How to figure out the source range of an implicit lambda field in clang-tidy, like that in clang-query?

Beginners
1

Given the following code:

class Foo {};
void f() {
  Foo* uooooo = nullptr;
  int* ip = nullptr;
  auto lambda = [uooooo, ip](){
    if (uooooo != nullptr) {
      ++*ip;
    }
  };
}

Runing the matcher in clang-query:

clang-query> m lambdaExpr(forEachDescendant(fieldDecl().bind("x")))

Match #1:

C:\llvm-project\clang-tools-extra\test\clang-tidy\.\temp.cpp(5,17): note: "root" binds here
    5 |   auto lambda = [uooooo, ip](){};
      |                 ^~~~~~~~~~~~~~~~
C:\llvm-project\clang-tools-extra\test\clang-tidy\.\temp.cpp(5,18): note: "x" binds here
    5 |   auto lambda = [uooooo, ip](){};
      |                  ^~~~~~

Match #2:

C:\llvm-project\clang-tools-extra\test\clang-tidy\.\temp.cpp(5,17): note: "root" binds here
    5 |   auto lambda = [uooooo, ip](){};
      |                 ^~~~~~~~~~~~~~~~
C:\llvm-project\clang-tools-extra\test\clang-tidy\.\temp.cpp(5,26): note: "x" binds here
    5 |   auto lambda = [uooooo, ip](){};
      |                          ^~
2 matches.
clang-query>

Implementing the same matcher in a clang-tidy check:

void LambdaCaptureRawPointerCheck::registerMatchers(
    MatchFinder *Finder) {
  auto Matcher = lambdaExpr(forEachDescendant(fieldDecl().bind("x")));
  Finder->addMatcher(Matcher, this);
}
void LambdaCaptureRawPointerCheck::check(
    const MatchFinder::MatchResult &Result) {
  const auto *Matched = Result.Nodes.getNodeAs<FieldDecl>("x");
  const auto &SM = Matched->getASTContext().getSourceManager();
  auto SR = Matched->getSourceRange();
  SR.dump(SM);
  Matched->getBeginLoc().dump(SM);
  Matched->getEndLoc().dump(SM);
}

The output of running the check on the sample code:

<C:\llvm-project\clang-tools-extra\test\clang-tidy\.\temp.cpp:5:18>
C:\llvm-project\clang-tools-extra\test\clang-tidy\.\temp.cpp:5:18
C:\llvm-project\clang-tools-extra\test\clang-tidy\.\temp.cpp:5:18
<C:\llvm-project\clang-tools-extra\test\clang-tidy\.\temp.cpp:5:26>
C:\llvm-project\clang-tools-extra\test\clang-tidy\.\temp.cpp:5:26
C:\llvm-project\clang-tools-extra\test\clang-tidy\.\temp.cpp:5:26

In clang-tidy the matched FieldDecl has a zero-length source range, I guess this is because it is an implicit one. However, clang-query has a way to figure out the original piece of code an implicit lambda field matches. This is indicated by the ~s marking the indentifier uooooo and ip. I want to know how can I do the same in a clang-tidy check?

Thanks

2

I have found that clang-query marks those identifiers by using Lexer::MeasureTokenLength to comupte the end location of the token, rather than the FieldDecl.