ASTDemangler: Add support for lowered function types

test/TypeDecoder/lowered_function_types.swift

@@ -0,0 +1,27 @@
+// RUN: %empty-directory(%t)
+
+// RUN: %target-build-swift -emit-executable %s -g -o %t/lowered_function_types -emit-module
+// RUN: sed -ne '/\/\/ *DEMANGLE: /s/\/\/ *DEMANGLE: *//p' < %s > %t/input
+// RUN: %lldb-moduleimport-test %t/lowered_function_types -type-from-mangled=%t/input | %FileCheck %s
+
+func blackHole(_: Any...) {}
+
+class Class {}
+
+do {
+  let fn: (Int, Class, __owned Class, Any, inout Int) -> (Int, Class, Any) = {
+    _, _, _, _, _ in fatalError()
+  }
+  blackHole(fn)
+}
+
+do {
+  let fn: () throws -> () = {}
+  blackHole(fn)
+}
+
+// DEMANGLE: $sSi22lowered_function_types5ClassCACypS2iACypIegygxnldor_D
+// DEMANGLE: $ss5Error_pIegzo_D
+
+// CHECK: @callee_guaranteed (Int, @guaranteed Class, @owned Class, @in_guaranteed Any, @inout Int) -> (Int, @owned Class, @out Any)
+// CHECK: @callee_guaranteed () -> @error Error