Add @supports statements

corpus/statements.txt

@@ -88,6 +88,41 @@ Media statements
     (binary_query (negated_query (keyword_query)) (parenthesized_query (keyword_query)))
     (block)))
 
+==============================
+Supports statements
+==============================
+
+@supports (animation-name: test) {
+  div { animation-name: test; }
+}
+@supports (transform-style: preserve) or (-moz-transform-style: preserve) {}
+@supports not ((text-align-last: justify) or (-moz-text-align-last: justify)) {}
+@supports not selector(:matches(a, b)) {}
+
+---
+
+(stylesheet
+  (supports_statement
+    (feature_query (feature_name) (plain_value))
+    (block
+      (rule_set (selectors (tag_name)) (block
+        (declaration (property_name) (plain_value))))))
+  (supports_statement
+    (binary_query
+      (feature_query (feature_name) (plain_value))
+      (feature_query (feature_name) (plain_value)))
+    (block))
+  (supports_statement
+    (negated_query (parenthesized_query (binary_query
+      (feature_query (feature_name) (plain_value))
+      (feature_query (feature_name) (plain_value)))))
+    (block))
+  (supports_statement
+    (negated_query (selector_query (pseudo_class_selector
+      (class_name)
+      (arguments (plain_value) (plain_value)))))
+    (block)))
+
 ==============================
 Charset statements
 ==============================

grammar.js

@@ -25,6 +25,7 @@ module.exports = grammar({
       $.charset_statement,
       $.namespace_statement,
       $.keyframes_statement,
+      $.supports_statement,
       $.at_rule
     ),
 
@@ -76,6 +77,12 @@ module.exports = grammar({
     from: $ => 'from',
     to: $ => 'to',
 
+    supports_statement: $ => seq(
+      '@supports',
+      $._query,
+      $.block
+    ),
+
     at_rule: $ => seq(
       $.at_keyword,
       commaSep($._query),
@@ -181,6 +188,7 @@ module.exports = grammar({
       $.feature_query,
       $.binary_query,
       $.negated_query,
+      $.selector_query,
       $.parenthesized_query
     ),
 
@@ -209,6 +217,13 @@ module.exports = grammar({
       $._query
     )),
 
+    selector_query: $ => seq(
+      'selector',
+      '(',
+      $._selector,
+      ')'
+    ),
+
     // Property Values
 
     _value: $ => choice(

src/grammar.json

@@ -35,6 +35,10 @@
           "type": "SYMBOL",
           "name": "keyframes_statement"
         },
+        {
+          "type": "SYMBOL",
+          "name": "supports_statement"
+        },
         {
           "type": "SYMBOL",
           "name": "at_rule"
@@ -265,6 +269,23 @@
       "type": "STRING",
       "value": "to"
     },
+    "supports_statement": {
+      "type": "SEQ",
+      "members": [
+        {
+          "type": "STRING",
+          "value": "@supports"
+        },
+        {
+          "type": "SYMBOL",
+          "name": "_query"
+        },
+        {
+          "type": "SYMBOL",
+          "name": "block"
+        }
+      ]
+    },
     "at_rule": {
       "type": "SEQ",
       "members": [
@@ -801,6 +822,10 @@
           "type": "SYMBOL",
           "name": "negated_query"
         },
+        {
+          "type": "SYMBOL",
+          "name": "selector_query"
+        },
         {
           "type": "SYMBOL",
           "name": "parenthesized_query"
@@ -901,6 +926,27 @@
         ]
       }
     },
+    "selector_query": {
+      "type": "SEQ",
+      "members": [
+        {
+          "type": "STRING",
+          "value": "selector"
+        },
+        {
+          "type": "STRING",
+          "value": "("
+        },
+        {
+          "type": "SYMBOL",
+          "name": "_selector"
+        },
+        {
+          "type": "STRING",
+          "value": ")"
+        }
+      ]
+    },
     "_value": {
       "type": "CHOICE",
       "members": [