Unfuck the MethodWriter nesting. All MethodWriters should only live separately from each other, no nesting

modules/lang-painless/src/main/java/org/elasticsearch/painless/MethodWriter.java

@@ -87,7 +87,6 @@ import static org.elasticsearch.painless.WriterConstants.UTILITY_TYPE;
  * shared by the nodes of the Painless tree.
  */
 public final class MethodWriter extends GeneratorAdapter {
-    private final ClassWriter parent;
     private final BitSet statements;
 
     private final Deque<List<org.objectweb.asm.Type>> stringConcatArgs =
@@ -97,17 +96,9 @@ public final class MethodWriter extends GeneratorAdapter {
         super(Opcodes.ASM5, cw.visitMethod(access, method.getName(), method.getDescriptor(), null, null),
                 access, method.getName(), method.getDescriptor());
 
-        this.parent = cw;
         this.statements = statements;
     }
 
-    /**
-     * @return A new {@link MethodWriter} with the specified access and signature.
-     */
-    public MethodWriter newMethodWriter(int access, Method method) {
-        return new MethodWriter(access, method, parent, statements);
-    }
-
     /**
      * Marks a new statement boundary.
      * <p>
@@ -362,4 +353,9 @@ public final class MethodWriter extends GeneratorAdapter {
         super.endMethod();
     }
 
+    @Override
+    public void visitEnd() {
+        throw new AssertionError("Should never call this method on MethodWriter, use endMethod() instead");
+    }
+
 }

modules/lang-painless/src/main/java/org/elasticsearch/painless/node/SFunction.java

@@ -29,11 +29,13 @@ import org.elasticsearch.painless.Locals.FunctionReserved;
 import org.elasticsearch.painless.Locals.Variable;
 import org.elasticsearch.painless.Location;
 import org.elasticsearch.painless.MethodWriter;
+import org.objectweb.asm.ClassWriter;
 import org.objectweb.asm.Opcodes;
 
 import java.lang.invoke.MethodType;
 import java.lang.reflect.Modifier;
 import java.util.ArrayList;
+import java.util.BitSet;
 import java.util.Collections;
 import java.util.List;
 
@@ -132,11 +134,16 @@ public class SFunction extends AStatement {
 
         locals.decrementScope();
     }
+    
+    /** Writes the function to given ClassWriter. */
+    void write (ClassWriter writer, BitSet statements) {
+        final MethodWriter function = new MethodWriter(Opcodes.ACC_PRIVATE | Opcodes.ACC_STATIC, method.method, writer, statements);
+        write(function);
+        function.endMethod();
+    }
 
     @Override
-    void write(MethodWriter writer) {
-        MethodWriter function = writer.newMethodWriter(Opcodes.ACC_PRIVATE | Opcodes.ACC_STATIC, method.method);
-
+    void write(MethodWriter function) {
         if (reserved.getMaxLoopCounter() > 0) {
             // if there is infinite loop protection, we do this once:
             // int #loop = settings.getMaxLoopCounter()
@@ -158,7 +165,5 @@ public class SFunction extends AStatement {
                 throw createError(new IllegalStateException("Illegal tree structure."));
             }
         }
-
-        function.endMethod();
     }
 }

modules/lang-painless/src/main/java/org/elasticsearch/painless/node/SSource.java

@@ -136,25 +136,29 @@ public final class SSource extends AStatement {
         writer.visit(classVersion, classAccess, className, null, classBase, classInterfaces);
         writer.visitSource(Location.computeSourceName(name, source), null);
 
-        // Create the execute MethodWriter.
-
         expressions = new BitSet(source.length());
-        MethodWriter execute = new MethodWriter(Opcodes.ACC_PUBLIC, EXECUTE, writer, expressions);
 
-        // Write the constructor.
+        // Write the constructor:
 
-        MethodWriter constructor = execute.newMethodWriter(Opcodes.ACC_PUBLIC, CONSTRUCTOR);
+        MethodWriter constructor = new MethodWriter(Opcodes.ACC_PUBLIC, CONSTRUCTOR, writer, expressions);
         constructor.loadThis();
         constructor.loadArgs();
         constructor.invokeConstructor(org.objectweb.asm.Type.getType(Executable.class), CONSTRUCTOR);
         constructor.returnValue();
         constructor.endMethod();
 
-        // Write the execute method.
+        // Write the execute method:
 
+        MethodWriter execute = new MethodWriter(Opcodes.ACC_PUBLIC, EXECUTE, writer, expressions);
         write(execute);
         execute.endMethod();
         
+        // Write all functions:
+        
+        for (SFunction function : functions) {
+            function.write(writer, expressions);
+        }
+
         if (!functions.isEmpty()) {
             // write a reference to each function
             for (SFunction function : functions) {
@@ -186,10 +190,6 @@ public final class SSource extends AStatement {
 
     @Override
     void write(MethodWriter writer) {
-        for (SFunction function : functions) {
-            function.write(writer);
-        }
-
         if (reserved.usesScore()) {
             // if the _score value is used, we do this once:
             // final double _score = scorer.score();