Ensure that existing blockParams and depths are respected on dupe programs

Fixes #1186

lib/handlebars/compiler/javascript-compiler.js

@@ -778,11 +778,11 @@ JavaScriptCompiler.prototype = {
       child = children[i];
       compiler = new this.compiler();    // eslint-disable-line new-cap
 
-      let index = this.matchExistingProgram(child);
+      let existing = this.matchExistingProgram(child);
 
-      if (index == null) {
+      if (existing == null) {
         this.context.programs.push('');     // Placeholder to prevent name conflicts for nested children
-        index = this.context.programs.length;
+        let index = this.context.programs.length;
         child.index = index;
         child.name = 'program' + index;
         this.context.programs[index] = compiler.compile(child, options, this.context, !this.precompile);
@@ -791,12 +791,14 @@ JavaScriptCompiler.prototype = {
 
         this.useDepths = this.useDepths || compiler.useDepths;
         this.useBlockParams = this.useBlockParams || compiler.useBlockParams;
+        child.useDepths = this.useDepths;
+        child.useBlockParams = this.useBlockParams;
       } else {
-        child.index = index;
-        child.name = 'program' + index;
+        child.index = existing.index;
+        child.name = 'program' + existing.index;
 
-        this.useDepths = this.useDepths || child.useDepths;
-        this.useBlockParams = this.useBlockParams || child.useBlockParams;
+        this.useDepths = this.useDepths || existing.useDepths;
+        this.useBlockParams = this.useBlockParams || existing.useBlockParams;
       }
     }
   },
@@ -804,7 +806,7 @@ JavaScriptCompiler.prototype = {
     for (let i = 0, len = this.context.environments.length; i < len; i++) {
       let environment = this.context.environments[i];
       if (environment && environment.equals(child)) {
-        return i;
+        return environment;
       }
     }
   },