From d7d642653acd3c45166f09711540b13488edd6b7 Mon Sep 17 00:00:00 2001
From: Tianguang <penn.zht@gmail.com>
Date: Mon, 13 Jan 2020 21:34:30 +0100
Subject: [PATCH] Add asserts requiring BoxConstraints' parameters to be
 non-null (#48295)

---
 packages/flutter/lib/src/rendering/box.dart   | 5 ++++-
 packages/flutter/test/rendering/box_test.dart | 7 +++++++
 2 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/packages/flutter/lib/src/rendering/box.dart b/packages/flutter/lib/src/rendering/box.dart
index 2edc25a11b..d12ec23d25 100644
--- a/packages/flutter/lib/src/rendering/box.dart
+++ b/packages/flutter/lib/src/rendering/box.dart
@@ -90,7 +90,10 @@ class BoxConstraints extends Constraints {
     this.maxWidth = double.infinity,
     this.minHeight = 0.0,
     this.maxHeight = double.infinity,
-  });
+  }) : assert (minWidth != null),
+       assert (maxWidth != null),
+       assert (minHeight != null),
+       assert (maxHeight != null);
 
   /// Creates box constraints that is respected only by the given size.
   BoxConstraints.tight(Size size)
diff --git a/packages/flutter/test/rendering/box_test.dart b/packages/flutter/test/rendering/box_test.dart
index 10a1ff2644..494c7bad97 100644
--- a/packages/flutter/test/rendering/box_test.dart
+++ b/packages/flutter/test/rendering/box_test.dart
@@ -1007,6 +1007,13 @@ void main() {
       expect(innerConstrained.localToGlobal(Offset.zero, ancestor: outerConstrained).dy, 25.0);
     });
   });
+
+  test('BoxConstraints parameters should be non-null', () {
+    expect(() => BoxConstraints(minWidth: null), throwsAssertionError);
+    expect(() => BoxConstraints(maxWidth: null), throwsAssertionError);
+    expect(() => BoxConstraints(minHeight: null), throwsAssertionError);
+    expect(() => BoxConstraints(maxHeight: null), throwsAssertionError);
+  });
 }
 
 class _DummyHitTestTarget implements HitTestTarget {