! not followed by important is just another declaration value.

Author: SimonSapin

declaration_list.json

@@ -13,7 +13,7 @@
 ],
 
 "z:x!;a:b", [
-    ["error", "invalid"],
+    ["declaration", "z", [["ident", "x"], "!"], false],
     ["declaration", "a", [["ident", "b"]], false]
 ],
 

one_declaration.json

@@ -23,8 +23,12 @@
     " ", ["number", "9000", 9000, "integer"], " "
 ], true],
 
-"foo: 9000  /* Dotted capital I */!İmportant", ["error", "invalid"],
-"foo: 9000  !important!", ["error", "invalid"],
+"foo: 9000  /* Dotted capital I */!İmportant", ["declaration", "foo", [
+    " ", ["number", "9000", 9000, "integer"], " ", "!", ["ident", "İmportant"]
+], false],
+"foo: 9000  !important!", ["declaration", "foo", [
+    " ", ["number", "9000", 9000, "integer"], " ", "!", ["ident", "important"], "!"
+], false],
 
 "foo: 9000  important", ["declaration", "foo", [
     " ", ["number", "9000", 9000, "integer"], " ", ["ident", "important"]