[clang-tools-extra] [clang-tidy] add check to suggest replacement of nested std::min or std::max with initializer lists (PR #85572)

[Julian Schmidt via cfe-commits]

================
@@ -0,0 +1,278 @@
+//===--- MinMaxUseInitializerListCheck.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 "MinMaxUseInitializerListCheck.h"
+#include "../utils/ASTUtils.h"
+#include "../utils/LexerUtils.h"
+#include "clang/ASTMatchers/ASTMatchFinder.h"
+#include "clang/Frontend/CompilerInstance.h"
+#include "clang/Lex/Lexer.h"
+
+using namespace clang;
+
+namespace {
+
+struct FindArgsResult {
+  const Expr *First;
+  const Expr *Last;
+  const Expr *Compare;
+  SmallVector<const clang::Expr *, 2> Args;
+};
+
+} // anonymous namespace
+
+using namespace clang::ast_matchers;
+
+namespace clang::tidy::modernize {
+
+static FindArgsResult findArgs(const CallExpr *Call) {
+  FindArgsResult Result;
+  Result.First = nullptr;
+  Result.Last = nullptr;
+  Result.Compare = nullptr;
+
+  //   check if the function has initializer list argument
+  if (Call->getNumArgs() < 3) {
+    auto ArgIterator = Call->arguments().begin();
+
+    const auto *InitListExpr =
+        dyn_cast<CXXStdInitializerListExpr>(*ArgIterator);
+    const auto *InitList =
+        InitListExpr != nullptr
+            ? dyn_cast<clang::InitListExpr>(
+                  InitListExpr->getSubExpr()->IgnoreImplicit())
+            : nullptr;
+
+    if (InitListExpr && InitList) {
+      Result.Args.insert(Result.Args.begin(), InitList->inits().begin(),
+                         InitList->inits().end());
+      Result.First = *ArgIterator;
+      Result.Last = *ArgIterator;
+
+      // check if there is a comparison argument
+      std::advance(ArgIterator, 1);
+      if (ArgIterator != Call->arguments().end()) {
+        Result.Compare = *ArgIterator;
+      }
+
+      return Result;
+    }
+    // if it has 3 arguments then the last will be the comparison
+  } else {
+    Result.Compare = *(std::next(Call->arguments().begin(), 2));
+  }
+
+  for (const Expr *Arg : Call->arguments()) {
+    if (!Result.First)
+      Result.First = Arg;
+
+    if (Arg == Result.Compare)
+      continue;
+
+    Result.Args.push_back(Arg);
+    Result.Last = Arg;
+  }
+
+  return Result;
+}
+
+static SmallVector<FixItHint>
+generateReplacement(const MatchFinder::MatchResult &Match,
+                    const CallExpr *TopCall, const FindArgsResult &Result) {
+  SmallVector<FixItHint> FixItHints;
+
+  const QualType ResultType = TopCall->getDirectCallee()
+                                  ->getReturnType()
+                                  .getNonReferenceType()
+                                  .getUnqualifiedType()
+                                  .getCanonicalType();
+  const auto &SourceMngr = *Match.SourceManager;
+  const auto LanguageOpts = Match.Context->getLangOpts();
+  const bool IsInitializerList = Result.First == Result.Last;
+
+  // add { and } if the top call doesn't have an initializer list arg
+  if (!IsInitializerList) {
+    FixItHints.push_back(
+        FixItHint::CreateInsertion(Result.First->getBeginLoc(), "{"));
+
+    if (Result.Compare)
+      FixItHints.push_back(FixItHint::CreateInsertion(
+          Lexer::getLocForEndOfToken(Result.Last->getEndLoc(), 0, SourceMngr,
+                                     LanguageOpts),
+          "}"));
+    else
+      FixItHints.push_back(
+          FixItHint::CreateInsertion(TopCall->getEndLoc(), "}"));
+  }
+
+  for (const Expr *Arg : Result.Args) {
+    const auto *InnerCall = dyn_cast<CallExpr>(Arg->IgnoreParenImpCasts());
+
+    // If the argument is not a nested call
+    if (!InnerCall) {
+      // check if typecast is required
+      const QualType ArgType = Arg->IgnoreParenImpCasts()
+                                   ->getType()
+                                   .getUnqualifiedType()
+                                   .getCanonicalType();
+
+      if (ArgType == ResultType)
+        continue;
+
+      const StringRef ArgText = Lexer::getSourceText(
+          CharSourceRange::getTokenRange(Arg->getSourceRange()), SourceMngr,
+          LanguageOpts);
+
+      Twine Replacement = llvm::Twine("static_cast<")
+                              .concat(ResultType.getAsString(LanguageOpts))
+                              .concat(">(")
+                              .concat(ArgText)
+                              .concat(")");
+
+      FixItHints.push_back(FixItHint::CreateReplacement(Arg->getSourceRange(),
+                                                        Replacement.str()));
+
+      continue;
+    }
+
+    const auto InnerResult = findArgs(InnerCall);
+    const auto InnerReplacements =
+        generateReplacement(Match, InnerCall, InnerResult);
+    const bool IsInnerInitializerList = InnerResult.First == InnerResult.Last;
+
+    // if the nested call doesn't have arguments skip it
+    if (!InnerResult.First || !InnerResult.Last)
+      continue;
+
+    // if the nested call is not the same as the top call
+    if (InnerCall->getDirectCallee()->getQualifiedNameAsString() !=
+        TopCall->getDirectCallee()->getQualifiedNameAsString())
+      continue;
+
+    // if the nested call doesn't have the same compare function
+    if ((Result.Compare || InnerResult.Compare) &&
+        !utils::areStatementsIdentical(Result.Compare, InnerResult.Compare,
+                                       *Match.Context))
+      continue;
+
+    // remove the function call
+    FixItHints.push_back(
+        FixItHint::CreateRemoval(CharSourceRange::getTokenRange(
+            InnerCall->getCallee()->getSourceRange())));
+
+    // remove the parentheses
+    const auto LParen = utils::lexer::findNextTokenSkippingComments(
+        InnerCall->getCallee()->getEndLoc(), SourceMngr, LanguageOpts);
+    FixItHints.push_back(
+        FixItHint::CreateRemoval(SourceRange(LParen->getLocation())));
+    FixItHints.push_back(
+        FixItHint::CreateRemoval(SourceRange(InnerCall->getRParenLoc())));
+
+    // if the inner call has an initializer list arg
+    if (IsInnerInitializerList) {
+      // remove the initializer list braces
+      FixItHints.push_back(FixItHint::CreateRemoval(
+          CharSourceRange::getTokenRange(InnerResult.First->getBeginLoc())));
+      FixItHints.push_back(FixItHint::CreateRemoval(
+          CharSourceRange::getTokenRange(InnerResult.First->getEndLoc())));
+    }
+
+    FixItHints.insert(FixItHints.end(),
+                      // ignore { and } insertions for the inner call if it does
+                      // not have an initializer list arg
+                      InnerReplacements.begin() + (!IsInnerInitializerList) * 2,
+                      InnerReplacements.end());
----------------
5chmidti wrote:

You can remove the need to drop `FitIt`s like this by moving the code that adds them inside `generateReplacement` to after you create the diagnostic with `diag` in the `check` method:
```c++
  const bool IsInitializerList = Result.First == Result.Last;

  // add { and } if the top call doesn't have an initializer list arg
  if (!IsInitializerList) {
    Diagnostic << FixItHint::CreateInsertion(Result.First->getBeginLoc(), "{");

    if (Result.Compare)
      Diagnostic << FixItHint::CreateInsertion(
          Lexer::getLocForEndOfToken(Result.Last->getEndLoc(), 0,
                                     *Match.SourceManager,
                                     Match.Context->getLangOpts()),
          "}");
    else
      Diagnostic << FixItHint::CreateInsertion(TopCall->getEndLoc(), "}");
  }
```
Then this code snippet can become: `FixItHints.append(generateReplacement(Match, InnerCall, InnerResult));` (with removal of `InnerReplacements` from above)

https://github.com/llvm/llvm-project/pull/85572