[clang-tidy] Fix an abseil-redundant-strcat-calls crash on 0-parameter StrCat().

[gribozavr2]

clang-tools-extra/clang-tidy/abseil/RedundantStrcatCallsCheck.cpp

51

Remove the whole call instead of returning?

clang-tools-extra/clang-tidy/abseil/RedundantStrcatCallsCheck.cpp

 namespace {
 
 struct StrCatCheckResult {
   int NumCalls = 0;
   std::vector<FixItHint> Hints;
 };
 
 void RemoveCallLeaveArgs(const CallExpr* Call, StrCatCheckResult* CheckResult) {
+  if (Call->getNumArgs() == 0)
+    return;
   // Remove 'Foo('
   CheckResult->Hints.push_back(
       FixItHint::CreateRemoval(CharSourceRange::getCharRange(
           Call->getBeginLoc(), Call->getArg(0)->getBeginLoc())));
   // Remove the ')'
   CheckResult->Hints.push_back(
       FixItHint::CreateRemoval(CharSourceRange::getCharRange(
           Call->getRParenLoc(), Call->getEndLoc().getLocWithOffset(1))));

clang-tools-extra/test/clang-tidy/checkers/abseil-redundant-strcat-calls.cpp

struct AlphaNum {
   AlphaNum(const string &str);
   AlphaNum(const string_view &pc);
 
  private:
   AlphaNum(const AlphaNum &);
   AlphaNum &operator=(const AlphaNum &);
 };
 
+string StrCat();
 string StrCat(const AlphaNum &A);
 string StrCat(const AlphaNum &A, const AlphaNum &B);
 string StrCat(const AlphaNum &A, const AlphaNum &B, const AlphaNum &C);
 string StrCat(const AlphaNum &A, const AlphaNum &B, const AlphaNum &C,
               const AlphaNum &D);
 
 // Support 5 or more arguments
 template <typename... AV>
void Positives() {
   // Too many args. Ignore for now.
   S = StrCat(1, 2, StrCat(3, 4, 5, 6, 7), 8, 9, 10,
              StrCat(11, 12, 13, 14, 15, 16, 17, 18), 19, 20, 21, 22, 23, 24, 25,
              26, 27);
   // CHECK-MESSAGES: :[[@LINE-3]]:7: warning: multiple calls to 'absl::StrCat' can be flattened into a single call
   StrAppend(&S, StrCat(1, 2, 3, 4, 5), StrCat(6, 7, 8, 9, 10));
   // CHECK-MESSAGES: :[[@LINE-1]]:3: warning: multiple calls to 'absl::StrCat' can be flattened into a single call
   // CHECK-FIXES: StrAppend(&S, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10);
+
+  StrCat(1, StrCat());
+  // CHECK-MESSAGES: :[[@LINE-1]]:3: warning: multiple calls to 'absl::StrCat' can be flattened into a single call
 }
 
 void Negatives() {
   // One arg. It is used for conversion. Ignore.
   string S = StrCat(1);
 
 #define A_MACRO(x, y, z) StrCat(x, y, z)
   S = A_MACRO(1, 2, StrCat("A", "B"));
 }