1 files changed, 116 insertions, 0 deletions
diff --git a/java/com/google/devtools/build/android/desugar/CloseResourceMethodScanner.java b/java/com/google/devtools/build/android/desugar/CloseResourceMethodScanner.java
new file mode 100644
index 0000000..a390d72
--- /dev/null
+++ b/java/com/google/devtools/build/android/desugar/CloseResourceMethodScanner.java
@@ -0,0 +1,116 @@
+// Copyright 2017 The Bazel Authors. All rights reserved.
+//
+// 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 com.google.devtools.build.android.desugar;
+
+import com.google.common.base.Preconditions;
+import org.objectweb.asm.ClassVisitor;
+import org.objectweb.asm.Label;
+import org.objectweb.asm.MethodVisitor;
+import org.objectweb.asm.Opcodes;
+
+/**
+ * A class scanner to check whether the class has the synthetic method $closeResource(Throwable,
+ * AutoCloseable).
+ */
+public class CloseResourceMethodScanner extends ClassVisitor {
+
+  private boolean hasCloseResourceMethod;
+  private String internalName;
+  private int classFileVersion;
+
+  public CloseResourceMethodScanner() {
+    super(Opcodes.ASM5);
+  }
+
+  @Override
+  public void visit(
+      int version,
+      int access,
+      String name,
+      String signature,
+      String superName,
+      String[] interfaces) {
+    Preconditions.checkState(internalName == null, "This scanner has been used.");
+    this.internalName = name;
+    this.classFileVersion = version;
+    super.visit(version, access, name, signature, superName, interfaces);
+  }
+
+  public boolean hasCloseResourceMethod() {
+    return hasCloseResourceMethod;
+  }
+
+  @Override
+  public MethodVisitor visitMethod(
+      int access, String name, String desc, String signature, String[] exceptions) {
+    if (classFileVersion <= 50) {
+      // A Java 6 or below class file should not have $closeResource method.
+      return null;
+    }
+    if (!hasCloseResourceMethod) {
+      hasCloseResourceMethod =
+          TryWithResourcesRewriter.isSyntheticCloseResourceMethod(access, name, desc);
+    }
+    return new StackMapFrameCollector(name, desc);
+  }
+
+  private class StackMapFrameCollector extends MethodVisitor {
+
+    private final String methodSignature;
+    private boolean hasCallToCloseResourceMethod;
+    private boolean hasJumpInstructions;
+    private boolean hasStackMapFrame;
+
+    public StackMapFrameCollector(String name, String desc) {
+      super(Opcodes.ASM5);
+      methodSignature = internalName + '.' + name + desc;
+    }
+
+    @Override
+    public void visitEnd() {
+      if (!hasCallToCloseResourceMethod) {
+        return;
+      }
+      if (hasJumpInstructions && !hasStackMapFrame) {
+        throw new UnsupportedOperationException(
+            "The method "
+                + methodSignature
+                + " calls $closeResource(Throwable, AutoCloseable), "
+                + "and Desugar thus needs to perform type inference for it "
+                + "to rewrite $closeResourceMethod. "
+                + "However, this method has jump instructions, but does not have stack map frames. "
+                + "Please recompile this class with stack map frames.");
+      }
+    }
+
+    @Override
+    public void visitMethodInsn(int opcode, String owner, String name, String desc, boolean itf) {
+      if (!hasCallToCloseResourceMethod
+          && TryWithResourcesRewriter.isCallToSyntheticCloseResource(
+              internalName, opcode, owner, name, desc)) {
+        hasCallToCloseResourceMethod = true;
+      }
+    }
+
+    @Override
+    public void visitFrame(int type, int nLocal, Object[] local, int nStack, Object[] stack) {
+      hasStackMapFrame = true;
+    }
+
+    @Override
+    public void visitJumpInsn(int opcode, Label label) {
+      hasJumpInstructions = true;
+    }
+  }
+}