add Unused

Author: muir

api.go

@@ -579,3 +579,11 @@ func (c *Collection) MustSetCallback(binderFunction interface{}) {
 		panic(DetailedError(err))
 	}
 }
+
+type unused struct{}
+
+// Unused is value that a function that returns injectors can return that will never be
+// included in an injection chain. Unused can be used in situations where you want to
+// call a function as part of generating a list of injectors and functions in such a list
+// must have a return value.
+var Unused = Provide("unused", unused{})

bind_test.go

@@ -305,6 +305,9 @@ func TestLiteral(t *testing.T) {
 		counts := make(map[string]int)
 		c := Sequence("TBF",
 			s1("s1 value"),
+			func() Provider {
+				return Unused
+			}(),
 			Cacheable(func(s s1) s2 {
 				counts["s2"]++
 				assert.Equal(t, s1("s1 value"), s)