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

[Piotr Zegar via cfe-commits]

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In-Reply-To: <llvm.org/llvm/llvm-project/pull/80541 at github.com>


================
@@ -0,0 +1,160 @@
+//===--- 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 "../utils/DesignatedInitializers.h"
+#include "clang/AST/APValue.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 "clang/ASTMatchers/ASTMatchersMacros.h"
+#include "clang/Basic/Diagnostic.h"
+#include "clang/Lex/Lexer.h"
+
+using namespace clang::ast_matchers;
+
+namespace clang::tidy::modernize {
+
+static constexpr char IgnoreSingleElementAggregatesName[] =
+    "IgnoreSingleElementAggregates";
+static constexpr bool IgnoreSingleElementAggregatesDefault = true;
+
+static constexpr char RestrictToPODTypesName[] = "RestrictToPODTypes";
+static constexpr bool RestrictToPODTypesDefault = false;
+
+static constexpr char IgnoreMacrosName[] = "IgnoreMacros";
+static constexpr bool IgnoreMacrosDefault = true;
+
+namespace {
+
+unsigned getNumberOfDesignated(const InitListExpr *SyntacticInitList) {
+  return llvm::count_if(*SyntacticInitList, [](auto *InitExpr) {
+    return isa<DesignatedInitExpr>(InitExpr);
+  });
+}
+
+AST_MATCHER(CXXRecordDecl, isAggregate) { return Node.isAggregate(); }
+
+AST_MATCHER(CXXRecordDecl, isPOD) { return Node.isPOD(); }
+
+AST_MATCHER(InitListExpr, isFullyDesignated) {
+  if (const InitListExpr *SyntacticForm =
+          Node.isSyntacticForm() ? &Node : Node.getSyntacticForm()) {
+    return getNumberOfDesignated(SyntacticForm) == SyntacticForm->getNumInits();
+  }
+  return true;
+}
+
+AST_MATCHER(InitListExpr, hasMoreThanOneElement) {
+  return Node.getNumInits() > 1;
+}
+
+} // namespace
+
+UseDesignatedInitializersCheck::UseDesignatedInitializersCheck(
+    StringRef Name, ClangTidyContext *Context)
+    : ClangTidyCheck(Name, Context), IgnoreSingleElementAggregates(Options.get(
+                                         IgnoreSingleElementAggregatesName,
+                                         IgnoreSingleElementAggregatesDefault)),
+      RestrictToPODTypes(
+          Options.get(RestrictToPODTypesName, RestrictToPODTypesDefault)),
+      IgnoreMacros(
+          Options.getLocalOrGlobal(IgnoreMacrosName, IgnoreMacrosDefault)) {}
+
+void UseDesignatedInitializersCheck::registerMatchers(MatchFinder *Finder) {
+  const auto HasBaseWithFields =
+      hasAnyBase(hasType(cxxRecordDecl(has(fieldDecl()))));
+  Finder->addMatcher(
+      initListExpr(
+          hasType(cxxRecordDecl(RestrictToPODTypes ? isPOD() : isAggregate(),
+                                unless(HasBaseWithFields))
+                      .bind("type")),
+          IgnoreSingleElementAggregates ? hasMoreThanOneElement() : anything(),
+          unless(isFullyDesignated()))
+          .bind("init"),
+      this);
+}
+
+void UseDesignatedInitializersCheck::check(
+    const MatchFinder::MatchResult &Result) {
+  const auto *InitList = Result.Nodes.getNodeAs<InitListExpr>("init");
+  const auto *Type = Result.Nodes.getNodeAs<CXXRecordDecl>("type");
+  if (!Type || !InitList) {
+    return;
+  }
+  const auto *SyntacticInitList = InitList->getSyntacticForm();
+  if (!SyntacticInitList) {
+    return;
+  }
+  std::optional<llvm::DenseMap<clang::SourceLocation, std::string>>
+      Designators{};
+  const auto LazyDesignators = [SyntacticInitList, &Designators] {
+    return Designators ? Designators
+                       : Designators.emplace(
+                             utils::getUnwrittenDesignators(SyntacticInitList));
+  };
+  const unsigned NumberOfDesignated = getNumberOfDesignated(SyntacticInitList);
+  if (0 == NumberOfDesignated) {
+    if (IgnoreMacros && InitList->getBeginLoc().isMacroID()) {
+      return;
+    }
+    if (SyntacticInitList->getNumInits() - NumberOfDesignated >
+        LazyDesignators()->size()) {
+      return;
+    }
+    {
+      DiagnosticBuilder Diag =
+          diag(InitList->getLBraceLoc(),
+               "use designated initializer list to initialize %0");
+      Diag << Type->getDeclName();
+      Diag << InitList->getSourceRange();
+      for (const Stmt *InitExpr : *SyntacticInitList) {
+        const std::string Designator =
+            LazyDesignators()->at(InitExpr->getBeginLoc());
+        if (!Designator.empty()) {
+          Diag << FixItHint::CreateInsertion(InitExpr->getBeginLoc(),
+                                             Designator + "=");
+        }
+      }
+    }
+    diag(Type->getBeginLoc(), "this is the type to initialize",
+         DiagnosticIDs::Note);
+    return;
+  }
+  for (const auto *InitExpr : *SyntacticInitList) {
+    if (isa<DesignatedInitExpr>(InitExpr)) {
+      continue;
+    }
+    if (IgnoreMacros && InitExpr->getBeginLoc().isMacroID()) {
+      continue;
+    }
+    const std::string Designator =
+        LazyDesignators()->at(InitExpr->getBeginLoc());
+    DiagnosticBuilder Diag =
+        diag(InitExpr->getBeginLoc(),
+             "use designated init expression to initialize field '%0'");
+    Diag << InitExpr->getSourceRange();
+    if (!Designator.empty() && Designator.front() == '.') {
+      Diag << Designator.substr(1); // Strip leading dot
----------------
PiotrZSL wrote:

consider using StringRef to avoid coping...

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