fix macro registration issue and match by kind for MVC and hero instead of its kind, so custom types like structs can be used without any issues. Add an example on how to register a custom macro it is just few lines and all in one place in this version.

Former-commit-id: 93c439560fcfad820f9f3e39c1d9557c83cef0ee

macro/macros.go

@@ -10,10 +10,10 @@ import (
 var (
 	// String type
 	// Allows anything (single path segment, as everything except the `Path`).
+	// Its functions can be used by the rest of the macros and param types whenever not available function by name is used.
+	// Because of its "master" boolean value to true (third parameter).
 	String = NewMacro("string", "", true, false, nil).
-		RegisterFunc("regexp", func(expr string) func(string) bool {
-			return MustRegexp(expr)
-		}).
+		RegisterFunc("regexp", MustRegexp).
 		// checks if param value starts with the 'prefix' arg
 		RegisterFunc("prefix", func(prefix string) func(string) bool {
 			return func(paramValue string) bool {
@@ -431,21 +431,22 @@ func (ms *Macros) Register(indent, alias string, isMaster, isTrailing bool, eval
 }
 
 func (ms *Macros) register(macro *Macro) bool {
-	if macro.Indent() == "" || macro.Evaluator == nil {
+	if macro.Indent() == "" {
 		return false
 	}
 
 	cp := *ms
 
 	for _, m := range cp {
-
 		// can't add more than one with the same ast characteristics.
 		if macro.Indent() == m.Indent() {
 			return false
 		}
 
-		if macro.Alias() == m.Alias() || macro.Alias() == m.Indent() {
-			return false
+		if alias := macro.Alias(); alias != "" {
+			if alias == m.Alias() || alias == m.Indent() {
+				return false
+			}
 		}
 
 		if macro.Master() && m.Master() {