[clang-tidy] New util `Aliasing` factored out from `bugprone-infinite-loop`

Function `hasPtrOrReferenceInfFunc()` of `bugprone-infinite-loop` is a
generic function which could be reused in another checks. This patch
moves this function into a newly created utility module.

Differential Revision: https://reviews.llvm.org/D81396
diff --git a/clang-tools-extra/clang-tidy/bugprone/InfiniteLoopCheck.cpp b/clang-tools-extra/clang-tidy/bugprone/InfiniteLoopCheck.cpp
index c9dd47e..310fbec 100644
--- a/clang-tools-extra/clang-tidy/bugprone/InfiniteLoopCheck.cpp
+++ b/clang-tools-extra/clang-tidy/bugprone/InfiniteLoopCheck.cpp
@@ -10,8 +10,10 @@
 #include "clang/AST/ASTContext.h"
 #include "clang/ASTMatchers/ASTMatchFinder.h"
 #include "clang/Analysis/Analyses/ExprMutationAnalyzer.h"
+#include "../utils/Aliasing.h"
 
 using namespace clang::ast_matchers;
+using clang::tidy::utils::hasPtrOrReferenceInFunc;
 
 namespace clang {
 namespace tidy {
@@ -24,54 +26,6 @@
                     callExpr(Internal, callee(functionDecl(isNoReturn())))));
 }
 
-/// Return whether `S` is a reference to the declaration of `Var`.
-static bool isAccessForVar(const Stmt *S, const VarDecl *Var) {
-  if (const auto *DRE = dyn_cast<DeclRefExpr>(S))
-    return DRE->getDecl() == Var;
-
-  return false;
-}
-
-/// Return whether `Var` has a pointer or reference in `S`.
-static bool isPtrOrReferenceForVar(const Stmt *S, const VarDecl *Var) {
-  if (const auto *DS = dyn_cast<DeclStmt>(S)) {
-    for (const Decl *D : DS->getDeclGroup()) {
-      if (const auto *LeftVar = dyn_cast<VarDecl>(D)) {
-        if (LeftVar->hasInit() && LeftVar->getType()->isReferenceType()) {
-          return isAccessForVar(LeftVar->getInit(), Var);
-        }
-      }
-    }
-  } else if (const auto *UnOp = dyn_cast<UnaryOperator>(S)) {
-    if (UnOp->getOpcode() == UO_AddrOf)
-      return isAccessForVar(UnOp->getSubExpr(), Var);
-  }
-
-  return false;
-}
-
-/// Return whether `Var` has a pointer or reference in `S`.
-static bool hasPtrOrReferenceInStmt(const Stmt *S, const VarDecl *Var) {
-  if (isPtrOrReferenceForVar(S, Var))
-    return true;
-
-  for (const Stmt *Child : S->children()) {
-    if (!Child)
-      continue;
-
-    if (hasPtrOrReferenceInStmt(Child, Var))
-      return true;
-  }
-
-  return false;
-}
-
-/// Return whether `Var` has a pointer or reference in `Func`.
-static bool hasPtrOrReferenceInFunc(const FunctionDecl *Func,
-                                    const VarDecl *Var) {
-  return hasPtrOrReferenceInStmt(Func->getBody(), Var);
-}
-
 /// Return whether `Var` was changed in `LoopStmt`.
 static bool isChanged(const Stmt *LoopStmt, const VarDecl *Var,
                       ASTContext *Context) {