Rename arguments from checked to enableAsserts (#2373)

For fewer references to the legacy name and to match the option that
users would pass.
diff --git a/lib/src/command/global_run.dart b/lib/src/command/global_run.dart
index cac856b..221d05c 100644
--- a/lib/src/command/global_run.dart
+++ b/lib/src/command/global_run.dart
@@ -58,7 +58,7 @@
     }
 
     var exitCode = await globals.runExecutable(package, executable, args,
-        checked: argResults['enable-asserts'] || argResults['checked']);
+        enableAsserts: argResults['enable-asserts'] || argResults['checked']);
     await flushThenExit(exitCode);
   }
 }
diff --git a/lib/src/command/run.dart b/lib/src/command/run.dart
index ad2a117..6f626c3 100644
--- a/lib/src/command/run.dart
+++ b/lib/src/command/run.dart
@@ -76,7 +76,7 @@
             !entrypoint.packageGraph.isPackageMutable(package));
 
     var exitCode = await runExecutable(entrypoint, package, executable, args,
-        checked: argResults['enable-asserts'] || argResults['checked'],
+        enableAsserts: argResults['enable-asserts'] || argResults['checked'],
         snapshotPath: useSnapshot ? snapshotPath : null, recompile: () {
       final pkg = entrypoint.packageGraph.packages[package];
       // The recompile function will only be called when [package] exists.
diff --git a/lib/src/executable.dart b/lib/src/executable.dart
index 1d8448e..720691c 100644
--- a/lib/src/executable.dart
+++ b/lib/src/executable.dart
@@ -22,7 +22,7 @@
 ///
 /// Arguments from [args] will be passed to the spawned Dart application.
 ///
-/// If [checked] is true, the program is run with assertions enabled.
+/// If [enableAsserts] is true, the program is run with assertions enabled.
 ///
 /// If [packagesFile] is passed, it's used as the package config file path for
 /// the executable. Otherwise, `entrypoint.packagesFile` is used.
@@ -36,7 +36,7 @@
 /// Returns the exit code of the spawned app.
 Future<int> runExecutable(Entrypoint entrypoint, String package,
     String executable, Iterable<String> args,
-    {bool checked = false,
+    {bool enableAsserts = false,
     String packagesFile,
     String snapshotPath,
     Future<void> Function() recompile}) async {
@@ -69,7 +69,9 @@
       entrypoint.assertUpToDate();
 
       var result = await _runOrCompileSnapshot(snapshotPath, args,
-          packagesFile: packagesFile, checked: checked, recompile: recompile);
+          packagesFile: packagesFile,
+          enableAsserts: enableAsserts,
+          recompile: recompile);
       if (result != null) return result;
     }
 
@@ -96,7 +98,7 @@
     var packageConfig = p.toUri(p.absolute(packagesFile));
 
     await isolate.runUri(p.toUri(executablePath), args.toList(), null,
-        checked: checked,
+        enableAsserts: enableAsserts,
         automaticPackageResolution: packageConfig == null,
         packageConfig: packageConfig);
     return exitCode;
@@ -123,7 +125,7 @@
 Future<int> _runOrCompileSnapshot(String path, Iterable<String> args,
     {Future<void> Function() recompile,
     String packagesFile,
-    bool checked = false}) async {
+    bool enableAsserts = false}) async {
   if (!fileExists(path)) {
     if (recompile == null) return null;
     await recompile();
@@ -131,7 +133,9 @@
   }
 
   return await _runSnapshot(path, args,
-      recompile: recompile, packagesFile: packagesFile, checked: checked);
+      recompile: recompile,
+      packagesFile: packagesFile,
+      enableAsserts: enableAsserts);
 }
 
 /// Runs the snapshot at [path] with [args] and hooks its stdout, stderr, and
@@ -141,7 +145,7 @@
 /// expected to regenerate a snapshot at [path], after which the snapshot will
 /// be re-run.
 ///
-/// If [checked] is set, runs the snapshot with assertions enabled.
+/// If [enableAsserts] is set, runs the snapshot with assertions enabled.
 ///
 /// Returns the snapshot's exit code.
 ///
@@ -149,7 +153,7 @@
 Future<int> _runSnapshot(String path, Iterable<String> args,
     {Future<void> Function() recompile,
     String packagesFile,
-    bool checked = false}) async {
+    bool enableAsserts = false}) async {
   Uri packageConfig;
   if (packagesFile != null) {
     // We use an absolute path here not because the VM insists but because it's
@@ -163,7 +167,7 @@
   var argList = args.toList();
   try {
     await isolate.runUri(url, argList, null,
-        checked: checked,
+        enableAsserts: enableAsserts,
         automaticPackageResolution: packageConfig == null,
         packageConfig: packageConfig);
   } on IsolateSpawnException catch (error) {
@@ -175,7 +179,7 @@
     log.fine('Precompiled executable is out of date.');
     await recompile();
     await isolate.runUri(url, argList, null,
-        checked: checked, packageConfig: packageConfig);
+        enableAsserts: enableAsserts, packageConfig: packageConfig);
   }
 
   return exitCode;
diff --git a/lib/src/global_packages.dart b/lib/src/global_packages.dart
index f17db39..2cb0b64 100644
--- a/lib/src/global_packages.dart
+++ b/lib/src/global_packages.dart
@@ -395,16 +395,16 @@
   /// recompiled if the SDK has been upgraded since it was first compiled and
   /// then run. Otherwise, it will be run from source.
   ///
-  /// If [checked] is true, the program is run with assertions enabled.
+  /// If [enableAsserts] is true, the program is run with assertions enabled.
   ///
   /// Returns the exit code from the executable.
   Future<int> runExecutable(
       String package, String executable, Iterable<String> args,
-      {bool checked = false}) {
+      {bool enableAsserts = false}) {
     var entrypoint = find(package);
     return exe.runExecutable(
         entrypoint, package, p.join('bin', '$executable.dart'), args,
-        checked: checked,
+        enableAsserts: enableAsserts,
         packagesFile:
             entrypoint.isCached ? _getPackagesFilePath(package) : null,
         // Don't use snapshots for executables activated from paths.
diff --git a/lib/src/isolate.dart b/lib/src/isolate.dart
index ed30f48..9d0a7aa 100644
--- a/lib/src/isolate.dart
+++ b/lib/src/isolate.dart
@@ -16,14 +16,14 @@
 /// If [buffered] is `true`, this uses [spawnBufferedUri] to spawn the isolate.
 Future runUri(Uri url, List<String> args, Object message,
     {bool buffered = false,
-    bool checked,
+    bool enableAsserts,
     bool automaticPackageResolution = false,
     Uri packageConfig}) async {
   var errorPort = ReceivePort();
   var exitPort = ReceivePort();
 
   await Isolate.spawnUri(url, args, message,
-      checked: checked,
+      checked: enableAsserts,
       automaticPackageResolution: automaticPackageResolution,
       packageConfig: packageConfig,
       onError: errorPort.sendPort,