Update license script to run with newer Dart versions (flutter/engine#5748)

engine/src/flutter/tools/licenses/lib/licenses.dart

@@ -114,7 +114,7 @@ abstract class License implements Comparable<License> {
       if (result is! UniqueLicense || result.type != type)
         throw 'tried to add a UniqueLicense $type, but it was a duplicate of a ${result.runtimeType} ${result.type}';
       return true;
-    });
+    }());
     return result;
   }
 
@@ -126,7 +126,7 @@ abstract class License implements Comparable<License> {
       if (result is! TemplateLicense || result.type != type)
         throw 'tried to add a TemplateLicense $type, but it was a duplicate of a ${result.runtimeType} ${result.type}';
       return true;
-    });
+    }());
     return result;
   }
 
@@ -138,7 +138,7 @@ abstract class License implements Comparable<License> {
       if (result is! MessageLicense || result.type != type)
         throw 'tried to add a MessageLicense $type, but it was a duplicate of a ${result.runtimeType} ${result.type}';
       return true;
-    });
+    }());
     return result;
   }
 
@@ -148,7 +148,7 @@ abstract class License implements Comparable<License> {
       if (result is! BlankLicense || result.type != type)
         throw 'tried to add a BlankLicense $type, but it was a duplicate of a ${result.runtimeType} ${result.type}';
       return true;
-    });
+    }());
     return result;
   }
 
@@ -310,7 +310,7 @@ abstract class License implements Comparable<License> {
         throw 'incorrectly created a $runtimeType for a $type';
       }
       return true;
-    });
+    }());
     final LicenseType detectedType = convertBodyToType(body);
     if (detectedType != LicenseType.unknown && detectedType != type && !yesWeKnowWhatItLooksLikeButItIsNot)
       throw 'Created a license of type $type but it looks like $detectedType\.';
@@ -789,7 +789,7 @@ Iterable<_LicenseMatch> _tryReferenceByType(String body, RegExp pattern, License
       String copyrights = _reformat(match.getCopyrights());
       assert(needsCopyright && copyrights.isNotEmpty || !needsCopyright && copyrights.isEmpty);
       return true;
-    });
+    }());
     if (needsCopyright)
       yield* _expand(template, match.getCopyrights(), match.getEntireLicense(), match.start, match.end, debug: '_tryReferenceByType', origin: origin);
     else

engine/src/flutter/tools/licenses/lib/main.dart

@@ -956,7 +956,7 @@ class RepositoryDirectory extends RepositoryEntry implements LicenseSource {
     }
   }
 
-  int get count => _files.length + _subdirectories.fold(0, (int count, RepositoryDirectory child) => count + child.count);
+  int get count => _files.length + _subdirectories.fold<int>(0, (int count, RepositoryDirectory child) => count + child.count);
 
   @override
   List<License> nearestLicensesFor(String name) {

engine/src/flutter/tools/licenses/pubspec.lock

@@ -1,53 +1,61 @@
 # Generated by pub
-# See http://pub.dartlang.org/doc/glossary.html#lockfile
+# See https://www.dartlang.org/tools/pub/glossary#lockfile
 packages:
   archive:
+    dependency: "direct main"
     description:
       name: archive
       url: "https://pub.dartlang.org"
     source: hosted
     version: "1.0.33"
   args:
+    dependency: "direct main"
     description:
       name: args
       url: "https://pub.dartlang.org"
     source: hosted
     version: "0.13.7"
   charcode:
+    dependency: transitive
     description:
       name: charcode
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.1.1"
+    version: "1.1.2"
   collection:
+    dependency: transitive
     description:
       name: collection
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.14.5"
+    version: "1.14.10"
   convert:
+    dependency: transitive
     description:
       name: convert
       url: "https://pub.dartlang.org"
     source: hosted
     version: "2.0.1"
   crypto:
+    dependency: "direct main"
     description:
       name: crypto
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "2.0.2+1"
+    version: "2.0.6"
   path:
+    dependency: "direct main"
     description:
       name: path
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.5.1"
+    version: "1.6.1"
   typed_data:
+    dependency: transitive
     description:
       name: typed_data
       url: "https://pub.dartlang.org"
     source: hosted
     version: "1.1.5"
 sdks:
-  dart: ">=1.21.0 <2.0.0"
+  dart: ">=2.0.0-dev.62.0 <=2.0.0-dev.67.0.flutter-84ca27a09e"