[kernel] Clear a few lists when loading dill

Prior to this change, loading the sdk dill twice for instance would
result in additional exports as well as parameter counts doubling,
essentially destroying the result.

Change-Id: I4d694bec1926d6df6572e9bb36e8a88ec0822e27
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/120785
Commit-Queue: Jens Johansen <jensj@google.com>
Reviewed-by: Johnni Winther <johnniwinther@google.com>

Author: jensjoha

pkg/front_end/test/load_dill_twice_lib_1.dart

@@ -0,0 +1,12 @@
+// Copyright (c) 2019, the Dart project authors.  Please see the AUTHORS file
+// 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.
+
+export 'load_dill_twice_lib_2.dart';
+
+// Use annotation to force proper printing.
+
+typedef myTypedefWithNamed(@Foo int a, {@Foo int b});
+typedef myTypedefWithOptionalPositional(@Foo int a, [@Foo int b]);
+
+const Foo = 42;

pkg/front_end/test/load_dill_twice_lib_2.dart

@@ -0,0 +1,5 @@
+// Copyright (c) 2019, the Dart project authors.  Please see the AUTHORS file
+// 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.
+
+int foo() => 42;

pkg/front_end/test/load_dill_twice_test.dart

@@ -0,0 +1,79 @@
+// Copyright (c) 2018, the Dart project authors.  Please see the AUTHORS file
+// 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.
+
+import 'dart:io' show Platform, exit;
+
+import 'package:kernel/binary/ast_from_binary.dart' show BinaryBuilder;
+
+import 'package:kernel/text/ast_to_text.dart' show componentToString;
+
+import 'package:kernel/kernel.dart' show Component;
+
+import 'incremental_load_from_dill_test.dart' show normalCompileToBytes;
+
+main() async {
+  List<int> bytes = await normalCompileToBytes(
+      Platform.script.resolve("load_dill_twice_lib_1.dart"));
+
+  Component c = new Component();
+  new BinaryBuilder(bytes).readComponent(c);
+  String loadedOnceString = componentToString(c);
+  new BinaryBuilder(bytes).readComponent(c);
+  String loadedTwiceString = componentToString(c);
+
+  if (loadedOnceString != loadedTwiceString) {
+    print("Loading the dill twice produces a different textual representation");
+    List<String> linesOnce = loadedOnceString.split("\n");
+    List<String> linesTwice = loadedTwiceString.split("\n");
+
+    if (linesOnce.length != linesTwice.length) {
+      print("Number of lines differ! "
+          "(${linesOnce.length} vs ${linesTwice.length})");
+    }
+
+    // Do some simple and stupid diff.
+    int i = 0;
+    int j = 0;
+    while (i < linesOnce.length || j < linesTwice.length) {
+      if (i < linesOnce.length && j < linesTwice.length) {
+        if (linesOnce[i] == linesTwice[j]) {
+          i++;
+          j++;
+        } else {
+          // Search for line from linesOnce in linesTwice
+          bool good = false;
+          for (int k = j + 1; k < linesTwice.length && k < j + 100; k++) {
+            if (linesOnce[i] == linesTwice[k]) {
+              // Inserted lines between j and k.
+              for (int k2 = j; k2 < k; k2++) {
+                print("+ ${linesTwice[k2]}");
+              }
+              i++;
+              j = k + 1;
+              good = true;
+              break;
+            }
+          }
+          if (!good) {
+            // Assume lines deleted.
+            print("- ${linesOnce[i]}");
+            i++;
+          }
+        }
+      } else if (i < linesOnce.length) {
+        // Rest from linesOnce was deleted.
+        for (; i < linesOnce.length; i++) {
+          print("- ${linesOnce[i]}");
+        }
+      } else if (j < linesTwice.length) {
+        // Rest from linesTwice was added.
+        for (; j < linesTwice.length; j++) {
+          print("+ ${linesTwice[j]}");
+        }
+      }
+    }
+
+    exit(1);
+  }
+}

pkg/kernel/lib/binary/ast_from_binary.dart

@@ -956,6 +956,7 @@ class BinaryBuilder {
   void _readAdditionalExports(Library library) {
     int numExportedReference = readUInt();
     if (numExportedReference != 0) {
+      library.additionalExports.clear();
       for (int i = 0; i < numExportedReference; i++) {
         CanonicalName exportedName = readCanonicalNameReference();
         Reference reference = exportedName.getReference();
@@ -1012,7 +1013,9 @@ class BinaryBuilder {
     readAndPushTypeParameterList(node.typeParameters, node);
     var type = readDartType();
     readAndPushTypeParameterList(node.typeParametersOfFunctionType, node);
+    node.positionalParameters.clear();
     node.positionalParameters.addAll(readAndPushVariableDeclarationList());
+    node.namedParameters.clear();
     node.namedParameters.addAll(readAndPushVariableDeclarationList());
     typeParameterStack.length = 0;
     variableStack.length = 0;