diff --git a/src/main/java/com/google/devtools/build/docgen/BUILD b/src/main/java/com/google/devtools/build/docgen/BUILD
index 7b9b279..68cfd2e 100644
--- a/src/main/java/com/google/devtools/build/docgen/BUILD
+++ b/src/main/java/com/google/devtools/build/docgen/BUILD
@@ -12,6 +12,7 @@
         "//src/main/java/com/google/devtools/build/lib:build-base",
         "//src/main/java/com/google/devtools/build/lib:common",
         "//src/main/java/com/google/devtools/build/lib:packages",
+        "//src/main/java/com/google/devtools/build/lib:skylarkinterface",
         "//third_party:apache_velocity",
         "//third_party:guava",
         "//third_party:jsr305",
diff --git a/src/main/java/com/google/devtools/build/docgen/SkylarkDocumentationCollector.java b/src/main/java/com/google/devtools/build/docgen/SkylarkDocumentationCollector.java
index b279cfd..bb34940 100644
--- a/src/main/java/com/google/devtools/build/docgen/SkylarkDocumentationCollector.java
+++ b/src/main/java/com/google/devtools/build/docgen/SkylarkDocumentationCollector.java
@@ -22,12 +22,12 @@
 import com.google.devtools.build.lib.analysis.TransitiveInfoCollection;
 import com.google.devtools.build.lib.rules.SkylarkModules;
 import com.google.devtools.build.lib.rules.SkylarkRuleContext;
+import com.google.devtools.build.lib.skylarkinterface.SkylarkCallable;
+import com.google.devtools.build.lib.skylarkinterface.SkylarkModule;
+import com.google.devtools.build.lib.skylarkinterface.SkylarkSignature;
 import com.google.devtools.build.lib.syntax.FuncallExpression;
 import com.google.devtools.build.lib.syntax.MethodLibrary;
 import com.google.devtools.build.lib.syntax.Runtime;
-import com.google.devtools.build.lib.syntax.SkylarkCallable;
-import com.google.devtools.build.lib.syntax.SkylarkModule;
-import com.google.devtools.build.lib.syntax.SkylarkSignature;
 
 import java.lang.reflect.Field;
 import java.lang.reflect.Method;
diff --git a/src/main/java/com/google/devtools/build/docgen/skylark/SkylarkBuiltinMethodDoc.java b/src/main/java/com/google/devtools/build/docgen/skylark/SkylarkBuiltinMethodDoc.java
index b1a0802..318ec24 100644
--- a/src/main/java/com/google/devtools/build/docgen/skylark/SkylarkBuiltinMethodDoc.java
+++ b/src/main/java/com/google/devtools/build/docgen/skylark/SkylarkBuiltinMethodDoc.java
@@ -13,9 +13,9 @@
 // limitations under the License.
 package com.google.devtools.build.docgen.skylark;
 
+import com.google.devtools.build.lib.skylarkinterface.SkylarkSignature;
+import com.google.devtools.build.lib.skylarkinterface.SkylarkSignature.Param;
 import com.google.devtools.build.lib.syntax.BaseFunction;
-import com.google.devtools.build.lib.syntax.SkylarkSignature;
-import com.google.devtools.build.lib.syntax.SkylarkSignature.Param;
 
 import java.util.ArrayList;
 import java.util.List;
diff --git a/src/main/java/com/google/devtools/build/docgen/skylark/SkylarkDoc.java b/src/main/java/com/google/devtools/build/docgen/skylark/SkylarkDoc.java
index 941849d..511e474 100644
--- a/src/main/java/com/google/devtools/build/docgen/skylark/SkylarkDoc.java
+++ b/src/main/java/com/google/devtools/build/docgen/skylark/SkylarkDoc.java
@@ -13,15 +13,15 @@
 // limitations under the License.
 package com.google.devtools.build.docgen.skylark;
 
+import com.google.devtools.build.lib.skylarkinterface.SkylarkModule;
+import com.google.devtools.build.lib.skylarkinterface.SkylarkSignature;
+import com.google.devtools.build.lib.skylarkinterface.SkylarkSignature.Param;
 import com.google.devtools.build.lib.syntax.EvalUtils;
 import com.google.devtools.build.lib.syntax.FuncallExpression;
 import com.google.devtools.build.lib.syntax.Runtime.NoneType;
 import com.google.devtools.build.lib.syntax.SkylarkList;
 import com.google.devtools.build.lib.syntax.SkylarkList.MutableList;
 import com.google.devtools.build.lib.syntax.SkylarkList.Tuple;
-import com.google.devtools.build.lib.syntax.SkylarkModule;
-import com.google.devtools.build.lib.syntax.SkylarkSignature;
-import com.google.devtools.build.lib.syntax.SkylarkSignature.Param;
 
 import java.util.Arrays;
 import java.util.Map;
diff --git a/src/main/java/com/google/devtools/build/docgen/skylark/SkylarkJavaMethodDoc.java b/src/main/java/com/google/devtools/build/docgen/skylark/SkylarkJavaMethodDoc.java
index adc3025..3ee3aab 100644
--- a/src/main/java/com/google/devtools/build/docgen/skylark/SkylarkJavaMethodDoc.java
+++ b/src/main/java/com/google/devtools/build/docgen/skylark/SkylarkJavaMethodDoc.java
@@ -13,7 +13,7 @@
 // limitations under the License.
 package com.google.devtools.build.docgen.skylark;
 
-import com.google.devtools.build.lib.syntax.SkylarkCallable;
+import com.google.devtools.build.lib.skylarkinterface.SkylarkCallable;
 import com.google.devtools.build.lib.util.StringUtilities;
 
 import java.lang.reflect.Method;
diff --git a/src/main/java/com/google/devtools/build/docgen/skylark/SkylarkMethodDoc.java b/src/main/java/com/google/devtools/build/docgen/skylark/SkylarkMethodDoc.java
index cf43ef9..bf254e1 100644
--- a/src/main/java/com/google/devtools/build/docgen/skylark/SkylarkMethodDoc.java
+++ b/src/main/java/com/google/devtools/build/docgen/skylark/SkylarkMethodDoc.java
@@ -17,9 +17,9 @@
 import com.google.common.base.Joiner;
 import com.google.common.collect.ImmutableList;
 import com.google.common.collect.Iterables;
-import com.google.devtools.build.lib.syntax.SkylarkCallable;
-import com.google.devtools.build.lib.syntax.SkylarkSignature;
-import com.google.devtools.build.lib.syntax.SkylarkSignature.Param;
+import com.google.devtools.build.lib.skylarkinterface.SkylarkCallable;
+import com.google.devtools.build.lib.skylarkinterface.SkylarkSignature;
+import com.google.devtools.build.lib.skylarkinterface.SkylarkSignature.Param;
 
 import java.lang.reflect.Method;
 import java.util.ArrayList;
diff --git a/src/main/java/com/google/devtools/build/docgen/skylark/SkylarkModuleDoc.java b/src/main/java/com/google/devtools/build/docgen/skylark/SkylarkModuleDoc.java
index eba1813..0e3c42b 100644
--- a/src/main/java/com/google/devtools/build/docgen/skylark/SkylarkModuleDoc.java
+++ b/src/main/java/com/google/devtools/build/docgen/skylark/SkylarkModuleDoc.java
@@ -14,7 +14,9 @@
 package com.google.devtools.build.docgen.skylark;
 
 import com.google.common.base.Preconditions;
-import com.google.devtools.build.lib.syntax.SkylarkModule;
+import com.google.devtools.build.lib.skylarkinterface.SkylarkCallable;
+import com.google.devtools.build.lib.skylarkinterface.SkylarkModule;
+import com.google.devtools.build.lib.skylarkinterface.SkylarkSignature;
 
 import java.util.ArrayList;
 import java.util.Collection;
diff --git a/src/main/java/com/google/devtools/build/docgen/skylark/SkylarkParamDoc.java b/src/main/java/com/google/devtools/build/docgen/skylark/SkylarkParamDoc.java
index 16e6414..37f6f16 100644
--- a/src/main/java/com/google/devtools/build/docgen/skylark/SkylarkParamDoc.java
+++ b/src/main/java/com/google/devtools/build/docgen/skylark/SkylarkParamDoc.java
@@ -13,7 +13,7 @@
 // limitations under the License.
 package com.google.devtools.build.docgen.skylark;
 
-import com.google.devtools.build.lib.syntax.SkylarkSignature.Param;
+import com.google.devtools.build.lib.skylarkinterface.SkylarkSignature.Param;
 
 /**
  * A class containing the documentation for a Skylark method parameter.
diff --git a/src/main/java/com/google/devtools/build/lib/BUILD b/src/main/java/com/google/devtools/build/lib/BUILD
index 0051bcb..5895f91 100644
--- a/src/main/java/com/google/devtools/build/lib/BUILD
+++ b/src/main/java/com/google/devtools/build/lib/BUILD
@@ -284,6 +284,16 @@
     ],
 )
 
+java_library(
+    name = "skylarkinterface",
+    srcs = glob([
+        "skylarkinterface/*.java",
+    ]),
+    deps = [
+        "//third_party:jsr305",
+    ],
+)
+
 ########################################################################
 #
 # The "cmdline" library: Label validation and target pattern
@@ -301,7 +311,7 @@
         ":base-util",
         ":common",
         ":concurrent",
-        ":syntax",
+        ":skylarkinterface",
         ":util",
         ":vfs",
         "//third_party:jsr305",
@@ -318,6 +328,7 @@
         ":common",
         ":concurrent",
         ":events",
+        ":skylarkinterface",
         ":util",
         ":vfs",
         "//third_party:asm",
@@ -364,6 +375,7 @@
         ":common",
         ":concurrent",
         ":events",
+        ":skylarkinterface",
         ":syntax",
         ":util",
         ":vfs",
@@ -432,6 +444,7 @@
         ":os_util",
         ":packages-internal",
         ":shell",
+        ":skylarkinterface",
         ":util",
         ":vfs",
         "//src/main/java/com/google/devtools/build/lib/actions",
@@ -475,6 +488,7 @@
         ":packages-internal",
         ":proto-rules",
         ":python-rules",
+        ":skylarkinterface",
         ":util",
         ":vfs",
         "//src/main/java/com/google/devtools/build/lib/actions",
@@ -627,6 +641,7 @@
         ":common",
         ":concurrent",
         ":packages-internal",
+        ":skylarkinterface",
         ":util",
         ":vfs",
         "//src/main/java/com/google/devtools/build/lib/actions",
@@ -656,6 +671,7 @@
         ":java-implicit-attributes",
         ":packages-internal",
         ":shell",
+        ":skylarkinterface",
         ":util",
         ":vfs",
         "//src/main/java/com/google/devtools/build/lib/actions",
@@ -707,8 +723,8 @@
         ":collect",
         ":common",
         ":concurrent",
-        ":nativedeps-rules",
         ":packages-internal",
+        ":skylarkinterface",
         ":util",
         ":vfs",
         "//src/main/java/com/google/devtools/build/lib/actions",
diff --git a/src/main/java/com/google/devtools/build/lib/actions/AbstractAction.java b/src/main/java/com/google/devtools/build/lib/actions/AbstractAction.java
index a340d2f..15cd421 100644
--- a/src/main/java/com/google/devtools/build/lib/actions/AbstractAction.java
+++ b/src/main/java/com/google/devtools/build/lib/actions/AbstractAction.java
@@ -27,8 +27,8 @@
 import com.google.devtools.build.lib.events.EventHandler;
 import com.google.devtools.build.lib.events.EventKind;
 import com.google.devtools.build.lib.events.Location;
+import com.google.devtools.build.lib.skylarkinterface.SkylarkValue;
 import com.google.devtools.build.lib.syntax.Printer;
-import com.google.devtools.build.lib.syntax.SkylarkValue;
 import com.google.devtools.build.lib.util.Preconditions;
 import com.google.devtools.build.lib.vfs.FileSystemUtils;
 import com.google.devtools.build.lib.vfs.Path;
diff --git a/src/main/java/com/google/devtools/build/lib/actions/Artifact.java b/src/main/java/com/google/devtools/build/lib/actions/Artifact.java
index b358b04..5a98552 100644
--- a/src/main/java/com/google/devtools/build/lib/actions/Artifact.java
+++ b/src/main/java/com/google/devtools/build/lib/actions/Artifact.java
@@ -25,10 +25,10 @@
 import com.google.devtools.build.lib.cmdline.Label;
 import com.google.devtools.build.lib.concurrent.ThreadSafety.Immutable;
 import com.google.devtools.build.lib.shell.ShellUtils;
+import com.google.devtools.build.lib.skylarkinterface.SkylarkCallable;
+import com.google.devtools.build.lib.skylarkinterface.SkylarkModule;
+import com.google.devtools.build.lib.skylarkinterface.SkylarkValue;
 import com.google.devtools.build.lib.syntax.Printer;
-import com.google.devtools.build.lib.syntax.SkylarkCallable;
-import com.google.devtools.build.lib.syntax.SkylarkModule;
-import com.google.devtools.build.lib.syntax.SkylarkValue;
 import com.google.devtools.build.lib.util.FileType;
 import com.google.devtools.build.lib.util.Preconditions;
 import com.google.devtools.build.lib.vfs.Path;
diff --git a/src/main/java/com/google/devtools/build/lib/actions/BUILD b/src/main/java/com/google/devtools/build/lib/actions/BUILD
index d3cfd66..8758fb1 100644
--- a/src/main/java/com/google/devtools/build/lib/actions/BUILD
+++ b/src/main/java/com/google/devtools/build/lib/actions/BUILD
@@ -17,6 +17,7 @@
         "//src/main/java/com/google/devtools/build/lib:io",
         "//src/main/java/com/google/devtools/build/lib:packages-internal",
         "//src/main/java/com/google/devtools/build/lib:shell",
+        "//src/main/java/com/google/devtools/build/lib:skylarkinterface",
         "//src/main/java/com/google/devtools/build/lib:util",
         "//src/main/java/com/google/devtools/build/lib:vfs",
         "//src/main/java/com/google/devtools/build/skyframe",
diff --git a/src/main/java/com/google/devtools/build/lib/actions/Root.java b/src/main/java/com/google/devtools/build/lib/actions/Root.java
index 8e78e24..b09dfa3 100644
--- a/src/main/java/com/google/devtools/build/lib/actions/Root.java
+++ b/src/main/java/com/google/devtools/build/lib/actions/Root.java
@@ -15,8 +15,8 @@
 package com.google.devtools.build.lib.actions;
 
 import com.google.common.annotations.VisibleForTesting;
-import com.google.devtools.build.lib.syntax.SkylarkCallable;
-import com.google.devtools.build.lib.syntax.SkylarkModule;
+import com.google.devtools.build.lib.skylarkinterface.SkylarkCallable;
+import com.google.devtools.build.lib.skylarkinterface.SkylarkModule;
 import com.google.devtools.build.lib.util.Preconditions;
 import com.google.devtools.build.lib.vfs.Path;
 import com.google.devtools.build.lib.vfs.PathFragment;
diff --git a/src/main/java/com/google/devtools/build/lib/analysis/FileProvider.java b/src/main/java/com/google/devtools/build/lib/analysis/FileProvider.java
index 95edd1b..b63ca8c 100644
--- a/src/main/java/com/google/devtools/build/lib/analysis/FileProvider.java
+++ b/src/main/java/com/google/devtools/build/lib/analysis/FileProvider.java
@@ -18,8 +18,8 @@
 import com.google.devtools.build.lib.cmdline.Label;
 import com.google.devtools.build.lib.collect.nestedset.NestedSet;
 import com.google.devtools.build.lib.concurrent.ThreadSafety.Immutable;
-import com.google.devtools.build.lib.syntax.SkylarkCallable;
-import com.google.devtools.build.lib.syntax.SkylarkModule;
+import com.google.devtools.build.lib.skylarkinterface.SkylarkCallable;
+import com.google.devtools.build.lib.skylarkinterface.SkylarkModule;
 
 import javax.annotation.Nullable;
 
diff --git a/src/main/java/com/google/devtools/build/lib/analysis/FilesToRunProvider.java b/src/main/java/com/google/devtools/build/lib/analysis/FilesToRunProvider.java
index 8811efd..2dab4b3 100644
--- a/src/main/java/com/google/devtools/build/lib/analysis/FilesToRunProvider.java
+++ b/src/main/java/com/google/devtools/build/lib/analysis/FilesToRunProvider.java
@@ -20,8 +20,8 @@
 import com.google.devtools.build.lib.actions.RunfilesSupplier;
 import com.google.devtools.build.lib.cmdline.Label;
 import com.google.devtools.build.lib.concurrent.ThreadSafety.Immutable;
-import com.google.devtools.build.lib.syntax.SkylarkCallable;
-import com.google.devtools.build.lib.syntax.SkylarkModule;
+import com.google.devtools.build.lib.skylarkinterface.SkylarkCallable;
+import com.google.devtools.build.lib.skylarkinterface.SkylarkModule;
 
 import javax.annotation.Nullable;
 
diff --git a/src/main/java/com/google/devtools/build/lib/analysis/Runfiles.java b/src/main/java/com/google/devtools/build/lib/analysis/Runfiles.java
index faaca79..83657f6 100644
--- a/src/main/java/com/google/devtools/build/lib/analysis/Runfiles.java
+++ b/src/main/java/com/google/devtools/build/lib/analysis/Runfiles.java
@@ -28,8 +28,8 @@
 import com.google.devtools.build.lib.events.EventHandler;
 import com.google.devtools.build.lib.events.Location;
 import com.google.devtools.build.lib.packages.BuildType;
-import com.google.devtools.build.lib.syntax.SkylarkCallable;
-import com.google.devtools.build.lib.syntax.SkylarkModule;
+import com.google.devtools.build.lib.skylarkinterface.SkylarkCallable;
+import com.google.devtools.build.lib.skylarkinterface.SkylarkModule;
 import com.google.devtools.build.lib.util.Preconditions;
 import com.google.devtools.build.lib.vfs.Path;
 import com.google.devtools.build.lib.vfs.PathFragment;
diff --git a/src/main/java/com/google/devtools/build/lib/analysis/TransitiveInfoCollection.java b/src/main/java/com/google/devtools/build/lib/analysis/TransitiveInfoCollection.java
index 044c0d0..2264d8f 100644
--- a/src/main/java/com/google/devtools/build/lib/analysis/TransitiveInfoCollection.java
+++ b/src/main/java/com/google/devtools/build/lib/analysis/TransitiveInfoCollection.java
@@ -17,7 +17,7 @@
 import com.google.common.collect.UnmodifiableIterator;
 import com.google.devtools.build.lib.analysis.config.BuildConfiguration;
 import com.google.devtools.build.lib.cmdline.Label;
-import com.google.devtools.build.lib.syntax.SkylarkModule;
+import com.google.devtools.build.lib.skylarkinterface.SkylarkModule;
 
 import javax.annotation.Nullable;
 
diff --git a/src/main/java/com/google/devtools/build/lib/analysis/config/BuildConfiguration.java b/src/main/java/com/google/devtools/build/lib/analysis/config/BuildConfiguration.java
index 468b86e..8ef6679 100644
--- a/src/main/java/com/google/devtools/build/lib/analysis/config/BuildConfiguration.java
+++ b/src/main/java/com/google/devtools/build/lib/analysis/config/BuildConfiguration.java
@@ -54,8 +54,8 @@
 import com.google.devtools.build.lib.packages.RuleClassProvider;
 import com.google.devtools.build.lib.packages.Target;
 import com.google.devtools.build.lib.rules.test.TestActionBuilder;
-import com.google.devtools.build.lib.syntax.SkylarkCallable;
-import com.google.devtools.build.lib.syntax.SkylarkModule;
+import com.google.devtools.build.lib.skylarkinterface.SkylarkCallable;
+import com.google.devtools.build.lib.skylarkinterface.SkylarkModule;
 import com.google.devtools.build.lib.syntax.SkylarkModuleNameResolver;
 import com.google.devtools.build.lib.util.CPU;
 import com.google.devtools.build.lib.util.Fingerprint;
diff --git a/src/main/java/com/google/devtools/build/lib/analysis/config/FragmentCollection.java b/src/main/java/com/google/devtools/build/lib/analysis/config/FragmentCollection.java
index 318f7f9..6a2bccc 100644
--- a/src/main/java/com/google/devtools/build/lib/analysis/config/FragmentCollection.java
+++ b/src/main/java/com/google/devtools/build/lib/analysis/config/FragmentCollection.java
@@ -18,8 +18,8 @@
 import com.google.devtools.build.lib.analysis.RuleContext;
 import com.google.devtools.build.lib.concurrent.ThreadSafety.Immutable;
 import com.google.devtools.build.lib.packages.Attribute.ConfigurationTransition;
+import com.google.devtools.build.lib.skylarkinterface.SkylarkModule;
 import com.google.devtools.build.lib.syntax.ClassObject;
-import com.google.devtools.build.lib.syntax.SkylarkModule;
 
 import javax.annotation.Nullable;
 
diff --git a/src/main/java/com/google/devtools/build/lib/cmdline/Label.java b/src/main/java/com/google/devtools/build/lib/cmdline/Label.java
index ac79766..89ac2f8 100644
--- a/src/main/java/com/google/devtools/build/lib/cmdline/Label.java
+++ b/src/main/java/com/google/devtools/build/lib/cmdline/Label.java
@@ -17,15 +17,15 @@
 import com.google.devtools.build.lib.cmdline.LabelValidator.BadLabelException;
 import com.google.devtools.build.lib.concurrent.ThreadSafety.Immutable;
 import com.google.devtools.build.lib.concurrent.ThreadSafety.ThreadSafe;
-import com.google.devtools.build.lib.syntax.Printer;
-import com.google.devtools.build.lib.syntax.SkylarkCallable;
-import com.google.devtools.build.lib.syntax.SkylarkModule;
-import com.google.devtools.build.lib.syntax.SkylarkPrintableValue;
+import com.google.devtools.build.lib.skylarkinterface.SkylarkCallable;
+import com.google.devtools.build.lib.skylarkinterface.SkylarkModule;
+import com.google.devtools.build.lib.skylarkinterface.SkylarkPrintableValue;
 import com.google.devtools.build.lib.util.Preconditions;
 import com.google.devtools.build.lib.util.StringCanonicalizer;
 import com.google.devtools.build.lib.util.StringUtilities;
 import com.google.devtools.build.lib.vfs.PathFragment;
 
+import java.io.IOException;
 import java.io.InvalidObjectException;
 import java.io.ObjectInputStream;
 import java.io.Serializable;
@@ -449,15 +449,33 @@
 
   @Override
   public void write(Appendable buffer, char quotationMark) {
+    // We don't use the Skylark Printer class here to avoid creating a circular dependency.
+    //
     // TODO(bazel-team): make the representation readable Label(//foo),
     // and isolate the legacy functions that want the unreadable variant.
-    Printer.write(buffer, toString(), quotationMark);
+    try {
+      // There is no need to escape the contents of the Label since characters that might otherwise
+      // require escaping are disallowed.
+      buffer.append(quotationMark);
+      buffer.append(toString());
+      buffer.append(quotationMark);
+    } catch (IOException e) {
+      // This function will only be used with in-memory Appendables, hence we should never get here.
+      throw new AssertionError(e);
+    }
   }
 
   @Override
   public void print(Appendable buffer, char quotationMark) {
+    // We don't use the Skylark Printer class here to avoid creating a circular dependency.
+    //
     // TODO(bazel-team): make the representation readable Label(//foo),
     // and isolate the legacy functions that want the unreadable variant.
-    Printer.append(buffer, toString());
+    try {
+      buffer.append(toString());
+    } catch (IOException e) {
+      // This function will only be used with in-memory Appendables, hence we should never get here.
+      throw new AssertionError(e);
+    }
   }
 }
diff --git a/src/main/java/com/google/devtools/build/lib/packages/Attribute.java b/src/main/java/com/google/devtools/build/lib/packages/Attribute.java
index 3bbccdf..daf6106 100644
--- a/src/main/java/com/google/devtools/build/lib/packages/Attribute.java
+++ b/src/main/java/com/google/devtools/build/lib/packages/Attribute.java
@@ -24,11 +24,11 @@
 import com.google.common.collect.Sets;
 import com.google.devtools.build.lib.cmdline.Label;
 import com.google.devtools.build.lib.packages.NativeAspectClass.NativeAspectFactory;
+import com.google.devtools.build.lib.skylarkinterface.SkylarkModule;
 import com.google.devtools.build.lib.syntax.ClassObject;
 import com.google.devtools.build.lib.syntax.ClassObject.SkylarkClassObject;
 import com.google.devtools.build.lib.syntax.EvalException;
 import com.google.devtools.build.lib.syntax.SkylarkCallbackFunction;
-import com.google.devtools.build.lib.syntax.SkylarkModule;
 import com.google.devtools.build.lib.syntax.Type;
 import com.google.devtools.build.lib.syntax.Type.ConversionException;
 import com.google.devtools.build.lib.util.FileType;
diff --git a/src/main/java/com/google/devtools/build/lib/packages/FilesetEntry.java b/src/main/java/com/google/devtools/build/lib/packages/FilesetEntry.java
index 032e678..210fa1b 100644
--- a/src/main/java/com/google/devtools/build/lib/packages/FilesetEntry.java
+++ b/src/main/java/com/google/devtools/build/lib/packages/FilesetEntry.java
@@ -20,9 +20,9 @@
 import com.google.common.collect.ImmutableSet;
 import com.google.common.collect.Lists;
 import com.google.devtools.build.lib.cmdline.Label;
+import com.google.devtools.build.lib.skylarkinterface.SkylarkModule;
+import com.google.devtools.build.lib.skylarkinterface.SkylarkValue;
 import com.google.devtools.build.lib.syntax.Printer;
-import com.google.devtools.build.lib.syntax.SkylarkModule;
-import com.google.devtools.build.lib.syntax.SkylarkValue;
 import com.google.devtools.build.lib.vfs.PathFragment;
 
 import java.util.Collection;
diff --git a/src/main/java/com/google/devtools/build/lib/packages/PackageFactory.java b/src/main/java/com/google/devtools/build/lib/packages/PackageFactory.java
index eb7a192..b81dfdf 100644
--- a/src/main/java/com/google/devtools/build/lib/packages/PackageFactory.java
+++ b/src/main/java/com/google/devtools/build/lib/packages/PackageFactory.java
@@ -32,6 +32,8 @@
 import com.google.devtools.build.lib.packages.GlobCache.BadGlobException;
 import com.google.devtools.build.lib.packages.License.DistributionType;
 import com.google.devtools.build.lib.packages.Preprocessor.AstAfterPreprocessing;
+import com.google.devtools.build.lib.skylarkinterface.SkylarkSignature;
+import com.google.devtools.build.lib.skylarkinterface.SkylarkSignature.Param;
 import com.google.devtools.build.lib.syntax.AssignmentStatement;
 import com.google.devtools.build.lib.syntax.BaseFunction;
 import com.google.devtools.build.lib.syntax.BuildFileAST;
@@ -52,8 +54,6 @@
 import com.google.devtools.build.lib.syntax.Runtime;
 import com.google.devtools.build.lib.syntax.SkylarkList;
 import com.google.devtools.build.lib.syntax.SkylarkList.MutableList;
-import com.google.devtools.build.lib.syntax.SkylarkSignature;
-import com.google.devtools.build.lib.syntax.SkylarkSignature.Param;
 import com.google.devtools.build.lib.syntax.SkylarkSignatureProcessor;
 import com.google.devtools.build.lib.syntax.Statement;
 import com.google.devtools.build.lib.syntax.Type;
diff --git a/src/main/java/com/google/devtools/build/lib/packages/SkylarkNativeModule.java b/src/main/java/com/google/devtools/build/lib/packages/SkylarkNativeModule.java
index 377464e..be648b0 100644
--- a/src/main/java/com/google/devtools/build/lib/packages/SkylarkNativeModule.java
+++ b/src/main/java/com/google/devtools/build/lib/packages/SkylarkNativeModule.java
@@ -14,15 +14,15 @@
 
 package com.google.devtools.build.lib.packages;
 
+import com.google.devtools.build.lib.skylarkinterface.SkylarkModule;
+import com.google.devtools.build.lib.skylarkinterface.SkylarkSignature;
+import com.google.devtools.build.lib.skylarkinterface.SkylarkSignature.Param;
 import com.google.devtools.build.lib.syntax.BuiltinFunction;
 import com.google.devtools.build.lib.syntax.Environment;
 import com.google.devtools.build.lib.syntax.EvalException;
 import com.google.devtools.build.lib.syntax.FuncallExpression;
 import com.google.devtools.build.lib.syntax.Runtime;
 import com.google.devtools.build.lib.syntax.SkylarkList;
-import com.google.devtools.build.lib.syntax.SkylarkModule;
-import com.google.devtools.build.lib.syntax.SkylarkSignature;
-import com.google.devtools.build.lib.syntax.SkylarkSignature.Param;
 import com.google.devtools.build.lib.syntax.SkylarkSignatureProcessor;
 import com.google.devtools.build.lib.syntax.Type.ConversionException;
 
diff --git a/src/main/java/com/google/devtools/build/lib/packages/Target.java b/src/main/java/com/google/devtools/build/lib/packages/Target.java
index 7fb42b6..dbf6b3c 100644
--- a/src/main/java/com/google/devtools/build/lib/packages/Target.java
+++ b/src/main/java/com/google/devtools/build/lib/packages/Target.java
@@ -17,8 +17,8 @@
 import com.google.devtools.build.lib.cmdline.Label;
 import com.google.devtools.build.lib.events.Location;
 import com.google.devtools.build.lib.packages.License.DistributionType;
-import com.google.devtools.build.lib.syntax.SkylarkCallable;
-import com.google.devtools.build.lib.syntax.SkylarkModule;
+import com.google.devtools.build.lib.skylarkinterface.SkylarkCallable;
+import com.google.devtools.build.lib.skylarkinterface.SkylarkModule;
 
 import java.util.Set;
 
diff --git a/src/main/java/com/google/devtools/build/lib/rules/SkylarkAttr.java b/src/main/java/com/google/devtools/build/lib/rules/SkylarkAttr.java
index 58b9386..aa2fef9 100644
--- a/src/main/java/com/google/devtools/build/lib/rules/SkylarkAttr.java
+++ b/src/main/java/com/google/devtools/build/lib/rules/SkylarkAttr.java
@@ -24,6 +24,9 @@
 import com.google.devtools.build.lib.packages.Attribute.SkylarkLateBound;
 import com.google.devtools.build.lib.packages.BuildType;
 import com.google.devtools.build.lib.rules.SkylarkRuleClassFunctions.SkylarkAspect;
+import com.google.devtools.build.lib.skylarkinterface.SkylarkModule;
+import com.google.devtools.build.lib.skylarkinterface.SkylarkSignature;
+import com.google.devtools.build.lib.skylarkinterface.SkylarkSignature.Param;
 import com.google.devtools.build.lib.syntax.BuiltinFunction;
 import com.google.devtools.build.lib.syntax.Environment;
 import com.google.devtools.build.lib.syntax.EvalException;
@@ -32,9 +35,6 @@
 import com.google.devtools.build.lib.syntax.Runtime;
 import com.google.devtools.build.lib.syntax.SkylarkCallbackFunction;
 import com.google.devtools.build.lib.syntax.SkylarkList;
-import com.google.devtools.build.lib.syntax.SkylarkModule;
-import com.google.devtools.build.lib.syntax.SkylarkSignature;
-import com.google.devtools.build.lib.syntax.SkylarkSignature.Param;
 import com.google.devtools.build.lib.syntax.SkylarkSignatureProcessor;
 import com.google.devtools.build.lib.syntax.Type;
 import com.google.devtools.build.lib.syntax.Type.ConversionException;
diff --git a/src/main/java/com/google/devtools/build/lib/rules/SkylarkCommandLine.java b/src/main/java/com/google/devtools/build/lib/rules/SkylarkCommandLine.java
index 8c41763fd..77d5b47 100644
--- a/src/main/java/com/google/devtools/build/lib/rules/SkylarkCommandLine.java
+++ b/src/main/java/com/google/devtools/build/lib/rules/SkylarkCommandLine.java
@@ -18,13 +18,13 @@
 import com.google.common.collect.Iterables;
 import com.google.devtools.build.lib.actions.Artifact;
 import com.google.devtools.build.lib.collect.nestedset.NestedSet;
+import com.google.devtools.build.lib.skylarkinterface.SkylarkModule;
+import com.google.devtools.build.lib.skylarkinterface.SkylarkSignature;
+import com.google.devtools.build.lib.skylarkinterface.SkylarkSignature.Param;
 import com.google.devtools.build.lib.syntax.BuiltinFunction;
 import com.google.devtools.build.lib.syntax.Environment;
 import com.google.devtools.build.lib.syntax.SkylarkList.MutableList;
-import com.google.devtools.build.lib.syntax.SkylarkModule;
 import com.google.devtools.build.lib.syntax.SkylarkNestedSet;
-import com.google.devtools.build.lib.syntax.SkylarkSignature;
-import com.google.devtools.build.lib.syntax.SkylarkSignature.Param;
 import com.google.devtools.build.lib.syntax.SkylarkSignatureProcessor;
 
 /**
diff --git a/src/main/java/com/google/devtools/build/lib/rules/SkylarkFileType.java b/src/main/java/com/google/devtools/build/lib/rules/SkylarkFileType.java
index 295914d..806b836 100644
--- a/src/main/java/com/google/devtools/build/lib/rules/SkylarkFileType.java
+++ b/src/main/java/com/google/devtools/build/lib/rules/SkylarkFileType.java
@@ -16,8 +16,8 @@
 import com.google.common.annotations.VisibleForTesting;
 import com.google.common.collect.ImmutableList;
 import com.google.devtools.build.lib.actions.Artifact;
-import com.google.devtools.build.lib.syntax.SkylarkCallable;
-import com.google.devtools.build.lib.syntax.SkylarkModule;
+import com.google.devtools.build.lib.skylarkinterface.SkylarkCallable;
+import com.google.devtools.build.lib.skylarkinterface.SkylarkModule;
 import com.google.devtools.build.lib.util.FileType;
 import com.google.devtools.build.lib.util.FileTypeSet;
 
diff --git a/src/main/java/com/google/devtools/build/lib/rules/SkylarkRuleClassFunctions.java b/src/main/java/com/google/devtools/build/lib/rules/SkylarkRuleClassFunctions.java
index ac705a5..3a9f804 100644
--- a/src/main/java/com/google/devtools/build/lib/rules/SkylarkRuleClassFunctions.java
+++ b/src/main/java/com/google/devtools/build/lib/rules/SkylarkRuleClassFunctions.java
@@ -63,6 +63,9 @@
 import com.google.devtools.build.lib.packages.TargetUtils;
 import com.google.devtools.build.lib.packages.TestSize;
 import com.google.devtools.build.lib.rules.SkylarkAttr.Descriptor;
+import com.google.devtools.build.lib.skylarkinterface.SkylarkSignature;
+import com.google.devtools.build.lib.skylarkinterface.SkylarkSignature.Param;
+import com.google.devtools.build.lib.skylarkinterface.SkylarkValue;
 import com.google.devtools.build.lib.syntax.BaseFunction;
 import com.google.devtools.build.lib.syntax.BuiltinFunction;
 import com.google.devtools.build.lib.syntax.ClassObject;
@@ -78,10 +81,7 @@
 import com.google.devtools.build.lib.syntax.SkylarkCallbackFunction;
 import com.google.devtools.build.lib.syntax.SkylarkList;
 import com.google.devtools.build.lib.syntax.SkylarkModuleNameResolver;
-import com.google.devtools.build.lib.syntax.SkylarkSignature;
-import com.google.devtools.build.lib.syntax.SkylarkSignature.Param;
 import com.google.devtools.build.lib.syntax.SkylarkSignatureProcessor;
-import com.google.devtools.build.lib.syntax.SkylarkValue;
 import com.google.devtools.build.lib.syntax.Type;
 import com.google.devtools.build.lib.syntax.Type.ConversionException;
 import com.google.devtools.build.lib.util.Pair;
diff --git a/src/main/java/com/google/devtools/build/lib/rules/SkylarkRuleContext.java b/src/main/java/com/google/devtools/build/lib/rules/SkylarkRuleContext.java
index d335cc4..83f2489 100644
--- a/src/main/java/com/google/devtools/build/lib/rules/SkylarkRuleContext.java
+++ b/src/main/java/com/google/devtools/build/lib/rules/SkylarkRuleContext.java
@@ -46,14 +46,14 @@
 import com.google.devtools.build.lib.packages.RawAttributeMapper;
 import com.google.devtools.build.lib.shell.ShellUtils;
 import com.google.devtools.build.lib.shell.ShellUtils.TokenizationException;
+import com.google.devtools.build.lib.skylarkinterface.SkylarkCallable;
+import com.google.devtools.build.lib.skylarkinterface.SkylarkModule;
 import com.google.devtools.build.lib.syntax.ClassObject.SkylarkClassObject;
 import com.google.devtools.build.lib.syntax.EvalException;
 import com.google.devtools.build.lib.syntax.FuncallExpression.FuncallException;
 import com.google.devtools.build.lib.syntax.Runtime;
-import com.google.devtools.build.lib.syntax.SkylarkCallable;
 import com.google.devtools.build.lib.syntax.SkylarkList;
 import com.google.devtools.build.lib.syntax.SkylarkList.MutableList;
-import com.google.devtools.build.lib.syntax.SkylarkModule;
 import com.google.devtools.build.lib.syntax.SkylarkType;
 import com.google.devtools.build.lib.syntax.Type;
 import com.google.devtools.build.lib.util.Preconditions;
diff --git a/src/main/java/com/google/devtools/build/lib/rules/SkylarkRuleImplementationFunctions.java b/src/main/java/com/google/devtools/build/lib/rules/SkylarkRuleImplementationFunctions.java
index fda1793..4103b81 100644
--- a/src/main/java/com/google/devtools/build/lib/rules/SkylarkRuleImplementationFunctions.java
+++ b/src/main/java/com/google/devtools/build/lib/rules/SkylarkRuleImplementationFunctions.java
@@ -44,6 +44,8 @@
 import com.google.devtools.build.lib.packages.Attribute;
 import com.google.devtools.build.lib.packages.Attribute.ConfigurationTransition;
 import com.google.devtools.build.lib.packages.AttributeMap;
+import com.google.devtools.build.lib.skylarkinterface.SkylarkSignature;
+import com.google.devtools.build.lib.skylarkinterface.SkylarkSignature.Param;
 import com.google.devtools.build.lib.syntax.BuiltinFunction;
 import com.google.devtools.build.lib.syntax.Environment;
 import com.google.devtools.build.lib.syntax.EvalException;
@@ -54,8 +56,6 @@
 import com.google.devtools.build.lib.syntax.SkylarkList.MutableList;
 import com.google.devtools.build.lib.syntax.SkylarkList.Tuple;
 import com.google.devtools.build.lib.syntax.SkylarkNestedSet;
-import com.google.devtools.build.lib.syntax.SkylarkSignature;
-import com.google.devtools.build.lib.syntax.SkylarkSignature.Param;
 import com.google.devtools.build.lib.syntax.SkylarkSignatureProcessor;
 import com.google.devtools.build.lib.syntax.Type;
 import com.google.devtools.build.lib.syntax.Type.ConversionException;
diff --git a/src/main/java/com/google/devtools/build/lib/rules/cpp/BUILD b/src/main/java/com/google/devtools/build/lib/rules/cpp/BUILD
index 1b7db3d..55e93bb 100644
--- a/src/main/java/com/google/devtools/build/lib/rules/cpp/BUILD
+++ b/src/main/java/com/google/devtools/build/lib/rules/cpp/BUILD
@@ -17,6 +17,7 @@
         "//src/main/java/com/google/devtools/build/lib:io",
         "//src/main/java/com/google/devtools/build/lib:packages-internal",
         "//src/main/java/com/google/devtools/build/lib:shell",
+        "//src/main/java/com/google/devtools/build/lib:skylarkinterface",
         "//src/main/java/com/google/devtools/build/lib:util",
         "//src/main/java/com/google/devtools/build/lib:vfs",
         "//src/main/java/com/google/devtools/build/lib/actions",
diff --git a/src/main/java/com/google/devtools/build/lib/rules/cpp/CcSkylarkApiProvider.java b/src/main/java/com/google/devtools/build/lib/rules/cpp/CcSkylarkApiProvider.java
index 803f00b..3ad8721 100644
--- a/src/main/java/com/google/devtools/build/lib/rules/cpp/CcSkylarkApiProvider.java
+++ b/src/main/java/com/google/devtools/build/lib/rules/cpp/CcSkylarkApiProvider.java
@@ -19,8 +19,8 @@
 import com.google.devtools.build.lib.collect.nestedset.NestedSet;
 import com.google.devtools.build.lib.collect.nestedset.NestedSetBuilder;
 import com.google.devtools.build.lib.rules.SkylarkApiProvider;
-import com.google.devtools.build.lib.syntax.SkylarkCallable;
-import com.google.devtools.build.lib.syntax.SkylarkModule;
+import com.google.devtools.build.lib.skylarkinterface.SkylarkCallable;
+import com.google.devtools.build.lib.skylarkinterface.SkylarkModule;
 import com.google.devtools.build.lib.vfs.PathFragment;
 
 /**
diff --git a/src/main/java/com/google/devtools/build/lib/rules/cpp/CppConfiguration.java b/src/main/java/com/google/devtools/build/lib/rules/cpp/CppConfiguration.java
index 7ae7beb..2f4c9e6 100644
--- a/src/main/java/com/google/devtools/build/lib/rules/cpp/CppConfiguration.java
+++ b/src/main/java/com/google/devtools/build/lib/rules/cpp/CppConfiguration.java
@@ -46,8 +46,8 @@
 import com.google.devtools.build.lib.events.EventHandler;
 import com.google.devtools.build.lib.rules.cpp.CppConfigurationLoader.CppConfigurationParameters;
 import com.google.devtools.build.lib.rules.cpp.FdoSupport.FdoException;
-import com.google.devtools.build.lib.syntax.SkylarkCallable;
-import com.google.devtools.build.lib.syntax.SkylarkModule;
+import com.google.devtools.build.lib.skylarkinterface.SkylarkCallable;
+import com.google.devtools.build.lib.skylarkinterface.SkylarkModule;
 import com.google.devtools.build.lib.util.IncludeScanningUtil;
 import com.google.devtools.build.lib.util.Preconditions;
 import com.google.devtools.build.lib.vfs.FileSystemUtils;
diff --git a/src/main/java/com/google/devtools/build/lib/rules/java/JavaConfiguration.java b/src/main/java/com/google/devtools/build/lib/rules/java/JavaConfiguration.java
index cab2b8f..246253a 100644
--- a/src/main/java/com/google/devtools/build/lib/rules/java/JavaConfiguration.java
+++ b/src/main/java/com/google/devtools/build/lib/rules/java/JavaConfiguration.java
@@ -26,8 +26,8 @@
 import com.google.devtools.build.lib.concurrent.ThreadSafety.Immutable;
 import com.google.devtools.build.lib.events.Event;
 import com.google.devtools.build.lib.events.EventHandler;
-import com.google.devtools.build.lib.syntax.SkylarkCallable;
-import com.google.devtools.build.lib.syntax.SkylarkModule;
+import com.google.devtools.build.lib.skylarkinterface.SkylarkCallable;
+import com.google.devtools.build.lib.skylarkinterface.SkylarkModule;
 import com.google.devtools.common.options.TriState;
 
 import java.util.List;
diff --git a/src/main/java/com/google/devtools/build/lib/rules/java/JavaRuntimeClasspathProvider.java b/src/main/java/com/google/devtools/build/lib/rules/java/JavaRuntimeClasspathProvider.java
index e8eb6bc..d53256a 100644
--- a/src/main/java/com/google/devtools/build/lib/rules/java/JavaRuntimeClasspathProvider.java
+++ b/src/main/java/com/google/devtools/build/lib/rules/java/JavaRuntimeClasspathProvider.java
@@ -18,9 +18,8 @@
 import com.google.devtools.build.lib.analysis.TransitiveInfoProvider;
 import com.google.devtools.build.lib.collect.nestedset.NestedSet;
 import com.google.devtools.build.lib.concurrent.ThreadSafety.Immutable;
-
-import com.google.devtools.build.lib.syntax.SkylarkCallable;
-import com.google.devtools.build.lib.syntax.SkylarkModule;
+import com.google.devtools.build.lib.skylarkinterface.SkylarkCallable;
+import com.google.devtools.build.lib.skylarkinterface.SkylarkModule;
 
 /**
  * Provider for the runtime classpath contributions of a Java binary.
diff --git a/src/main/java/com/google/devtools/build/lib/rules/java/JavaSkylarkApiProvider.java b/src/main/java/com/google/devtools/build/lib/rules/java/JavaSkylarkApiProvider.java
index 11ec680..6b21ebe 100644
--- a/src/main/java/com/google/devtools/build/lib/rules/java/JavaSkylarkApiProvider.java
+++ b/src/main/java/com/google/devtools/build/lib/rules/java/JavaSkylarkApiProvider.java
@@ -19,8 +19,8 @@
 import com.google.devtools.build.lib.collect.nestedset.NestedSetBuilder;
 import com.google.devtools.build.lib.collect.nestedset.Order;
 import com.google.devtools.build.lib.rules.SkylarkApiProvider;
-import com.google.devtools.build.lib.syntax.SkylarkCallable;
-import com.google.devtools.build.lib.syntax.SkylarkModule;
+import com.google.devtools.build.lib.skylarkinterface.SkylarkCallable;
+import com.google.devtools.build.lib.skylarkinterface.SkylarkModule;
 
 /**
  * A class that exposes the Java providers to Skylark. It is intended to provide a
diff --git a/src/main/java/com/google/devtools/build/lib/rules/java/Jvm.java b/src/main/java/com/google/devtools/build/lib/rules/java/Jvm.java
index ba27ebc..b4fc376 100644
--- a/src/main/java/com/google/devtools/build/lib/rules/java/Jvm.java
+++ b/src/main/java/com/google/devtools/build/lib/rules/java/Jvm.java
@@ -19,8 +19,8 @@
 import com.google.devtools.build.lib.analysis.config.BuildConfiguration;
 import com.google.devtools.build.lib.cmdline.Label;
 import com.google.devtools.build.lib.concurrent.ThreadSafety.Immutable;
-import com.google.devtools.build.lib.syntax.SkylarkCallable;
-import com.google.devtools.build.lib.syntax.SkylarkModule;
+import com.google.devtools.build.lib.skylarkinterface.SkylarkCallable;
+import com.google.devtools.build.lib.skylarkinterface.SkylarkModule;
 import com.google.devtools.build.lib.util.OsUtils;
 import com.google.devtools.build.lib.util.Preconditions;
 import com.google.devtools.build.lib.vfs.PathFragment;
diff --git a/src/main/java/com/google/devtools/build/lib/rules/proto/ProtoSourcesProvider.java b/src/main/java/com/google/devtools/build/lib/rules/proto/ProtoSourcesProvider.java
index 6cacf43..d8624c4 100644
--- a/src/main/java/com/google/devtools/build/lib/rules/proto/ProtoSourcesProvider.java
+++ b/src/main/java/com/google/devtools/build/lib/rules/proto/ProtoSourcesProvider.java
@@ -20,8 +20,8 @@
 import com.google.devtools.build.lib.analysis.TransitiveInfoProvider;
 import com.google.devtools.build.lib.collect.nestedset.NestedSet;
 import com.google.devtools.build.lib.concurrent.ThreadSafety.Immutable;
-import com.google.devtools.build.lib.syntax.SkylarkCallable;
-import com.google.devtools.build.lib.syntax.SkylarkModule;
+import com.google.devtools.build.lib.skylarkinterface.SkylarkCallable;
+import com.google.devtools.build.lib.skylarkinterface.SkylarkModule;
 
 /**
  * Configured target classes that implement this class can contribute .proto files to the
diff --git a/src/main/java/com/google/devtools/build/lib/rules/python/PythonSourcesProvider.java b/src/main/java/com/google/devtools/build/lib/rules/python/PythonSourcesProvider.java
index 4662c46..b818987 100644
--- a/src/main/java/com/google/devtools/build/lib/rules/python/PythonSourcesProvider.java
+++ b/src/main/java/com/google/devtools/build/lib/rules/python/PythonSourcesProvider.java
@@ -17,8 +17,8 @@
 import com.google.devtools.build.lib.analysis.TransitiveInfoProvider;
 import com.google.devtools.build.lib.collect.nestedset.NestedSet;
 import com.google.devtools.build.lib.concurrent.ThreadSafety.Immutable;
-import com.google.devtools.build.lib.syntax.SkylarkCallable;
-import com.google.devtools.build.lib.syntax.SkylarkModule;
+import com.google.devtools.build.lib.skylarkinterface.SkylarkCallable;
+import com.google.devtools.build.lib.skylarkinterface.SkylarkModule;
 
 /**
  * A provider interface for configured targets that provide source files to
diff --git a/src/main/java/com/google/devtools/build/lib/skylarkinterface/README.md b/src/main/java/com/google/devtools/build/lib/skylarkinterface/README.md
new file mode 100644
index 0000000..ef59534
--- /dev/null
+++ b/src/main/java/com/google/devtools/build/lib/skylarkinterface/README.md
@@ -0,0 +1,4 @@
+# Skylark interface framework
+
+The classes in this package define annotations and interfaces used to enable
+Skylark access to data types and methods implemented in Java.
diff --git a/src/main/java/com/google/devtools/build/lib/syntax/SkylarkCallable.java b/src/main/java/com/google/devtools/build/lib/skylarkinterface/SkylarkCallable.java
similarity index 95%
rename from src/main/java/com/google/devtools/build/lib/syntax/SkylarkCallable.java
rename to src/main/java/com/google/devtools/build/lib/skylarkinterface/SkylarkCallable.java
index 4b90672..a2a720b 100644
--- a/src/main/java/com/google/devtools/build/lib/syntax/SkylarkCallable.java
+++ b/src/main/java/com/google/devtools/build/lib/skylarkinterface/SkylarkCallable.java
@@ -11,7 +11,7 @@
 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 // See the License for the specific language governing permissions and
 // limitations under the License.
-package com.google.devtools.build.lib.syntax;
+package com.google.devtools.build.lib.skylarkinterface;
 
 import java.lang.annotation.ElementType;
 import java.lang.annotation.Retention;
diff --git a/src/main/java/com/google/devtools/build/lib/syntax/SkylarkModule.java b/src/main/java/com/google/devtools/build/lib/skylarkinterface/SkylarkModule.java
similarity index 95%
rename from src/main/java/com/google/devtools/build/lib/syntax/SkylarkModule.java
rename to src/main/java/com/google/devtools/build/lib/skylarkinterface/SkylarkModule.java
index 95dff6b..92be3ba 100644
--- a/src/main/java/com/google/devtools/build/lib/syntax/SkylarkModule.java
+++ b/src/main/java/com/google/devtools/build/lib/skylarkinterface/SkylarkModule.java
@@ -11,7 +11,7 @@
 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 // See the License for the specific language governing permissions and
 // limitations under the License.
-package com.google.devtools.build.lib.syntax;
+package com.google.devtools.build.lib.skylarkinterface;
 
 import java.lang.annotation.ElementType;
 import java.lang.annotation.Retention;
diff --git a/src/main/java/com/google/devtools/build/lib/syntax/SkylarkPrintableValue.java b/src/main/java/com/google/devtools/build/lib/skylarkinterface/SkylarkPrintableValue.java
similarity index 94%
rename from src/main/java/com/google/devtools/build/lib/syntax/SkylarkPrintableValue.java
rename to src/main/java/com/google/devtools/build/lib/skylarkinterface/SkylarkPrintableValue.java
index b56d6d8..24353ce 100644
--- a/src/main/java/com/google/devtools/build/lib/syntax/SkylarkPrintableValue.java
+++ b/src/main/java/com/google/devtools/build/lib/skylarkinterface/SkylarkPrintableValue.java
@@ -11,7 +11,7 @@
 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 // See the License for the specific language governing permissions and
 // limitations under the License.
-package com.google.devtools.build.lib.syntax;
+package com.google.devtools.build.lib.skylarkinterface;
 
 /**
  * A Skylark value that is represented by {@code print()} differently than by {@code write()}.
diff --git a/src/main/java/com/google/devtools/build/lib/syntax/SkylarkSignature.java b/src/main/java/com/google/devtools/build/lib/skylarkinterface/SkylarkSignature.java
similarity index 97%
rename from src/main/java/com/google/devtools/build/lib/syntax/SkylarkSignature.java
rename to src/main/java/com/google/devtools/build/lib/skylarkinterface/SkylarkSignature.java
index 6654ed5..ffaab00 100644
--- a/src/main/java/com/google/devtools/build/lib/syntax/SkylarkSignature.java
+++ b/src/main/java/com/google/devtools/build/lib/skylarkinterface/SkylarkSignature.java
@@ -11,7 +11,7 @@
 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 // See the License for the specific language governing permissions and
 // limitations under the License.
-package com.google.devtools.build.lib.syntax;
+package com.google.devtools.build.lib.skylarkinterface;
 
 import java.lang.annotation.ElementType;
 import java.lang.annotation.Retention;
diff --git a/src/main/java/com/google/devtools/build/lib/syntax/SkylarkValue.java b/src/main/java/com/google/devtools/build/lib/skylarkinterface/SkylarkValue.java
similarity index 95%
rename from src/main/java/com/google/devtools/build/lib/syntax/SkylarkValue.java
rename to src/main/java/com/google/devtools/build/lib/skylarkinterface/SkylarkValue.java
index 4f58787..bf72821 100644
--- a/src/main/java/com/google/devtools/build/lib/syntax/SkylarkValue.java
+++ b/src/main/java/com/google/devtools/build/lib/skylarkinterface/SkylarkValue.java
@@ -12,7 +12,7 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-package com.google.devtools.build.lib.syntax;
+package com.google.devtools.build.lib.skylarkinterface;
 
 /**
  * Java objects that are also Skylark values.
diff --git a/src/main/java/com/google/devtools/build/lib/syntax/BaseFunction.java b/src/main/java/com/google/devtools/build/lib/syntax/BaseFunction.java
index cd8497b..662ac2f 100644
--- a/src/main/java/com/google/devtools/build/lib/syntax/BaseFunction.java
+++ b/src/main/java/com/google/devtools/build/lib/syntax/BaseFunction.java
@@ -20,6 +20,8 @@
 import com.google.common.collect.Ordering;
 import com.google.common.collect.Sets;
 import com.google.devtools.build.lib.events.Location;
+import com.google.devtools.build.lib.skylarkinterface.SkylarkSignature;
+import com.google.devtools.build.lib.skylarkinterface.SkylarkValue;
 import com.google.devtools.build.lib.syntax.SkylarkList.Tuple;
 import com.google.devtools.build.lib.syntax.Type.ConversionException;
 import com.google.devtools.build.lib.syntax.compiler.ByteCodeUtils;
diff --git a/src/main/java/com/google/devtools/build/lib/syntax/BuiltinFunction.java b/src/main/java/com/google/devtools/build/lib/syntax/BuiltinFunction.java
index 991f2ed..eb28b68 100644
--- a/src/main/java/com/google/devtools/build/lib/syntax/BuiltinFunction.java
+++ b/src/main/java/com/google/devtools/build/lib/syntax/BuiltinFunction.java
@@ -16,6 +16,7 @@
 import com.google.devtools.build.lib.events.Location;
 import com.google.devtools.build.lib.profiler.Profiler;
 import com.google.devtools.build.lib.profiler.ProfilerTask;
+import com.google.devtools.build.lib.skylarkinterface.SkylarkSignature;
 import com.google.devtools.build.lib.syntax.SkylarkType.SkylarkFunctionType;
 import com.google.devtools.build.lib.util.Preconditions;
 
diff --git a/src/main/java/com/google/devtools/build/lib/syntax/ClassObject.java b/src/main/java/com/google/devtools/build/lib/syntax/ClassObject.java
index 22eed90..359f4e4 100644
--- a/src/main/java/com/google/devtools/build/lib/syntax/ClassObject.java
+++ b/src/main/java/com/google/devtools/build/lib/syntax/ClassObject.java
@@ -21,6 +21,7 @@
 import com.google.common.collect.Sets.SetView;
 import com.google.devtools.build.lib.concurrent.ThreadSafety.Immutable;
 import com.google.devtools.build.lib.events.Location;
+import com.google.devtools.build.lib.skylarkinterface.SkylarkModule;
 import com.google.devtools.build.lib.util.Preconditions;
 
 import java.io.Serializable;
diff --git a/src/main/java/com/google/devtools/build/lib/syntax/EvalUtils.java b/src/main/java/com/google/devtools/build/lib/syntax/EvalUtils.java
index 205075c..d94d10e 100644
--- a/src/main/java/com/google/devtools/build/lib/syntax/EvalUtils.java
+++ b/src/main/java/com/google/devtools/build/lib/syntax/EvalUtils.java
@@ -21,6 +21,8 @@
 import com.google.devtools.build.lib.collect.nestedset.NestedSet;
 import com.google.devtools.build.lib.concurrent.ThreadSafety.Immutable;
 import com.google.devtools.build.lib.events.Location;
+import com.google.devtools.build.lib.skylarkinterface.SkylarkModule;
+import com.google.devtools.build.lib.skylarkinterface.SkylarkValue;
 import com.google.devtools.build.lib.syntax.compiler.ByteCodeUtils;
 import com.google.devtools.build.lib.util.Preconditions;
 import com.google.devtools.build.lib.vfs.PathFragment;
diff --git a/src/main/java/com/google/devtools/build/lib/syntax/FuncallExpression.java b/src/main/java/com/google/devtools/build/lib/syntax/FuncallExpression.java
index e5678cb..64ce78a 100644
--- a/src/main/java/com/google/devtools/build/lib/syntax/FuncallExpression.java
+++ b/src/main/java/com/google/devtools/build/lib/syntax/FuncallExpression.java
@@ -25,6 +25,8 @@
 import com.google.common.collect.ImmutableMap;
 import com.google.common.collect.Lists;
 import com.google.devtools.build.lib.events.Location;
+import com.google.devtools.build.lib.skylarkinterface.SkylarkCallable;
+import com.google.devtools.build.lib.skylarkinterface.SkylarkModule;
 import com.google.devtools.build.lib.syntax.EvalException.EvalExceptionWithJavaCause;
 import com.google.devtools.build.lib.syntax.compiler.ByteCodeMethodCalls;
 import com.google.devtools.build.lib.syntax.compiler.ByteCodeUtils;
diff --git a/src/main/java/com/google/devtools/build/lib/syntax/GlobList.java b/src/main/java/com/google/devtools/build/lib/syntax/GlobList.java
index 00b2c9a..a95c7de 100644
--- a/src/main/java/com/google/devtools/build/lib/syntax/GlobList.java
+++ b/src/main/java/com/google/devtools/build/lib/syntax/GlobList.java
@@ -20,6 +20,8 @@
 import com.google.common.collect.ImmutableList;
 import com.google.common.collect.ImmutableList.Builder;
 import com.google.common.collect.Iterables;
+import com.google.devtools.build.lib.skylarkinterface.SkylarkModule;
+import com.google.devtools.build.lib.skylarkinterface.SkylarkValue;
 import com.google.devtools.build.lib.util.Preconditions;
 
 import java.util.ArrayList;
diff --git a/src/main/java/com/google/devtools/build/lib/syntax/MethodLibrary.java b/src/main/java/com/google/devtools/build/lib/syntax/MethodLibrary.java
index 2a64a0e..3c272ac 100644
--- a/src/main/java/com/google/devtools/build/lib/syntax/MethodLibrary.java
+++ b/src/main/java/com/google/devtools/build/lib/syntax/MethodLibrary.java
@@ -24,10 +24,12 @@
 import com.google.devtools.build.lib.collect.nestedset.Order;
 import com.google.devtools.build.lib.events.Event;
 import com.google.devtools.build.lib.events.Location;
+import com.google.devtools.build.lib.skylarkinterface.SkylarkModule;
+import com.google.devtools.build.lib.skylarkinterface.SkylarkSignature;
+import com.google.devtools.build.lib.skylarkinterface.SkylarkSignature.Param;
 import com.google.devtools.build.lib.syntax.ClassObject.SkylarkClassObject;
 import com.google.devtools.build.lib.syntax.SkylarkList.MutableList;
 import com.google.devtools.build.lib.syntax.SkylarkList.Tuple;
-import com.google.devtools.build.lib.syntax.SkylarkSignature.Param;
 import com.google.devtools.build.lib.syntax.Type.ConversionException;
 
 import java.util.ArrayList;
diff --git a/src/main/java/com/google/devtools/build/lib/syntax/Printer.java b/src/main/java/com/google/devtools/build/lib/syntax/Printer.java
index 26e6fda..98a483b 100644
--- a/src/main/java/com/google/devtools/build/lib/syntax/Printer.java
+++ b/src/main/java/com/google/devtools/build/lib/syntax/Printer.java
@@ -16,6 +16,8 @@
 import com.google.common.collect.ImmutableList;
 import com.google.common.collect.ImmutableSet;
 import com.google.common.collect.Iterables;
+import com.google.devtools.build.lib.skylarkinterface.SkylarkPrintableValue;
+import com.google.devtools.build.lib.skylarkinterface.SkylarkValue;
 import com.google.devtools.build.lib.syntax.SkylarkList.Tuple;
 import com.google.devtools.build.lib.vfs.PathFragment;
 
diff --git a/src/main/java/com/google/devtools/build/lib/syntax/Runtime.java b/src/main/java/com/google/devtools/build/lib/syntax/Runtime.java
index ff13a25..09d0abd 100644
--- a/src/main/java/com/google/devtools/build/lib/syntax/Runtime.java
+++ b/src/main/java/com/google/devtools/build/lib/syntax/Runtime.java
@@ -16,6 +16,9 @@
 
 import com.google.common.collect.ImmutableSet;
 import com.google.devtools.build.lib.concurrent.ThreadSafety.Immutable;
+import com.google.devtools.build.lib.skylarkinterface.SkylarkModule;
+import com.google.devtools.build.lib.skylarkinterface.SkylarkSignature;
+import com.google.devtools.build.lib.skylarkinterface.SkylarkValue;
 import com.google.devtools.build.lib.syntax.compiler.ByteCodeUtils;
 import com.google.devtools.build.lib.util.Preconditions;
 
diff --git a/src/main/java/com/google/devtools/build/lib/syntax/SkylarkList.java b/src/main/java/com/google/devtools/build/lib/syntax/SkylarkList.java
index 74031d3..97cdd4e 100644
--- a/src/main/java/com/google/devtools/build/lib/syntax/SkylarkList.java
+++ b/src/main/java/com/google/devtools/build/lib/syntax/SkylarkList.java
@@ -18,6 +18,8 @@
 import com.google.common.collect.Iterables;
 import com.google.devtools.build.lib.concurrent.ThreadSafety.Immutable;
 import com.google.devtools.build.lib.events.Location;
+import com.google.devtools.build.lib.skylarkinterface.SkylarkModule;
+import com.google.devtools.build.lib.skylarkinterface.SkylarkValue;
 import com.google.devtools.build.lib.syntax.Mutability.Freezable;
 import com.google.devtools.build.lib.syntax.Mutability.MutabilityException;
 
diff --git a/src/main/java/com/google/devtools/build/lib/syntax/SkylarkModuleNameResolver.java b/src/main/java/com/google/devtools/build/lib/syntax/SkylarkModuleNameResolver.java
index 5941354..0f7f23a 100644
--- a/src/main/java/com/google/devtools/build/lib/syntax/SkylarkModuleNameResolver.java
+++ b/src/main/java/com/google/devtools/build/lib/syntax/SkylarkModuleNameResolver.java
@@ -13,6 +13,8 @@
 // limitations under the License.
 package com.google.devtools.build.lib.syntax;
 
+import com.google.devtools.build.lib.skylarkinterface.SkylarkModule;
+
 /**
  * Helper class that resolves the name of classes with SkylarkModule annotation.
  */
diff --git a/src/main/java/com/google/devtools/build/lib/syntax/SkylarkNestedSet.java b/src/main/java/com/google/devtools/build/lib/syntax/SkylarkNestedSet.java
index 2154fd9..b00413c 100644
--- a/src/main/java/com/google/devtools/build/lib/syntax/SkylarkNestedSet.java
+++ b/src/main/java/com/google/devtools/build/lib/syntax/SkylarkNestedSet.java
@@ -20,6 +20,8 @@
 import com.google.devtools.build.lib.collect.nestedset.Order;
 import com.google.devtools.build.lib.concurrent.ThreadSafety.Immutable;
 import com.google.devtools.build.lib.events.Location;
+import com.google.devtools.build.lib.skylarkinterface.SkylarkModule;
+import com.google.devtools.build.lib.skylarkinterface.SkylarkValue;
 import com.google.devtools.build.lib.util.Preconditions;
 
 import java.util.ArrayList;
diff --git a/src/main/java/com/google/devtools/build/lib/syntax/SkylarkSignatureProcessor.java b/src/main/java/com/google/devtools/build/lib/syntax/SkylarkSignatureProcessor.java
index 7271428..c27da11 100644
--- a/src/main/java/com/google/devtools/build/lib/syntax/SkylarkSignatureProcessor.java
+++ b/src/main/java/com/google/devtools/build/lib/syntax/SkylarkSignatureProcessor.java
@@ -13,8 +13,9 @@
 // limitations under the License.
 package com.google.devtools.build.lib.syntax;
 
+import com.google.devtools.build.lib.skylarkinterface.SkylarkSignature;
+import com.google.devtools.build.lib.skylarkinterface.SkylarkSignature.Param;
 import com.google.devtools.build.lib.syntax.BuiltinFunction.ExtraArgKind;
-import com.google.devtools.build.lib.syntax.SkylarkSignature.Param;
 import com.google.devtools.build.lib.util.Preconditions;
 
 import java.lang.reflect.Field;