[clang-tidy] Fix readability-simplify-boolean-expr when Ifs have an init statement or condition variable

[njames93]

Summary

Fixes https://github.com/llvm/llvm-project/issues/55553.

[LegalizeAdulthood]

Good catch!

[njames93]

Rebase.

clang-tools-extra/clang-tidy/readability/SimplifyBooleanExprCheck.cpp

static auto checkSingleStatement(Stmt *S, Functor F) -> decltype(F(S)) {
     return F(S);
   }
 
   Stmt *parent() const {
     return StmtStack.size() < 2 ? nullptr : StmtStack[StmtStack.size() - 2];
   }
 
   bool VisitIfStmt(IfStmt *If) {
+    // Skip any if's that have a condition var or an init statement.
+    if (If->hasInitStorage() || If->hasVarStorage())
+      return true;
     /*
      * if (true) ThenStmt(); -> ThenStmt();
      * if (false) ThenStmt(); -> <Empty>;
      * if (false) ThenStmt(); else ElseStmt() -> ElseStmt();
      */
     Expr *Cond = If->getCond()->IgnoreImplicit();
     if (Optional<bool> Bool = getAsBoolLiteral(Cond, true)) {
       if (*Bool)
for (auto First = CS->body_begin(), Second = std::next(First),
         continue;
 
       if (CurIf) {
         /*
          * if (Cond) return true; return false; -> return Cond;
          * if (Cond) return false; return true; -> return !Cond;
          */
         auto *If = cast<IfStmt>(*First);
+        if (!If->hasInitStorage() && !If->hasVarStorage()) {
           ExprAndBool ThenReturnBool =
               checkSingleStatement(If->getThen(), parseReturnLiteralBool);
-        if (ThenReturnBool && ThenReturnBool.Bool != TrailingReturnBool.Bool) {
+          if (ThenReturnBool &&
+              ThenReturnBool.Bool != TrailingReturnBool.Bool) {
             if (Check->ChainedConditionalReturn ||
                 (!PrevIf && If->getElse() == nullptr)) {
               Check->replaceCompoundReturnWithCondition(
-                Context, cast<ReturnStmt>(*Second), TrailingReturnBool.Bool, If,
-                ThenReturnBool.Item);
+                  Context, cast<ReturnStmt>(*Second), TrailingReturnBool.Bool,
+                  If, ThenReturnBool.Item);
+            }
           }
         }
       } else if (isa<LabelStmt, CaseStmt, DefaultStmt>(*First)) {
         /*
          * (case X|label_X|default): if (Cond) return BoolLiteral;
          *                           return !BoolLiteral
          */
         Stmt *SubStmt =
             isa<LabelStmt>(*First)  ? cast<LabelStmt>(*First)->getSubStmt()
             : isa<CaseStmt>(*First) ? cast<CaseStmt>(*First)->getSubStmt()
                                     : cast<DefaultStmt>(*First)->getSubStmt();
         auto *SubIf = dyn_cast<IfStmt>(SubStmt);
-        if (SubIf && !SubIf->getElse()) {
+        if (SubIf && !SubIf->getElse() && !SubIf->hasInitStorage() &&
+            !SubIf->hasVarStorage()) {
           ExprAndBool ThenReturnBool =
               checkSingleStatement(SubIf->getThen(), parseReturnLiteralBool);
           if (ThenReturnBool &&
               ThenReturnBool.Bool != TrailingReturnBool.Bool) {
             Check->replaceCompoundReturnWithCondition(
                 Context, cast<ReturnStmt>(*Second), TrailingReturnBool.Bool,
                 SubIf, ThenReturnBool.Item);
           }

clang-tools-extra/test/clang-tidy/checkers/readability-simplify-bool-expr-cxx17.cpp

+// RUN: clang-tidy %s -checks='-*,readability-simplify-boolean-expr' -- -std=c++17 | count 0
+struct RAII {};
+bool foo(bool Cond) {
+  bool Result;
+
+  if (RAII Object; Cond)
+    Result = true;
+  else
+    Result = false;
+
+  if (bool X = Cond; X)
+    Result = true;
+  else
+    Result = false;
+
+  if (bool X = Cond; X)
+    return true;
+  return false;
+}

clang-tools-extra/test/clang-tidy/checkers/readability-simplify-bool-expr.cpp

auto lambda6 = [](int n) -> bool {
     }
   };
   // CHECK-MESSAGES: :[[@LINE-5]]:16: warning: {{.*}} in conditional return statement
   // CHECK-FIXES:      {{^}}  auto lambda6 = [](int n) -> bool {{{$}}
   // CHECK-FIXES-NEXT: {{^}}    return n <= 0;{{$}}
   // CHECK-FIXES-NEXT: {{^}}  };{{$}}
 }
 
+bool condition_variable_return_stmt(int i) {
+  // Unchanged: condition variable.
+  if (bool Res = i == 0)
+    return true;
+  else
+    return false;
+}
+
 void simple_conditional_assignment_statements(int i) {
   bool b;
   if (i > 10)
     b = true;
   else
     b = false;
   bool bb = false;
   // CHECK-MESSAGES: :[[@LINE-4]]:9: warning: {{.*}} in conditional assignment
void complex_conditional_assignment_statements(int i) {
 
   // Unchanged: multiple statements.
   bool h;
   if (j > 10) {
     j = 10;
     h = true;
   } else
     h = false;
+
+  // Unchanged: condition variable.
+  bool k;
+  if (bool Res = j > 10)
+    k = true;
+  else
+    k = false;
 }
 
 // Unchanged: chained return statements, but ChainedConditionalReturn not set.
 bool chained_conditional_compound_return(int i) {
   if (i < 0) {
     return true;
   } else if (i < 10) {
     return false;