Fix property interpolation for @* values

Author: seven-phases-max

lib/less/tree/rule.js

@@ -1,14 +1,15 @@
 (function (tree) {
 
-tree.Rule = function (name, value, important, merge, index, currentFileInfo, inline) {
+tree.Rule = function (name, value, important, merge, index, currentFileInfo, inline, variable) {
     this.name = name;
     this.value = (value instanceof tree.Value || value instanceof tree.Ruleset) ? value : new(tree.Value)([value]);
     this.important = important ? ' ' + important.trim() : '';
     this.merge = merge;
     this.index = index;
     this.currentFileInfo = currentFileInfo;
     this.inline = inline || false;
-    this.variable = name.charAt && (name.charAt(0) === '@');
+    this.variable = (variable !== undefined) ? variable
+        : (name.charAt && (name.charAt(0) === '@'));
 };
 
 tree.Rule.prototype = {
@@ -30,13 +31,14 @@ tree.Rule.prototype = {
     },
     toCSS: tree.toCSS,
     eval: function (env) {
-        var strictMathBypass = false, name = this.name, evaldValue;
+        var strictMathBypass = false, name = this.name, variable = this.variable, evaldValue;
         if (typeof name !== "string") {
             // expand 'primitive' name directly to get
             // things faster (~10% for benchmark.less):
             name = (name.length === 1) 
                 && (name[0] instanceof tree.Keyword)
                     ? name[0].value : evalName(env, name);
+            variable = false; // never treat expanded interpolation as new variable name
         }
         if (name === "font" && !env.strictMath) {
             strictMathBypass = true;
@@ -54,7 +56,8 @@ tree.Rule.prototype = {
                               evaldValue,
                               this.important,
                               this.merge,
-                              this.index, this.currentFileInfo, this.inline);
+                              this.index, this.currentFileInfo, this.inline,
+                              variable);
         }
         catch(e) {
             if (typeof e.index !== 'number') {

test/css/property-name-interp.css

@@ -1,5 +1,6 @@
 pi-test {
   border: 0;
+  @not-variable: @not-variable;
   ufo-width: 50%;
   *-z-border: 1px dashed blue;
   -www-border-top: 2px;

test/less/property-name-interp.less

@@ -6,8 +6,11 @@ pi-test {
     @c_c:    left;
     @d-d4: radius;
     @-:         -;
-    
+
+    @var: ~'@not-variable';
+
     @{a}: 0;
+    @{var}: @var;
     @{prefix}width: 50%;
     *-z-@{a} :1px dashed blue;
     -www-@{a}-@{bb}: 2px;