Work around a possible bug in the Checker Framework (issue #359).

The issue https://github.com/typetools/checker-framework/issues/1712 affects all
uses of the visitor pattern in this project.  This commit adds utility methods
for working around the issue and calls them from all "match" methods.

8 files changed, 73 insertions, 20 deletions

diff --git a/api/src/main/java/io/opencensus/internal/NullnessUtils.java b/api/src/main/java/io/opencensus/internal/NullnessUtils.java
new file mode 100644
index 00000000..ca3419cd
--- /dev/null
+++ b/api/src/main/java/io/opencensus/internal/NullnessUtils.java
@@ -0,0 +1,40 @@
+/*
+ * Copyright 2017, OpenCensus Authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * 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 io.opencensus.internal;
+
+import io.opencensus.common.Function;
+
+/*>>>
+import org.checkerframework.checker.nullness.qual.KeyForBottom;
+*/
+
+/** Utility methods for working around Checker Framework issues. */
+public final class NullnessUtils {
+  private NullnessUtils() {}
+
+  /**
+   * Work around https://github.com/typetools/checker-framework/issues/1712 by removing {@code ?
+   * super} from a {@code Function}'s argument type.
+   */
+  // TODO(sebright): Remove this method once the issue is fixed.
+  public static <A, B> Function<A, B> removeSuperFromFunctionParameterType(
+      Function<? super /*@KeyForBottom*/ A, B> function) {
+    @SuppressWarnings("unchecked")
+    Function<A, B> castFunction = (Function<A, B>) function;
+    return castFunction;
+  }
+}
diff --git a/api/src/main/java/io/opencensus/stats/Aggregation.java b/api/src/main/java/io/opencensus/stats/Aggregation.java
index 0fe905ce..7a612313 100644
--- a/api/src/main/java/io/opencensus/stats/Aggregation.java
+++ b/api/src/main/java/io/opencensus/stats/Aggregation.java
@@ -20,6 +20,7 @@ import static com.google.common.base.Preconditions.checkNotNull;
 
 import com.google.auto.value.AutoValue;
 import io.opencensus.common.Function;
+import io.opencensus.internal.NullnessUtils;
 import javax.annotation.concurrent.Immutable;
 
 /**
@@ -79,7 +80,7 @@ public abstract class Aggregation {
         Function<? super Mean, T> p2,
         Function<? super Distribution, T> p3,
         Function<? super Aggregation, T> defaultFunction) {
-      return p0.apply(this);
+      return NullnessUtils.<Sum, T>removeSuperFromFunctionParameterType(p0).apply(this);
     }
   }
 
@@ -111,7 +112,7 @@ public abstract class Aggregation {
         Function<? super Mean, T> p2,
         Function<? super Distribution, T> p3,
         Function<? super Aggregation, T> defaultFunction) {
-      return p1.apply(this);
+      return NullnessUtils.<Count, T>removeSuperFromFunctionParameterType(p1).apply(this);
     }
   }
 
@@ -143,7 +144,7 @@ public abstract class Aggregation {
         Function<? super Mean, T> p2,
         Function<? super Distribution, T> p3,
         Function<? super Aggregation, T> defaultFunction) {
-      return p2.apply(this);
+      return NullnessUtils.<Mean, T>removeSuperFromFunctionParameterType(p2).apply(this);
     }
   }
 
@@ -179,7 +180,7 @@ public abstract class Aggregation {
         Function<? super Mean, T> p2,
         Function<? super Distribution, T> p3,
         Function<? super Aggregation, T> defaultFunction) {
-      return p3.apply(this);
+      return NullnessUtils.<Distribution, T>removeSuperFromFunctionParameterType(p3).apply(this);
     }
   }
 }
diff --git a/api/src/main/java/io/opencensus/stats/AggregationData.java b/api/src/main/java/io/opencensus/stats/AggregationData.java
index 822c9296..bdf618bc 100644
--- a/api/src/main/java/io/opencensus/stats/AggregationData.java
+++ b/api/src/main/java/io/opencensus/stats/AggregationData.java
@@ -22,6 +22,7 @@ import static com.google.common.base.Preconditions.checkNotNull;
 import com.google.auto.value.AutoValue;
 import com.google.common.collect.Lists;
 import io.opencensus.common.Function;
+import io.opencensus.internal.NullnessUtils;
 import java.util.Collections;
 import java.util.List;
 import javax.annotation.concurrent.Immutable;
@@ -92,7 +93,7 @@ public abstract class AggregationData {
         Function<? super MeanData, T> p3,
         Function<? super DistributionData, T> p4,
         Function<? super AggregationData, T> defaultFunction) {
-      return p0.apply(this);
+      return NullnessUtils.<SumDataDouble, T>removeSuperFromFunctionParameterType(p0).apply(this);
     }
   }
 
@@ -131,7 +132,7 @@ public abstract class AggregationData {
         Function<? super MeanData, T> p3,
         Function<? super DistributionData, T> p4,
         Function<? super AggregationData, T> defaultFunction) {
-      return p1.apply(this);
+      return NullnessUtils.<SumDataLong, T>removeSuperFromFunctionParameterType(p1).apply(this);
     }
   }
 
@@ -170,7 +171,7 @@ public abstract class AggregationData {
         Function<? super MeanData, T> p3,
         Function<? super DistributionData, T> p4,
         Function<? super AggregationData, T> defaultFunction) {
-      return p2.apply(this);
+      return NullnessUtils.<CountData, T>removeSuperFromFunctionParameterType(p2).apply(this);
     }
   }
 
@@ -217,7 +218,7 @@ public abstract class AggregationData {
         Function<? super MeanData, T> p3,
         Function<? super DistributionData, T> p4,
         Function<? super AggregationData, T> defaultFunction) {
-      return p3.apply(this);
+      return NullnessUtils.<MeanData, T>removeSuperFromFunctionParameterType(p3).apply(this);
     }
   }
 
@@ -317,7 +318,8 @@ public abstract class AggregationData {
         Function<? super MeanData, T> p3,
         Function<? super DistributionData, T> p4,
         Function<? super AggregationData, T> defaultFunction) {
-      return p4.apply(this);
+      return NullnessUtils.<DistributionData, T>removeSuperFromFunctionParameterType(p4)
+          .apply(this);
     }
   }
 }
diff --git a/api/src/main/java/io/opencensus/stats/Measure.java b/api/src/main/java/io/opencensus/stats/Measure.java
index 209e946f..70210f4e 100644
--- a/api/src/main/java/io/opencensus/stats/Measure.java
+++ b/api/src/main/java/io/opencensus/stats/Measure.java
@@ -21,6 +21,7 @@ import static com.google.common.base.Preconditions.checkArgument;
 import com.google.auto.value.AutoValue;
 import com.google.common.annotations.VisibleForTesting;
 import io.opencensus.common.Function;
+import io.opencensus.internal.NullnessUtils;
 import io.opencensus.internal.StringUtil;
 import javax.annotation.concurrent.Immutable;
 
@@ -99,7 +100,7 @@ public abstract class Measure {
         Function<? super MeasureDouble, T> p0,
         Function<? super MeasureLong, T> p1,
         Function<? super Measure, T> defaultFunction) {
-      return p0.apply(this);
+      return NullnessUtils.<MeasureDouble, T>removeSuperFromFunctionParameterType(p0).apply(this);
     }
 
     @Override
@@ -144,7 +145,7 @@ public abstract class Measure {
         Function<? super MeasureDouble, T> p0,
         Function<? super MeasureLong, T> p1,
         Function<? super Measure, T> defaultFunction) {
-      return p1.apply(this);
+      return NullnessUtils.<MeasureLong, T>removeSuperFromFunctionParameterType(p1).apply(this);
     }
 
     @Override
diff --git a/api/src/main/java/io/opencensus/stats/Measurement.java b/api/src/main/java/io/opencensus/stats/Measurement.java
index 6e4b6597..954cf43a 100644
--- a/api/src/main/java/io/opencensus/stats/Measurement.java
+++ b/api/src/main/java/io/opencensus/stats/Measurement.java
@@ -18,6 +18,7 @@ package io.opencensus.stats;
 
 import com.google.auto.value.AutoValue;
 import io.opencensus.common.Function;
+import io.opencensus.internal.NullnessUtils;
 import io.opencensus.stats.Measure.MeasureDouble;
 import io.opencensus.stats.Measure.MeasureLong;
 import javax.annotation.concurrent.Immutable;
@@ -62,7 +63,8 @@ public abstract class Measurement {
         Function<? super MeasurementDouble, T> p0,
         Function<? super MeasurementLong, T> p1,
         Function<? super Measurement, T> defaultFunction) {
-      return p0.apply(this);
+      return NullnessUtils.<MeasurementDouble, T>removeSuperFromFunctionParameterType(p0)
+          .apply(this);
     }
   }
 
@@ -90,7 +92,7 @@ public abstract class Measurement {
         Function<? super MeasurementDouble, T> p0,
         Function<? super MeasurementLong, T> p1,
         Function<? super Measurement, T> defaultFunction) {
-      return p1.apply(this);
+      return NullnessUtils.<MeasurementLong, T>removeSuperFromFunctionParameterType(p1).apply(this);
     }
   }
 }
diff --git a/api/src/main/java/io/opencensus/stats/View.java b/api/src/main/java/io/opencensus/stats/View.java
index e077baf4..4f852c77 100644
--- a/api/src/main/java/io/opencensus/stats/View.java
+++ b/api/src/main/java/io/opencensus/stats/View.java
@@ -22,6 +22,7 @@ import com.google.auto.value.AutoValue;
 import com.google.common.annotations.VisibleForTesting;
 import io.opencensus.common.Duration;
 import io.opencensus.common.Function;
+import io.opencensus.internal.NullnessUtils;
 import io.opencensus.internal.StringUtil;
 import io.opencensus.tags.TagKey;
 import java.util.ArrayList;
@@ -178,7 +179,7 @@ public abstract class View {
           Function<? super Cumulative, T> p0,
           Function<? super Interval, T> p1,
           Function<? super AggregationWindow, T> defaultFunction) {
-        return p0.apply(this);
+        return NullnessUtils.<Cumulative, T>removeSuperFromFunctionParameterType(p0).apply(this);
       }
     }
 
@@ -220,7 +221,7 @@ public abstract class View {
           Function<? super Cumulative, T> p0,
           Function<? super Interval, T> p1,
           Function<? super AggregationWindow, T> defaultFunction) {
-        return p1.apply(this);
+        return NullnessUtils.<Interval, T>removeSuperFromFunctionParameterType(p1).apply(this);
       }
     }
   }
diff --git a/api/src/main/java/io/opencensus/stats/ViewData.java b/api/src/main/java/io/opencensus/stats/ViewData.java
index c711e6f3..dc8fd555 100644
--- a/api/src/main/java/io/opencensus/stats/ViewData.java
+++ b/api/src/main/java/io/opencensus/stats/ViewData.java
@@ -23,6 +23,7 @@ import com.google.common.collect.Maps;
 import io.opencensus.common.Function;
 import io.opencensus.common.Functions;
 import io.opencensus.common.Timestamp;
+import io.opencensus.internal.NullnessUtils;
 import io.opencensus.stats.Aggregation.Count;
 import io.opencensus.stats.Aggregation.Distribution;
 import io.opencensus.stats.Aggregation.Mean;
@@ -237,7 +238,8 @@ public abstract class ViewData {
           Function<? super CumulativeData, T> p0,
           Function<? super IntervalData, T> p1,
           Function<? super AggregationWindowData, T> defaultFunction) {
-        return p0.apply(this);
+        return NullnessUtils.<CumulativeData, T>removeSuperFromFunctionParameterType(p0)
+            .apply(this);
       }
 
       /** Constructs a new {@link CumulativeData}. */
@@ -271,7 +273,7 @@ public abstract class ViewData {
           Function<? super CumulativeData, T> p0,
           Function<? super IntervalData, T> p1,
           Function<? super AggregationWindowData, T> defaultFunction) {
-        return p1.apply(this);
+        return NullnessUtils.<IntervalData, T>removeSuperFromFunctionParameterType(p1).apply(this);
       }
 
       /** Constructs a new {@link IntervalData}. */
diff --git a/api/src/main/java/io/opencensus/trace/AttributeValue.java b/api/src/main/java/io/opencensus/trace/AttributeValue.java
index 6c938bd6..2de8fc91 100644
--- a/api/src/main/java/io/opencensus/trace/AttributeValue.java
+++ b/api/src/main/java/io/opencensus/trace/AttributeValue.java
@@ -20,6 +20,7 @@ import static com.google.common.base.Preconditions.checkNotNull;
 
 import com.google.auto.value.AutoValue;
 import io.opencensus.common.Function;
+import io.opencensus.internal.NullnessUtils;
 import javax.annotation.concurrent.Immutable;
 
 /**
@@ -100,7 +101,8 @@ public abstract class AttributeValue {
         Function<? super Boolean, T> booleanFunction,
         Function<? super Long, T> longFunction,
         Function<Object, T> defaultFunction) {
-      return stringFunction.apply(getStringValue());
+      return NullnessUtils.<String, T>removeSuperFromFunctionParameterType(stringFunction)
+          .apply(getStringValue());
     }
 
     abstract String getStringValue();
@@ -126,7 +128,8 @@ public abstract class AttributeValue {
         Function<? super Boolean, T> booleanFunction,
         Function<? super Long, T> longFunction,
         Function<Object, T> defaultFunction) {
-      return booleanFunction.apply(getBooleanValue());
+      return NullnessUtils.<Boolean, T>removeSuperFromFunctionParameterType(booleanFunction)
+          .apply(getBooleanValue());
     }
 
     abstract Boolean getBooleanValue();
@@ -152,7 +155,8 @@ public abstract class AttributeValue {
         Function<? super Boolean, T> booleanFunction,
         Function<? super Long, T> longFunction,
         Function<Object, T> defaultFunction) {
-      return longFunction.apply(getLongValue());
+      return NullnessUtils.<Long, T>removeSuperFromFunctionParameterType(longFunction)
+          .apply(getLongValue());
     }
 
     abstract Long getLongValue();