Optimize replaceStack for inline methods

Only use case was with inline input so most of this code was unnecessary.

lib/handlebars/compiler/javascript-compiler.js

@@ -731,9 +731,7 @@ JavaScriptCompiler.prototype = {
     this.flushInline();
 
     var stack = this.incrStack();
-    if (item) {
-      this.pushSource(stack + " = " + item + ";");
-    }
+    this.pushSource(stack + " = " + item + ";");
     this.compileStack.push(stack);
     return stack;
   },
@@ -745,54 +743,40 @@ JavaScriptCompiler.prototype = {
         createdStack,
         usedLiteral;
 
-    // If we are currently inline then we want to merge the inline statement into the
-    // replacement statement via ','
-    if (inline) {
-      var top = this.popStack(true);
+    /* istanbul ignore next */
+    if (!this.isInline()) {
+      throw new Exception('replaceStack on non-inline');
+    }
 
-      if (top instanceof Literal) {
-        // Literals do not need to be inlined
-        stack = top.value;
-        usedLiteral = true;
+    // We want to merge the inline statement into the replacement statement via ','
+    var top = this.popStack(true);
 
-        if (chain) {
-          prefix = stack;
-        }
-      } else {
-        // Get or create the current stack name for use by the inline
-        createdStack = !this.stackSlot;
-        var name = !createdStack ? this.topStackName() : this.incrStack();
+    if (top instanceof Literal) {
+      // Literals do not need to be inlined
+      stack = top.value;
+      usedLiteral = true;
 
-        prefix = '(' + this.push(name) + ' = ' + top + (chain ? ')' : '),');
-        stack = this.topStack();
+      if (chain) {
+        prefix = stack;
       }
     } else {
+      // Get or create the current stack name for use by the inline
+      createdStack = !this.stackSlot;
+      var name = !createdStack ? this.topStackName() : this.incrStack();
+
+      prefix = '(' + this.push(name) + ' = ' + top + (chain ? ')' : '),');
       stack = this.topStack();
     }
 
     var item = callback.call(this, stack);
 
-    if (inline) {
-      if (!usedLiteral) {
-        this.popStack();
-      }
-      if (createdStack) {
-        this.stackSlot--;
-      }
-      this.push('(' + prefix + item + ')');
-    } else {
-      // Prevent modification of the context depth variable. Through replaceStack
-      if (!/^stack/.test(stack)) {
-        stack = this.nextStack();
-      }
-
-      this.pushSource(stack + " = (" + prefix + item + ");");
+    if (!usedLiteral) {
+      this.popStack();
     }
-    return stack;
-  },
-
-  nextStack: function() {
-    return this.pushStack();
+    if (createdStack) {
+      this.stackSlot--;
+    }
+    this.push('(' + prefix + item + ')');
   },
 
   incrStack: function() {