When building a block-to-func reabstraction thunk, be sure to bridge

the block's formal parameter and result types, because otherwise
the bridging code gets real confused.

Fixes rdar://35402696

Author: rjmccall

lib/SILGen/SILGenBridging.cpp

@@ -355,6 +355,12 @@ expandTupleTypes(AnyFunctionType::CanParamArrayRef params) {
   return results;
 }
 
+static CanAnyFunctionType getBridgedBlockType(SILGenModule &SGM,
+                                              CanAnyFunctionType blockType) {
+  return SGM.Types.getBridgedFunctionType(AbstractionPattern(blockType),
+                                         blockType, blockType->getExtInfo());
+}
+
 static void buildFuncToBlockInvokeBody(SILGenFunction &SGF,
                                        SILLocation loc,
                                        CanAnyFunctionType formalFuncType,
@@ -368,10 +374,7 @@ static void buildFuncToBlockInvokeBody(SILGenFunction &SGF,
   SILFunctionConventions funcConv(funcTy, SGF.SGM.M);
 
   // Make sure we lower the component types of the formal block type.
-  formalBlockType =
-    SGF.SGM.Types.getBridgedFunctionType(AbstractionPattern(formalBlockType),
-                                         formalBlockType,
-                                         formalBlockType->getExtInfo());
+  formalBlockType = getBridgedBlockType(SGF.SGM, formalBlockType);
 
   // Set up the indirect result.
   SILType blockResultTy = blockTy->getAllResultsType();
@@ -764,6 +767,9 @@ static void buildBlockToFuncThunkBody(SILGenFunction &SGF,
   // Collect the native arguments, which should all be +1.
   Scope scope(SGF.Cleanups, CleanupLocation::get(loc));
 
+  // Make sure we lower the component types of the formal block type.
+  formalBlockTy = getBridgedBlockType(SGF.SGM, formalBlockTy);
+
   assert(blockTy->getNumParameters() == funcTy->getNumParameters()
          && "block and function types don't match");
 

test/SILGen/Inputs/usr/include/BridgeTestFoundation.h

@@ -93,3 +93,5 @@ void escapeBlockAlias(dispatch_block_t block);
 @interface ObjectWithSplitProperty : NSObject
 @property (nonatomic, setter=private_setFlagForSomething:) BOOL flagForSomething;
 @end
+
+extern NSString * __nonnull (^ const __nonnull GlobalBlock)(NSString * __nonnull);

test/SILGen/objc_blocks_bridging.swift

@@ -188,3 +188,11 @@ struct GenericStruct<T> {
 // CHECK-LABEL: sil shared [transparent] [serializable] [reabstraction_thunk] @_T0Ix_Ixx_IyB_IyBy_TR : $@convention(c) (@inout_aliasable @block_storage @noescape @callee_owned (@owned @noescape @callee_owned () -> ()) -> (), @convention(block) @noescape () -> ()) -> ()
 // CHECK-LABEL: sil shared [transparent] [serializable] [reabstraction_thunk] @_T0IyB_Ix_TR : $@convention(thin) (@owned @convention(block) @noescape () -> ()) -> ()
 
+// rdar://35402696
+func takeOptStringFunction(fn: (String) -> String?) {}
+func testGlobalBlock() {
+  takeOptStringFunction(fn: GlobalBlock)
+}
+// CHECK-LABEL: sil hidden @_T020objc_blocks_bridging15testGlobalBlockyyF
+// CHECK: global_addr @GlobalBlock : $*@convention(block) (NSString) -> @autoreleased Optional<NSString>
+// CHECK: function_ref @_T0So8NSStringCABSgIeyBya_S2SIexxo_TR : $@convention(thin) (@owned String, @owned @convention(block) (NSString) -> @autoreleased Optional<NSString>) -> @owned String