Bump VM packages to language version 3.12.

This CL is part of an effort to bump the SDK requirement to `3.12.0-0`
for all the packages in `pkg` that are not published to `pub`, so that
we can get better testing of the "private named parameters" feature.

(Packages that *are* published to `pub` can't be safely bumped yet,
because SDK 3.12 hasn't been released, and I don't want to block those
packages' ability to publish useful updates to customers.)

This change covers the following packages, which are owned by
OWNERS_VM:
- pkg/dart2bytecode
- pkg/dart2native
- pkg/dtd_impl (jointly owned with OWNERS_DEVTOOLS)
- pkg/mmap
- pkg/observatory
- pkg/vm

Changes to `pubspec.yaml` files were made manually.

Changes to `.dart` files were made automatically, using `dart
fix`. Two kinds of changes were made:

- Migrate to using private named parameters where it is possible to do
  so without changing semantics. Note that this migration is
  conservative; see https://github.com/dart-lang/sdk/issues/58607 for
  details.

- Migrate to using null aware elements.

Tested: Standard trybots
Change-Id: I1666e5771a34ef3c30ceeadced3d505d6a6a6964
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/487942
Auto-Submit: Paul Berry <paulberry@google.com>
Commit-Queue: Paul Berry <paulberry@google.com>
Reviewed-by: Daco Harkes <dacoharkes@google.com>

pkg/dart2bytecode/pubspec.yaml

@@ -3,7 +3,7 @@ name: dart2bytecode
 publish_to: none
 
 environment:
-  sdk: ^3.5.0
+  sdk: '^3.12.0-0'
 
 resolution: workspace
 

pkg/dart2native/lib/dart2native.dart

@@ -123,7 +123,7 @@ Future<ProcessResult> generateKernelHelper({
     if (depFile != null) '--depfile=$depFile',
     '--output=$kernelFile',
     ...extraGenKernelOptions,
-    if (sourceFile != null) sourceFile,
+    ?sourceFile,
   ];
   return Process.run(sdk.dartAotRuntime, args);
 }

pkg/dart2native/lib/generate.dart

@@ -166,39 +166,26 @@ class _Generator {
   final String _targetDartAotRuntime;
 
   _Generator({
-    required String genSnapshot,
-    required String targetDartAotRuntime,
+    required this._genSnapshot,
+    required this._targetDartAotRuntime,
     required String sourceFile,
-    required List<String> defines,
-    required Kind kind,
-    String? outputFile,
-    String? debugFile,
+    required this._defines,
+    required this._kind,
+    this._outputFile,
+    this._debugFile,
     String? packages,
-    OS? targetOS,
-    String? depFile,
-    required String enableExperiment,
-    required bool enableAsserts,
-    required bool verbose,
-    required String verbosity,
+    this._targetOS,
+    this._depFile,
+    required this._enableExperiment,
+    required this._enableAsserts,
+    required this._verbose,
+    required this._verbosity,
     required Directory tempDir,
-    bool progressUpdatesOnStderr = false,
-  })  : _kind = kind,
-        _verbose = verbose,
-        _tempDir = tempDir,
-        _verbosity = verbosity,
-        _enableAsserts = enableAsserts,
-        _enableExperiment = enableExperiment,
-        _targetOS = targetOS,
-        _debugFile = debugFile,
-        _outputFile = outputFile,
-        _defines = defines,
-        _depFile = depFile,
-        _progressUpdatesOnStderr = progressUpdatesOnStderr,
+    this._progressUpdatesOnStderr = false,
+  })  : _tempDir = tempDir,
         _programKernelFile = path.join(tempDir.path, 'program.dill'),
         _sourcePath = _normalize(sourceFile)!,
-        _packages = _normalize(packages),
-        _genSnapshot = genSnapshot,
-        _targetDartAotRuntime = targetDartAotRuntime {
+        _packages = _normalize(packages) {
     if (_kind == Kind.exe) {
       if (_targetOS == null) {
         throw ArgumentError('targetOS must be specified for executables.');

pkg/dart2native/pubspec.yaml

@@ -3,7 +3,7 @@ name: dart2native
 publish_to: none
 
 environment:
-  sdk: ^3.5.0
+  sdk: '^3.12.0-0'
 
 resolution: workspace
 

pkg/dtd_impl/lib/src/dart_tooling_daemon.dart

@@ -180,13 +180,11 @@ class DartToolingDaemon {
     required this.secret,
     required bool unrestrictedMode,
     bool disableServiceAuthCodes = false,
-    bool ipv6 = false,
-    bool shouldLogRequests = false,
+    this._ipv6 = false,
+    this._shouldLogRequests = false,
     bool useFakeAnalytics = false,
     this.pingInterval,
-  })  : _ipv6 = ipv6,
-        _uriAuthCode = disableServiceAuthCodes ? null : _generateSecret(),
-        _shouldLogRequests = shouldLogRequests {
+  })  : _uriAuthCode = disableServiceAuthCodes ? null : _generateSecret() {
     streamManager = DTDStreamManager(this);
     clientManager = DTDClientManager();
 

pkg/dtd_impl/lib/src/dtd_client.dart

@@ -352,9 +352,9 @@ class DTDClient extends Client {
     Map<String, Object?>? capabilities,
   }) {
     return {
-      if (service != null) DtdParameters.service: service,
+      DtdParameters.service: ?service,
       DtdParameters.method: method,
-      if (capabilities != null) DtdParameters.capabilities: capabilities,
+      DtdParameters.capabilities: ?capabilities,
     };
   }
 

pkg/dtd_impl/pubspec.yaml

@@ -4,7 +4,7 @@ repository: https://github.com/dart-lang/sdk/tree/main/pkg/dtd_impl
 publish_to: none
 
 environment:
-  sdk: ^3.5.0
+  sdk: '^3.12.0-0'
 
 resolution: workspace
 

pkg/mmap/pubspec.yaml

@@ -4,7 +4,7 @@ name: mmap
 publish_to: none
 
 environment:
-  sdk: ^3.5.0
+  sdk: '^3.12.0-0'
 
 resolution: workspace
 

pkg/observatory/pubspec.yaml

@@ -2,7 +2,7 @@ name: observatory
 publish_to: none
 
 environment:
-  sdk: ^3.8.0
+  sdk: '^3.12.0-0'
 
 dependencies:
   args: any

pkg/vm/pubspec.yaml

@@ -4,7 +4,7 @@ description: VM specific Dart code and helper scripts
 publish_to: none
 
 environment:
-  sdk: ^3.7.0
+  sdk: '^3.12.0-0'
 
 resolution: workspace