diff --git a/src/main/java/com/android/tools/r8/ir/analysis/value/AbstractValue.java b/src/main/java/com/android/tools/r8/ir/analysis/value/AbstractValue.java
index e7a1e8b..32e2621 100644
--- a/src/main/java/com/android/tools/r8/ir/analysis/value/AbstractValue.java
+++ b/src/main/java/com/android/tools/r8/ir/analysis/value/AbstractValue.java
@@ -11,7 +11,7 @@
    * concretization of this abstract value has size 1).
    */
   public boolean isSingleValue() {
-    return false;
+    return isSingleEnumValue() || isSingleNumberValue() || isSingleStringValue();
   }
 
   public boolean isSingleEnumValue() {
@@ -22,6 +22,22 @@
     return null;
   }
 
+  public boolean isSingleNumberValue() {
+    return false;
+  }
+
+  public SingleNumberValue asSingleNumberValue() {
+    return null;
+  }
+
+  public boolean isSingleStringValue() {
+    return false;
+  }
+
+  public SingleStringValue asSingleStringValue() {
+    return null;
+  }
+
   public boolean isUnknown() {
     return false;
   }
diff --git a/src/main/java/com/android/tools/r8/ir/analysis/value/AbstractValueFactory.java b/src/main/java/com/android/tools/r8/ir/analysis/value/AbstractValueFactory.java
index c58addb..7e34815 100644
--- a/src/main/java/com/android/tools/r8/ir/analysis/value/AbstractValueFactory.java
+++ b/src/main/java/com/android/tools/r8/ir/analysis/value/AbstractValueFactory.java
@@ -5,13 +5,25 @@
 package com.android.tools.r8.ir.analysis.value;
 
 import com.android.tools.r8.graph.DexField;
+import com.android.tools.r8.graph.DexString;
 import java.util.concurrent.ConcurrentHashMap;
 
 public class AbstractValueFactory {
 
   private ConcurrentHashMap<DexField, SingleEnumValue> singleEnumValues = new ConcurrentHashMap<>();
+  private ConcurrentHashMap<Long, SingleNumberValue> singleNumberValues = new ConcurrentHashMap<>();
+  private ConcurrentHashMap<DexString, SingleStringValue> singleStringValues =
+      new ConcurrentHashMap<>();
 
   public SingleEnumValue createSingleEnumValue(DexField field) {
     return singleEnumValues.computeIfAbsent(field, SingleEnumValue::new);
   }
+
+  public SingleNumberValue createSingleNumberValue(long value) {
+    return singleNumberValues.computeIfAbsent(value, SingleNumberValue::new);
+  }
+
+  public SingleStringValue createSingleStringValue(DexString string) {
+    return singleStringValues.computeIfAbsent(string, SingleStringValue::new);
+  }
 }
diff --git a/src/main/java/com/android/tools/r8/ir/analysis/value/SingleEnumValue.java b/src/main/java/com/android/tools/r8/ir/analysis/value/SingleEnumValue.java
index 6a3d96b..a9050ef 100644
--- a/src/main/java/com/android/tools/r8/ir/analysis/value/SingleEnumValue.java
+++ b/src/main/java/com/android/tools/r8/ir/analysis/value/SingleEnumValue.java
@@ -16,11 +16,6 @@
   }
 
   @Override
-  public boolean isSingleValue() {
-    return true;
-  }
-
-  @Override
   public boolean isSingleEnumValue() {
     return true;
   }
diff --git a/src/main/java/com/android/tools/r8/ir/analysis/value/SingleNumberValue.java b/src/main/java/com/android/tools/r8/ir/analysis/value/SingleNumberValue.java
new file mode 100644
index 0000000..914516a
--- /dev/null
+++ b/src/main/java/com/android/tools/r8/ir/analysis/value/SingleNumberValue.java
@@ -0,0 +1,39 @@
+// Copyright (c) 2019, the R8 project authors. Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+package com.android.tools.r8.ir.analysis.value;
+
+public class SingleNumberValue extends AbstractValue {
+
+  private final long value;
+
+  /** Intentionally package private, use {@link AbstractValueFactory} instead. */
+  SingleNumberValue(long value) {
+    this.value = value;
+  }
+
+  @Override
+  public boolean isSingleNumberValue() {
+    return true;
+  }
+
+  @Override
+  public SingleNumberValue asSingleNumberValue() {
+    return this;
+  }
+
+  public long getValue() {
+    return value;
+  }
+
+  @Override
+  public boolean equals(Object o) {
+    return this == o;
+  }
+
+  @Override
+  public int hashCode() {
+    return System.identityHashCode(this);
+  }
+}
diff --git a/src/main/java/com/android/tools/r8/ir/analysis/value/SingleStringValue.java b/src/main/java/com/android/tools/r8/ir/analysis/value/SingleStringValue.java
new file mode 100644
index 0000000..acb2f69
--- /dev/null
+++ b/src/main/java/com/android/tools/r8/ir/analysis/value/SingleStringValue.java
@@ -0,0 +1,41 @@
+// Copyright (c) 2019, the R8 project authors. Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+package com.android.tools.r8.ir.analysis.value;
+
+import com.android.tools.r8.graph.DexString;
+
+public class SingleStringValue extends AbstractValue {
+
+  private final DexString string;
+
+  /** Intentionally package private, use {@link AbstractValueFactory} instead. */
+  SingleStringValue(DexString string) {
+    this.string = string;
+  }
+
+  @Override
+  public boolean isSingleStringValue() {
+    return true;
+  }
+
+  @Override
+  public SingleStringValue asSingleStringValue() {
+    return this;
+  }
+
+  public DexString getDexString() {
+    return string;
+  }
+
+  @Override
+  public boolean equals(Object o) {
+    return this == o;
+  }
+
+  @Override
+  public int hashCode() {
+    return string.hashCode();
+  }
+}
diff --git a/src/main/java/com/android/tools/r8/ir/conversion/MethodOptimizationFeedback.java b/src/main/java/com/android/tools/r8/ir/conversion/MethodOptimizationFeedback.java
index 2f70beb..1ffe1ad 100644
--- a/src/main/java/com/android/tools/r8/ir/conversion/MethodOptimizationFeedback.java
+++ b/src/main/java/com/android/tools/r8/ir/conversion/MethodOptimizationFeedback.java
@@ -30,9 +30,11 @@
 
   void methodReturnsArgument(DexEncodedMethod method, int argument);
 
-  void methodReturnsConstantNumber(DexEncodedMethod method, long value);
+  void methodReturnsConstantNumber(
+      DexEncodedMethod method, AppView<?> appView, long value);
 
-  void methodReturnsConstantString(DexEncodedMethod method, DexString value);
+  void methodReturnsConstantString(
+      DexEncodedMethod method, AppView<?> appView, DexString value);
 
   void methodReturnsObjectWithUpperBoundType(
       DexEncodedMethod method, AppView<?> appView, TypeLatticeElement type);
diff --git a/src/main/java/com/android/tools/r8/ir/optimize/info/ConstantData.java b/src/main/java/com/android/tools/r8/ir/optimize/info/ConstantData.java
deleted file mode 100644
index 6c10d58..0000000
--- a/src/main/java/com/android/tools/r8/ir/optimize/info/ConstantData.java
+++ /dev/null
@@ -1,75 +0,0 @@
-// Copyright (c) 2019, the R8 project authors. Please see the AUTHORS file
-// for details. All rights reserved. Use of this source code is governed by a
-// BSD-style license that can be found in the LICENSE file.
-package com.android.tools.r8.ir.optimize.info;
-
-import com.android.tools.r8.graph.DexString;
-import java.util.Optional;
-import java.util.OptionalLong;
-
-// Simple data class that encapsulates constant values. Usages are:
-//   * return value in a method summary when the method returns a constant.
-//   * call-site optimization info if a certain method is always invoked with a constant.
-//
-// Note that this data class mimics C-like union. That is, a constant content that a value can hold
-// should be *one* of constant kinds, not multiple things at the same time. E.g., a value cannot
-// have ConstNumber and ConstString simultaneously. Content's orthogonality will be checked at
-// {@link #hasConstant()}.
-class ConstantData {
-  private static final ConstantData INSTANCE = new ConstantData();
-
-  static ConstantData getDefaultInstance() {
-    return INSTANCE;
-  }
-
-  private final OptionalLong constantNumber;
-  // TODO(b/69963623): item-based string?
-  private final Optional<DexString> constantString;
-  // TODO(b/69963623): constantClass?
-
-  private ConstantData() {
-    this.constantNumber = OptionalLong.empty();
-    this.constantString = Optional.empty();
-  }
-
-  private ConstantData(long constantNumber) {
-    this.constantNumber = OptionalLong.of(constantNumber);
-    this.constantString = Optional.empty();
-  }
-
-  private ConstantData(DexString constantString) {
-    this.constantNumber = OptionalLong.empty();
-    this.constantString = Optional.of(constantString);
-  }
-
-  static ConstantData fromConstantNumber(long constantNumber) {
-    return new ConstantData(constantNumber);
-  }
-
-  static ConstantData fromConstantString(DexString constantString) {
-    return new ConstantData(constantString);
-  }
-
-  boolean hasConstant() {
-    assert !(hasConstantNumber() && hasConstantString());
-    return hasConstantNumber() || hasConstantString();
-  }
-
-  boolean hasConstantNumber() {
-    return constantNumber.isPresent();
-  }
-
-  boolean hasConstantString() {
-    return constantString.isPresent();
-  }
-
-  long getConstantNumber() {
-    assert hasConstantNumber() && !hasConstantString();
-    return constantNumber.getAsLong();
-  }
-
-  DexString getConstantString() {
-    assert !hasConstantNumber() && hasConstantString();
-    return constantString.get();
-  }
-}
diff --git a/src/main/java/com/android/tools/r8/ir/optimize/info/DefaultMethodOptimizationInfo.java b/src/main/java/com/android/tools/r8/ir/optimize/info/DefaultMethodOptimizationInfo.java
index fd641f3..3b64d1c 100644
--- a/src/main/java/com/android/tools/r8/ir/optimize/info/DefaultMethodOptimizationInfo.java
+++ b/src/main/java/com/android/tools/r8/ir/optimize/info/DefaultMethodOptimizationInfo.java
@@ -9,6 +9,8 @@
 import com.android.tools.r8.graph.DexType;
 import com.android.tools.r8.ir.analysis.type.ClassTypeLatticeElement;
 import com.android.tools.r8.ir.analysis.type.TypeLatticeElement;
+import com.android.tools.r8.ir.analysis.value.AbstractValue;
+import com.android.tools.r8.ir.analysis.value.UnknownValue;
 import com.android.tools.r8.ir.optimize.info.ParameterUsagesInfo.ParameterUsage;
 import com.android.tools.r8.ir.optimize.info.initializer.ClassInitializerInfo;
 import com.android.tools.r8.ir.optimize.info.initializer.DefaultInstanceInitializerInfo;
@@ -25,10 +27,10 @@
   static int UNKNOWN_RETURNED_ARGUMENT = -1;
   static boolean UNKNOWN_NEVER_RETURNS_NULL = false;
   static boolean UNKNOWN_NEVER_RETURNS_NORMALLY = false;
-  static ConstantData UNKNOWN_CONSTANT_DATA = ConstantData.getDefaultInstance();
+  static AbstractValue UNKNOWN_CONSTANT_VALUE = UnknownValue.getInstance();
   static TypeLatticeElement UNKNOWN_TYPE = null;
   static ClassTypeLatticeElement UNKNOWN_CLASS_TYPE = null;
-  static boolean DOES_NOT_USE_IDNETIFIER_NAME_STRING = false;
+  static boolean DOES_NOT_USE_IDENTIFIER_NAME_STRING = false;
   static boolean UNKNOWN_CHECKS_NULL_RECEIVER_BEFORE_ANY_SIDE_EFFECT = false;
   static boolean UNKNOWN_TRIGGERS_CLASS_INIT_BEFORE_ANY_SIDE_EFFECT = false;
   static ClassInlinerEligibility UNKNOWN_CLASS_INLINER_ELIGIBILITY = null;
@@ -139,18 +141,13 @@
   }
 
   @Override
-  public boolean returnsConstant() {
-    return UNKNOWN_CONSTANT_DATA.hasConstant();
-  }
-
-  @Override
   public boolean returnsConstantNumber() {
-    return UNKNOWN_CONSTANT_DATA.hasConstantNumber();
+    return UNKNOWN_CONSTANT_VALUE.isSingleNumberValue();
   }
 
   @Override
   public boolean returnsConstantString() {
-    return UNKNOWN_CONSTANT_DATA.hasConstantString();
+    return UNKNOWN_CONSTANT_VALUE.isSingleStringValue();
   }
 
   @Override
@@ -161,13 +158,13 @@
   @Override
   public long getReturnedConstantNumber() {
     assert returnsConstantNumber();
-    return UNKNOWN_CONSTANT_DATA.getConstantNumber();
+    return UNKNOWN_CONSTANT_VALUE.asSingleNumberValue().getValue();
   }
 
   @Override
   public DexString getReturnedConstantString() {
     assert returnsConstantString();
-    return UNKNOWN_CONSTANT_DATA.getConstantString();
+    return UNKNOWN_CONSTANT_VALUE.asSingleStringValue().getDexString();
   }
 
   @Override
@@ -177,7 +174,7 @@
 
   @Override
   public boolean useIdentifierNameString() {
-    return DOES_NOT_USE_IDNETIFIER_NAME_STRING;
+    return DOES_NOT_USE_IDENTIFIER_NAME_STRING;
   }
 
   @Override
diff --git a/src/main/java/com/android/tools/r8/ir/optimize/info/MethodOptimizationInfo.java b/src/main/java/com/android/tools/r8/ir/optimize/info/MethodOptimizationInfo.java
index 9ea0777..93cdc1b 100644
--- a/src/main/java/com/android/tools/r8/ir/optimize/info/MethodOptimizationInfo.java
+++ b/src/main/java/com/android/tools/r8/ir/optimize/info/MethodOptimizationInfo.java
@@ -55,7 +55,9 @@
 
   boolean neverReturnsNormally();
 
-  boolean returnsConstant();
+  default boolean returnsConstant() {
+    return returnsConstantNumber() || returnsConstantString();
+  }
 
   boolean returnsConstantNumber();
 
diff --git a/src/main/java/com/android/tools/r8/ir/optimize/info/MethodOptimizationInfoCollector.java b/src/main/java/com/android/tools/r8/ir/optimize/info/MethodOptimizationInfoCollector.java
index 371850d..7f8cfc4 100644
--- a/src/main/java/com/android/tools/r8/ir/optimize/info/MethodOptimizationInfoCollector.java
+++ b/src/main/java/com/android/tools/r8/ir/optimize/info/MethodOptimizationInfoCollector.java
@@ -251,11 +251,12 @@
       if (aliasedValue.isConstant()) {
         if (aliasedValue.definition.isConstNumber()) {
           long value = aliasedValue.definition.asConstNumber().getRawValue();
-          feedback.methodReturnsConstantNumber(method, value);
+          feedback.methodReturnsConstantNumber(method, appView, value);
         } else if (aliasedValue.definition.isConstString()) {
           ConstString constStringInstruction = aliasedValue.definition.asConstString();
           if (!constStringInstruction.instructionInstanceCanThrow()) {
-            feedback.methodReturnsConstantString(method, constStringInstruction.getValue());
+            feedback.methodReturnsConstantString(
+                method, appView, constStringInstruction.getValue());
           }
         }
       }
diff --git a/src/main/java/com/android/tools/r8/ir/optimize/info/OptimizationFeedbackDelayed.java b/src/main/java/com/android/tools/r8/ir/optimize/info/OptimizationFeedbackDelayed.java
index 3f5c226..4c3578e 100644
--- a/src/main/java/com/android/tools/r8/ir/optimize/info/OptimizationFeedbackDelayed.java
+++ b/src/main/java/com/android/tools/r8/ir/optimize/info/OptimizationFeedbackDelayed.java
@@ -157,13 +157,15 @@
   }
 
   @Override
-  public synchronized void methodReturnsConstantNumber(DexEncodedMethod method, long value) {
-    getMethodOptimizationInfoForUpdating(method).markReturnsConstantNumber(value);
+  public synchronized void methodReturnsConstantNumber(
+      DexEncodedMethod method, AppView<?> appView, long value) {
+    getMethodOptimizationInfoForUpdating(method).markReturnsConstantNumber(appView, value);
   }
 
   @Override
-  public synchronized void methodReturnsConstantString(DexEncodedMethod method, DexString value) {
-    getMethodOptimizationInfoForUpdating(method).markReturnsConstantString(value);
+  public synchronized void methodReturnsConstantString(
+      DexEncodedMethod method, AppView<?> appView, DexString value) {
+    getMethodOptimizationInfoForUpdating(method).markReturnsConstantString(appView, value);
   }
 
   @Override
diff --git a/src/main/java/com/android/tools/r8/ir/optimize/info/OptimizationFeedbackIgnore.java b/src/main/java/com/android/tools/r8/ir/optimize/info/OptimizationFeedbackIgnore.java
index 2803998..1b3e982 100644
--- a/src/main/java/com/android/tools/r8/ir/optimize/info/OptimizationFeedbackIgnore.java
+++ b/src/main/java/com/android/tools/r8/ir/optimize/info/OptimizationFeedbackIgnore.java
@@ -68,10 +68,12 @@
   public void methodReturnsArgument(DexEncodedMethod method, int argument) {}
 
   @Override
-  public void methodReturnsConstantNumber(DexEncodedMethod method, long value) {}
+  public void methodReturnsConstantNumber(
+      DexEncodedMethod method, AppView<?> appView, long value) {}
 
   @Override
-  public void methodReturnsConstantString(DexEncodedMethod method, DexString value) {}
+  public void methodReturnsConstantString(
+      DexEncodedMethod method, AppView<?> appView, DexString value) {}
 
   @Override
   public void methodReturnsObjectWithUpperBoundType(
diff --git a/src/main/java/com/android/tools/r8/ir/optimize/info/OptimizationFeedbackSimple.java b/src/main/java/com/android/tools/r8/ir/optimize/info/OptimizationFeedbackSimple.java
index 122b6bb..ade0e2d 100644
--- a/src/main/java/com/android/tools/r8/ir/optimize/info/OptimizationFeedbackSimple.java
+++ b/src/main/java/com/android/tools/r8/ir/optimize/info/OptimizationFeedbackSimple.java
@@ -90,12 +90,14 @@
   }
 
   @Override
-  public void methodReturnsConstantNumber(DexEncodedMethod method, long value) {
+  public void methodReturnsConstantNumber(
+      DexEncodedMethod method, AppView<?> appView, long value) {
     // Ignored.
   }
 
   @Override
-  public void methodReturnsConstantString(DexEncodedMethod method, DexString value) {
+  public void methodReturnsConstantString(
+      DexEncodedMethod method, AppView<?> appView, DexString value) {
     // Ignored.
   }
 
diff --git a/src/main/java/com/android/tools/r8/ir/optimize/info/UpdatableMethodOptimizationInfo.java b/src/main/java/com/android/tools/r8/ir/optimize/info/UpdatableMethodOptimizationInfo.java
index c9faaa5..d553a4c 100644
--- a/src/main/java/com/android/tools/r8/ir/optimize/info/UpdatableMethodOptimizationInfo.java
+++ b/src/main/java/com/android/tools/r8/ir/optimize/info/UpdatableMethodOptimizationInfo.java
@@ -11,6 +11,7 @@
 import com.android.tools.r8.graph.DexType;
 import com.android.tools.r8.ir.analysis.type.ClassTypeLatticeElement;
 import com.android.tools.r8.ir.analysis.type.TypeLatticeElement;
+import com.android.tools.r8.ir.analysis.value.AbstractValue;
 import com.android.tools.r8.ir.optimize.info.ParameterUsagesInfo.ParameterUsage;
 import com.android.tools.r8.ir.optimize.info.initializer.ClassInitializerInfo;
 import com.android.tools.r8.ir.optimize.info.initializer.DefaultInstanceInitializerInfo;
@@ -34,14 +35,14 @@
   private boolean neverReturnsNull = DefaultMethodOptimizationInfo.UNKNOWN_NEVER_RETURNS_NULL;
   private boolean neverReturnsNormally =
       DefaultMethodOptimizationInfo.UNKNOWN_NEVER_RETURNS_NORMALLY;
-  private ConstantData constantData = DefaultMethodOptimizationInfo.UNKNOWN_CONSTANT_DATA;
+  private AbstractValue constantValue = DefaultMethodOptimizationInfo.UNKNOWN_CONSTANT_VALUE;
   private TypeLatticeElement returnsObjectWithUpperBoundType =
       DefaultMethodOptimizationInfo.UNKNOWN_TYPE;
   private ClassTypeLatticeElement returnsObjectWithLowerBoundType =
       DefaultMethodOptimizationInfo.UNKNOWN_CLASS_TYPE;
   private InlinePreference inlining = InlinePreference.Default;
   private boolean useIdentifierNameString =
-      DefaultMethodOptimizationInfo.DOES_NOT_USE_IDNETIFIER_NAME_STRING;
+      DefaultMethodOptimizationInfo.DOES_NOT_USE_IDENTIFIER_NAME_STRING;
   private boolean checksNullReceiverBeforeAnySideEffect =
       DefaultMethodOptimizationInfo.UNKNOWN_CHECKS_NULL_RECEIVER_BEFORE_ANY_SIDE_EFFECT;
   private boolean triggersClassInitBeforeAnySideEffect =
@@ -92,7 +93,7 @@
     returnValueOnlyDependsOnArguments = template.returnValueOnlyDependsOnArguments;
     neverReturnsNull = template.neverReturnsNull;
     neverReturnsNormally = template.neverReturnsNormally;
-    constantData = template.constantData;
+    constantValue = template.constantValue;
     returnsObjectWithUpperBoundType = template.returnsObjectWithUpperBoundType;
     returnsObjectWithLowerBoundType = template.returnsObjectWithLowerBoundType;
     inlining = template.inlining;
@@ -234,18 +235,13 @@
   }
 
   @Override
-  public boolean returnsConstant() {
-    return constantData.hasConstant();
-  }
-
-  @Override
   public boolean returnsConstantNumber() {
-    return constantData.hasConstantNumber();
+    return constantValue.isSingleNumberValue();
   }
 
   @Override
   public boolean returnsConstantString() {
-    return constantData.hasConstantString();
+    return constantValue.isSingleStringValue();
   }
 
   @Override
@@ -256,13 +252,13 @@
   @Override
   public long getReturnedConstantNumber() {
     assert returnsConstantNumber();
-    return constantData.getConstantNumber();
+    return constantValue.asSingleNumberValue().getValue();
   }
 
   @Override
   public DexString getReturnedConstantString() {
     assert returnsConstantString();
-    return constantData.getConstantString();
+    return constantValue.asSingleStringValue().getDexString();
   }
 
   @Override
@@ -359,20 +355,22 @@
     neverReturnsNormally = true;
   }
 
-  void markReturnsConstantNumber(long value) {
-    assert !constantData.hasConstantString();
-    assert !constantData.hasConstantNumber() || constantData.getConstantNumber() == value
+  void markReturnsConstantNumber(AppView<?> appView, long value) {
+    assert !constantValue.isSingleStringValue();
+    assert !constantValue.isSingleNumberValue()
+            || constantValue.asSingleNumberValue().getValue() == value
         : "return constant number changed from "
-            + constantData.getConstantNumber() + " to " + value;
-    constantData = ConstantData.fromConstantNumber(value);
+            + constantValue.asSingleNumberValue().getValue() + " to " + value;
+    constantValue = appView.abstractValueFactory().createSingleNumberValue(value);
   }
 
-  void markReturnsConstantString(DexString value) {
-    assert !constantData.hasConstantNumber();
-    assert !constantData.hasConstantString() || constantData.getConstantString() == value
+  void markReturnsConstantString(AppView<?> appView, DexString value) {
+    assert !constantValue.isSingleNumberValue();
+    assert !constantValue.isSingleStringValue()
+            || constantValue.asSingleStringValue().getDexString() == value
         : "return constant string changed from "
-            + constantData.getConstantString() + " to " + value;
-    constantData = ConstantData.fromConstantString(value);
+            + constantValue.asSingleStringValue().getDexString() + " to " + value;
+    constantValue = appView.abstractValueFactory().createSingleStringValue(value);
   }
 
   void markReturnsObjectWithUpperBoundType(AppView<?> appView, TypeLatticeElement type) {
@@ -474,7 +472,7 @@
     // code is not changed, and thus the following *return* info is not changed either.
     //   * neverReturnsNull
     //   * neverReturnsNormally
-    //   * constantData
+    //   * constantValue
     //   * returnsObjectWithUpperBoundType
     //   * returnsObjectWithLowerBoundType
     // inlining: it is not inlined, and thus staticized. No more chance of inlining, though.