SILGen: +1 function when converting for a reabstraction

Author: jckarter

lib/SILGen/SILGenPoly.cpp

@@ -3485,7 +3485,7 @@ ManagedValue Transform::transformFunction(ManagedValue fn,
   // escaping->noescape conversion.
   if (fnType != newFnType) {
     SILType resTy = SILType::getPrimitiveObjectType(newFnType);
-    fn = SGF.B.createConvertFunction(Loc, fn, resTy);
+    fn = SGF.B.createConvertFunction(Loc, fn.ensurePlusOne(SGF, Loc), resTy);
   }
 
   // Now do thin-to-thick if necessary.

test/SILGen/function_conversion.swift

@@ -676,3 +676,14 @@ func dontCrash() {
   let userInfo = ["hello": "world"]
   let d = [AnyHashable: Any](uniqueKeysWithValues: userInfo.map { ($0.key, $0.value) })
 }
+
+struct Butt<T> {
+  var foo: () throws -> T
+}
+
+@_silgen_name("butt")
+func butt() -> Butt<Any>
+
+func foo() throws -> Any {
+  return try butt().foo()
+}