[clang] [analyzer] Add std::variant checker (PR #66481)

[via cfe-commits]

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@@ -0,0 +1,312 @@
+//===- StdVariantChecker.cpp -------------------------------------*- C++ -*-==//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "clang/AST/Type.h"
+#include "clang/StaticAnalyzer/Checkers/BuiltinCheckerRegistration.h"
+#include "clang/StaticAnalyzer/Core/BugReporter/BugType.h"
+#include "clang/StaticAnalyzer/Core/Checker.h"
+#include "clang/StaticAnalyzer/Core/CheckerManager.h"
+#include "clang/StaticAnalyzer/Core/PathSensitive/CallDescription.h"
+#include "clang/StaticAnalyzer/Core/PathSensitive/CallEvent.h"
+#include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h"
+#include "llvm/ADT/FoldingSet.h"
+
+#include "TaggedUnionModeling.h"
+
+using namespace clang;
+using namespace ento;
+using namespace variant_modeling;
+
+REGISTER_MAP_WITH_PROGRAMSTATE(VariantHeldTypeMap, const MemRegion *, QualType)
+
+namespace clang {
+namespace ento {
+namespace variant_modeling {
+
+// Returns the CallEvent representing the caller of the function
+// It is needed because the CallEvent class does not contain enough information
+// to tell who called it. Checker context is needed.
+CallEventRef<> getCaller(const CallEvent &Call, const ProgramStateRef &State) {
+  const auto *CallLocationContext = Call.getLocationContext();
+  if (!CallLocationContext) {
+    return nullptr;
+  }
+
+  if (CallLocationContext->inTopFrame()) {
+    return nullptr;
+  }
+  const auto *CallStackFrameContext = CallLocationContext->getStackFrame();
+  if (!CallStackFrameContext) {
+    return nullptr;
+  }
----------------
DonatNagyE wrote:

```suggestion
  if (!CallStackFrameContext)
    return nullptr;
```
See the [LLVM Coding Standards](https://llvm.org/docs/CodingStandards.html#don-t-use-braces-on-simple-single-statement-bodies-of-if-else-loop-statements); also check the braces in the rest of the code.

https://github.com/llvm/llvm-project/pull/66481