golang fmt String()、Error()、Format()、GoString()优先级

func (p *pp) handleMethods(verb rune) (handled bool) {
	if p.erroring {
		return
	}
	if verb == 'w' {
		// It is invalid to use %w other than with Errorf, more than once,
		// or with a non-error arg.
		err, ok := p.arg.(error)
		if !ok || !p.wrapErrs || p.wrappedErr != nil {
			p.wrappedErr = nil
			p.wrapErrs = false
			p.badVerb(verb)
			return true
		}
		p.wrappedErr = err
		// If the arg is a Formatter, pass 'v' as the verb to it.
		verb = 'v'
	}

	// Is it a Formatter?
	if formatter, ok := p.arg.(Formatter); ok {
		handled = true
		defer p.catchPanic(p.arg, verb, "Format")
		formatter.Format(p, verb)
		return
	}

	// If we're doing Go syntax and the argument knows how to supply it, take care of it now.
	if p.fmt.sharpV {
		if stringer, ok := p.arg.(GoStringer); ok {
			handled = true
			defer p.catchPanic(p.arg, verb, "GoString")
			// Print the result of GoString unadorned.
			p.fmt.fmtS(stringer.GoString())
			return
		}
	} else {
		// If a string is acceptable according to the format, see if
		// the value satisfies one of the string-valued interfaces.
		// Println etc. set verb to %v, which is "stringable".
		switch verb {
		case 'v', 's', 'x', 'X', 'q':
			// Is it an error or Stringer?
			// The duplication in the bodies is necessary:
			// setting handled and deferring catchPanic
			// must happen before calling the method.
			switch v := p.arg.(type) {
			case error:
				handled = true
				defer p.catchPanic(p.arg, verb, "Error")
				p.fmtString(v.Error(), verb)
				return

			case Stringer:
				handled = true
				defer p.catchPanic(p.arg, verb, "String")
				p.fmtString(v.String(), verb)
				return
			}
		}
	}
	return false
}

	// If the type is not simple, it might have methods.
		if !p.handleMethods(verb) {
			// Need to use reflection, since the type had no
			// interface methods that could be used for formatting.
			p.printValue(reflect.ValueOf(f), verb, 0)
		}

根据代码可知优先级为：Format()>('#') GoString()> ('v', 's', 'x', 'X', 'q') Error()> ('v', 's', 'x', 'X', 'q') String() >反射