support @host. Fixes #1560

lib/less/parser.js

@@ -1508,6 +1508,7 @@ less.Parser = function Parser(env) {
                     case "@right-bottom":
                         hasBlock = true;
                         break;
+                    case "@host":
                     case "@page":
                     case "@document":
                     case "@supports":

test/css/css-3.css

@@ -115,3 +115,11 @@ h1 {
 .upper-test {
   UpperCaseProperties: allowed;
 }
+@host {
+  div {
+    display: block;
+  }
+}
+::distributed(input::placeholder) {
+  color: #b3b3b3;
+}

test/less/css-3.less

@@ -114,4 +114,12 @@ foo|* { color: yellow; }
 h1 { color: green; }
 .upper-test {
   UpperCaseProperties: allowed;
+}
+@host {
+  div {
+    display: block;
+  }
+}
+::distributed(input::placeholder) {
+  color: #b3b3b3;
 }