made builder required (#51993)

31df1d45 · Chad Nehemiah · GitHub · 5b0a79db · 31df1d45
Unverified Commit 31df1d45 authored Mar 09, 2020 by Chad Nehemiah Committed by GitHub Mar 09, 2020
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layout_builder.dart packages/flutter/lib/src/widgets/layout_builder.dart +3 -2

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--- a/packages/flutter/lib/src/widgets/layout_builder.dart
+++ b/packages/flutter/lib/src/widgets/layout_builder.dart
@@ -202,8 +202,9 @@ class LayoutBuilder extends ConstrainedLayoutBuilder<BoxConstraints> {
  /// The [builder] argument must not be null.
  const LayoutBuilder({
    Key key,
-    LayoutWidgetBuilder builder,
-  }) : super(key: key, builder: builder);
+    @required LayoutWidgetBuilder builder,
+  }) : assert(builder != null),
+       super(key: key, builder: builder);

  @override
  LayoutWidgetBuilder get builder => super.builder;