[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 +1,132 @@
+//===--- 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/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"
+#include "clang/Tooling/DesignatedInitializers.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 {
+
+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 llvm::all_of(SyntacticForm->children(), [](auto *InitExpr) {
+      return isa<DesignatedInitExpr>(InitExpr);
+    });
+  }
+  return true;
+}
+
+AST_MATCHER(InitListExpr, hasSingleElement) { 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.get(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")),
+          unless(IgnoreSingleElementAggregates ? hasSingleElement()
+                                               : unless(anything())),
+          unless(isFullyDesignated()))
+          .bind("init"),
+      this);
+}
+
+static bool isFullyUndesignated(const InitListExpr *SyntacticInitList) {
+  return std::all_of(
+      SyntacticInitList->begin(), SyntacticInitList->end(),
+      [](auto *InitExpr) { return !isa<DesignatedInitExpr>(InitExpr); });
+}
+
+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;
+  if (const auto *SyntacticInitList = InitList->getSyntacticForm()) {
+    const llvm::DenseMap<clang::SourceLocation, std::string> Designators =
+        clang::tooling::getUnwrittenDesignators(SyntacticInitList);
+    if (isFullyUndesignated(SyntacticInitList)) {
+      if (IgnoreMacros && InitList->getBeginLoc().isMacroID()) {
+        return;
+      }
+      DiagnosticBuilder Diag =
+          diag(InitList->getLBraceLoc(), "use designated initializer list");
+      Diag << InitList->getSourceRange();
+      for (const Stmt *InitExpr : *SyntacticInitList) {
+        Diag << FixItHint::CreateInsertion(
+            InitExpr->getBeginLoc(),
+            Designators.at(InitExpr->getBeginLoc()) + "=");
+      }
+      return;
+    }
+    for (const auto *InitExpr : *SyntacticInitList) {
+      if (isa<DesignatedInitExpr>(InitExpr)) {
+        continue;
+      }
+      if (IgnoreMacros && InitExpr->getBeginLoc().isMacroID()) {
+        continue;
+      }
+      diag(InitExpr->getBeginLoc(), "use designated init expression")
----------------
PiotrZSL wrote:

in theory you could write here an name of  field, like "use designated init expression for field 'a'", or something like that. This may help figuring out easily, about what field it is about.
If you would have SourceLocation for field, then it could be pointed out in note. 

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