[clang-tools-extra] [clang-tidy] Add new check `modernize-use-designated-initializers` (PR #80541)

[Piotr Zegar via cfe-commits]

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Danny =?utf-8?q?Mösch?= <danny.moesch at icloud.com>,
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Message-ID:
In-Reply-To: <llvm.org/llvm/llvm-project/pull/80541 at github.com>


================
@@ -0,0 +1,77 @@
+//===--- UseDesignatedInitializersCheck.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 "UseDesignatedInitializersCheck.h"
+#include "clang/AST/Decl.h"
+#include "clang/AST/Expr.h"
+#include "clang/AST/Stmt.h"
+#include "clang/ASTMatchers/ASTMatchFinder.h"
+#include "clang/ASTMatchers/ASTMatchers.h"
+#include <algorithm>
+#include <iterator>
+#include <vector>
+
+using namespace clang::ast_matchers;
+
+namespace clang::tidy::modernize {
+
+static constexpr auto IgnoreSingleElementAggregatesName =
+    "IgnoreSingleElementAggregates";
+static constexpr auto IgnoreSingleElementAggregatesDefault = true;
+
+static std::vector<Stmt *>
+getUndesignatedComponents(const InitListExpr *SyntacticInitList) {
+  std::vector<Stmt *> Result;
+  std::copy_if(SyntacticInitList->begin(), SyntacticInitList->end(),
+               std::back_inserter(Result),
+               [](auto S) { return !isa<DesignatedInitExpr>(S); });
+  return Result;
+}
+
+UseDesignatedInitializersCheck::UseDesignatedInitializersCheck(
+    StringRef Name, ClangTidyContext *Context)
+    : ClangTidyCheck(Name, Context),
+      IgnoreSingleElementAggregates(
+          Options.getLocalOrGlobal(IgnoreSingleElementAggregatesName,
+                                   IgnoreSingleElementAggregatesDefault)) {}
+
+void UseDesignatedInitializersCheck::registerMatchers(MatchFinder *Finder) {
+  Finder->addMatcher(
+      initListExpr(hasType(recordDecl().bind("type"))).bind("init"), this);
----------------
PiotrZSL wrote:

Handle anonymous structures and unions, unions, and classes with anonymous fields. (ignore them, do some tests).
```

    bool isAnonymousDecl(const RecordDecl* p_record) noexcept
    {
        return p_record and (p_record->isAnonymousStructOrUnion() or p_record->getIdentifier() == nullptr);
    }

    AST_MATCHER(RecordDecl, isUnion) { return Node.isUnion(); }
    AST_MATCHER(RecordDecl, isAnonymousStructOrUnion) { return isAnonymousDecl(&Node); }
    AST_MATCHER(RecordDecl, hasAnonymousFields) {
        for(auto&& field : Node.fields())
        {
            if (isAnonymousDecl(field->getType().getCanonicalType()->getAsRecordDecl()))
            {
                return true;
            }
        }
        return false;
    }
```
```
struct StructWithAnonymous
{
    struct {
        int ala;
    } value;
};


StructWithAnonymous g_value = { 5 };
```

https://github.com/llvm/llvm-project/pull/80541