[clangd] Fix some clang-tidy warnings on SourceCodeTests.cpp, NFC.

using llvm::Failed;

using llvm::HasValue;

using ::testing::UnorderedElementsAreArray;

MATCHER_P2(Pos, Line, Col, "") {

  return arg.line == int(Line) && arg.character == int(Col);

MATCHER_P(MacroName, Name, "") { return arg.Name == Name; }

/// A helper to make tests easier to read.

Position position(int line, int character) {

Position position(int Line, int Character) {

  Position Pos;

  Pos.line = line;

  Pos.character = character;

  Pos.line = Line;

  Pos.character = Character;

  return Pos;

}

Range range(const std::pair<int, int> p1, const std::pair<int, int> p2) {

  Range range;

  range.start = position(p1.first, p1.second);

  range.end = position(p2.first, p2.second);

  return range;

Range range(const std::pair<int, int> &P1, const std::pair<int, int> &P2) {

  Range Range;

  Range.start = position(P1.first, P1.second);

  Range.end = position(P2.first, P2.second);

  return Range;

}

TEST(SourceCodeTests, lspLength) {