Clang Rewrite: Locate top of a call expression - clang

Question

I am working on some clang rewrite in source. I want to insert one line before a statement. Like if I have a call from inside an if statement like following:
if (cmp(a,b) > 0 && cmp(c,d) < 0){
//do something
}
I want to rewrite a comment before that if statement, like following:
//there are call inside
if (cmp(a,b) > 0 && cmp(c,d) < 0){
//do something
}
What I could do till now is, I could detect the call with VisitCallExpr(). But how could I find out the location before that if statement to write the comment.
N.B. The if statement here could be for too, like following:
for (int a = 0; a < range(s); a++){
//do something
}
Can anyone help me to find out a way to do this.

Answer 1

I have found a way to do this, although it's not a generalized way to do it. I have opened another question regarding that problem. But, if we consider only the specified situation here like following:
// add something here
if (cmp(a,b)){
//do something
}
We could do with a simple AST matcher:
Matcher.addMatcher(ifStmt(hasCondition(callExpr()))
.bind("call_from_if"),&handleIFCALL);
and handler define should be like:
class IFCALL : public MatchFinder::MatchCallback {
public:
IFCALL(Rewriter &Rewrite) : Rewrite(Rewrite) {}
virtual void run(const MatchFinder::MatchResult &Result) {
const IfStmt *statement =
Result.Nodes.getNodeAs<clang::IfStmt>("call_from_if");
SourceLocation ST = statement->getLocStart();
std::stringstream SSBefore;
SSBefore << "\n \\\\ if statement have call inside \n";
Rewrite.InsertText(ST, SSBefore.str(), true, true);
}
}
private:
Rewriter &Rewrite;
};
This link help me find this solution:
https://jonasdevlieghere.com/understanding-the-clang-ast/
The link to new issue is following:
Clang IfStmt with shortcut binary operator in condition