add directives to Variable definitions

Author: Stevan Little

ast/ast.ast

@@ -41,6 +41,7 @@ T VariableDefinition
 S Variable variable
 S Type type
 S? Value defaultValue
+P? Directive directives
 
 T SelectionSet
 P Selection selections

parser.ypp

@@ -391,7 +391,7 @@ variable:       VARIABLE { $$ = new Variable(@$, new Name(@1, strdup($1))); }
         ;
 
 variable_definition:
-                variable ":" type default_value_opt { $$ = new VariableDefinition(@$, $1, $3, $4); }
+                variable ":" type default_value_opt directives_opt { $$ = new VariableDefinition(@$, $1, $3, $4, $5); }
         ;
 
 default_value_opt:

test/kitchen-sink.graphql

@@ -57,3 +57,10 @@ fragment frag on Friend {
   unnamed(truthy: true, falsey: false, nullish: null),
   query
 }
+
+query queryByName($name: String @default(value: 100)) {
+  findByName(name: $name) {
+    name
+  }
+}
+