Migrate microbrenchmarks to null safety (#83619)

dev/benchmarks/microbenchmarks/lib/common.dart

@@ -4,8 +4,6 @@
 
 import 'dart:convert' show json;
 
-import 'package:meta/meta.dart';
-
 /// This class knows how to format benchmark results for machine and human
 /// consumption.
 ///
@@ -31,7 +29,7 @@ class BenchmarkResultPrinter {
   /// result value. [unit] is the unit of measurement, such as "ms", "km", "h".
   /// [name] is a computer-readable name of the result used as a key in the JSON
   /// serialization of the results.
-  void addResult({ @required String description, @required double value, @required String unit, @required String name }) {
+  void addResult({ required String description, required double value, required String unit, required String name }) {
     _results.add(_BenchmarkResult(description, value, unit, name));
   }
 

dev/benchmarks/microbenchmarks/lib/foundation/all_elements_bench.dart

@@ -44,24 +44,24 @@ Future<void> main() async {
 
   // Wait for frame rendering to stabilize.
   for (int i = 0; i < 5; i++) {
-    await SchedulerBinding.instance.endOfFrame;
+    await SchedulerBinding.instance?.endOfFrame;
   }
 
   final Stopwatch watch = Stopwatch();
 
-  print('flutter_test allElements benchmark... (${WidgetsBinding.instance.renderViewElement})');
+  print('flutter_test allElements benchmark... (${WidgetsBinding.instance?.renderViewElement})');
   // Make sure we get enough elements to process for consistent benchmark runs
-  int elementCount = collectAllElementsFrom(WidgetsBinding.instance.renderViewElement, skipOffstage: false).length;
+  int elementCount = collectAllElementsFrom(WidgetsBinding.instance!.renderViewElement!, skipOffstage: false).length;
   while (elementCount < 2458) {
     await Future<void>.delayed(Duration.zero);
-    elementCount = collectAllElementsFrom(WidgetsBinding.instance.renderViewElement, skipOffstage: false).length;
+    elementCount = collectAllElementsFrom(WidgetsBinding.instance!.renderViewElement!, skipOffstage: false).length;
   }
   print('element count: $elementCount');
 
   watch.start();
   for (int i = 0; i < _kNumIters; i += 1) {
     final List<Element> allElements = collectAllElementsFrom(
-      WidgetsBinding.instance.renderViewElement,
+      WidgetsBinding.instance!.renderViewElement!,
       skipOffstage: false,
     ).toList();
     allElements.clear();

dev/benchmarks/microbenchmarks/lib/geometry/curves_bench.dart

@@ -9,7 +9,7 @@ import '../common.dart';
 
 const int _kNumIters = 10000;
 
-void _testCurve(Curve curve, {String name, String description, BenchmarkResultPrinter printer}) {
+void _testCurve(Curve curve, {required String name, required String description, required BenchmarkResultPrinter printer}) {
   final Stopwatch watch = Stopwatch();
   print('$description benchmark...');
   watch.start();

dev/benchmarks/microbenchmarks/lib/gestures/apps/button_matrix_app.dart

@@ -5,7 +5,7 @@
 import 'package:flutter/material.dart';
 
 class ButtonMatrixApp extends StatefulWidget {
-  const ButtonMatrixApp({Key key}) : super(key: key);
+  const ButtonMatrixApp({Key? key}) : super(key: key);
 
   @override
   ButtonMatrixAppState createState() => ButtonMatrixAppState();

dev/benchmarks/microbenchmarks/lib/gestures/velocity_tracker_bench.dart

@@ -10,7 +10,7 @@ import 'data/velocity_tracker_data.dart';
 const int _kNumIters = 10000;
 
 class TrackerBenchmark {
-  TrackerBenchmark({ this.name, this.tracker });
+  TrackerBenchmark({required this.name, required this.tracker });
 
   final VelocityTracker tracker;
   final String name;

dev/benchmarks/microbenchmarks/lib/language/sync_star_semantics_bench.dart

@@ -80,7 +80,7 @@ String consumeSpan(Iterable<InlineSpanSemanticsInformation> items) {
 
 Iterable<InlineSpanSemanticsInformation> combineSemanticsInfoSyncStar(List<InlineSpanSemanticsInformation> inputs) sync* {
   String workingText = '';
-  String workingLabel;
+  String? workingLabel;
   for (final InlineSpanSemanticsInformation info in inputs) {
     if (info.requiresOwnNode) {
       if (workingText != null) {
@@ -92,8 +92,9 @@ Iterable<InlineSpanSemanticsInformation> combineSemanticsInfoSyncStar(List<Inlin
     } else {
       workingText += info.text;
       workingLabel ??= '';
-      if (info.semanticsLabel != null) {
-        workingLabel += info.semanticsLabel;
+      final String? infoSemanticsLabel = info.semanticsLabel;
+      if (infoSemanticsLabel != null) {
+        workingLabel += infoSemanticsLabel;
       } else {
         workingLabel += info.text;
       }
@@ -108,7 +109,7 @@ Iterable<InlineSpanSemanticsInformation> combineSemanticsInfoSyncStar(List<Inlin
 
 Iterable<InlineSpanSemanticsInformation> combineSemanticsInfoList(List<InlineSpanSemanticsInformation> inputs) {
   String workingText = '';
-  String workingLabel;
+  String? workingLabel;
   final List<InlineSpanSemanticsInformation> result = <InlineSpanSemanticsInformation>[];
   for (final InlineSpanSemanticsInformation info in inputs) {
     if (info.requiresOwnNode) {
@@ -121,8 +122,9 @@ Iterable<InlineSpanSemanticsInformation> combineSemanticsInfoList(List<InlineSpa
     } else {
       workingText += info.text;
       workingLabel ??= '';
-      if (info.semanticsLabel != null) {
-        workingLabel += info.semanticsLabel;
+      final String? infoSemanticsLabel = info.semanticsLabel;
+      if (infoSemanticsLabel != null) {
+        workingLabel += infoSemanticsLabel;
       } else {
         workingLabel += info.text;
       }

dev/benchmarks/microbenchmarks/lib/stocks/animation_bench.dart

@@ -17,7 +17,7 @@ class BenchmarkingBinding extends LiveTestWidgetsFlutterBinding {
   final Stopwatch stopwatch;
 
   @override
-  void handleBeginFrame(Duration rawTimeStamp) {
+  void handleBeginFrame(Duration? rawTimeStamp) {
     stopwatch.start();
     super.handleBeginFrame(rawTimeStamp);
   }
@@ -68,7 +68,7 @@ Future<void> main() async {
 
       // Time how long each frame takes
       cpuWatch.reset();
-      while (SchedulerBinding.instance.hasScheduledFrame) {
+      while (SchedulerBinding.instance!.hasScheduledFrame) {
         await tester.pump();
         totalSubsequentFramesIterationCount += 1;
       }

dev/benchmarks/microbenchmarks/lib/stocks/layout_bench.dart

@@ -33,18 +33,18 @@ Future<void> main() async {
 
     final TestViewConfiguration big = TestViewConfiguration(
       size: const Size(360.0, 640.0),
-      window: RendererBinding.instance.window,
+      window: RendererBinding.instance?.window,
     );
     final TestViewConfiguration small = TestViewConfiguration(
       size: const Size(355.0, 635.0),
-      window: RendererBinding.instance.window,
+      window: RendererBinding.instance?.window,
     );
-    final RenderView renderView = WidgetsBinding.instance.renderView;
+    final RenderView? renderView = WidgetsBinding.instance?.renderView;
     binding.framePolicy = LiveTestWidgetsFlutterBindingFramePolicy.benchmark;
 
     watch.start();
     while (watch.elapsed < kBenchmarkTime) {
-      renderView.configuration = iterations.isEven ? big : small;
+      renderView?.configuration = iterations.isEven ? big : small;
       await tester.pumpBenchmark(Duration(milliseconds: iterations * 16));
       iterations += 1;
     }

dev/benchmarks/microbenchmarks/pubspec.yaml

@@ -2,7 +2,7 @@ name: microbenchmarks
 description: Small benchmarks for very specific parts of the Flutter framework.
 
 environment:
-  sdk: ">=2.0.0-dev.68.0 <3.0.0"
+  sdk: ">=2.12.0 <3.0.0"
 
 dependencies:
   meta: 1.4.0