1 files changed, 40 insertions, 19 deletions

diff --git a/java/com/google/devtools/build/android/desugar/TryWithResourcesRewriter.java b/java/com/google/devtools/build/android/desugar/TryWithResourcesRewriter.java
index 8e6d6d5..98eef45 100644
--- a/java/com/google/devtools/build/android/desugar/TryWithResourcesRewriter.java
+++ b/java/com/google/devtools/build/android/desugar/TryWithResourcesRewriter.java
@@ -29,6 +29,7 @@ import com.google.common.collect.ImmutableMap;
 import com.google.common.collect.ImmutableMultimap;
 import com.google.common.collect.ImmutableSet;
 import com.google.devtools.build.android.desugar.BytecodeTypeInference.InferredType;
+import com.google.devtools.build.android.desugar.io.BitFlags;
 import java.util.Collections;
 import java.util.LinkedHashSet;
 import java.util.Optional;
@@ -165,14 +166,12 @@ public class TryWithResourcesRewriter extends ClassVisitor {
             new CloseResourceMethodSpecializer(cv, resourceInternalName, isInterface));
       }
     } else {
+      // It is possible that all calls to $closeResources(...) are in dead code regions, and the
+      // calls are eliminated, which leaving the method $closeResources() unused. (b/78030676).
+      // In this case, we just discard the method body.
       checkState(
-          closeResourceMethod == null,
-          "The field resourceTypeInternalNames is empty. "
-              + "But the class has the $closeResource method.");
-      checkState(
-          !hasCloseResourceMethod,
-          "The class %s has close resource method, but resourceTypeInternalNames is empty.",
-          internalName);
+          !hasCloseResourceMethod || closeResourceMethod != null,
+          "There should be $closeResources(...) in the class file.");
     }
     super.visitEnd();
   }
@@ -311,18 +310,20 @@ public class TryWithResourcesRewriter extends ClassVisitor {
 
         InferredType resourceType = typeInference.getTypeOfOperandFromTop(0);
         Optional<String> resourceClassInternalName = resourceType.getInternalName();
-        checkState(
-            resourceClassInternalName.isPresent(),
-            "The resource class %s is not a reference type in %s.%s",
-            resourceType,
-            internalName,
-            methodSignature);
-        checkState(
-            isAssignableFrom(
-                "java.lang.AutoCloseable", resourceClassInternalName.get().replace('/', '.')),
-            "The resource type should be a subclass of java.lang.AutoCloseable: %s",
-            resourceClassInternalName);
-
+        {
+          // Check the resource type.
+          checkState(
+              resourceClassInternalName.isPresent(),
+              "The resource class %s is not a reference type in %s.%s",
+              resourceType,
+              internalName,
+              methodSignature);
+          String resourceClassName = resourceClassInternalName.get().replace('/', '.');
+          checkState(
+              hasCloseMethod(resourceClassName),
+              "The resource class %s should have a close() method.",
+              resourceClassName);
+        }
         resourceTypeInternalNames.add(resourceClassInternalName.get());
         super.visitMethodInsn(
             opcode,
@@ -356,6 +357,26 @@ public class TryWithResourcesRewriter extends ClassVisitor {
       return isAssignableFrom("java.lang.Throwable", owner.replace('/', '.'));
     }
 
+    private boolean hasCloseMethod(String resourceClassName) {
+      try {
+        Class<?> klass = classLoader.loadClass(resourceClassName);
+        klass.getMethod("close");
+        return true;
+      } catch (ClassNotFoundException e) {
+        throw new AssertionError(
+            "Failed to load class "
+                + resourceClassName
+                + " when desugaring method "
+                + internalName
+                + "."
+                + methodSignature,
+            e);
+      } catch (NoSuchMethodException e) {
+        // There is no close() method in the class, so return false.
+        return false;
+      }
+    }
+
     private boolean isAssignableFrom(String baseClassName, String subClassName) {
       try {
         Class<?> baseClass = classLoader.loadClass(baseClassName);