[clang] [clang-tools-extra] [clang-tidy][dataflow] Add `bugprone-null-check-after-dereference` check (PR #84166)

[via cfe-commits]

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@@ -0,0 +1,171 @@
+//===--- NullCheckAfterDereferenceCheck.cpp - clang-tidy-------------------===//
+//
+// 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 "NullCheckAfterDereferenceCheck.h"
+#include "clang/AST/ASTContext.h"
+#include "clang/AST/DeclCXX.h"
+#include "clang/AST/DeclTemplate.h"
+#include "clang/ASTMatchers/ASTMatchFinder.h"
+#include "clang/ASTMatchers/ASTMatchers.h"
+#include "clang/Analysis/CFG.h"
+#include "clang/Analysis/FlowSensitive/ControlFlowContext.h"
+#include "clang/Analysis/FlowSensitive/DataflowAnalysisContext.h"
+#include "clang/Analysis/FlowSensitive/DataflowEnvironment.h"
+#include "clang/Analysis/FlowSensitive/DataflowLattice.h"
+#include "clang/Analysis/FlowSensitive/Models/NullPointerAnalysisModel.h"
+#include "clang/Analysis/FlowSensitive/WatchedLiteralsSolver.h"
+#include "clang/Basic/SourceLocation.h"
+#include "llvm/ADT/Any.h"
+#include "llvm/ADT/STLExtras.h"
+#include "llvm/Support/Error.h"
+#include <memory>
+#include <vector>
+
+namespace clang::tidy::bugprone {
+
+using ast_matchers::MatchFinder;
+using dataflow::NullCheckAfterDereferenceDiagnoser;
+using dataflow::NullPointerAnalysisModel;
+
+static constexpr llvm::StringLiteral FuncID("fun");
+
+struct ExpandedResult {
+  SourceLocation WarningLoc;
+  std::optional<SourceLocation> DerefLoc;
+};
+
+using ExpandedResultType =
+    std::pair<std::vector<ExpandedResult>, std::vector<ExpandedResult>>;
+
+static std::optional<ExpandedResultType>
+analyzeFunction(const FunctionDecl &FuncDecl) {
+  using dataflow::ControlFlowContext;
+  using dataflow::DataflowAnalysisState;
+  using llvm::Expected;
+
+  ASTContext &ASTCtx = FuncDecl.getASTContext();
+
+  if (FuncDecl.getBody() == nullptr) {
+    return std::nullopt;
+  }
+
+  Expected<ControlFlowContext> Context =
+      ControlFlowContext::build(FuncDecl, *FuncDecl.getBody(), ASTCtx);
+  if (!Context)
+    return std::nullopt;
+
+  dataflow::DataflowAnalysisContext AnalysisContext(
+      std::make_unique<dataflow::WatchedLiteralsSolver>());
+  dataflow::Environment Env(AnalysisContext, FuncDecl);
+  NullPointerAnalysisModel Analysis(ASTCtx);
+  NullCheckAfterDereferenceDiagnoser Diagnoser;
+  NullCheckAfterDereferenceDiagnoser::ResultType Diagnostics;
+
+  using LatticeState = DataflowAnalysisState<NullPointerAnalysisModel::Lattice>;
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martinboehme wrote:

Nit: This isn't just the "lattice state" -- it's the entire state, comprising the `Environment` and the lattice. Maybe simply `State`?

https://github.com/llvm/llvm-project/pull/84166