Fix NSNumber() null pointer exception (#28)

* Fix NSNumber() null pointer exception

* Update FoundationTests.swift

Author: stephencelis

Sources/CustomDump/Dump.swift

@@ -59,13 +59,18 @@ public func customDump<T, TargetStream>(
 
   var visitedItems: Set<ObjectIdentifier> = []
 
-  func customDumpHelp<TargetStream>(
-    _ value: Any,
+  func customDumpHelp<T, TargetStream>(
+    _ value: T,
     to target: inout TargetStream,
     name: String?,
     indent: Int,
     maxDepth: Int
   ) where TargetStream: TextOutputStream {
+    if T.self is AnyObject.Type, withUnsafeBytes(of: value, { $0.allSatisfy { $0 == 0 } }) {
+      target.write((name.map { "\($0): " } ?? "").appending("(null pointer)").indenting(by: indent))
+      return
+    }
+
     let mirror = Mirror(customDumpReflecting: value)
     var out = ""
 

Tests/CustomDumpTests/Conformances/FoundationTests.swift

@@ -432,7 +432,7 @@ final class FoundationTests: XCTestCase {
   func testNSNumber() {
     var dump = ""
     customDump(
-      NSNumber(booleanLiteral: true),
+      1 as NSNumber,
       to: &dump
     )
     XCTAssertNoDifference(
@@ -441,6 +441,20 @@ final class FoundationTests: XCTestCase {
       1
       """
     )
+
+    #if canImport(ObjectiveC)
+      dump = ""
+      customDump(
+        NSNumber(),
+        to: &dump
+      )
+      XCTAssertNoDifference(
+        dump,
+        """
+        (null pointer)
+        """
+      )
+    #endif
   }
 
   func testNSOrderedSet() {