[clang-tools-extra] [clang-tidy] introduce a unused local non trival variable check (PR #76101)

[Piotr Zegar via cfe-commits]

================
@@ -0,0 +1,89 @@
+//===--- UnusedLocalNonTrivialVariableCheck.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 "UnusedLocalNonTrivialVariableCheck.h"
+#include "../utils/Matchers.h"
+#include "../utils/OptionsUtils.h"
+#include "clang/AST/ASTContext.h"
+#include "clang/AST/ASTTypeTraits.h"
+#include "clang/AST/Type.h"
+#include "clang/ASTMatchers/ASTMatchFinder.h"
+#include "clang/ASTMatchers/ASTMatchers.h"
+#include "clang/ASTMatchers/ASTMatchersMacros.h"
+
+using namespace clang::ast_matchers;
+using namespace clang::tidy::matchers;
+
+namespace clang::tidy::bugprone {
+
+namespace {
+static constexpr StringRef DefaultIncludeTypeRegex = "std::.*mutex;std::future";
+
+AST_MATCHER(VarDecl, isLocalVarDecl) { return Node.isLocalVarDecl(); }
+AST_MATCHER(VarDecl, isReferenced) { return Node.isReferenced(); }
+AST_MATCHER(Type, isReferenceType) { return Node.isReferenceType(); }
+} // namespace
+
+UnusedLocalNonTrivialVariableCheck::UnusedLocalNonTrivialVariableCheck(
+    StringRef Name, ClangTidyContext *Context)
+    : ClangTidyCheck(Name, Context),
+      IncludeTypeRegex(utils::options::parseStringList(
+          Options.get("IncludeTypeRegex", DefaultIncludeTypeRegex))),
+      ExcludeTypeRegex(utils::options::parseStringList(
+          Options.get("ExcludeTypeRegex", ""))) {}
+
+void UnusedLocalNonTrivialVariableCheck::storeOptions(
+    ClangTidyOptions::OptionMap &Opts) {
+  Options.store(Opts, "IncludeTypeRegex",
+                utils::options::serializeStringList(IncludeTypeRegex));
+  Options.store(Opts, "ExcludeTypeRegex",
+                utils::options::serializeStringList(ExcludeTypeRegex));
+}
+
+void UnusedLocalNonTrivialVariableCheck::registerMatchers(MatchFinder *Finder) {
+  if (IncludeTypeRegex.empty())
+    return;
+
+  Finder->addMatcher(
+      varDecl(
+          isLocalVarDecl(), unless(isReferenced()),
+          unless(isExpansionInSystemHeader()), unless(isImplicit()),
+          unless(isExceptionVariable()), hasLocalStorage(), isDefinition(),
+          unless(hasType(isReferenceType())),
+          hasType(hasUnqualifiedDesugaredType(recordType(hasDeclaration(
+              recordDecl(matchesAnyListedName(IncludeTypeRegex)))))),
+          unless(hasType(hasUnqualifiedDesugaredType(recordType(hasDeclaration(
+              recordDecl(matchesAnyListedName(ExcludeTypeRegex))))))))
----------------
PiotrZSL wrote:

merge those two:
```
 hasType(hasUnqualifiedDesugaredType(recordType(hasDeclaration(
              recordDecl(matchesAnyListedName(IncludeTypeRegex), unless(matchesAnyListedName(ExcludeTypeRegex)))
```

Also in this place you could also exclude all recordDecl that aren't Trivial, maybe by puting that trivial check into matcher.

https://github.com/llvm/llvm-project/pull/76101