[clang] [clang][AST] Handle implicit first argument in CallExpr::getBeginLoc() (PR #135757)

[Nathan Ridge via cfe-commits]

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@@ -1652,8 +1652,11 @@ SourceLocation CallExpr::getBeginLoc() const {
   if (!isTypeDependent()) {
     if (const auto *Method =
             dyn_cast_if_present<const CXXMethodDecl>(getCalleeDecl());
-        Method && Method->isExplicitObjectMemberFunction())
-      return getArg(0)->getBeginLoc();
+        Method && Method->isExplicitObjectMemberFunction()) {
+      if (auto FirstArgLoc = getArg(0)->getBeginLoc(); FirstArgLoc.isValid()) {
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HighCommander4 wrote:

Note, I took the approach of falling through if `FirstArgLoc` is invalid for any reason; presumably we never want to return an invalid location when we might fall through to a valid one in `getCallee()->getBeginLoc()`.

We could alternatively make the check more specific, to e.g. `!getArg(0)->isImplicitCXXThis()`.

https://github.com/llvm/llvm-project/pull/135757