[clang-tidy] Added check to disable bugprone-infinite-loop on known false condition

[njames93]

Summary

Addresses bugprone-infinite-loop false positive with CATCH2 by disabling the check on loops where the condition is known to always eval as false, in other words not a loop.

clang-tools-extra/clang-tidy/bugprone/InfiniteLoopCheck.cpp

for (const Stmt *Child : Cond->children()) {
     std::string NewNames = getCondVarNames(Child);
     if (!Result.empty() && !NewNames.empty())
       Result += ", ";
     Result += NewNames;
   }
   return Result;
 }
 
+static bool isKnownFalse(const Expr &Cond, const ASTContext &Ctx) {
+  bool Result = false;
+  if (Cond.EvaluateAsBooleanCondition(Result, Ctx))
+    return !Result;
+  return false;
+}
+
 void InfiniteLoopCheck::registerMatchers(MatchFinder *Finder) {
   const auto LoopCondition = allOf(
       hasCondition(
           expr(forFunction(functionDecl().bind("func"))).bind("condition")),
       unless(hasBody(hasDescendant(
           loopEndingStmt(forFunction(equalsBoundNode("func")))))));
 
   Finder->addMatcher(stmt(anyOf(whileStmt(LoopCondition), doStmt(LoopCondition),
                                 forStmt(LoopCondition)))
                          .bind("loop-stmt"),
                      this);
 }
 
 void InfiniteLoopCheck::check(const MatchFinder::MatchResult &Result) {
   const auto *Cond = Result.Nodes.getNodeAs<Expr>("condition");
   const auto *LoopStmt = Result.Nodes.getNodeAs<Stmt>("loop-stmt");
   const auto *Func = Result.Nodes.getNodeAs<FunctionDecl>("func");
 
+  if (isKnownFalse(*Cond, *Result.Context))
+    return;
+
   bool ShouldHaveConditionVariables = true;
   if (const auto *While = dyn_cast<WhileStmt>(LoopStmt)) {
     if (const VarDecl *LoopVarDecl = While->getConditionVariable()) {
       if (const Expr *Init = LoopVarDecl->getInit()) {
         ShouldHaveConditionVariables = false;
         Cond = Init;
       }
     }

clang-tools-extra/test/clang-tidy/checkers/bugprone-infinite-loop.cpp

while (i < Limit) {
     auto l = [&i]() { ++i; };
   }
 
   do {
     int *p = &i;
     (*p)++;
   } while (i < Limit);
 }
+
+void evaluatable(bool CondVar) {
+  for (; false && CondVar;) {
+  }
+  while (false && CondVar) {
+  }
+  do {
+  } while (false && CondVar);
+}