renderer: put var declarations at right places

lib/spoon/block.js

@@ -24,6 +24,7 @@ function Block(cfg) {
   this.instructions = [];
   this.root = null;
   this.parentRoot = null;
+  this.fn = cfg.currentRoot;
   this.loop = false;
   this.exits = null;
 

lib/spoon/cfg.js

@@ -7,12 +7,12 @@ function Cfg() {
   this.blockId = 0;
 
   this.root = null;
-  this.currentRoot = null;
   this.exits = null;
   this.blocks = [];
   this.roots = [];
   this.rootQueue = [];
   this.current = null;
+  this.currentRoot = null;
   this.asyncifyState = null;
 
   this.breakInfo = null;
@@ -78,9 +78,11 @@ Cfg.prototype.translate = function translate(ast) {
     var root = this.rootQueue.shift(),
         block = this.createBlock();
 
-    if (!this.root) this.root = block;
+    if (!this.root) {
+      this.root = block;
+    }
     this.currentRoot = block;
-
+    block.fn = block;
     this.exits = block.exits = [];
 
     this.roots.push(block);

lib/spoon/instruction.js

@@ -3,6 +3,7 @@ var instruction = exports,
 
 function Instruction(block, type, args) {
   this.block = block;
+  this.fn = block.fn;
   this.cfg = block.cfg;
   this.id = block.cfg.instructionId++;
   this.until = null;
@@ -16,6 +17,7 @@ function Instruction(block, type, args) {
     if (!(arg instanceof Instruction)) return;
     arg.uses.push(this);
   }, this);
+
 };
 instruction.Instruction = Instruction;
 instruction.create = function create(block, type, args) {

lib/spoon/renderer.js

@@ -9,6 +9,7 @@ function Renderer(cfg) {
   // Queue of blocks to visit
   this.queue = null;
   this.slots = null;
+  this.fns = null;
   this.defaultSlots = null;
 
   // Track block visits to perfrom preorder traversal
@@ -71,6 +72,7 @@ Renderer.prototype.render = function render() {
 
   this.queue = [ this.cfg.root ];
   this.slots = {};
+  this.fns = {};
   this.defaultSlots = [ null, result[1] ];
 
   while (this.queue.length > 0) {
@@ -208,10 +210,27 @@ Renderer.prototype.renderInstruction = function renderInstruction(instr) {
   }
 
   var ast = fn.call(this, args, instr);
+  if (external) {
+    if (!instr.fn || instr.fn.id === 0) {
+      if (ast === null) {
+        ast = ['var', [[name[1]]]];
+      } else {
+        ast = ['var', [[name[1], ast]]];
+      }
+    } else {
+      if (ast !== null) {
+        // Wrap instructions with external use into variable declaration.
+        // Insert declaration on the level accessible for both instruction
+        // and it's every use.
+        ast = ['assign', true, name, ast];
+      }
+
+      var decl = ['var', [[name[1]]]];
+      this.fns[instr.fn.id].unshift(decl);
+    }
+  }
   this.instructions[instr.id] = ast;
 
-  // Wrap instructions with external use into variable declaration
-  if (external) ast = ['var', [[name[1], ast]]];
   return ast;
 };
 
@@ -266,6 +285,7 @@ Renderer.prototype.renderFn = function renderFn(args, instr) {
 
   this.queue.unshift(args[0]);
   this.defaultSlots.push(slot);
+  this.fns[instr.args[0].id] = slot;
 
   return [prefix, name, inputs, slot];
 };