Copy try-catch blocks when merging static initializers

This also causes the merged method to work as expected if the target method contains more than one RETURN instruction.

src/main/java/org/spongepowered/asm/mixin/transformer/MixinApplicatorStandard.java

@@ -745,19 +745,31 @@ protected final void appendInsns(MixinTargetContext mixin, MethodNode method) {
         MethodNode target = this.findTargetMethod(method);
 
         if (target != null) {
-            AbstractInsnNode returnNode = Bytecode.findInsn(target, Opcodes.RETURN);
-
-            if (returnNode != null) {
+            List<AbstractInsnNode> returnNodes = Bytecode.findAllInsns(target, Opcodes.RETURN);
+            if (!returnNodes.isEmpty()) {
+                // Replace all existing return instructions with a GOTO to the start of the newly appended code
+                LabelNode appendedCodeStartLabel = new LabelNode();
+                for (AbstractInsnNode returnNode : returnNodes) {
+                    target.instructions.set(returnNode, new JumpInsnNode(Opcodes.GOTO, appendedCodeStartLabel));
+                }
+                target.instructions.add(appendedCodeStartLabel);
+
+                // Append all the new code to the end of the target method, excluding line numbers
                 Iterator<AbstractInsnNode> injectIter = method.instructions.iterator();
                 while (injectIter.hasNext()) {
                     AbstractInsnNode insn = injectIter.next();
-                    if (!(insn instanceof LineNumberNode) && insn.getOpcode() != Opcodes.RETURN) {
-                        target.instructions.insertBefore(returnNode, insn);
+                    if (!(insn instanceof LineNumberNode)) {
+                        injectIter.remove();
+                        target.instructions.add(insn);
                     }
                 }
 
                 target.maxLocals = Math.max(target.maxLocals, method.maxLocals);
                 target.maxStack = Math.max(target.maxStack, method.maxStack);
+
+                // Merge incoming try-catch blocks into the target method
+                target.tryCatchBlocks.addAll(method.tryCatchBlocks);
+                // We could probably copy over local variable information as well?
             }
 
             return;

src/main/java/org/spongepowered/asm/util/Bytecode.java

@@ -285,16 +285,35 @@ public static MethodNode findMethod(ClassNode classNode, String name, String des
      * @return found node or null if not found 
      */
     public static AbstractInsnNode findInsn(MethodNode method, int opcode) {
-        Iterator<AbstractInsnNode> findReturnIter = method.instructions.iterator();
-        while (findReturnIter.hasNext()) {
-            AbstractInsnNode insn = findReturnIter.next();
+        Iterator<AbstractInsnNode> findInsnIter = method.instructions.iterator();
+        while (findInsnIter.hasNext()) {
+            AbstractInsnNode insn = findInsnIter.next();
             if (insn.getOpcode() == opcode) {
                 return insn;
             }
         }
         return null;
     }
 
+    /**
+     * Find all insn nodes with a matching opcode in the specified method
+     *
+     * @param method method to search
+     * @param opcode opcode to search for
+     * @return a list containing the found nodes, may be empty if not found
+     */
+    public static List<AbstractInsnNode> findAllInsns(MethodNode method, int opcode) {
+        List<AbstractInsnNode> insns = new ArrayList<AbstractInsnNode>();
+        Iterator<AbstractInsnNode> findInsnIter = method.instructions.iterator();
+        while (findInsnIter.hasNext()) {
+            AbstractInsnNode insn = findInsnIter.next();
+            if (insn.getOpcode() == opcode) {
+                insns.add(insn);
+            }
+        }
+        return insns;
+    }
+
     /**
      * Find the call to <tt>super()</tt> or <tt>this()</tt> in a constructor.
      * This attempts to locate the first call to <tt>&lt;init&gt;</tt> which