return "", err
			}
			return "", &Error{ErrInvalidNamedCapture, s}
		}

		capture := t[:end+1]        // "(?P<name>" or "(?<name>"
		name := t[exprStartPos:end] // "name"
		if err = checkUTF8(name); err != nil {
			return "", err
		}
		if !isValidCaptureName(name) {
			return "", &Error{ErrInvalidNamedCapture, capture}
		}

		// Like ordinary capture, but named.