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diff --git a/clang-tools-extra/clang-tidy/readability/InconsistentDeclarationParameterNameCheck.cpp b/clang-tools-extra/clang-tidy/readability/InconsistentDeclarationParameterNameCheck.cpp
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+++ b/clang-tools-extra/clang-tidy/readability/InconsistentDeclarationParameterNameCheck.cpp
@@ -0,0 +1,336 @@
+//===--- InconsistentDeclarationParameterNameCheck.cpp - clang-tidy-------===//
+//
+//           The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "InconsistentDeclarationParameterNameCheck.h"
+#include "clang/AST/ASTContext.h"
+#include "clang/ASTMatchers/ASTMatchFinder.h"
+
+#include <algorithm>
+#include <functional>
+#include <sstream>
+
+namespace clang {
+namespace tidy {
+namespace readability {
+
+using namespace ast_matchers;
+
+namespace {
+
+AST_MATCHER(FunctionDecl, hasOtherDeclarations) {
+  auto It = Node.redecls_begin();
+  auto EndIt = Node.redecls_end();
+
+  if (It == EndIt)
+    return false;
+
+  ++It;
+  return It != EndIt;
+}
+
+struct DifferingParamInfo {
+  DifferingParamInfo(StringRef SourceName, StringRef OtherName,
+                     SourceRange OtherNameRange, bool GenerateFixItHint)
+      : SourceName(SourceName), OtherName(OtherName),
+        OtherNameRange(OtherNameRange), GenerateFixItHint(GenerateFixItHint) {}
+
+  StringRef SourceName;
+  StringRef OtherName;
+  SourceRange OtherNameRange;
+  bool GenerateFixItHint;
+};
+
+using DifferingParamsContainer = llvm::SmallVector<DifferingParamInfo, 10>;
+
+struct InconsistentDeclarationInfo {
+  InconsistentDeclarationInfo(SourceLocation DeclarationLocation,
+                              DifferingParamsContainer &&DifferingParams)
+      : DeclarationLocation(DeclarationLocation),
+        DifferingParams(std::move(DifferingParams)) {}
+
+  SourceLocation DeclarationLocation;
+  DifferingParamsContainer DifferingParams;
+};
+
+using InconsistentDeclarationsContainer =
+    llvm::SmallVector<InconsistentDeclarationInfo, 2>;
+
+bool checkIfFixItHintIsApplicable(
+    const FunctionDecl *ParameterSourceDeclaration,
+    const ParmVarDecl *SourceParam, const FunctionDecl *OriginalDeclaration) {
+  // Assumptions with regard to function declarations/definition:
+  //  * If both function declaration and definition are seen, assume that
+  //  definition is most up-to-date, and use it to generate replacements.
+  //  * If only function declarations are seen, there is no easy way to tell
+  //  which is up-to-date and which is not, so don't do anything.
+  // TODO: This may be changed later, but for now it seems the reasonable
+  // solution.
+  if (!ParameterSourceDeclaration->isThisDeclarationADefinition())
+    return false;
+
+  // Assumption: if parameter is not referenced in function defintion body, it
+  // may indicate that it's outdated, so don't touch it.
+  if (!SourceParam->isReferenced())
+    return false;
+
+  // In case there is the primary template definition and (possibly several)
+  // template specializations (and each with possibly several redeclarations),
+  // it is not at all clear what to change.
+  if (OriginalDeclaration->getTemplatedKind() ==
+      FunctionDecl::TK_FunctionTemplateSpecialization)
+    return false;
+
+  // Other cases seem OK to allow replacements.
+  return true;
+}
+
+DifferingParamsContainer
+findDifferingParamsInDeclaration(const FunctionDecl *ParameterSourceDeclaration,
+                                 const FunctionDecl *OtherDeclaration,
+                                 const FunctionDecl *OriginalDeclaration) {
+  DifferingParamsContainer DifferingParams;
+
+  auto SourceParamIt = ParameterSourceDeclaration->param_begin();
+  auto OtherParamIt = OtherDeclaration->param_begin();
+
+  while (SourceParamIt != ParameterSourceDeclaration->param_end() &&
+         OtherParamIt != OtherDeclaration->param_end()) {
+    auto SourceParamName = (*SourceParamIt)->getName();
+    auto OtherParamName = (*OtherParamIt)->getName();
+
+    // FIXME: Provide a way to extract commented out parameter name from comment
+    // next to it.
+    if (!SourceParamName.empty() && !OtherParamName.empty() &&
+        SourceParamName != OtherParamName) {
+      SourceRange OtherParamNameRange =
+          DeclarationNameInfo((*OtherParamIt)->getDeclName(),
+                              (*OtherParamIt)->getLocation()).getSourceRange();
+
+      bool GenerateFixItHint = checkIfFixItHintIsApplicable(
+          ParameterSourceDeclaration, *SourceParamIt, OriginalDeclaration);
+
+      DifferingParams.emplace_back(SourceParamName, OtherParamName,
+                                   OtherParamNameRange, GenerateFixItHint);
+    }
+
+    ++SourceParamIt;
+    ++OtherParamIt;
+  }
+
+  return DifferingParams;
+}
+
+InconsistentDeclarationsContainer
+findInconsitentDeclarations(const FunctionDecl *OriginalDeclaration,
+                            const FunctionDecl *ParameterSourceDeclaration,
+                            SourceManager &SM) {
+  InconsistentDeclarationsContainer InconsistentDeclarations;
+  SourceLocation ParameterSourceLocation =
+      ParameterSourceDeclaration->getLocation();
+
+  for (const FunctionDecl *OtherDeclaration : OriginalDeclaration->redecls()) {
+    SourceLocation OtherLocation = OtherDeclaration->getLocation();
+    if (OtherLocation != ParameterSourceLocation) { // Skip self.
+      DifferingParamsContainer DifferingParams =
+          findDifferingParamsInDeclaration(ParameterSourceDeclaration,
+                                           OtherDeclaration,
+                                           OriginalDeclaration);
+      if (!DifferingParams.empty()) {
+        InconsistentDeclarations.emplace_back(OtherDeclaration->getLocation(),
+                                              std::move(DifferingParams));
+      }
+    }
+  }
+
+  // Sort in order of appearance in translation unit to generate clear
+  // diagnostics.
+  std::sort(InconsistentDeclarations.begin(), InconsistentDeclarations.end(),
+            [&SM](const InconsistentDeclarationInfo &Info1,
+                  const InconsistentDeclarationInfo &Info2) {
+              return SM.isBeforeInTranslationUnit(Info1.DeclarationLocation,
+                                                  Info2.DeclarationLocation);
+            });
+  return InconsistentDeclarations;
+}
+
+const FunctionDecl *
+getParameterSourceDeclaration(const FunctionDecl *OriginalDeclaration) {
+  const FunctionTemplateDecl *PrimaryTemplate =
+      OriginalDeclaration->getPrimaryTemplate();
+  if (PrimaryTemplate != nullptr) {
+    // In case of template specializations, use primary template declaration as
+    // the source of parameter names.
+    return PrimaryTemplate->getTemplatedDecl();
+  }
+
+  // In other cases, try to change to function definition, if available.
+
+  if (OriginalDeclaration->isThisDeclarationADefinition())
+    return OriginalDeclaration;
+
+  for (const FunctionDecl *OtherDeclaration : OriginalDeclaration->redecls()) {
+    if (OtherDeclaration->isThisDeclarationADefinition()) {
+      return OtherDeclaration;
+    }
+  }
+
+  // No definition found, so return original declaration.
+  return OriginalDeclaration;
+}
+
+std::string joinParameterNames(
+    const DifferingParamsContainer &DifferingParams,
+    std::function<StringRef(const DifferingParamInfo &)> ChooseParamName) {
+  llvm::SmallVector<char, 40> Buffer;
+  llvm::raw_svector_ostream Str(Buffer);
+  bool First = true;
+  for (const DifferingParamInfo &ParamInfo : DifferingParams) {
+    if (First)
+      First = false;
+    else
+      Str << ", ";
+
+    Str << "'" << ChooseParamName(ParamInfo).str() << "'";
+  }
+  return Str.str().str();
+}
+
+void formatDifferingParamsDiagnostic(
+    InconsistentDeclarationParameterNameCheck *Check,
+    const SourceLocation &Location, StringRef OtherDeclarationDescription,
+    const DifferingParamsContainer &DifferingParams) {
+  auto ChooseOtherName =
+      [](const DifferingParamInfo &ParamInfo) { return ParamInfo.OtherName; };
+  auto ChooseSourceName =
+      [](const DifferingParamInfo &ParamInfo) { return ParamInfo.SourceName; };
+
+  auto ParamDiag =
+      Check->diag(Location,
+                  "differing parameters are named here: (%0), in %1: (%2)",
+                  DiagnosticIDs::Level::Note)
+      << joinParameterNames(DifferingParams, ChooseOtherName)
+      << OtherDeclarationDescription
+      << joinParameterNames(DifferingParams, ChooseSourceName);
+
+  for (const DifferingParamInfo &ParamInfo : DifferingParams) {
+    if (ParamInfo.GenerateFixItHint) {
+      ParamDiag << FixItHint::CreateReplacement(
+          CharSourceRange::getTokenRange(ParamInfo.OtherNameRange),
+          ParamInfo.SourceName);
+    }
+  }
+}
+
+void formatDiagnosticsForDeclarations(
+    InconsistentDeclarationParameterNameCheck *Check,
+    const FunctionDecl *ParameterSourceDeclaration,
+    const FunctionDecl *OriginalDeclaration,
+    const InconsistentDeclarationsContainer &InconsistentDeclarations) {
+  Check->diag(
+      OriginalDeclaration->getLocation(),
+      "function %q0 has %1 other declaration%s1 with different parameter names")
+      << OriginalDeclaration
+      << static_cast<int>(InconsistentDeclarations.size());
+  int Count = 1;
+  for (const InconsistentDeclarationInfo &InconsistentDeclaration :
+       InconsistentDeclarations) {
+    Check->diag(InconsistentDeclaration.DeclarationLocation,
+                "the %ordinal0 inconsistent declaration seen here",
+                DiagnosticIDs::Level::Note)
+        << Count;
+
+    formatDifferingParamsDiagnostic(
+        Check, InconsistentDeclaration.DeclarationLocation,
+        "the other declaration", InconsistentDeclaration.DifferingParams);
+
+    ++Count;
+  }
+}
+
+void formatDiagnostics(
+    InconsistentDeclarationParameterNameCheck *Check,
+    const FunctionDecl *ParameterSourceDeclaration,
+    const FunctionDecl *OriginalDeclaration,
+    const InconsistentDeclarationsContainer &InconsistentDeclarations,
+    StringRef FunctionDescription, StringRef ParameterSourceDescription) {
+  for (const InconsistentDeclarationInfo &InconsistentDeclaration :
+       InconsistentDeclarations) {
+    Check->diag(InconsistentDeclaration.DeclarationLocation,
+                "%0 %q1 has a %2 with different parameter names")
+        << FunctionDescription << OriginalDeclaration
+        << ParameterSourceDescription;
+
+    Check->diag(ParameterSourceDeclaration->getLocation(), "the %0 seen here",
+                DiagnosticIDs::Level::Note)
+        << ParameterSourceDescription;
+
+    formatDifferingParamsDiagnostic(
+        Check, InconsistentDeclaration.DeclarationLocation,
+        ParameterSourceDescription, InconsistentDeclaration.DifferingParams);
+  }
+}
+
+} // anonymous namespace
+
+void InconsistentDeclarationParameterNameCheck::registerMatchers(
+    MatchFinder *Finder) {
+  Finder->addMatcher(functionDecl(unless(isImplicit()), hasOtherDeclarations())
+                         .bind("functionDecl"),
+                     this);
+}
+
+void InconsistentDeclarationParameterNameCheck::check(
+    const MatchFinder::MatchResult &Result) {
+  const auto *OriginalDeclaration =
+      Result.Nodes.getNodeAs<FunctionDecl>("functionDecl");
+
+  if (VisitedDeclarations.count(OriginalDeclaration) > 0)
+    return; // Avoid multiple warnings.
+
+  const FunctionDecl *ParameterSourceDeclaration =
+      getParameterSourceDeclaration(OriginalDeclaration);
+
+  InconsistentDeclarationsContainer InconsistentDeclarations =
+      findInconsitentDeclarations(OriginalDeclaration,
+                                  ParameterSourceDeclaration,
+                                  *Result.SourceManager);
+  if (InconsistentDeclarations.empty()) {
+    // Avoid unnecessary further visits.
+    markRedeclarationsAsVisited(OriginalDeclaration);
+    return;
+  }
+
+  if (OriginalDeclaration->getTemplatedKind() ==
+      FunctionDecl::TK_FunctionTemplateSpecialization) {
+    formatDiagnostics(this, ParameterSourceDeclaration, OriginalDeclaration,
+                      InconsistentDeclarations,
+                      "function template specialization",
+                      "primary template declaration");
+  } else if (ParameterSourceDeclaration->isThisDeclarationADefinition()) {
+    formatDiagnostics(this, ParameterSourceDeclaration, OriginalDeclaration,
+                      InconsistentDeclarations, "function", "definition");
+  } else {
+    formatDiagnosticsForDeclarations(this, ParameterSourceDeclaration,
+                                     OriginalDeclaration,
+                                     InconsistentDeclarations);
+  }
+
+  markRedeclarationsAsVisited(OriginalDeclaration);
+}
+
+void InconsistentDeclarationParameterNameCheck::markRedeclarationsAsVisited(
+    const FunctionDecl *OriginalDeclaration) {
+  for (const FunctionDecl *Redecl : OriginalDeclaration->redecls()) {
+    VisitedDeclarations.insert(Redecl);
+  }
+}
+
+} // namespace readability
+} // namespace tidy
+} // namespace clang