add NonElement() (#11)

* add NonElement()

* lint

parsetag.go

@@ -245,10 +245,3 @@ func WithTag(tag string) FillOptArg {
 		o.tag = tag
 	}
 }
-
-func NonPointer(t reflect.Type) reflect.Type {
-	for t.Kind() == reflect.Ptr {
-		t = t.Elem()
-	}
-	return t
-}

simple.go

@@ -0,0 +1,29 @@
+package reflectutils
+
+import (
+	"reflect"
+)
+
+// NonPointer unwraps pointer types until a type that isn't
+// a pointer is found.
+func NonPointer(t reflect.Type) reflect.Type {
+	for t.Kind() == reflect.Ptr {
+		t = t.Elem()
+	}
+	return t
+}
+
+// NonElement unwraps pointers, slices, arrays, and maps until
+// it finds a type that doesn't support Elem.  It returns that
+// type.
+func NonElement(t reflect.Type) reflect.Type {
+	for {
+		//nolint:exhaustive // deliberately
+		switch t.Kind() {
+		case reflect.Ptr, reflect.Map, reflect.Array, reflect.Slice:
+			t = t.Elem()
+		default:
+			return t
+		}
+	}
+}

simple_test.go

@@ -0,0 +1,21 @@
+package reflectutils_test
+
+import (
+	"reflect"
+	"testing"
+
+	"github.com/muir/reflectutils"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestNonElement(t *testing.T) {
+	a := []map[string][3]int{
+		{
+			"foo": {8, 3, 9},
+		},
+	}
+	got := reflectutils.NonElement(reflect.TypeOf(&a)).String()
+	t.Log(got)
+	assert.Equal(t, reflect.Int.String(), reflectutils.NonElement(reflect.TypeOf(&a)).String())
+}