Method scanUnicodeEscape

internal/scanner/scanner.go:1855–1903

Known to be at \u

(shouldEmitInvalidEscapeError bool)

// Known to be at \u
func (s *Scanner) scanUnicodeEscape(shouldEmitInvalidEscapeError bool) rune {
	s.pos += 2
	start := s.pos
	extended := s.char() == '{'
	var hexDigits string
	if extended {
		s.pos++
		hexDigits = s.scanHexDigits(1, true, false)
	} else {
		s.tokenFlags |= ast.TokenFlagsUnicodeEscape
		hexDigits = s.scanHexDigits(4, false, false)
	}
	if hexDigits == "" {
		s.tokenFlags |= ast.TokenFlagsContainsInvalidEscape
		if shouldEmitInvalidEscapeError {
			s.error(diagnostics.Hexadecimal_digit_expected)
		}
		return -1
	}
	hexValue, _ := strconv.ParseInt(hexDigits, 16, 32)
	if extended {
		isInvalidExtendedEscape := false
		if hexValue > 0x10FFFF {
			if shouldEmitInvalidEscapeError {
				s.errorAt(diagnostics.An_extended_Unicode_escape_value_must_be_between_0x0_and_0x10FFFF_inclusive, start+1, s.pos-start-1)
			}
			isInvalidExtendedEscape = true
		}
		if s.pos >= s.end {
			if shouldEmitInvalidEscapeError {
				s.error(diagnostics.Unexpected_end_of_text)
			}
			isInvalidExtendedEscape = true
		} else if s.char() == '}' {
			s.pos++
		} else {
			if shouldEmitInvalidEscapeError {
				s.error(diagnostics.Unterminated_Unicode_escape_sequence)
			}
			isInvalidExtendedEscape = true
		}
		if isInvalidExtendedEscape {
			s.tokenFlags |= ast.TokenFlagsContainsInvalidEscape
			return -1
		}
		s.tokenFlags |= ast.TokenFlagsExtendedUnicodeEscape
	}
	return rune(hexValue)
}

// scanLowSurrogateEscape attempts to consume a low-surrogate Unicode escape
// (either '\uLow' or '\u{Low}') immediately following an already-scanned high