kataras/iris · error

invalid syntax: the standard go type: %s found in controller

Error message

invalid syntax: the standard go type: %s found in controller's function: %s at position: %d does not match any valid macro

What it means

When binding a controller method to a route, the mvc parser inspects each function parameter's Go type to infer a macro (int, int64, string, bool, etc.). If the parameter's type is a standard Go type that has no registered macro (e.g. float32, uint, time.Time, or a custom struct used as a path parameter), parsing aborts with this error, naming the type, the method, and the argument position.

Source

Thrown at mvc/controller_method_parser.go:267

		// validMacros := p.macros.LookupForGoType(goType)

		// instead of mapping with a reflect.Kind which has its limitation,
		// we map the param types with a go type as a string,
		// so custom structs such as "user" can be mapped to a macro with indent || alias == "user".
		m = p.macros.Get(strings.ToLower(goType.String()))

		if m == nil {
			if typ.NumIn() > funcArgPos {
				// has more input arguments but we are not in the correct
				// index now, maybe the first argument was an `iris/context.Context`
				// so retry with the "funcArgPos" incremented.
				//
				// the "funcArgPos" will be updated to the caller as well
				// because we return it among the path and the error.
				return p.parsePathParam(path, w, funcArgPos+1)
			}

			return "", 0, fmt.Errorf("invalid syntax: the standard go type: %s found in controller's function: %s at position: %d does not match any valid macro", goType, p.fn.Name, funcArgPos)
		}
	}

	// /{argfirst:path}, /{argfirst:int64}...
	if path[len(path)-1] != '/' {
		path += "/"
	}
	path += fmt.Sprintf("{%s:%s}", paramKey, m.Indent())

	if nextWord == "" && typ.NumIn() > funcArgPos+1 {
		// By is the latest word but func is expected
		// more path parameters values, i.e:
		// GetBy(name string, age int)
		// The caller (parse) doesn't need to know
		// about the incremental funcArgPos because
		// it will not need it.
		return p.parsePathParam(path, nextWord, funcArgPos+1)
	}

View on GitHub (pinned to 7bedaf55a0)

Solutions

1. Change the method parameter to a supported macro type (int, int64, string, bool, float64, etc.).
2. Take the value as string and convert inside the method (e.g. parse UUID/time manually).
3. Register a custom macro for the type via macro registry (context.RegisterMacro / handler.Macro) if it must stay typed.
4. Check the reported position (funcArgPos, 0-based) to find the offending parameter quickly.

Example fix

// before
func (c *Controller) Get(id uint) {}
// after
func (c *Controller) Get(id int64) {}

var supported = map[reflect.Kind]bool{
    reflect.String: true, reflect.Int: true, reflect.Int64: true,
    reflect.Float64: true, reflect.Bool: true,
}
func paramTypeOK(t reflect.Type) bool { return supported[t.Kind()] }

func isMacroCompatible(v any) bool {
    switch v.(type) {
    case string, int, int8, int16, int32, int64,
        uint, uint8, uint16, uint32, uint64,
        float32, float64, bool:
        return true
    }
    return false
}

if err := mvc.New(app).Handle(new(MyController)); err != nil {
    if strings.Contains(err.Error(), "does not match any valid macro") {
        log.Fatalf("controller param type unsupported: %v", err)
    }
}

When it happens

Trigger: Defining a controller method with a path parameter whose Go type is not one of the supported macro types (string, int, int8..., int64, uint..., float32/float64, bool) and binding it via Handle or PartyController.

Common situations: Using float32/uint for path params, or custom types like time.Time/uuid.UUID directly as dynamic path arguments without registering a custom macro or pre-converting to string.

Related errors

• errors joined from param parser: strings.Join(p.errors, "\n"
• parameter is not alphabetical
• parameter is not a file
• parameter is not a valid weekday
• no trailing path parameter found

AI-assisted analysis of kataras/iris@7bedaf55a0 (2026-08-30). Data as JSON: /api/errors/9f13eda574d15048. Report an issue: GitHub.