Better names for declared providers-related classes.

Follows
https://docs.google.com/document/d/1aAIVWvHPERDz2cv_PCFGwr8dvh5FcAkENFoRsNS4clk/.

RELNOTES: None.
PiperOrigin-RevId: 163728291

11 files changed, 186 insertions, 232 deletions

diff --git a/src/main/java/com/google/devtools/build/lib/packages/AdvertisedProviderSet.java b/src/main/java/com/google/devtools/build/lib/packages/AdvertisedProviderSet.java
index 1f1ddd6d85..3f8686b16a 100644
--- a/src/main/java/com/google/devtools/build/lib/packages/AdvertisedProviderSet.java
+++ b/src/main/java/com/google/devtools/build/lib/packages/AdvertisedProviderSet.java
@@ -164,7 +164,7 @@ public final class AdvertisedProviderSet {
       return this;
     }
 
-    public Builder addSkylark(ClassObjectConstructor.Key id) {
+    public Builder addSkylark(Provider.Key id) {
       skylarkProviders.add(SkylarkProviderIdentifier.forKey(id));
       return this;
     }
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 7114040300..bd3605627f 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
@@ -950,18 +950,18 @@ public final class Attribute implements Comparable<Attribute> {
 
     /**
      * If this is a label or label-list attribute, then this sets the allowed rule types with
-     * warning for the labels occurring in the attribute. This must be a disjoint set from
-     * {@link #allowedRuleClasses}.
+     * warning for the labels occurring in the attribute. This must be a disjoint set from {@link
+     * #allowedRuleClasses}.
      *
      * <p>If the attribute contains Labels of any other rule type (other than this or those set in
-     * allowedRuleClasses()) and they fulfill {@link #getRequiredProviders()}}, the build
-     * continues without error. Else the build fails during analysis.
+     * allowedRuleClasses()) and they fulfill {@link #getRequiredProviders()}}, the build continues
+     * without error. Else the build fails during analysis.
      *
-     * <p>If neither this nor {@link #allowedRuleClassesForLabels} is set, only rules that
-     * fulfill {@link #getRequiredProviders()} build without error.
+     * <p>If neither this nor {@link #allowedRuleClassesForLabels} is set, only rules that fulfill
+     * {@link #getRequiredProviders()} build without error.
      *
-     * <p>This only works on a per-target basis, not on a per-file basis; with other words, it
-     * works for 'deps' attributes, but not 'srcs' attributes.
+     * <p>This only works on a per-target basis, not on a per-file basis; with other words, it works
+     * for 'deps' attributes, but not 'srcs' attributes.
      */
     public Builder<TYPE> allowedRuleClassesWithWarning(String... allowedRuleClasses) {
       return allowedRuleClassesWithWarning(ImmutableSet.copyOf(allowedRuleClasses));
@@ -1514,7 +1514,7 @@ public final class Attribute implements Comparable<Attribute> {
     private Object invokeCallback(Map<String, Object> attrValues)
         throws EvalException, InterruptedException {
       ClassObject attrs =
-          NativeClassObjectConstructor.STRUCT.create(
+          NativeProvider.STRUCT.create(
               attrValues, "No such regular (non computed) attribute '%s'.");
       Object result = callback.call(attrs);
       try {
@@ -1792,19 +1792,16 @@ public final class Attribute implements Comparable<Attribute> {
   private final ImmutableList<RuleAspect<?>> aspects;
 
   /**
-   * Constructs a rule attribute with the specified name, type and default
-   * value.
+   * Constructs a rule attribute with the specified name, type and default value.
    *
    * @param name the name of the attribute
    * @param type the type of the attribute
-   * @param defaultValue the default value to use for this attribute if none is
-   *        specified in rule declaration in the BUILD file. Must be null, or of
-   *        type "type". May be an instance of ComputedDefault, in which case
-   *        its getDefault() method must return an instance of "type", or null.
-   *        Must be immutable.
-   * @param configTransition the configuration transition for this attribute
-   *        (which must be of type LABEL, LABEL_LIST, NODEP_LABEL or
-   *        NODEP_LABEL_LIST).
+   * @param defaultValue the default value to use for this attribute if none is specified in rule
+   *     declaration in the BUILD file. Must be null, or of type "type". May be an instance of
+   *     ComputedDefault, in which case its getDefault() method must return an instance of "type",
+   *     or null. Must be immutable.
+   * @param configTransition the configuration transition for this attribute (which must be of type
+   *     LABEL, LABEL_LIST, NODEP_LABEL or NODEP_LABEL_LIST).
    */
   private Attribute(
       String name,
diff --git a/src/main/java/com/google/devtools/build/lib/packages/ImplicitOutputsFunction.java b/src/main/java/com/google/devtools/build/lib/packages/ImplicitOutputsFunction.java
index 525055476c..ecb9cf862f 100644
--- a/src/main/java/com/google/devtools/build/lib/packages/ImplicitOutputsFunction.java
+++ b/src/main/java/com/google/devtools/build/lib/packages/ImplicitOutputsFunction.java
@@ -94,10 +94,11 @@ public abstract class ImplicitOutputsFunction {
           attrValues.put(attrName, value == null ? Runtime.NONE : value);
         }
       }
-      ClassObject attrs = NativeClassObjectConstructor.STRUCT.create(
-          attrValues,
-          "Attribute '%s' either doesn't exist "
-          + "or uses a select() (i.e. could have multiple values)");
+      ClassObject attrs =
+          NativeProvider.STRUCT.create(
+              attrValues,
+              "Attribute '%s' either doesn't exist "
+                  + "or uses a select() (i.e. could have multiple values)");
       try {
         ImmutableMap.Builder<String, String> builder = ImmutableMap.builder();
         for (Map.Entry<String, String> entry : castMap(callback.call(attrs),
diff --git a/src/main/java/com/google/devtools/build/lib/packages/SkylarkClassObject.java b/src/main/java/com/google/devtools/build/lib/packages/Info.java
index fa84c3eff6..059c55efb2 100644
--- a/src/main/java/com/google/devtools/build/lib/packages/SkylarkClassObject.java
+++ b/src/main/java/com/google/devtools/build/lib/packages/Info.java
@@ -21,7 +21,6 @@ import com.google.common.collect.Ordering;
 import com.google.common.collect.Sets;
 import com.google.common.collect.Sets.SetView;
 import com.google.devtools.build.lib.events.Location;
-import com.google.devtools.build.lib.packages.NativeClassObjectConstructor.StructConstructor;
 import com.google.devtools.build.lib.skylarkinterface.SkylarkModule;
 import com.google.devtools.build.lib.skylarkinterface.SkylarkModuleCategory;
 import com.google.devtools.build.lib.skylarkinterface.SkylarkPrinter;
@@ -40,7 +39,7 @@ import java.util.List;
 import java.util.Map;
 import javax.annotation.Nullable;
 
-/** An implementation class of ClassObject for structs created in Skylark code. */
+/** Represents information provided by a {@link Provider}. */
 @SkylarkModule(
   name = "struct",
   category = SkylarkModuleCategory.BUILTIN,
@@ -49,53 +48,48 @@ import javax.annotation.Nullable;
           + "See the global <a href=\"globals.html#struct\">struct</a> function "
           + "for more details."
 )
-public class SkylarkClassObject implements ClassObject, SkylarkValue, Concatable, Serializable {
-  private final ClassObjectConstructor constructor;
+public class Info implements ClassObject, SkylarkValue, Concatable, Serializable {
+  private final Provider provider;
   private final ImmutableMap<String, Object> values;
   private final Location creationLoc;
   private final String errorMessage;
 
   /** Creates an empty struct with a given location. */
-  public SkylarkClassObject(ClassObjectConstructor constructor, Location location) {
-    this.constructor = constructor;
+  public Info(Provider provider, Location location) {
+    this.provider = provider;
     this.values = ImmutableMap.of();
     this.creationLoc = location;
-    this.errorMessage = constructor.getErrorMessageFormatForInstances();
+    this.errorMessage = provider.getErrorMessageFormatForInstances();
   }
 
-  /**
-   * Creates a built-in struct (i.e. without creation loc).
-   */
-  public SkylarkClassObject(ClassObjectConstructor constructor,
-      Map<String, Object> values) {
-    this.constructor = constructor;
+  /** Creates a built-in struct (i.e. without creation loc). */
+  public Info(Provider provider, Map<String, Object> values) {
+    this.provider = provider;
     this.values = copyValues(values);
     this.creationLoc = null;
-    this.errorMessage = constructor.getErrorMessageFormatForInstances();
+    this.errorMessage = provider.getErrorMessageFormatForInstances();
   }
 
   /**
    * Creates a built-in struct (i.e. without creation loc).
    *
-   * Allows to supply a specific error message.
-   * Only used in {@link StructConstructor#create(Map, String)}
-   * If you need to override an error message, preferred way is to create a specific
-   * {@link NativeClassObjectConstructor}.
+   * <p>Allows to supply a specific error message. Only used in
+   * {@link com.google.devtools.build.lib.packages.NativeProvider.StructConstructor#create(Map,
+   * String)} If you need to override an error message, preferred way is to create a specific {@link
+   * NativeProvider}.
    */
-  SkylarkClassObject(ClassObjectConstructor constructor,
-      Map<String, Object> values, String errorMessage) {
-    this.constructor = constructor;
+  Info(Provider provider, Map<String, Object> values, String errorMessage) {
+    this.provider = provider;
     this.values = copyValues(values);
     this.creationLoc = null;
     this.errorMessage = Preconditions.checkNotNull(errorMessage);
   }
 
-  public SkylarkClassObject(ClassObjectConstructor constructor,
-      Map<String, Object> values, Location creationLoc) {
-    this.constructor = constructor;
+  public Info(Provider provider, Map<String, Object> values, Location creationLoc) {
+    this.provider = provider;
     this.values = copyValues(values);
     this.creationLoc = Preconditions.checkNotNull(creationLoc);
-    this.errorMessage = constructor.getErrorMessageFormatForInstances();
+    this.errorMessage = provider.getErrorMessageFormatForInstances();
   }
 
   // Ensure that values are all acceptable to Skylark before to stuff them in a ClassObject
@@ -117,9 +111,7 @@ public class SkylarkClassObject implements ClassObject, SkylarkValue, Concatable
     return values.containsKey(name);
   }
 
-  /**
-   *  Returns a value and try to cast it into specified type
-   */
+  /** Returns a value and try to cast it into specified type */
   public <TYPE> TYPE getValue(String key, Class<TYPE> type) throws EvalException {
     Object obj = values.get(key);
     if (obj == null) {
@@ -135,17 +127,16 @@ public class SkylarkClassObject implements ClassObject, SkylarkValue, Concatable
   }
 
   public Location getCreationLoc() {
-    return Preconditions.checkNotNull(creationLoc,
-        "This struct was not created in a Skylark code");
+    return Preconditions.checkNotNull(creationLoc, "This struct was not created in a Skylark code");
   }
 
   @Override
   public Concatter getConcatter() {
     return StructConcatter.INSTANCE;
   }
-  
-  public ClassObjectConstructor getConstructor() {
-    return constructor;
+
+  public Provider getProvider() {
+    return provider;
   }
 
   @Nullable
@@ -159,27 +150,25 @@ public class SkylarkClassObject implements ClassObject, SkylarkValue, Concatable
     private StructConcatter() {}
 
     @Override
-    public SkylarkClassObject concat(
-        Concatable left, Concatable right, Location loc) throws EvalException {
-      SkylarkClassObject lval = (SkylarkClassObject) left;
-      SkylarkClassObject rval = (SkylarkClassObject) right;
-      if (!lval.constructor.equals(rval.constructor)) {
-        throw new EvalException(loc,
-            String.format("Cannot concat %s with %s",
-                lval.constructor.getPrintableName(),
-                rval.constructor.getPrintableName()));
+    public Info concat(Concatable left, Concatable right, Location loc) throws EvalException {
+      Info lval = (Info) left;
+      Info rval = (Info) right;
+      if (!lval.provider.equals(rval.provider)) {
+        throw new EvalException(
+            loc,
+            String.format(
+                "Cannot concat %s with %s",
+                lval.provider.getPrintableName(), rval.provider.getPrintableName()));
       }
-      SetView<String> commonFields = Sets
-          .intersection(lval.values.keySet(), rval.values.keySet());
+      SetView<String> commonFields = Sets.intersection(lval.values.keySet(), rval.values.keySet());
       if (!commonFields.isEmpty()) {
-        throw new EvalException(loc, "Cannot concat structs with common field(s): "
-            + Joiner.on(",").join(commonFields));
+        throw new EvalException(
+            loc,
+            "Cannot concat structs with common field(s): " + Joiner.on(",").join(commonFields));
       }
-      return new SkylarkClassObject(lval.constructor,
-          ImmutableMap.<String, Object>builder()
-              .putAll(lval.values)
-              .putAll(rval.values)
-              .build(),
+      return new Info(
+          lval.provider,
+          ImmutableMap.<String, Object>builder().putAll(lval.values).putAll(rval.values).build(),
           loc);
     }
   }
@@ -194,8 +183,8 @@ public class SkylarkClassObject implements ClassObject, SkylarkValue, Concatable
 
   @Override
   public boolean isImmutable() {
-    // If the constructor is not yet exported the hash code of the object is subject to change
-    if (!constructor.isExported()) {
+    // If the provider is not yet exported the hash code of the object is subject to change
+    if (!provider.isExported()) {
       return false;
     }
     for (Object item : values.values()) {
@@ -208,14 +197,14 @@ public class SkylarkClassObject implements ClassObject, SkylarkValue, Concatable
 
   @Override
   public boolean equals(Object otherObject) {
-    if (!(otherObject instanceof SkylarkClassObject)) {
+    if (!(otherObject instanceof Info)) {
       return false;
     }
-    SkylarkClassObject other = (SkylarkClassObject) otherObject;
+    Info other = (Info) otherObject;
     if (this == other) {
       return true;
     }
-    if (!this.constructor.equals(other.constructor)) {
+    if (!this.provider.equals(other.provider)) {
       return false;
     }
     // Compare objects' keys and values
@@ -235,7 +224,7 @@ public class SkylarkClassObject implements ClassObject, SkylarkValue, Concatable
     List<String> keys = new ArrayList<>(getKeys());
     Collections.sort(keys);
     List<Object> objectsToHash = new ArrayList<>();
-    objectsToHash.add(constructor);
+    objectsToHash.add(provider);
     for (String key : keys) {
       objectsToHash.add(key);
       objectsToHash.add(getValue(key));
@@ -267,7 +256,7 @@ public class SkylarkClassObject implements ClassObject, SkylarkValue, Concatable
   @Override
   public void reprLegacy(SkylarkPrinter printer) {
     boolean first = true;
-    printer.append(constructor.getPrintableName());
+    printer.append(provider.getPrintableName());
     printer.append("(");
     // Sort by key to ensure deterministic output.
     for (String key : Ordering.natural().sortedCopy(values.keySet())) {
diff --git a/src/main/java/com/google/devtools/build/lib/packages/NativeClassObjectConstructor.java b/src/main/java/com/google/devtools/build/lib/packages/NativeProvider.java
index 6bcce0fc00..f6f7d8ecb6 100644
--- a/src/main/java/com/google/devtools/build/lib/packages/NativeClassObjectConstructor.java
+++ b/src/main/java/com/google/devtools/build/lib/packages/NativeProvider.java
@@ -23,31 +23,27 @@ import java.util.Map;
 import javax.annotation.Nullable;
 
 /**
- * Base class for declared providers {@see ClassObjectConstructor} defined in native code.
+ * Base class for declared providers {@see Provider} defined in native code.
  *
- * <p>Every non-abstract derived class of {@link NativeClassObjectConstructor} corresponds to a
- * single declared provider. This is enforced by final {@link #equals(Object)} and {@link
- * #hashCode()}.
+ * <p>Every non-abstract derived class of {@link NativeProvider} corresponds to a single declared
+ * provider. This is enforced by final {@link #equals(Object)} and {@link #hashCode()}.
  *
  * <p>Typical implementation of a non-constructable from Skylark declared provider is as follows:
  *
  * <pre>
- *     public static final ClassObjectConstructor CC_LINK_PARAMS =
- *       new NativeClassObjectConstructor("link_params") { };
+ *     public static final Provider CC_LINK_PARAMS =
+ *       new NativeProvider("link_params") { };
  * </pre>
  *
  * To allow construction from Skylark and custom construction logic, override {@link
  * #createInstanceFromSkylark(Object[], Location)} (see {@link #STRUCT} for an example.
  */
 @Immutable
-public abstract class NativeClassObjectConstructor<VALUE extends SkylarkClassObject>
-    extends ClassObjectConstructor {
+public abstract class NativeProvider<VALUE extends Info> extends Provider {
   private final NativeKey key;
   private final String errorMessageForInstances;
 
-  /**
-   * "struct" function.
-   */
+  /** "struct" function. */
   public static final StructConstructor STRUCT = new StructConstructor();
 
   private final Class<VALUE> valueClass;
@@ -57,13 +53,11 @@ public abstract class NativeClassObjectConstructor<VALUE extends SkylarkClassObj
   }
 
   /**
-   * Implement this to mark that a native provider should be exported with
-   * certain name to Skylark.
-   * Broken: only works for rules, not for aspects.
-   * DO NOT USE FOR NEW CODE!
+   * Implement this to mark that a native provider should be exported with certain name to Skylark.
+   * Broken: only works for rules, not for aspects. DO NOT USE FOR NEW CODE!
    *
-   * Use native declared providers mechanism
-   * exclusively to expose providers to both native and Skylark code.
+   * <p>Use native declared providers mechanism exclusively to expose providers to both native and
+   * Skylark code.
    */
   @Deprecated
   public static interface WithLegacySkylarkName {
@@ -75,36 +69,35 @@ public abstract class NativeClassObjectConstructor<VALUE extends SkylarkClassObj
    *
    * <p>Singleton, instance is {@link #STRUCT}.
    */
-  public static final class StructConstructor
-      extends NativeClassObjectConstructor<SkylarkClassObject> {
+  public static final class StructConstructor extends NativeProvider<Info> {
     private StructConstructor() {
-      super(SkylarkClassObject.class, "struct");
+      super(Info.class, "struct");
     }
 
     @Override
-    protected SkylarkClassObject createInstanceFromSkylark(Object[] args, Location loc) {
+    protected Info createInstanceFromSkylark(Object[] args, Location loc) {
       @SuppressWarnings("unchecked")
       Map<String, Object> kwargs = (Map<String, Object>) args[0];
-      return new SkylarkClassObject(this, kwargs, loc);
+      return new Info(this, kwargs, loc);
     }
 
-    public SkylarkClassObject create(Map<String, Object> values, String message) {
-      return new SkylarkClassObject(this, values, message);
+    public Info create(Map<String, Object> values, String message) {
+      return new Info(this, values, message);
     }
 
-    public SkylarkClassObject create(Location loc) {
-      return new SkylarkClassObject(this, loc);
+    public Info create(Location loc) {
+      return new Info(this, loc);
     }
   }
 
   private static final FunctionSignature.WithValues<Object, SkylarkType> SIGNATURE =
       FunctionSignature.WithValues.create(FunctionSignature.KWARGS);
 
-  protected NativeClassObjectConstructor(Class<VALUE> clazz, String name) {
+  protected NativeProvider(Class<VALUE> clazz, String name) {
     this(clazz, name, SIGNATURE);
   }
 
-  protected NativeClassObjectConstructor(
+  protected NativeProvider(
       Class<VALUE> valueClass,
       String name,
       FunctionSignature.WithValues<Object, SkylarkType> signature) {
@@ -117,8 +110,8 @@ public abstract class NativeClassObjectConstructor<VALUE extends SkylarkClassObj
   /**
    * equals() implements singleton class semantics.
    *
-   * Every non-abstract derived class of {@link NativeClassObjectConstructor}
-   * corresponds to a single declared provider.
+   * <p>Every non-abstract derived class of {@link NativeProvider} corresponds to a single declared
+   * provider.
    */
   @Override
   public final boolean equals(@Nullable Object other) {
@@ -128,8 +121,8 @@ public abstract class NativeClassObjectConstructor<VALUE extends SkylarkClassObj
   /**
    * hashCode() implements singleton class semantics.
    *
-   * Every non-abstract derived class of {@link NativeClassObjectConstructor}
-   * corresponds to a single declared provider.
+   * <p>Every non-abstract derived class of {@link NativeProvider} corresponds to a single declared
+   * provider.
    */
   @Override
   public final int hashCode() {
@@ -157,10 +150,9 @@ public abstract class NativeClassObjectConstructor<VALUE extends SkylarkClassObj
   }
 
   @Override
-  protected SkylarkClassObject createInstanceFromSkylark(Object[] args, Location loc)
-      throws EvalException {
-    throw new EvalException(loc,
-        String.format("'%s' cannot be constructed from Skylark", getPrintableName()));
+  protected Info createInstanceFromSkylark(Object[] args, Location loc) throws EvalException {
+    throw new EvalException(
+        loc, String.format("'%s' cannot be constructed from Skylark", getPrintableName()));
   }
 
   public static Pair<String, String> getSerializedRepresentationForNativeKey(NativeKey key) {
@@ -169,26 +161,24 @@ public abstract class NativeClassObjectConstructor<VALUE extends SkylarkClassObj
 
   public static NativeKey getNativeKeyFromSerializedRepresentation(Pair<String, String> serialized)
       throws ClassNotFoundException {
-    Class<? extends NativeClassObjectConstructor> aClass =
-        Class.forName(serialized.second).asSubclass(NativeClassObjectConstructor.class);
+    Class<? extends NativeProvider> aClass =
+        Class.forName(serialized.second).asSubclass(NativeProvider.class);
     return new NativeKey(serialized.first, aClass);
   }
 
   /**
-   * A serializable representation of {@link NativeClassObjectConstructor}.
+   * A serializable representation of {@link NativeProvider}.
    *
-   * Just a wrapper around its class.
+   * <p>Just a wrapper around its class.
    */
   // todo(vladmos,dslomov): when we allow declared providers in `requiredProviders`,
   // we will need to serialize this somehow.
   @Immutable
   public static final class NativeKey extends Key {
     private final String name;
-    private final Class<? extends NativeClassObjectConstructor> aClass;
+    private final Class<? extends NativeProvider> aClass;
 
-    private NativeKey(
-        String name,
-        Class<? extends NativeClassObjectConstructor> aClass) {
+    private NativeKey(String name, Class<? extends NativeProvider> aClass) {
       this.name = name;
       this.aClass = aClass;
     }
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 1ca18e2129..b03acc5610 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
@@ -1592,8 +1592,7 @@ public final class PackageFactory {
         builder.put(function.getName(), function);
       }
     }
-    return NativeClassObjectConstructor.STRUCT.create(
-        builder.build(), "no native function or rule '%s'");
+    return NativeProvider.STRUCT.create(builder.build(), "no native function or rule '%s'");
   }
 
   /** @param fakeEnv specify if we declare no-op functions, or real functions. */
diff --git a/src/main/java/com/google/devtools/build/lib/packages/ClassObjectConstructor.java b/src/main/java/com/google/devtools/build/lib/packages/Provider.java
index 2356d7190a..b497b76131 100644
--- a/src/main/java/com/google/devtools/build/lib/packages/ClassObjectConstructor.java
+++ b/src/main/java/com/google/devtools/build/lib/packages/Provider.java
@@ -25,16 +25,16 @@ import com.google.devtools.build.lib.syntax.SkylarkType;
 import javax.annotation.Nullable;
 
 /**
- * Declared Provider (a constructor for {@link SkylarkClassObject}).
+ * Declared Provider (a constructor for {@link Info}).
  *
- * <p>Declared providers can be declared either natively ({@link NativeClassObjectConstructor} or in
- * Skylark {@link SkylarkClassObjectConstructor}.
+ * <p>Declared providers can be declared either natively ({@link NativeProvider} or in Skylark
+ * {@link SkylarkProvider}.
  *
- * <p>{@link ClassObjectConstructor} serves both as "type identifier" for declared provider
- * instances and as a function that can be called to construct a provider.
+ * <p>{@link Provider} serves both as "type identifier" for declared provider instances and as a
+ * function that can be called to construct a provider.
  *
- * <p>Prefer to use {@link Key} as a serializable identifier of {@link ClassObjectConstructor}. In
- * particular, {@link Key} should be used in all data structures exposed to Skyframe.
+ * <p>Prefer to use {@link Key} as a serializable identifier of {@link Provider}. In particular,
+ * {@link Key} should be used in all data structures exposed to Skyframe.
  */
 @SkylarkModule(
   name = "Provider",
@@ -60,35 +60,29 @@ import javax.annotation.Nullable;
           + "<a href=\"globals.html#provider\">provider</a> function."
 )
 @Immutable
-public abstract class ClassObjectConstructor extends BaseFunction {
+public abstract class Provider extends BaseFunction {
 
-  protected ClassObjectConstructor(String name,
-      FunctionSignature.WithValues<Object, SkylarkType> signature,
-      Location location) {
+  protected Provider(
+      String name, FunctionSignature.WithValues<Object, SkylarkType> signature, Location location) {
     super(name, signature, location);
   }
 
   /**
-   * Has this {@link ClassObjectConstructor} been exported?
-   * All native constructors are always exported. Skylark constructors are exported
-   * if they are assigned to top-level name in a Skylark module.
+   * Has this {@link Provider} been exported? All native providers are always exported. Skylark
+   * providers are exported if they are assigned to top-level name in a Skylark module.
    */
   public abstract boolean isExported();
 
-  /**
-   * Returns a serializable representation of this constructor.
-   */
+  /** Returns a serializable representation of this {@link Provider}. */
   public abstract Key getKey();
 
-  /**
-   * Returns a name of this constructor that should be used in error messages.
-   */
+  /** Returns a name of this {@link Provider} that should be used in error messages. */
   public abstract String getPrintableName();
 
   /**
    * Returns an error message format for instances.
    *
-   * Must contain one '%s' placeholder for field name.
+   * <p>Must contain one '%s' placeholder for field name.
    */
   public abstract String getErrorMessageFormatForInstances();
 
@@ -104,22 +98,17 @@ public abstract class ClassObjectConstructor extends BaseFunction {
   }
 
   /**
-   * Override this method to provide logic that is used to instantiate a declared provider
-   * from Skylark.
+   * Override this method to provide logic that is used to instantiate a declared provider from
+   * Skylark.
    *
-   * This is a method that is called when a constructor {@code c} is invoked as<br>
+   * <p>This is a method that is called when a constructor {@code c} is invoked as<br>
    * {@code c(arg1 = val1, arg2 = val2, ...)}.
    *
-   * @param args an array of argument values sorted as per the signature
-   *          ({@see BaseFunction#call})
+   * @param args an array of argument values sorted as per the signature ({@see BaseFunction#call})
    */
-  protected abstract SkylarkClassObject createInstanceFromSkylark(Object[] args, Location loc)
+  protected abstract Info createInstanceFromSkylark(Object[] args, Location loc)
       throws EvalException;
 
-  /**
-   * A serializable representation of {@link ClassObjectConstructor}.
-   */
-  // todo(vladmos,dslomov): when we allow declared providers in `requiredProviders`,
-  // we will need to serialize this somehow.
+  /** A serializable representation of {@link Provider}. */
   public abstract static class Key {}
 }
diff --git a/src/main/java/com/google/devtools/build/lib/packages/RequiredProviders.java b/src/main/java/com/google/devtools/build/lib/packages/RequiredProviders.java
index e9298bd08c..5b494b7d07 100644
--- a/src/main/java/com/google/devtools/build/lib/packages/RequiredProviders.java
+++ b/src/main/java/com/google/devtools/build/lib/packages/RequiredProviders.java
@@ -72,7 +72,8 @@ public final class RequiredProviders {
       }
 
       @Override
-      public boolean satisfies(Predicate<Class<?>> hasNativeProvider,
+      public boolean satisfies(
+          Predicate<Class<?>> hasNativeProvider,
           Predicate<SkylarkProviderIdentifier> hasSkylarkProvider,
           RequiredProviders requiredProviders,
           Builder missingProviders) {
@@ -100,7 +101,8 @@ public final class RequiredProviders {
       }
 
       @Override
-      public boolean satisfies(Predicate<Class<?>> hasNativeProvider,
+      public boolean satisfies(
+          Predicate<Class<?>> hasNativeProvider,
           Predicate<SkylarkProviderIdentifier> hasSkylarkProvider,
           RequiredProviders requiredProviders,
           Builder missingProviders) {
@@ -121,19 +123,23 @@ public final class RequiredProviders {
     /** Accept a dependency that has all providers from one of the sets. */
     RESTRICTED {
       @Override
-      public boolean satisfies(final AdvertisedProviderSet advertisedProviderSet,
-          RequiredProviders requiredProviders, Builder missing) {
+      public boolean satisfies(
+          final AdvertisedProviderSet advertisedProviderSet,
+          RequiredProviders requiredProviders,
+          Builder missing) {
         if (advertisedProviderSet.canHaveAnyProvider()) {
           return true;
         }
         return satisfies(
             advertisedProviderSet.getNativeProviders()::contains,
             advertisedProviderSet.getSkylarkProviders()::contains,
-            requiredProviders, missing);
+            requiredProviders,
+            missing);
       }
 
       @Override
-      public boolean satisfies(Predicate<Class<?>> hasNativeProvider,
+      public boolean satisfies(
+          Predicate<Class<?>> hasNativeProvider,
           Predicate<SkylarkProviderIdentifier> hasSkylarkProvider,
           RequiredProviders requiredProviders,
           Builder missingProviders) {
@@ -145,10 +151,11 @@ public final class RequiredProviders {
           // Collect missing providers
           if (missingProviders != null) {
             missingProviders.addNativeSet(
-                nativeProviderSet.stream().filter(hasNativeProvider.negate())
+                nativeProviderSet
+                    .stream()
+                    .filter(hasNativeProvider.negate())
                     .collect(ImmutableSet.toImmutableSet()));
           }
-
         }
 
         for (ImmutableSet<SkylarkProviderIdentifier> skylarkProviderSet
@@ -159,7 +166,9 @@ public final class RequiredProviders {
           // Collect missing providers
           if (missingProviders != null) {
             missingProviders.addSkylarkSet(
-                skylarkProviderSet.stream().filter(hasSkylarkProvider.negate())
+                skylarkProviderSet
+                    .stream()
+                    .filter(hasSkylarkProvider.negate())
                     .collect(ImmutableSet.toImmutableSet()));
           }
         }
@@ -185,30 +194,28 @@ public final class RequiredProviders {
         describe(result, providers.nativeProviders, Class::getSimpleName);
         describe(result, providers.skylarkProviders, id -> "'" + id.toString() + "'");
         return result.toString();
-
       }
     };
 
     /** Checks if {@code advertisedProviderSet} satisfies these {@code RequiredProviders} */
-    public abstract boolean satisfies(AdvertisedProviderSet advertisedProviderSet,
-        RequiredProviders requiredProviders, Builder missing);
+    public abstract boolean satisfies(
+        AdvertisedProviderSet advertisedProviderSet,
+        RequiredProviders requiredProviders,
+        Builder missing);
 
     /**
-     * Checks if a set of providers encoded by predicates {@code hasNativeProviders}
-     * and {@code hasSkylarkProvider} satisfies these {@code RequiredProviders}
+     * Checks if a set of providers encoded by predicates {@code hasNativeProviders} and {@code
+     * hasSkylarkProvider} satisfies these {@code RequiredProviders}
      */
     abstract boolean satisfies(
         Predicate<Class<?>> hasNativeProvider,
         Predicate<SkylarkProviderIdentifier> hasSkylarkProvider,
         RequiredProviders requiredProviders,
-        @Nullable
-        Builder missingProviders);
+        @Nullable Builder missingProviders);
 
     abstract Builder copyAsBuilder(RequiredProviders providers);
 
-    /**
-     * Returns a string describing the providers that can be presented to the user.
-     */
+    /** Returns a string describing the providers that can be presented to the user. */
     abstract String getDescription(RequiredProviders providers);
   }
 
@@ -228,8 +235,8 @@ public final class RequiredProviders {
   }
 
   /**
-   * Returns providers that are missing. If none are missing, returns
-   * {@code RequiredProviders} that accept anything.
+   * Returns providers that are missing. If none are missing, returns {@code RequiredProviders} that
+   * accept anything.
    */
   public RequiredProviders getMissing(
       Predicate<Class<?>> hasNativeProvider,
@@ -243,8 +250,8 @@ public final class RequiredProviders {
   }
 
   /**
-   * Returns providers that are missing. If none are missing, returns
-   * {@code RequiredProviders} that accept anything.
+   * Returns providers that are missing. If none are missing, returns {@code RequiredProviders} that
+   * accept anything.
    */
   public RequiredProviders getMissing(AdvertisedProviderSet set) {
     Builder builder = acceptAnyBuilder();
@@ -255,10 +262,7 @@ public final class RequiredProviders {
     return builder.build();
   }
 
-
-  /**
-   * Returns true if this {@code RequiredProviders} instance accept any set of providers.
-   */
+  /** Returns true if this {@code RequiredProviders} instance accept any set of providers. */
   public boolean acceptsAny() {
     return constraint.equals(Constraint.ANY);
   }
@@ -278,11 +282,11 @@ public final class RequiredProviders {
     this.skylarkProviders = skylarkProviders;
   }
 
-  /**
-   * Helper method to describe lists of sets of things.
-   */
-  private static <T> void describe(StringBuilder result,
-      ImmutableList<ImmutableSet<T>> listOfSets, Function<T, String> describeOne) {
+  /** Helper method to describe lists of sets of things. */
+  private static <T> void describe(
+      StringBuilder result,
+      ImmutableList<ImmutableSet<T>> listOfSets,
+      Function<T, String> describeOne) {
     Joiner joiner = Joiner.on(", ");
     for (ImmutableSet<T> ids : listOfSets) {
       if (result.length() > 0) {
@@ -294,7 +298,6 @@ public final class RequiredProviders {
     }
   }
 
-
   /**
    * A builder for {@link RequiredProviders} that accepts any dependency
    * unless restriction provider sets are added.
@@ -311,9 +314,7 @@ public final class RequiredProviders {
     return new Builder(true);
   }
 
-  /**
-   * Returns a Builder initialized to the same value as this {@code RequiredProvider}
-   */
+  /** Returns a Builder initialized to the same value as this {@code RequiredProvider} */
   public Builder copyAsBuilder() {
     return constraint.copyAsBuilder(this);
   }
diff --git a/src/main/java/com/google/devtools/build/lib/packages/SkylarkClassObjectConstructor.java b/src/main/java/com/google/devtools/build/lib/packages/SkylarkProvider.java
index 8bd600852a..ea341b3171 100644
--- a/src/main/java/com/google/devtools/build/lib/packages/SkylarkClassObjectConstructor.java
+++ b/src/main/java/com/google/devtools/build/lib/packages/SkylarkProvider.java
@@ -31,40 +31,36 @@ import javax.annotation.Nullable;
  * <p>This is a result of calling {@code provider()} function from Skylark ({@link
  * com.google.devtools.build.lib.rules.SkylarkRuleClassFunctions#provider}).
  */
-public class SkylarkClassObjectConstructor extends ClassObjectConstructor
-    implements SkylarkExportable {
+public class SkylarkProvider extends Provider implements SkylarkExportable {
 
   private static final FunctionSignature.WithValues<Object, SkylarkType> SIGNATURE =
       FunctionSignature.WithValues.create(FunctionSignature.KWARGS);
 
-  @Nullable
-  private SkylarkKey key;
-  @Nullable
-  private String errorMessageFormatForInstances;
+  @Nullable private SkylarkKey key;
+  @Nullable private String errorMessageFormatForInstances;
 
   private static final String DEFAULT_ERROR_MESSAFE = "Object has no '%s' attribute.";
 
   /**
-   * Creates a Skylark-defined Declared Provider ({@link SkylarkClassObject} constructor).
+   * Creates a Skylark-defined Declared Provider ({@link Info} constructor).
    *
-   * Needs to be exported later.
+   * <p>Needs to be exported later.
    */
-  public SkylarkClassObjectConstructor(String name, Location location) {
+  public SkylarkProvider(String name, Location location) {
     this(name, SIGNATURE, location);
   }
 
-  public SkylarkClassObjectConstructor(
+  public SkylarkProvider(
       String name, FunctionSignature.WithValues<Object, SkylarkType> signature, Location location) {
     super(name, signature, location);
     this.errorMessageFormatForInstances = DEFAULT_ERROR_MESSAFE;
   }
 
   @Override
-  protected SkylarkClassObject createInstanceFromSkylark(Object[] args, Location loc)
-      throws EvalException {
+  protected Info createInstanceFromSkylark(Object[] args, Location loc) throws EvalException {
     @SuppressWarnings("unchecked")
     Map<String, Object> kwargs = (Map<String, Object>) args[0];
-    return new SkylarkClassObject(this, kwargs, loc);
+    return new Info(this, kwargs, loc);
   }
 
   @Override
@@ -92,8 +88,8 @@ public class SkylarkClassObjectConstructor extends ClassObjectConstructor
   public void export(Label extensionLabel, String exportedName) {
     Preconditions.checkState(!isExported());
     this.key = new SkylarkKey(extensionLabel, exportedName);
-    this.errorMessageFormatForInstances = String.format(
-        "'%s' object has no attribute '%%s'", exportedName);
+    this.errorMessageFormatForInstances =
+        String.format("'%s' object has no attribute '%%s'", exportedName);
   }
 
   @Override
@@ -106,10 +102,10 @@ public class SkylarkClassObjectConstructor extends ClassObjectConstructor
 
   @Override
   public boolean equals(@Nullable Object otherObject) {
-    if (!(otherObject instanceof  SkylarkClassObjectConstructor)) {
+    if (!(otherObject instanceof SkylarkProvider)) {
       return false;
     }
-    SkylarkClassObjectConstructor other = (SkylarkClassObjectConstructor) otherObject;
+    SkylarkProvider other = (SkylarkProvider) otherObject;
 
     if (this.isExported() && other.isExported()) {
       return this.getKey().equals(other.getKey());
@@ -130,9 +126,8 @@ public class SkylarkClassObjectConstructor extends ClassObjectConstructor
   }
 
   /**
-   * A serializable representation of Skylark-defined {@link SkylarkClassObjectConstructor}
-   * that uniquely identifies all {@link SkylarkClassObjectConstructor}s that
-   * are exposed to SkyFrame.
+   * A serializable representation of Skylark-defined {@link SkylarkProvider} that uniquely
+   * identifies all {@link SkylarkProvider}s that are exposed to SkyFrame.
    */
   public static class SkylarkKey extends Key {
     private final Label extensionLabel;
diff --git a/src/main/java/com/google/devtools/build/lib/packages/SkylarkProviderIdentifier.java b/src/main/java/com/google/devtools/build/lib/packages/SkylarkProviderIdentifier.java
index d9e663c43c..34b507af88 100644
--- a/src/main/java/com/google/devtools/build/lib/packages/SkylarkProviderIdentifier.java
+++ b/src/main/java/com/google/devtools/build/lib/packages/SkylarkProviderIdentifier.java
@@ -19,21 +19,17 @@ import java.util.Objects;
 import javax.annotation.Nullable;
 
 /**
- * A wrapper around Skylark provider identifier,
- * representing either a declared provider ({@see SkylarkClassObjectConstructor})
- * or a "legacy" string identifier.
+ * A wrapper around Skylark provider identifier, representing either a declared provider ({@see
+ * SkylarkProvider}) or a "legacy" string identifier.
  */
 public final class SkylarkProviderIdentifier {
 
   @Nullable
   private final String legacyId;
-  @Nullable
-  private final ClassObjectConstructor.Key key;
+  @Nullable private final Provider.Key key;
 
-  /**
-   * Creates an id for a declared provider with a given key ({@see SkylarkClassObjectConstructor}).
-   */
-  public static SkylarkProviderIdentifier forKey(ClassObjectConstructor.Key key) {
+  /** Creates an id for a declared provider with a given key ({@see SkylarkProvider}). */
+  public static SkylarkProviderIdentifier forKey(Provider.Key key) {
     return new SkylarkProviderIdentifier(key);
   }
 
@@ -49,7 +45,7 @@ public final class SkylarkProviderIdentifier {
     this.key = null;
   }
 
-  private SkylarkProviderIdentifier(ClassObjectConstructor.Key key) {
+  private SkylarkProviderIdentifier(Provider.Key key) {
     this.legacyId = null;
     this.key = key;
   }
@@ -70,10 +66,8 @@ public final class SkylarkProviderIdentifier {
     return legacyId;
   }
 
-  /**
-   * Returns a key identifying the declared provider (only for non-legacy providers).
-   */
-  public ClassObjectConstructor.Key getKey() {
+  /** Returns a key identifying the declared provider (only for non-legacy providers). */
+  public Provider.Key getKey() {
     Preconditions.checkState(!isLegacy(), "Check !isLegacy() first");
     return key;
   }
diff --git a/src/main/java/com/google/devtools/build/lib/packages/WorkspaceFactory.java b/src/main/java/com/google/devtools/build/lib/packages/WorkspaceFactory.java
index ccb81e1201..292ce4d635 100644
--- a/src/main/java/com/google/devtools/build/lib/packages/WorkspaceFactory.java
+++ b/src/main/java/com/google/devtools/build/lib/packages/WorkspaceFactory.java
@@ -528,8 +528,7 @@ public class WorkspaceFactory {
     }
 
     builder.put("bazel_version", version);
-    return NativeClassObjectConstructor.STRUCT.create(
-        builder.build(), "no native function or rule '%s'");
+    return NativeProvider.STRUCT.create(builder.build(), "no native function or rule '%s'");
   }
 
   static ClassObject newNativeModule(RuleClassProvider ruleClassProvider, String version) {