Fix negative usableCrossAxisExtent in release mode (#64441)

AUTHORS

@@ -64,3 +64,4 @@ Brian Wang <xinlei966@gmail.com>
 CaiJingLong <cjl_spy@163.com>
 Alex Li <google@alexv525.com>
 Ram Navan <hiramprasad@gmail.com>
+meritozh <ah841814092@gmail.com>

packages/flutter/lib/src/rendering/sliver_grid.dart

@@ -326,7 +326,8 @@ class SliverGridDelegateWithFixedCrossAxisCount extends SliverGridDelegate {
   @override
   SliverGridLayout getLayout(SliverConstraints constraints) {
     assert(_debugAssertIsValid());
-    final double usableCrossAxisExtent = constraints.crossAxisExtent - crossAxisSpacing * (crossAxisCount - 1);
+    final double usableCrossAxisExtent = math.max(0.0,
+        constraints.crossAxisExtent - crossAxisSpacing * (crossAxisCount - 1));
     final double childCrossAxisExtent = usableCrossAxisExtent / crossAxisCount;
     final double childMainAxisExtent = childCrossAxisExtent / childAspectRatio;
     return SliverGridRegularTileLayout(
@@ -425,7 +426,8 @@ class SliverGridDelegateWithMaxCrossAxisExtent extends SliverGridDelegate {
   SliverGridLayout getLayout(SliverConstraints constraints) {
     assert(_debugAssertIsValid(constraints.crossAxisExtent));
     final int crossAxisCount = (constraints.crossAxisExtent / (maxCrossAxisExtent + crossAxisSpacing)).ceil();
-    final double usableCrossAxisExtent = constraints.crossAxisExtent - crossAxisSpacing * (crossAxisCount - 1);
+    final double usableCrossAxisExtent = math.max(0.0,
+        constraints.crossAxisExtent - crossAxisSpacing * (crossAxisCount - 1));
     final double childCrossAxisExtent = usableCrossAxisExtent / crossAxisCount;
     final double childMainAxisExtent = childCrossAxisExtent / childAspectRatio;
     return SliverGridRegularTileLayout(

packages/flutter/test/widgets/slivers_test.dart

@@ -308,6 +308,44 @@ void main() {
     },
   );
 
+  testWidgets(
+    'SliverGrid negative usableCrossAxisExtent',
+    (WidgetTester tester) async {
+      await tester.pumpWidget(
+        Directionality(
+          textDirection: TextDirection.ltr,
+          child: Center(
+            child: SizedBox(
+              width: 4,
+              height: 4,
+              child: CustomScrollView(
+                slivers: <Widget>[
+                  SliverGrid(
+                    gridDelegate: const SliverGridDelegateWithFixedCrossAxisCount(
+                      crossAxisCount: 2,
+                      crossAxisSpacing: 8,
+                      mainAxisSpacing: 8,
+                    ),
+                    delegate: SliverChildListDelegate(
+                      <Widget>[
+                        Container(child: const Center(child: Text('A'))),
+                        Container(child: const Center(child: Text('B'))),
+                        Container(child: const Center(child: Text('C'))),
+                        Container(child: const Center(child: Text('D'))),
+                      ],
+                    ),
+                  ),
+                ],
+              ),
+            ),
+          ),
+        ),
+      );
+
+      expect(tester.takeException(), isNull);
+    },
+  );
+
   testWidgets(
     'SliverList can handle inaccurate scroll offset due to changes in children list',
       (WidgetTester tester) async {