[Sema] TypeCheckStmt: Prevent crash when PatternBindingInitializer is already checked

Author: hank121314

lib/Sema/TypeCheckStmt.cpp

@@ -82,7 +82,13 @@ namespace {
         if (CE->getParent() == ParentDC
             && CE->getDiscriminator() != AutoClosureExpr::InvalidDiscriminator)
           return { false, E };
-        
+        // Stop the recursion if the autoclosure is already checked in
+        // default initializer.
+        if (auto *initContext = dyn_cast<PatternBindingInitializer>(ParentDC))
+          if (initContext->getBinding()->isInitializerChecked(0) &&
+              CE->getDiscriminator() != AutoClosureExpr::InvalidDiscriminator)
+            return { false, E };
+
         assert(CE->getDiscriminator() == AutoClosureExpr::InvalidDiscriminator);
         CE->setDiscriminator(NextDiscriminator++);
         CE->setParent(ParentDC);

test/Sema/property_wrapper_parameter.swift

@@ -137,3 +137,14 @@ func takesWrapperClosure<T>(_: ProjectionWrapper<[S<T>]>, closure: (ProjectionWr
 func testGenericPropertyWrapper<U>(@ProjectionWrapper wrappers: [S<U>]) {
   takesWrapperClosure($wrappers) { $wrapper in }
 }
+
+@propertyWrapper
+public class SR_15940Bar<Value> {
+  public init(wrappedValue: @autoclosure () -> Value) {}
+  public var wrappedValue: Value {} // expected-error {{missing return in accessor expected to return 'Value'}}
+}
+
+// SR-15940
+class SR_15940 {
+  @SR_15940Bar var a: Bool?
+}