Parse dart files with the SDK version from the pubspec

lib/src/dependency_validator.dart

@@ -131,11 +131,16 @@ Future<bool> checkPackage({required String root}) async {
       '${bulletItems(publicLessFiles.map((f) => f.path))}\n',
     );
 
+  // The language version that the dart files of this package are parsed with.
+  final featureSet = featureSetForPubspec(pubspec);
+
   // Read each file in lib/ and parse the package names from every import and
   // export directive.
   final packagesUsedInPublicFiles = <String>{};
   for (final file in publicDartFiles) {
-    packagesUsedInPublicFiles.addAll(getDartDirectivePackageNames(file));
+    packagesUsedInPublicFiles.addAll(
+      getDartDirectivePackageNames(file, featureSet: featureSet),
+    );
   }
   for (final file in publicScssFiles) {
     final matches = importScssPackageRegex.allMatches(file.readAsStringSync());
@@ -201,7 +206,9 @@ Future<bool> checkPackage({required String root}) async {
     if (optionsIncludePackage != null) optionsIncludePackage,
   };
   for (final file in nonPublicDartFiles) {
-    packagesUsedOutsidePublicDirs.addAll(getDartDirectivePackageNames(file));
+    packagesUsedOutsidePublicDirs.addAll(
+      getDartDirectivePackageNames(file, featureSet: featureSet),
+    );
   }
   for (final file in nonPublicScssFiles) {
     final matches = importScssPackageRegex.allMatches(file.readAsStringSync());

lib/src/import_export_ast_visitor.dart

@@ -1,16 +1,31 @@
 import 'dart:io';
 
+import 'package:analyzer/dart/analysis/features.dart';
 import 'package:analyzer/dart/analysis/results.dart';
 import 'package:analyzer/dart/analysis/utilities.dart';
 import 'package:analyzer/dart/ast/ast.dart';
 import 'package:analyzer/dart/ast/visitor.dart';
+import 'package:pub_semver/pub_semver.dart';
+import 'package:pubspec_parse/pubspec_parse.dart';
+
+import 'utils.dart';
 
 /// Returns the list of package names that are exported and imported into the
-/// provided dart file
-Set<String> getDartDirectivePackageNames(File file) {
+/// provided dart file, which is parsed with the given [featureSet].
+///
+/// See [featureSetForPubspec] for resolving the [featureSet] of the package
+/// that [file] belongs to.
+Set<String> getDartDirectivePackageNames(
+  File file, {
+  required FeatureSet featureSet,
+}) {
   ParseStringResult parsed;
   try {
-    parsed = parseString(content: file.readAsStringSync(), path: file.path);
+    parsed = parseString(
+      content: file.readAsStringSync(),
+      path: file.path,
+      featureSet: featureSet,
+    );
   } on ArgumentError catch (e) {
     print('Error parsing: ${file.path}');
     print(e.message);
@@ -22,6 +37,42 @@ Set<String> getDartDirectivePackageNames(File file) {
   return visitor.packageNames;
 }
 
+/// Returns the [FeatureSet] that matches the Dart SDK version declared by the
+/// `environment: sdk:` constraint of [pubspec].
+///
+/// Falls back to [FeatureSet.latestLanguageVersion] when [pubspec] does not
+/// declare an SDK constraint with a lower bound.
+FeatureSet featureSetForPubspec(Pubspec pubspec) {
+  final languageVersion = _sdkLanguageVersionOf(pubspec);
+  if (languageVersion == null) {
+    logger.fine(
+      'No SDK version found for ${pubspec.name}, '
+      'parsing with the latest language version.',
+    );
+    return FeatureSet.latestLanguageVersion();
+  }
+
+  logger.fine('Using language version $languageVersion for ${pubspec.name}');
+  return FeatureSet.fromEnableFlags2(
+    sdkLanguageVersion: languageVersion,
+    flags: const [],
+  );
+}
+
+/// Returns the language version implied by the `environment: sdk:` constraint
+/// of [pubspec], or null if it has none.
+Version? _sdkLanguageVersionOf(Pubspec pubspec) {
+  final sdkConstraint = pubspec.environment['sdk'];
+
+  // `Version` also implements `VersionRange`, with itself as the lower bound.
+  final minSdkVersion =
+      sdkConstraint is VersionRange ? sdkConstraint.min : null;
+  if (minSdkVersion == null) return null;
+
+  // A language version is only major.minor.
+  return Version(minSdkVersion.major, minSdkVersion.minor, 0);
+}
+
 class ImportExportVisitor extends GeneralizingAstVisitor {
   Set<String> packageNames = {};