.swift

@@ -18,9 +18,13 @@ public struct FishAndChips {
   }
 }
 
-final class Beer {
-  var abv: Int {
+public final class Beer {
+  public var abv: Int {
     get { return 7 }
     set { }
   }
 }
+
+public class LazyCat {
+  public lazy var purrs: Int = 10
+}

test/multifile/synthesized-accessors/one-module-public/main.swift

@@ -19,5 +19,11 @@ protocol Beverage {
 
 extension Beer : Beverage {}
 
+protocol PurrExtractor {
+  var purrs: Int { get set }
+}
+
+extension LazyCat : PurrExtractor {}
+
 // Dummy statement
 _ = ()

test/multifile/synthesized-accessors/two-modules/library.swift

@@ -24,3 +24,7 @@ public final class Beer {
     set { }
   }
 }
+
+public class LazyCat {
+  public lazy var purrs: Int = 10
+}

test/multifile/synthesized-accessors/two-modules/main.swift

@@ -23,5 +23,11 @@ protocol Beverage {
 
 extension Beer : Beverage {}
 
+protocol PurrExtractor {
+  var purrs: Int { get set }
+}
+
+extension LazyCat : PurrExtractor {}
+
 // Dummy statement
 _ = ()