[clang-tools-extra] Add bugprone-loop-variable-copied-then-modified clang-tidy check. (PR #157213)

[Julia Hansbrough via cfe-commits]

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+
+//===----------------------------------------------------------------------===//
+//
+// 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 "LoopVariableCopiedThenModifiedCheck.h"
+#include "../utils/Matchers.h"
+#include "../utils/TypeTraits.h"
+#include "clang/ASTMatchers/ASTMatchFinder.h"
+#include "clang/Analysis/Analyses/ExprMutationAnalyzer.h"
+#include "clang/Basic/Diagnostic.h"
+
+using namespace clang::ast_matchers;
+
+namespace clang::tidy::bugprone {
+
+LoopVariableCopiedThenModifiedCheck::LoopVariableCopiedThenModifiedCheck(
+    StringRef Name, ClangTidyContext *Context)
+    : ClangTidyCheck(Name, Context),
+      IgnoreInexpensiveVariables(
+          Options.get("IgnoreInexpensiveVariables", false)) {}
+
+void LoopVariableCopiedThenModifiedCheck::storeOptions(
+    ClangTidyOptions::OptionMap &Opts) {
+  Options.store(Opts, "IgnoreInexpensiveVariables", IgnoreInexpensiveVariables);
+}
+
+void LoopVariableCopiedThenModifiedCheck::registerMatchers(
+    MatchFinder *Finder) {
+  auto HasReferenceOrPointerTypeOrIsAllowed = hasType(qualType(
+      unless(hasCanonicalType(anyOf(referenceType(), pointerType())))));
+  auto IteratorReturnsValueType = cxxOperatorCallExpr(
+      hasOverloadedOperatorName("*"),
+      callee(
+          cxxMethodDecl(returns(unless(hasCanonicalType(referenceType()))))));
+  auto NotConstructedByCopy = cxxConstructExpr(
+      hasDeclaration(cxxConstructorDecl(unless(isCopyConstructor()))));
+  auto ConstructedByConversion = cxxMemberCallExpr(callee(cxxConversionDecl()));
+  auto LoopVar =
+      varDecl(HasReferenceOrPointerTypeOrIsAllowed,
+              unless(hasInitializer(expr(hasDescendant(expr(
+                  anyOf(materializeTemporaryExpr(), IteratorReturnsValueType,
+                        NotConstructedByCopy, ConstructedByConversion)))))));
+  Finder->addMatcher(
+      traverse(TK_AsIs,
+               cxxForRangeStmt(hasLoopVariable(LoopVar.bind("loopVar")))
+                   .bind("forRange")),
+      this);
+}
+
+void LoopVariableCopiedThenModifiedCheck::check(
+    const MatchFinder::MatchResult &Result) {
+  const auto *Var = Result.Nodes.getNodeAs<VarDecl>("loopVar");
+  if (Var->getBeginLoc().isMacroID())
+    return;
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flowerhack wrote:

I'm sorry, I don't think I understand the case you provided.  Can you explain in a little more detail?

https://github.com/llvm/llvm-project/pull/157213