cmp/report_reflect.go
func (opts formatOptions) FormatType(t reflect.Type, s textNode) textNode {
	// Check whether to emit the type or not.
	switch opts.TypeMode {
	case autoType:
		switch t.Kind() {
		case reflect.Struct, reflect.Slice, reflect.Array, reflect.Map:
			if s.Equal(textNil) {
				return s
			}
		default:
			return s
		}
	case elideType:
		return s
	}

	// Determine the type label, applying special handling for unnamed types.
	typeName := t.String()
	if t.Name() == "" {
		// According to Go grammar, certain type literals contain symbols that
		// do not strongly bind to the next lexicographical token (e.g., *T).
		switch t.Kind() {
		case reflect.Chan, reflect.Func, reflect.Ptr:
			typeName = "(" + typeName + ")"
		}
		typeName = strings.Replace(typeName, "struct {", "struct{", -1)
		typeName = strings.Replace(typeName, "interface {", "interface{", -1)
	}

	// Avoid wrap the value in parenthesis if unnecessary.
	if s, ok := s.(textWrap); ok {
		hasParens := strings.HasPrefix(s.Prefix, "(") && strings.HasSuffix(s.Suffix, ")")
		hasBraces := strings.HasPrefix(s.Prefix, "{") && strings.HasSuffix(s.Suffix, "}")
		if hasParens || hasBraces {
			return textWrap{typeName, s, ""}
		}
	}
	return textWrap{typeName + "(", s, ")"}
}
func (opts formatOptions) FormatType(t reflect.Type, s textNode) textNode {
	// Check whether to emit the type or not.
	switch opts.TypeMode {
	case autoType:
		switch t.Kind() {
		case reflect.Struct, reflect.Slice, reflect.Array, reflect.Map:
			if s.Equal(textNil) {
				return s
			}
		default:
			return s
		}
	case elideType:
		return s
	}

	// Determine the type label, applying special handling for unnamed types.
	typeName := t.String()
	if t.Name() == "" {
		// According to Go grammar, certain type literals contain symbols that
		// do not strongly bind to the next lexicographical token (e.g., *T).
		switch t.Kind() {
		case reflect.Chan, reflect.Func, reflect.Ptr:
			typeName = "(" + typeName + ")"
		}
		typeName = strings.Replace(typeName, "struct {", "struct{", -1)
		typeName = strings.Replace(typeName, "interface {", "interface{", -1)
	}

	// Avoid wrap the value in parenthesis if unnecessary.
	if s, ok := s.(textWrap); ok {
		hasParens := strings.HasPrefix(s.Prefix, "(") && strings.HasSuffix(s.Suffix, ")")
		hasBraces := strings.HasPrefix(s.Prefix, "{") && strings.HasSuffix(s.Suffix, "}")
		if hasParens || hasBraces {
			return textWrap{typeName, s, ""}
		}
	}
	return textWrap{typeName + "(", s, ")"}
}
// FormatType prints the type as if it were wrapping s.
// This may return s as-is depending on the current type and TypeMode mode.