SILGen: Handle C functions imported as labeled unit constructors.

Author: jckarter

lib/SIL/AbstractionPattern.cpp

@@ -17,6 +17,7 @@
 
 #define DEBUG_TYPE "libsil"
 #include "swift/SIL/TypeLowering.h"
+#include "swift/AST/ASTContext.h"
 #include "swift/AST/Decl.h"
 #include "swift/AST/ForeignErrorConvention.h"
 #include "swift/Basic/Fallthrough.h"
@@ -261,10 +262,16 @@ AbstractionPattern::getTupleElementType(unsigned index) const {
       return AbstractionPattern::getOpaque();
     return AbstractionPattern(getGenericSignature(),
                               cast<TupleType>(getType()).getElementType(index));
-  case Kind::ClangFunctionParamTupleType:
+  case Kind::ClangFunctionParamTupleType: {
+    // Handle the (label: ()) param used by functions imported as labeled
+    // nullary initializers.
+    if (isVoidLike(getType()))
+      return AbstractionPattern(getType()->getASTContext().TheEmptyTupleType);
+    
     return AbstractionPattern(getGenericSignature(),
                               cast<TupleType>(getType()).getElementType(index),
                           getClangFunctionParameterType(getClangType(), index));
+  }
 
   case Kind::ObjCMethodFormalParamTupleType: {
     auto swiftEltType = cast<TupleType>(getType()).getElementType(index);

test/IDE/Inputs/custom-modules/ImportAsMemberC.h

@@ -27,6 +27,8 @@ void CCRefrigeratorSetPowerSupply(CCRefrigeratorRef fridge,
 extern const CCPowerSupplyRef kCCPowerSupplySemiModular
   __attribute__((swift_name("CCPowerSupplyRef.semiModular")));
 
+_Nonnull CCPowerSupplyRef CCPowerSupplyCreateDangerous(void)
+  __attribute__((swift_name("CCPowerSupply.init(dangerous:)")));
 #pragma clang arc_cf_code_audited end
 
 extern const double kCCPowerSupplyDefaultPower

test/IDE/import_as_member_cf.swift

@@ -7,6 +7,7 @@
 // PRINTC:      extension CCPowerSupply {
 // PRINTC-NEXT:   /*not inherited*/ init(watts watts: Double)
 // PRINTC-NEXT:   class let semiModular: CCPowerSupply!
+// PRINTC-NEXT:   /*not inherited*/ init(dangerous dangerous: ())
 // PRINTC-NEXT:   class let defaultPower: Double
 // PRINTC-NEXT:   class let AC: CCPowerSupply
 // PRINTC-NEXT:   class let DC: CCPowerSupply?

test/SILGen/cf_members.swift

@@ -6,6 +6,14 @@ import ImportAsMember
 
 func makeMetatype() -> Struct1.Type { return Struct1.self }
 
+// CHECK-LABEL: sil @_TF10cf_members17importAsUnaryInitFT_T_
+public func importAsUnaryInit() {
+  // CHECK: function_ref @CCPowerSupplyCreateDangerous : $@convention(c) () -> @owned CCPowerSupply
+  var a = CCPowerSupply(dangerous: ())
+  let f: () -> CCPowerSupply = CCPowerSupply.init(dangerous:)
+  a = f()
+}
+
 // CHECK-LABEL: sil @_TF10cf_members3foo
 public func foo(_ x: Double) {
 // CHECK: bb0([[X:%.*]] : $Double):