[VM generic function reification] Support generic functions in Invocation class.

runtime/lib/invocation_mirror_patch.dart

Index: runtime/lib/invocation_mirror_patch.dart
diff --git a/runtime/lib/invocation_mirror_patch.dart b/runtime/lib/invocation_mirror_patch.dart
index ef325e35b8e917467629d3da7d4560e3f58b3be1..7fd57bde529c57f6df11ac2c32b68292ca0283de 100644
--- a/runtime/lib/invocation_mirror_patch.dart
+++ b/runtime/lib/invocation_mirror_patch.dart
@@ -5,6 +5,7 @@
 // NOTE: When making changes to this class, please also update
 // `VmTarget.instantiateInvocation` and `VmTarget._invocationType` in
 // `pkg/kernel/lib/target/vm.dart`.
+// TODO(regis): See above NOTE.
 class _InvocationMirror implements Invocation {
   // Constants describing the invocation type.
   // _FIELD cannot be generated by regular invocation mirrors.
@@ -43,6 +44,7 @@ class _InvocationMirror implements Invocation {
   // External representation of the invocation mirror; populated on demand.
   Symbol _memberName;
   int _type;
+  List _typeArguments;
   List _positionalArguments;
   Map<Symbol, dynamic> _namedArguments;
 
@@ -67,16 +69,36 @@ class _InvocationMirror implements Invocation {
     return _memberName;
   }
 
+  List get typeArguments {
+    if (_typeArguments == null) {
+      int typeArgsLen = _argumentsDescriptor[_TYPE_ARGS_LEN];
+      if (typeArgsLen == 0) {
+        return _typeArguments = const [];
+      }
+      // A TypeArguments object does not have a corresponding Dart class and
+      // cannot be accessed as an array in Dart. Therefore, we need a native
+      // call to unpack the individual types into a list.
+      _typeArguments = _unpackTypeArguments(_arguments[0]);
+    }
+    return _typeArguments;
+  }
+
+  // Unpack the given TypeArguments object into a new list of individual types.
+  static List _unpackTypeArguments(typeArguments)
+      native "InvocationMirror_unpackTypeArguments";
+
   List get positionalArguments {
     if (_positionalArguments == null) {
-      int numPositionalArguments = _argumentsDescriptor[_POSITIONAL_COUNT];
-      // Don't count receiver.
-      if (numPositionalArguments == 1) {
+      // The argument descriptor counts the receiver, but not the type arguments
+      // as positional arguments.
+      int numPositionalArguments = _argumentsDescriptor[_POSITIONAL_COUNT] - 1;
+      if (numPositionalArguments == 0) {
         return _positionalArguments = const [];
       }
-      // Exclude receiver.
-      _positionalArguments =
-          new _ImmutableList._from(_arguments, 1, numPositionalArguments - 1);
+      // Exclude receiver and type args in the returned list.
+      int receiverIndex = _argumentsDescriptor[_TYPE_ARGS_LEN] > 0 ? 1 : 0;
+      _positionalArguments = new _ImmutableList._from(
+          _arguments, receiverIndex + 1, numPositionalArguments);
     }
     return _positionalArguments;
   }
@@ -89,11 +111,13 @@ class _InvocationMirror implements Invocation {
       if (numNamedArguments == 0) {
         return _namedArguments = const {};
       }
+      int receiverIndex = _argumentsDescriptor[_TYPE_ARGS_LEN] > 0 ? 1 : 0;
       _namedArguments = new Map<Symbol, dynamic>();
       for (int i = 0; i < numNamedArguments; i++) {
         int namedEntryIndex = _FIRST_NAMED_ENTRY + 2 * i;
         String arg_name = _argumentsDescriptor[namedEntryIndex];
-        var arg_value = _arguments[_argumentsDescriptor[namedEntryIndex + 1]];
+        var arg_value = _arguments[
+            receiverIndex + _argumentsDescriptor[namedEntryIndex + 1]];
         _namedArguments[new internal.Symbol.unvalidated(arg_name)] = arg_value;
       }
       _namedArguments = new Map.unmodifiable(_namedArguments);