Handle deferred stub with type

src/spectator/double.cr

@@ -1,18 +1,30 @@
 module Spectator
   abstract class Double
     macro stub(definition, &block)
-      delegate {{definition.name.id}}, to: @internal
+      {%
+        name = nil
+        args = nil
+        body = nil
+        if definition.is_a?(Call) # stub foo { :bar }
+          name = definition.name.id
+          args = definition.args
+          body = definition.block.is_a?(Nop) ? block : definition.block
+        elsif definition.is_a?(TypeDeclaration) # stub foo : Symbol
+          name = definition.var
+          args = [] of MacroId
+          body = block
+        else
+          raise "Unrecognized stub format"
+        end
+      %}
+      delegate {{name}}, to: @internal
 
       private class Internal
-        def {{definition.name.id}}({{definition.args.splat}})
-          {% if definition.block.is_a?(Nop) %}
-            {% if block.is_a?(Nop) %}
-              raise "Stubbed method called without being allowed"
-            {% else %}
-              {{block.body}}
-            {% end %}
+        def {{name}}({{args.splat}})
+          {% if body && !body.is_a?(Nop) %}
+            {{body.body}}
           {% else %}
-            {{definition.block.body}}
+            raise "Stubbed method called without being allowed"
           {% end %}
         end
       end