Fail on duplicate declarations

When compiling source code we will get errors here but for byte code
we will load the code but in some cases it will be doing the wrong thing.

community/codegen/src/main/java/org/neo4j/codegen/LocalVariables.java

@@ -32,8 +32,12 @@ public class LocalVariables
     private final AtomicInteger counter = new AtomicInteger( 0 );
     private final Map<String,LocalVariable> localVariables = new HashMap<>();
 
-    public LocalVariable createNew( TypeReference type, String name )
+    LocalVariable createNew( TypeReference type, String name )
     {
+        if ( localVariables.containsKey( name ) )
+        {
+            throw new IllegalStateException( String.format( "Local variable %s already in scope", name  ) );
+        }
         LocalVariable localVariable = new LocalVariable( type, name, counter.getAndIncrement() );
         localVariables.put( name, localVariable );
         //if 64 bit types we need to give it one more index

community/codegen/src/main/java/org/neo4j/codegen/bytecode/MethodByteCodeEmitter.java

@@ -63,13 +63,11 @@ class MethodByteCodeEmitter implements MethodEmitter
     private final MethodVisitor methodVisitor;
     private final MethodDeclaration declaration;
     private final ExpressionVisitor expressionVisitor;
-    private final TypeReference base;
     private Deque<Block> stateStack = new LinkedList<>();
 
-    MethodByteCodeEmitter( ClassVisitor classVisitor, MethodDeclaration declaration, TypeReference base )
+    MethodByteCodeEmitter( ClassVisitor classVisitor, MethodDeclaration declaration, TypeReference ignore )
     {
         this.declaration = declaration;
-        this.base = base;
         for ( Parameter parameter : declaration.parameters() )
         {
             TypeReference type = parameter.type();