Allow identical as a compile-time constant.

pkg/front_end/lib/src/fasta/kernel/body_builder.dart

 // Copyright (c) 2016, 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.
 
 library fasta.body_builder;
 
 import '../parser/parser.dart' show FormalParameterType, optional;
 
 import '../parser/error_kind.dart' show ErrorKind;
 
@@ skipping 501 matching lines @@
       push(receiver);
     } else {
       push(finishSend(receiver, arguments, beginToken.charOffset));
     }
   }
 
   @override
   finishSend(Object receiver, Arguments arguments, int charOffset) {
     if (receiver is BuilderAccessor) {
       if (constantExpressionRequired) {
-        addCompileTimeError(charOffset, "Not a constant expression.");
+        if (!(receiver is StaticAccessor &&

[karlklose, 2017/03/24 08:42:30]

Maybe move the checks in l. 523-525 to a helper called 'isIdentical' and merge
the condition with l. 521.

[ahe, 2017/03/24 13:14:35]

Done.

+            receiver.readTarget ==
+                coreTypes.tryGetTopLevelMember(
+                    "dart:core", null, "identical"))) {
+          addCompileTimeError(charOffset, "Not a constant expression.");
+        }
       }
       return receiver.doInvocation(charOffset, arguments);
     } else if (receiver is UnresolvedIdentifier) {
       return throwNoSuchMethodError(
           receiver.name.name, arguments, receiver.fileOffset);
     } else {
       return buildMethodInvocation(
           toValue(receiver), callName, arguments, charOffset);
     }
   }
@@ skipping 259 matching lines @@
         setter = builder;
       } else if (builder.isGetter) {
         setter = scope.lookupSetter(name, charOffset, uri);
       } else if (builder.isField && !builder.isFinal) {
         setter = builder;
       }
       StaticAccessor accessor =
           new StaticAccessor.fromBuilder(this, builder, charOffset, setter);
       if (constantExpressionRequired) {
         Member readTarget = accessor.readTarget;
-        if (!(readTarget is Field && readTarget.isConst)) {
+        if (!(readTarget is Field && readTarget.isConst ||
+            // Static tear-offs are also compile time constants.
+            readTarget is Procedure)) {
           addCompileTimeError(charOffset, "Not a constant expression.");
         }
       }
       return accessor;
     }
   }
 
   @override
   void handleQualified(Token period) {
     debugEvent("Qualified");
@@ skipping 2037 matching lines @@
   } else if (node is PrefixBuilder) {
     return node.name;
   } else if (node is ThisAccessor) {
     return node.isSuper ? "super" : "this";
   } else if (node is BuilderAccessor) {
     return node.plainNameForRead;
   } else {
     return internalError("Unhandled: ${node.runtimeType}");
   }
 }