[clang-tools-extra] Fix the issue #139467 ([clang-tidy] false positive narrowing conversion) (PR #139474)

[Baranov Victor via cfe-commits]

================
@@ -554,15 +554,23 @@ bool NarrowingConversionsCheck::handleConditionalOperator(
     // We have an expression like so: `output = cond ? lhs : rhs`
     // From the point of view of narrowing conversion we treat it as two
     // expressions `output = lhs` and `output = rhs`.
-    handleBinaryOperator(Context, CO->getLHS()->getExprLoc(), Lhs,
-                         *CO->getLHS());
-    handleBinaryOperator(Context, CO->getRHS()->getExprLoc(), Lhs,
-                         *CO->getRHS());
+    handleConditionalOperatorArgument(Context, Lhs, CO->getLHS());
+    handleConditionalOperatorArgument(Context, Lhs, CO->getRHS());
     return true;
   }
   return false;
 }
 
+void NarrowingConversionsCheck::handleConditionalOperatorArgument(
+    const ASTContext &Context, const Expr &Lhs, const Expr *Arg) {
+  if (const auto *ICE = llvm::dyn_cast<ImplicitCastExpr>(Arg)) {
+    if (!Arg->getIntegerConstantExpr(Context)) {
+      Arg = ICE->getSubExpr();
+    }
+  }
----------------
vbvictor wrote:

As per LLVM coding-style, there shouldn't be any braces for single-stmt ifs.
```cpp
if (const auto *ICE = llvm::dyn_cast<ImplicitCastExpr>(Arg))
    if (!Arg->getIntegerConstantExpr(Context))
      Arg = ICE->getSubExpr();
```

https://github.com/llvm/llvm-project/pull/139474