Migrate a few test/tool/completion_metrics/ libraries.

R=brianwilkerson@google.com

Change-Id: I8221b0c2f97ada211b101d31420e60062f30887d
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/194115
Reviewed-by: Brian Wilkerson <brianwilkerson@google.com>
Commit-Queue: Konstantin Shcheglov <scheglov@google.com>

pkg/analysis_server/test/tool/completion_metrics/metrics_util_test.dart

@@ -2,8 +2,6 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-// @dart = 2.9
-
 import 'package:test/test.dart';
 
 import '../../../tool/code_completion/metrics_util.dart';
@@ -172,8 +170,6 @@ class _DoubleEquals extends Matcher {
   @override
   bool matches(item, Map matchState) {
     return item is num &&
-        item != null &&
-        _value != null &&
         num.parse(item.toStringAsFixed(fractionDigits)) ==
             num.parse(_value.toStringAsFixed(fractionDigits));
   }

pkg/analysis_server/test/tool/completion_metrics/test_all.dart

@@ -2,8 +2,6 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-// @dart = 2.9
-
 import 'package:test_reflective_loader/test_reflective_loader.dart';
 
 import 'metrics_util_test.dart' as metrics_util_test;

pkg/analysis_server/tool/code_completion/implicit_type_declarations.dart

@@ -2,8 +2,6 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-// @dart = 2.9
-
 import 'dart:io' as io;
 
 import 'package:analysis_server/src/status/pages.dart';
@@ -17,7 +15,6 @@ import 'package:analyzer/diagnostic/diagnostic.dart';
 import 'package:analyzer/file_system/physical_file_system.dart';
 import 'package:analyzer/src/util/file_paths.dart' as file_paths;
 import 'package:args/args.dart';
-import 'package:meta/meta.dart';
 
 /// Compute metrics to determine which untyped variable declarations can be used
 /// to imply an expected context type, i.e. the RHS of 'var string = ^' could be
@@ -63,7 +60,7 @@ ArgParser createArgParser() {
 }
 
 /// Print usage information for this tool.
-void printUsage(ArgParser parser, {String error}) {
+void printUsage(ArgParser parser, {String? error}) {
   if (error != null) {
     print(error);
     print('');
@@ -104,7 +101,7 @@ class ImpliedTypeCollector extends RecursiveAstVisitor<void> {
   /// [data].
   ImpliedTypeCollector(this.data);
 
-  void handleVariableDeclaration(VariableDeclaration node, DartType dartType) {
+  void handleVariableDeclaration(VariableDeclaration node, DartType? dartType) {
     // If some untyped variable declaration
     if (node.equals != null && dartType == null ||
         (dartType != null && (dartType.isDynamic || dartType.isVoid))) {
@@ -141,7 +138,7 @@ class ImpliedTypeComputer {
   /// Compute the metrics for the file(s) in the [rootPath].
   /// If [corpus] is true, treat rootPath as a container of packages, creating
   /// a new context collection for each subdirectory.
-  Future<void> compute(String rootPath, {@required bool verbose}) async {
+  Future<void> compute(String rootPath, {required bool verbose}) async {
     final collection = AnalysisContextCollection(
       includedPaths: [rootPath],
       resourceProvider: PhysicalResourceProvider.INSTANCE,
@@ -174,7 +171,7 @@ class ImpliedTypeComputer {
   /// output if [verbose] is `true`.
   Future<void> _computeInContext(
       ContextRoot root, ImpliedTypeCollector collector,
-      {@required bool verbose}) async {
+      {required bool verbose}) async {
     // Create a new collection to avoid consuming large quantities of memory.
     final collection = AnalysisContextCollection(
       includedPaths: root.includedPaths.toList(),
@@ -191,13 +188,7 @@ class ImpliedTypeComputer {
           //
           // Check for errors that cause the file to be skipped.
           //
-          if (resolvedUnitResult == null) {
-            print('File $filePath skipped because resolved unit was null.');
-            if (verbose) {
-              print('');
-            }
-            continue;
-          } else if (resolvedUnitResult.state != ResultState.VALID) {
+          if (resolvedUnitResult.state != ResultState.VALID) {
             print('File $filePath skipped because it could not be analyzed.');
             if (verbose) {
               print('');
@@ -217,7 +208,7 @@ class ImpliedTypeComputer {
             continue;
           }
 
-          resolvedUnitResult.unit.accept(collector);
+          resolvedUnitResult.unit!.accept(collector);
         } catch (exception, stacktrace) {
           print('Exception caught analyzing: "$filePath"');
           print(exception);
@@ -243,8 +234,6 @@ class ImpliedTypeData {
 
   /// Record the variable name with the type.
   void recordImpliedType(String name, String displayString) {
-    assert(name != null);
-    assert(displayString != null);
     var nameMap = impliedTypesMap.putIfAbsent(name, () => {});
     nameMap[displayString] = (nameMap[displayString] ?? 0) + 1;
   }

pkg/analysis_server/tool/code_completion/metrics_util.dart

@@ -2,8 +2,6 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-// @dart = 2.9
-
 import 'package:analysis_server/src/status/pages.dart';
 import 'package:analyzer/src/generated/utilities_general.dart';
 
@@ -96,12 +94,12 @@ class Counter {
   }
 
   void count(String id, [int countNumber = 1]) {
-    assert(id != null && id.isNotEmpty && 1 <= countNumber);
-    if (_buckets.containsKey(id)) {
-      _buckets[id] += countNumber;
-    } else {
-      _buckets.putIfAbsent(id, () => countNumber);
-    }
+    assert(id.isNotEmpty && 1 <= countNumber);
+    _buckets.update(
+      id,
+      (value) => value + countNumber,
+      ifAbsent: () => countNumber,
+    );
     _totalCount += countNumber;
   }