[clang-tidy] Rewrite modernize-avoid-bind check

[zturner]

Summary

This represents largely a full re-write of modernize-avoid-bind, adding significant new functionality in the process. In particular:

1. Both boost::bind and std::bind are now supported
2. Function objects are supported in addition to functions
3. Member functions are supported
4. Nested calls are supported using capture-init syntax
5. std::ref() and boost::ref() are now recognized, and will capture by reference.
6. Rather than capturing with a global =, we now build up an individual capture list that is both necessary and sufficient for the call.
7. Fixits are supported in a much larger variety of scenarios than before.

All previous tests pass under the re-write, but a large number of new tests have been added as well.

I don't know who the best person to review this is, so I've put a couple of people on here. Feel free to re-direct if there's someone better.

[Eugene.Zelenko]

Please describe changes in documentation and Release Notes.

[aaron.ballman]

This is a great re-write, thank you for working on it!

clang-tools-extra/clang-tidy/modernize/AvoidBindCheck.cpp

98

You can remove some newlines here.

106

What about CXXBindTemporaryExpr?

Would Expr::IgnoreImplicit() do too much stripping because it removes FullExpr as well?

114

Spurious newline

120

Similar question here about bound temporaries as above.

133–137

llvm::utostr() instead of using a streaming interface?

134

I think you can drop the llvm:: here and elsewhere in the file.

143

This should probably use cast<> if it's going to assume the returned value is never null.

186–189

return llvm::any_of(Statement->children(), anyDescendantIsLocal);?

374–377

It seems like return Candidates; will suffice. :-)

[zturner]

clang-tools-extra/clang-tidy/modernize/AvoidBindCheck.cpp

106

I don't actually know. This patch is literally my first exposure to clang's frontend and AST manipulations, so I was kind of just trying different things until something worked here. I didn't even know about IgnoreImplicit() or FullExpr. I'll play around with them and report back.

143

Good point. Since we're talking about this code anyway, it felt super hacky to instantiate an AST matcher just to check for the qualified name of a Decl. Is there a better way to do this?

[zturner]

Updated with suggestions from @aaron.ballman

[zturner]

Forgot to remove spurious llvm:: namespace qualifications.

[aaron.ballman]

clang-tools-extra/clang-tidy/modernize/AvoidBindCheck.cpp

143

Since you only care about named call declarations, I think you could probably get away with:

if (const auto *ND = dyn_cast<NamedDecl>(CE->getCalleeDecl())) {
  const std::string &Str = ND->getQualifiedNameAsString();
  if (Str == "::boost::ref" || Str == "::std::ref") {
    ...
  }
}

161

isa<CXXThisExpr>(Statement)

422–423

I think this can be replaced with: return dyn_cast<FunctionDecl>(DRE->getDecl());

[zturner]

• Updated documentation for this check
• Incorporated additional suggestions from @aaron.ballman
• Fixed an invalid transformation that was generated when binding a member function and the second argument of bind (the object pointer) was a placeholder. Test is added for this case as well.
• Fixed an invalid transformation that was generated when a placeholder index was entirely skipped, as in the call std::bind(add, 0, _2); In this case we need to generate an unused placeholder in the first position of the resulting lambda's parameter list.
• Added a clang-tidy option PermissiveParameterList which appends auto&&... to the end of every lambda's placeholder list. This is necessary in some situations to prevent clang-tidy from applying a fixit that causes the code to no longer compile.

[Eugene.Zelenko]

Changes should be also reflected in Release Notes.

clang-tools-extra/docs/clang-tidy/checks/modernize-avoid-bind.rst

7

Please fix double space. Same in other places.

12

Please use double back-ticks for bind.

13

fixit -> fix-it.

49

Please use double back-ticks for auto&&....

50

fixit -> fix-it.

51

Please use double back-ticks for bind.

64

Please use double back-ticks for ignore_args.

75

Please use double back-ticks for operator().

[zturner]

Addressed suggestions from @Eugene.Zelenko

[Eugene.Zelenko]

clang-tools-extra/docs/ReleaseNotes.rst

203

Please use single back-tics for options.

clang-tools-extra/docs/clang-tidy/checks/modernize-avoid-bind.rst

50

Double space here and in other places are still not fixed. Same for fixit.

[Eugene.Zelenko]

Please mark addressed comments as done.

[aaron.ballman]

LGTM once you handle the last remaining nits from @Eugene.Zelenko.

clang-tools-extra/clang-tidy/modernize/AvoidBindCheck.cpp

106

Unless you find some reason why they're critical in the initial version of your patch, I'm fine handling this as a follow-up if needed.

clang-tools-extra/clang-tidy/modernize/AvoidBindCheck.h

 /// Replace simple uses of std::bind with a lambda.
 ///
 /// FIXME: Add support for function references and member function references.
 ///
 /// For the user-facing documentation see:
 /// http://clang.llvm.org/extra/clang-tidy/checks/modernize-avoid-std-bind.html
 class AvoidBindCheck : public ClangTidyCheck {
 public:
-  AvoidBindCheck(StringRef Name, ClangTidyContext *Context)
-      : ClangTidyCheck(Name, Context) {}
+  AvoidBindCheck(StringRef Name, ClangTidyContext *Context);
   void registerMatchers(ast_matchers::MatchFinder *Finder) override;
   void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
+
+private:
+  bool PermissiveParameterList = false;
 };
 } // namespace modernize
 } // namespace tidy
 } // namespace clang
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_MODERNIZE_AVOID_BIND_H

clang-tools-extra/clang-tidy/modernize/AvoidBindCheck.cpp

 //===--- AvoidBindCheck.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 "AvoidBindCheck.h"
 #include "clang/AST/ASTContext.h"
 #include "clang/ASTMatchers/ASTMatchFinder.h"
 #include "clang/Basic/LLVM.h"
 #include "clang/Basic/LangOptions.h"
 #include "clang/Basic/SourceLocation.h"
 #include "clang/Lex/Lexer.h"
 #include "llvm/ADT/ArrayRef.h"
+#include "llvm/ADT/STLExtras.h"
 #include "llvm/ADT/SmallSet.h"
 #include "llvm/ADT/SmallVector.h"
-#include "llvm/ADT/STLExtras.h"
 #include "llvm/ADT/StringRef.h"
 #include "llvm/Support/Casting.h"
+#include "llvm/Support/FormatVariadic.h"
 #include "llvm/Support/Regex.h"
 #include "llvm/Support/raw_ostream.h"
 #include <algorithm>
 #include <cstddef>
 #include <string>
 
 using namespace clang::ast_matchers;
 
 namespace clang {
 namespace tidy {
 namespace modernize {
 
 namespace {
 
 enum BindArgumentKind { BK_Temporary, BK_Placeholder, BK_CallExpr, BK_Other };
+enum CaptureMode { CM_None, CM_ByRef, CM_ByValue, CM_InitExpression };
+
+enum CallableType {
+  CT_Other,          // unknown
+  CT_Function,       // global or static function
+  CT_MemberFunction, // member function with implicit this
+  CT_Object,         // object with operator()
+};
+
+enum CallableMaterializationKind {
+  CMK_Other,       // unknown
+  CMK_Function,    // callable is the name of a member or non-member function.
+  CMK_VariableRef, // callable is a simple expression involving a global or
+                   // local variable.
+  CMK_CallExpression, // callable is obtained as the result of a call expression
+};
 
 struct BindArgument {
-  StringRef Tokens;
+  // A rough classification of the type of expression this argument was.
   BindArgumentKind Kind = BK_Other;
+
+  // If this argument required a capture, a value indicating how it was
+  // captured.
+  CaptureMode CaptureMode = CM_None;
+
+  // The exact spelling of this argument in the source code.
+  StringRef SourceTokens;
+
+  // The identifier of the variable within the capture list.  This may be
+  // different from UsageIdentifier for example in the expression *d, where the
+  // variable is captured as d, but referred to as *d.
+  std::string CaptureIdentifier;
+
+  // If this is a placeholder or capture init expression, contains the tokens
+  // used to refer to this parameter from within the body of the lambda.
+  std::string UsageIdentifier;
+
+  // If Kind == BK_Placeholder, the index of the placeholder.
   size_t PlaceHolderIndex = 0;
+
+  // True if the argument is used inside the lambda, false otherwise.
+  bool IsUsed = false;
+
+  // The actual Expr object representing this expression.
+  const Expr *E = nullptr;
+};
+
+struct CallableInfo {
+  CallableType Type = CT_Other;
+  CallableMaterializationKind Materialization = CMK_Other;
+  CaptureMode CaptureMode = CM_None;
+  StringRef SourceTokens;
+  std::string CaptureIdentifier;
+  std::string UsageIdentifier;
+  StringRef CaptureInitializer;
+  const FunctionDecl *Decl = nullptr;
+};
+
+struct LambdaProperties {
+  CallableInfo Callable;
+  SmallVector<BindArgument, 4> BindArguments;
+  StringRef BindNamespace;
+  bool IsFixitSupported = false;
 };
 
 } // end namespace
 
+static const Expr *ignoreTemporariesAndPointers(const Expr *E) {
+  if (const auto *T = dyn_cast<UnaryOperator>(E))
+    return ignoreTemporariesAndPointers(T->getSubExpr());
+
+  const Expr *F = E->IgnoreImplicit();
+  if (E != F)
+    return ignoreTemporariesAndPointers(F);
+
+  return E;
+}
+
+static const Expr *ignoreTemporariesAndConstructors(const Expr *E) {
+  if (const auto *T = dyn_cast<CXXConstructExpr>(E))
+    return ignoreTemporariesAndConstructors(T->getArg(0));
+
+  const Expr *F = E->IgnoreImplicit();
+  if (E != F)
+    return ignoreTemporariesAndPointers(F);
+
+  return E;
+}
+
+static StringRef getSourceTextForExpr(const MatchFinder::MatchResult &Result,
+                                      const Expr *E) {
+  return Lexer::getSourceText(
+      CharSourceRange::getTokenRange(E->getBeginLoc(), E->getEndLoc()),
+      *Result.SourceManager, Result.Context->getLangOpts());
+}
+
+static bool isCallExprNamed(const Expr *E, StringRef Name) {
+  const auto *CE = dyn_cast<CallExpr>(E->IgnoreImplicit());
+  if (!CE)
+    return false;
+  const auto *ND = dyn_cast<NamedDecl>(CE->getCalleeDecl());
+  if (!ND)
+    return false;
+  return ND->getQualifiedNameAsString() == Name;
+}
+
+static void
+initializeBindArgumentForCallExpr(const MatchFinder::MatchResult &Result,
+                                  BindArgument &B, const CallExpr *CE,
+                                  unsigned &CaptureIndex) {
+  // std::ref(x) means to capture x by reference.
+  if (isCallExprNamed(CE, "boost::ref") || isCallExprNamed(CE, "std::ref")) {
+    B.Kind = BK_Other;
+    B.CaptureMode = CM_ByRef;
+    B.UsageIdentifier = getSourceTextForExpr(Result, CE->getArg(0));
+  } else {
+    B.Kind = BK_CallExpr;
+    B.CaptureMode = CM_InitExpression;
+    B.UsageIdentifier = "capture" + llvm::utostr(CaptureIndex++);
+  }
+  B.CaptureIdentifier = B.UsageIdentifier;
+}
+
+static bool anyDescendantIsLocal(const Stmt *Statement) {
+  if (const auto *DeclRef = dyn_cast<DeclRefExpr>(Statement)) {
+    const ValueDecl *Decl = DeclRef->getDecl();
+    if (const auto *Var = dyn_cast_or_null<VarDecl>(Decl)) {
+      if (Var->isLocalVarDeclOrParm())
+        return true;
+    }
+  } else if (isa<CXXThisExpr>(Statement))
+    return true;
+
+  return any_of(Statement->children(), anyDescendantIsLocal);
+}
+
+static bool tryCaptureAsLocalVariable(const MatchFinder::MatchResult &Result,
+                                      BindArgument &B, const Expr *E) {
+  if (const auto *BTE = dyn_cast<CXXBindTemporaryExpr>(E)) {
+    if (const auto *CE = dyn_cast<CXXConstructExpr>(BTE->getSubExpr()))
+      return tryCaptureAsLocalVariable(Result, B, CE->getArg(0));
+    return false;
+  }
+
+  const auto *DRE = dyn_cast<DeclRefExpr>(E->IgnoreImplicit());
+  if (!DRE)
+    return false;
+
+  const auto *VD = dyn_cast<VarDecl>(DRE->getDecl());
+  if (!VD || !VD->isLocalVarDeclOrParm())
+    return false;
+
+  B.CaptureMode = CM_ByValue;
+  B.UsageIdentifier = getSourceTextForExpr(Result, E);
+  B.CaptureIdentifier = B.UsageIdentifier;
+  return true;
+}
+
+static bool tryCaptureAsMemberVariable(const MatchFinder::MatchResult &Result,
+                                       BindArgument &B, const Expr *E) {
+  if (const auto *BTE = dyn_cast<CXXBindTemporaryExpr>(E)) {
+    if (const auto *CE = dyn_cast<CXXConstructExpr>(BTE->getSubExpr()))
+      return tryCaptureAsMemberVariable(Result, B, CE->getArg(0));
+    return false;
+  }
+
+  E = E->IgnoreImplicit();
+  if (isa<CXXThisExpr>(E)) {
+    B.CaptureMode = CM_ByValue;
+    B.UsageIdentifier = getSourceTextForExpr(Result, E);
+    B.CaptureIdentifier = "this";
+    return true;
+  }
+
+  const auto *ME = dyn_cast<MemberExpr>(E);
+  if (!ME)
+    return false;
+
+  if (!ME->isLValue() || !isa<FieldDecl>(ME->getMemberDecl()))
+    return false;
+
+  B.CaptureMode = CM_ByValue;
+  B.UsageIdentifier = getSourceTextForExpr(Result, E);
+  B.CaptureIdentifier = "this";
+  return true;
+}
+
 static SmallVector<BindArgument, 4>
-buildBindArguments(const MatchFinder::MatchResult &Result, const CallExpr *C) {
+buildBindArguments(const MatchFinder::MatchResult &Result,
+                   const CallableInfo &Callable) {
   SmallVector<BindArgument, 4> BindArguments;
   llvm::Regex MatchPlaceholder("^_([0-9]+)$");
 
+  const auto *BindCall = Result.Nodes.getNodeAs<CallExpr>("bind");
+
   // Start at index 1 as first argument to bind is the function name.
-  for (size_t I = 1, ArgCount = C->getNumArgs(); I < ArgCount; ++I) {
-    const Expr *E = C->getArg(I);
-    BindArgument B;
-    if (const auto *M = dyn_cast<MaterializeTemporaryExpr>(E)) {
-      const auto *TE = M->getSubExpr();
-      B.Kind = isa<CallExpr>(TE) ? BK_CallExpr : BK_Temporary;
-    }
+  unsigned CaptureIndex = 0;
+  for (size_t I = 1, ArgCount = BindCall->getNumArgs(); I < ArgCount; ++I) {
 
-    B.Tokens = Lexer::getSourceText(
-        CharSourceRange::getTokenRange(E->getBeginLoc(), E->getEndLoc()),
-        *Result.SourceManager, Result.Context->getLangOpts());
+    const Expr *E = BindCall->getArg(I);
+    BindArgument &B = BindArguments.emplace_back();
+
+    size_t ArgIndex = I - 1;
+    if (Callable.Type == CT_MemberFunction)
+      --ArgIndex;
+
+    bool IsObjectPtr = (I == 1 && Callable.Type == CT_MemberFunction);
+    B.E = E;
+    B.SourceTokens = getSourceTextForExpr(Result, E);
+
+    if (!Callable.Decl || ArgIndex < Callable.Decl->getNumParams() ||
+        IsObjectPtr)
+      B.IsUsed = true;
 
     SmallVector<StringRef, 2> Matches;
-    if (B.Kind == BK_Other && MatchPlaceholder.match(B.Tokens, &Matches)) {
+    if (MatchPlaceholder.match(B.SourceTokens, &Matches)) {
       B.Kind = BK_Placeholder;
       B.PlaceHolderIndex = std::stoi(Matches[1]);
+      B.UsageIdentifier = "PH" + llvm::utostr(B.PlaceHolderIndex);
+      B.CaptureIdentifier = B.UsageIdentifier;
+      continue;
+    }
+
+    if (const auto *CE =
+            dyn_cast<CallExpr>(ignoreTemporariesAndConstructors(E))) {
+      initializeBindArgumentForCallExpr(Result, B, CE, CaptureIndex);
+      continue;
+    }
+
+    if (tryCaptureAsLocalVariable(Result, B, B.E) ||
+        tryCaptureAsMemberVariable(Result, B, B.E))
+      continue;
+
+    // If it's not something we recognize, capture it by init expression to be
+    // safe.
+    B.Kind = BK_Other;
+    if (IsObjectPtr) {
+      B.CaptureMode = CM_InitExpression;
+      B.UsageIdentifier = "ObjectPtr";
+      B.CaptureIdentifier = B.UsageIdentifier;
+    } else if (anyDescendantIsLocal(B.E)) {
+      B.CaptureMode = CM_InitExpression;
+      B.CaptureIdentifier = "capture" + llvm::utostr(CaptureIndex++);
+      B.UsageIdentifier = B.CaptureIdentifier;
     }
-    BindArguments.push_back(B);
   }
   return BindArguments;
 }
 
-static void addPlaceholderArgs(const ArrayRef<BindArgument> Args,
-                               llvm::raw_ostream &Stream) {
+static int findPositionOfPlaceholderUse(ArrayRef<BindArgument> Args,
+                                        size_t PlaceholderIndex) {
+  for (size_t I = 0; I < Args.size(); ++I)
+    if (Args[I].PlaceHolderIndex == PlaceholderIndex)
+      return I;
+
+  return -1;
+}
+
+static void addPlaceholderArgs(const LambdaProperties &LP,
+                               llvm::raw_ostream &Stream,
+                               bool PermissiveParameterList) {
+
+  ArrayRef<BindArgument> Args = LP.BindArguments;
+
   auto MaxPlaceholderIt =
       std::max_element(Args.begin(), Args.end(),
                        [](const BindArgument &B1, const BindArgument &B2) {
                          return B1.PlaceHolderIndex < B2.PlaceHolderIndex;
                        });
 
   // Placeholders (if present) have index 1 or greater.
-  if (MaxPlaceholderIt == Args.end() || MaxPlaceholderIt->PlaceHolderIndex == 0)
+  if (!PermissiveParameterList && (MaxPlaceholderIt == Args.end() ||
+                                   MaxPlaceholderIt->PlaceHolderIndex == 0))
     return;
 
   size_t PlaceholderCount = MaxPlaceholderIt->PlaceHolderIndex;
   Stream << "(";
   StringRef Delimiter = "";
   for (size_t I = 1; I <= PlaceholderCount; ++I) {
-    Stream << Delimiter << "auto && arg" << I;
+    Stream << Delimiter << "auto &&";
+
+    int ArgIndex = findPositionOfPlaceholderUse(Args, I);
+
+    if (ArgIndex != -1 && Args[ArgIndex].IsUsed)
+      Stream << " " << Args[ArgIndex].UsageIdentifier;
     Delimiter = ", ";
   }
+  if (PermissiveParameterList)
+    Stream << Delimiter << "auto && ...";
   Stream << ")";
 }
 
-static void addFunctionCallArgs(const ArrayRef<BindArgument> Args,
+static void addFunctionCallArgs(ArrayRef<BindArgument> Args,
                                 llvm::raw_ostream &Stream) {
   StringRef Delimiter = "";
-  for (const auto &B : Args) {
-    if (B.PlaceHolderIndex)
-      Stream << Delimiter << "arg" << B.PlaceHolderIndex;
-    else
-      Stream << Delimiter << B.Tokens;
+
+  for (int I = 0, Size = Args.size(); I < Size; ++I) {
+    const BindArgument &B = Args[I];
+
+    Stream << Delimiter;
+
+    if (B.Kind == BK_Placeholder || B.CaptureMode != CM_None)
+      Stream << B.UsageIdentifier;
+    else if (B.CaptureMode == CM_None)
+      Stream << B.SourceTokens;
+
     Delimiter = ", ";
   }
 }
 
 static bool isPlaceHolderIndexRepeated(const ArrayRef<BindArgument> Args) {
   llvm::SmallSet<size_t, 4> PlaceHolderIndices;
   for (const BindArgument &B : Args) {
     if (B.PlaceHolderIndex) {
       if (!PlaceHolderIndices.insert(B.PlaceHolderIndex).second)
         return true;
     }
   }
   return false;
 }
 
+static std::vector<const CXXMethodDecl *>
+findCandidateCallOperators(const CXXRecordDecl *RecordDecl, size_t NumArgs) {
+  std::vector<const CXXMethodDecl *> Candidates;
+
+  for (const clang::CXXMethodDecl *Method : RecordDecl->methods()) {
+    OverloadedOperatorKind OOK = Method->getOverloadedOperator();
+
+    if (OOK != OverloadedOperatorKind::OO_Call)
+      continue;
+
+    if (Method->getNumParams() > NumArgs)
+      continue;
+
+    Candidates.push_back(Method);
+  }
+
+  return Candidates;
+}
+
+static bool isFixitSupported(const CallableInfo &Callee,
+                             ArrayRef<BindArgument> Args) {
+  // Do not attempt to create fixits for nested std::bind or std::ref.
+  // Supporting nested std::bind will be more difficult due to placeholder
+  // sharing between outer and inner std::bind invocations, and std::ref
+  // requires us to capture some parameters by reference instead of by value.
+  if (any_of(Args, [](const BindArgument &B) {
+        return isCallExprNamed(B.E, "boost::bind") ||
+               isCallExprNamed(B.E, "std::bind");
+      })) {
+    return false;
+  }
+
+  // Do not attempt to create fixits when placeholders are reused.
+  // Unused placeholders are supported by requiring C++14 generic lambdas.
+  // FIXME: Support this case by deducing the common type.
+  if (isPlaceHolderIndexRepeated(Args))
+    return false;
+
+  // If we can't determine the Decl being used, don't offer a fixit.
+  if (!Callee.Decl)
+    return false;
+
+  if (Callee.Type == CT_Other || Callee.Materialization == CMK_Other)
+    return false;
+
+  return true;
+}
+
+const FunctionDecl *getCallOperator(const CXXRecordDecl *Callable,
+                                    size_t NumArgs) {
+  std::vector<const CXXMethodDecl *> Candidates =
+      findCandidateCallOperators(Callable, NumArgs);
+  if (Candidates.size() != 1)
+    return nullptr;
+
+  return Candidates.front();
+}
+
+const FunctionDecl *
+getCallMethodDecl(const MatchFinder::MatchResult &Result, CallableType Type,
+                  CallableMaterializationKind Materialization) {
+
+  const Expr *Callee = Result.Nodes.getNodeAs<Expr>("ref");
+  const Expr *CallExpression = ignoreTemporariesAndPointers(Callee);
+
+  if (Type == CT_Object) {
+    const auto *BindCall = Result.Nodes.getNodeAs<CallExpr>("bind");
+    size_t NumArgs = BindCall->getNumArgs() - 1;
+    return getCallOperator(Callee->getType()->getAsCXXRecordDecl(), NumArgs);
+  }
+
+  if (Materialization == CMK_Function) {
+    if (const auto *DRE = dyn_cast<DeclRefExpr>(CallExpression))
+      return dyn_cast<FunctionDecl>(DRE->getDecl());
+  }
+
+  // Maybe this is an indirect call through a function pointer or something
+  // where we can't determine the exact decl.
+  return nullptr;
+}
+
+static CallableType getCallableType(const MatchFinder::MatchResult &Result) {
+  const auto *CallableExpr = Result.Nodes.getNodeAs<Expr>("ref");
+
+  QualType QT = CallableExpr->getType();
+  if (QT->isMemberFunctionPointerType())
+    return CT_MemberFunction;
+
+  if (QT->isFunctionPointerType() || QT->isFunctionReferenceType() ||
+      QT->isFunctionType())
+    return CT_Function;
+
+  if (QT->isRecordType()) {
+    const CXXRecordDecl *Decl = QT->getAsCXXRecordDecl();
+    if (!Decl)
+      return CT_Other;
+
+    return CT_Object;
+  }
+
+  return CT_Other;
+}
+
+static CallableMaterializationKind
+getCallableMaterialization(const MatchFinder::MatchResult &Result) {
+  const auto *CallableExpr = Result.Nodes.getNodeAs<Expr>("ref");
+
+  const auto *NoTemporaries = ignoreTemporariesAndPointers(CallableExpr);
+
+  if (isa<CallExpr>(NoTemporaries))
+    return CMK_CallExpression;
+
+  if (isa<CXXFunctionalCastExpr>(NoTemporaries) ||
+      isa<CXXConstructExpr>(NoTemporaries))
+    return CMK_Function;
+
+  if (const auto *DRE = dyn_cast<DeclRefExpr>(NoTemporaries)) {
+    if (const auto *FD = dyn_cast<FunctionDecl>(DRE->getDecl()))
+      return CMK_Function;
+    if (const auto *VD = dyn_cast<VarDecl>(DRE->getDecl()))
+      return CMK_VariableRef;
+  }
+
+  return CMK_Other;
+}
+
+static LambdaProperties
+getLambdaProperties(const MatchFinder::MatchResult &Result) {
+  const auto *CalleeExpr = Result.Nodes.getNodeAs<Expr>("ref");
+
+  LambdaProperties LP;
+
+  const auto *Bind = Result.Nodes.getNodeAs<CallExpr>("bind");
+  const auto *Decl = dyn_cast<FunctionDecl>(Bind->getCalleeDecl());
+  const auto *NS =
+      dyn_cast<NamespaceDecl>(Decl->getEnclosingNamespaceContext());
+  while (NS->isInlineNamespace())
+    NS = dyn_cast<NamespaceDecl>(NS->getDeclContext());
+  LP.BindNamespace = NS->getName();
+
+  LP.Callable.Type = getCallableType(Result);
+  LP.Callable.Materialization = getCallableMaterialization(Result);
+  LP.Callable.Decl =
+      getCallMethodDecl(Result, LP.Callable.Type, LP.Callable.Materialization);
+  LP.Callable.SourceTokens = getSourceTextForExpr(Result, CalleeExpr);
+  if (LP.Callable.Materialization == CMK_VariableRef) {
+    LP.Callable.CaptureMode = CM_ByValue;
+    LP.Callable.UsageIdentifier = getSourceTextForExpr(Result, CalleeExpr);
+    LP.Callable.CaptureIdentifier =
+        getSourceTextForExpr(Result, ignoreTemporariesAndPointers(CalleeExpr));
+  } else if (LP.Callable.Materialization == CMK_CallExpression) {
+    LP.Callable.CaptureMode = CM_InitExpression;
+    LP.Callable.UsageIdentifier = "Func";
+    LP.Callable.CaptureIdentifier = "Func";
+    LP.Callable.CaptureInitializer = getSourceTextForExpr(Result, CalleeExpr);
+  }
+
+  LP.BindArguments = buildBindArguments(Result, LP.Callable);
+
+  LP.IsFixitSupported = isFixitSupported(LP.Callable, LP.BindArguments);
+
+  return LP;
+}
+
+static bool emitCapture(llvm::StringSet<> &CaptureSet, StringRef Delimiter,
+                        CaptureMode CM, StringRef Identifier,
+                        StringRef InitExpression, raw_ostream &Stream) {
+  if (CM == CM_None)
+    return false;
+
+  // This capture has already been emitted.
+  if (CaptureSet.count(Identifier) != 0)
+    return false;
+
+  Stream << Delimiter;
+
+  if (CM == CM_ByRef)
+    Stream << "&";
+  Stream << Identifier;
+  if (CM == CM_InitExpression)
+    Stream << " = " << InitExpression;
+
+  CaptureSet.insert(Identifier);
+  return true;
+}
+
+static void emitCaptureList(const LambdaProperties &LP,
+                            const MatchFinder::MatchResult &Result,
+                            raw_ostream &Stream) {
+  llvm::StringSet<> CaptureSet;
+  bool AnyCapturesEmitted = false;
+
+  AnyCapturesEmitted = emitCapture(CaptureSet, "", LP.Callable.CaptureMode,
+                                   LP.Callable.CaptureIdentifier,
+                                   LP.Callable.CaptureInitializer, Stream);
+
+  for (const BindArgument &B : LP.BindArguments) {
+    if (B.CaptureMode == CM_None || !B.IsUsed)
+      continue;
+
+    StringRef Delimiter = AnyCapturesEmitted ? ", " : "";
+
+    if (emitCapture(CaptureSet, Delimiter, B.CaptureMode, B.CaptureIdentifier,
+                    B.SourceTokens, Stream))
+      AnyCapturesEmitted = true;
+  }
+}
+
+static ArrayRef<BindArgument>
+getForwardedArgumentList(const LambdaProperties &P) {
+  ArrayRef<BindArgument> Args = makeArrayRef(P.BindArguments);
+  if (P.Callable.Type != CT_MemberFunction)
+    return Args;
+
+  return Args.drop_front();
+}
+AvoidBindCheck::AvoidBindCheck(StringRef Name, ClangTidyContext *Context)
+    : ClangTidyCheck(Name, Context),
+      PermissiveParameterList(Options.get("PermissiveParameterList", 0) != 0) {}
+
 void AvoidBindCheck::registerMatchers(MatchFinder *Finder) {
   if (!getLangOpts().CPlusPlus14) // Need C++14 for generic lambdas.
     return;
 
   Finder->addMatcher(
       callExpr(
-          callee(namedDecl(hasName("::std::bind"))),
-          hasArgument(0, declRefExpr(to(functionDecl().bind("f"))).bind("ref")))
+          callee(namedDecl(
+              anyOf(hasName("::boost::bind"), hasName("::std::bind")))),
+          hasArgument(
+              0, anyOf(expr(hasType(memberPointerType())).bind("ref"),
+                       expr(hasParent(materializeTemporaryExpr().bind("ref"))),
+                       expr().bind("ref"))))
           .bind("bind"),
       this);
 }
 
 void AvoidBindCheck::check(const MatchFinder::MatchResult &Result) {
   const auto *MatchedDecl = Result.Nodes.getNodeAs<CallExpr>("bind");
-  auto Diag = diag(MatchedDecl->getBeginLoc(), "prefer a lambda to std::bind");
 
-  const auto Args = buildBindArguments(Result, MatchedDecl);
-
-  // Do not attempt to create fixits for nested call expressions.
-  // FIXME: Create lambda capture variables to capture output of calls.
-  // NOTE: Supporting nested std::bind will be more difficult due to placeholder
-  // sharing between outer and inner std:bind invocations.
-  if (llvm::any_of(Args,
-                   [](const BindArgument &B) { return B.Kind == BK_CallExpr; }))
+  LambdaProperties LP = getLambdaProperties(Result);
+  auto Diag =
+      diag(MatchedDecl->getBeginLoc(),
+           formatv("prefer a lambda to {0}::bind", LP.BindNamespace).str());
+  if (!LP.IsFixitSupported)
     return;
 
-  // Do not attempt to create fixits when placeholders are reused.
-  // Unused placeholders are supported by requiring C++14 generic lambdas.
-  // FIXME: Support this case by deducing the common type.
-  if (isPlaceHolderIndexRepeated(Args))
-    return;
-
-  const auto *F = Result.Nodes.getNodeAs<FunctionDecl>("f");
-
-  // std::bind can support argument count mismatch between its arguments and the
-  // bound function's arguments. Do not attempt to generate a fixit for such
-  // cases.
-  // FIXME: Support this case by creating unused lambda capture variables.
-  if (F->getNumParams() != Args.size())
-    return;
+  const auto *Ref = Result.Nodes.getNodeAs<Expr>("ref");
 
   std::string Buffer;
   llvm::raw_string_ostream Stream(Buffer);
 
-  bool HasCapturedArgument = llvm::any_of(
-      Args, [](const BindArgument &B) { return B.Kind == BK_Other; });
-  const auto *Ref = Result.Nodes.getNodeAs<DeclRefExpr>("ref");
-  Stream << "[" << (HasCapturedArgument ? "=" : "") << "]";
-  addPlaceholderArgs(Args, Stream);
+  Stream << "[";
+  emitCaptureList(LP, Result, Stream);
+  Stream << "]";
+
+  ArrayRef<BindArgument> FunctionCallArgs = makeArrayRef(LP.BindArguments);
+
+  addPlaceholderArgs(LP, Stream, PermissiveParameterList);
+
+  if (LP.Callable.Type == CT_Function) {
+    StringRef SourceTokens = LP.Callable.SourceTokens;
+    SourceTokens.consume_front("&");
+    Stream << " { return " << SourceTokens;
+  } else if (LP.Callable.Type == CT_MemberFunction) {
+    const auto *MethodDecl = dyn_cast<CXXMethodDecl>(LP.Callable.Decl);
+    const BindArgument &ObjPtr = FunctionCallArgs.front();
+
+    Stream << " { ";
+    if (!isa<CXXThisExpr>(ignoreTemporariesAndPointers(ObjPtr.E))) {
+      Stream << ObjPtr.UsageIdentifier;
+      Stream << "->";
+    }
+
+    Stream << MethodDecl->getName();
+  } else {
     Stream << " { return ";
+    switch (LP.Callable.CaptureMode) {
+    case CM_ByValue:
+    case CM_ByRef:
+      if (LP.Callable.UsageIdentifier != LP.Callable.CaptureIdentifier) {
+        Stream << "(" << LP.Callable.UsageIdentifier << ")";
+        break;
+      }
+      LLVM_FALLTHROUGH;
+    case CM_InitExpression:
+      Stream << LP.Callable.UsageIdentifier;
+      break;
+    default:
       Ref->printPretty(Stream, nullptr, Result.Context->getPrintingPolicy());
+    }
+  }
+
   Stream << "(";
-  addFunctionCallArgs(Args, Stream);
+
+  addFunctionCallArgs(getForwardedArgumentList(LP), Stream);
   Stream << "); }";
 
   Diag << FixItHint::CreateReplacement(MatchedDecl->getSourceRange(),
                                        Stream.str());
 }
 
 } // namespace modernize
 } // namespace tidy
 } // namespace clang

clang-tools-extra/docs/ReleaseNotes.rst

- Improved :doc:`readability-redundant-member-init
   The check  now supports the ``IgnoreBaseInCopyConstructors`` option to avoid
   `"base class 'Foo' should be explicitly initialized in the copy constructor"`
   warnings or errors with ``gcc -Wextra`` or ``gcc -Werror=extra``.
 
 - The :doc:`readability-redundant-string-init
   <clang-tidy/checks/readability-redundant-string-init>` check now supports a
   `StringNames` option enabling its application to custom string classes.
 
+- Improved :doc:`modernize-avoid-bind
+  <clang-tidy/checks/modernize-avoid-bind>` check.
+
+  The check now supports supports diagnosing and fixing arbitrary callables instead of
+  only simple free functions. The `PermissiveParameterList` option has also been
+  added to address situations where the existing fix-it logic would sometimes generate
+  code that no longer compiles.
+
 Improvements to include-fixer
 -----------------------------
 
 The improvements are...
 
 Improvements to clang-include-fixer
 -----------------------------------
 

clang-tools-extra/docs/clang-tidy/checks/modernize-avoid-bind.rst

 .. title:: clang-tidy - modernize-avoid-bind
 
 modernize-avoid-bind
 ====================
 
-The check finds uses of ``std::bind`` and replaces simple uses with lambdas.
-Lambdas will use value-capture where required.
-
-Right now it only handles free functions, not member functions.
+The check finds uses of ``std::bind`` and ``boost::bind`` and replaces them
+with lambdas. Lambdas will use value-capture unless reference capture is
+explicitly requested with ``std::ref`` or ``boost::ref``.
+
+It supports arbitrary callables including member functions, function objects,
+and free functions, and all variations thereof. Anything that you can pass
+to the first argument of ``bind`` should be diagnosable. Currently, the only
+known case where a fix-it is unsupported is when the same placeholder is
+specified multiple times in the parameter list.
 
 Given:
 
 .. code-block:: c++
 
   int add(int x, int y) { return x + y; }
 
 Then:
.. code-block:: c++
   void f() {
     int x = 2;
     auto clj = [=](auto && arg1) { return add(x, arg1); };
   }
 
 ``std::bind`` can be hard to read and can result in larger object files and
 binaries due to type information that will not be produced by equivalent
 lambdas.
+
+Options
+-------
+
+.. option:: PermissiveParameterList
+
+  If the option is set to non-zero, the check will append ``auto&&...`` to the end
+  of every placeholder parameter list. Without this, it is possible for a fix-it
+  to perform an incorrect transformation in the case where the result of the ``bind``
+  is used in the context of a type erased functor such as ``std::function`` which
+  allows mismatched arguments. For example:
+  
+
+.. code-block:: c++
+
+  int add(int x, int y) { return x + y; }
+  int foo() {
+    std::function<int(int,int)> ignore_args = std::bind(add, 2, 2);
+    return ignore_args(3, 3);
+  }
+
+is valid code, and returns `4`. The actual values passed to ``ignore_args`` are
+simply ignored. Without ``PermissiveParameterList``, this would be transformed into
+
+.. code-block:: c++
+
+  int add(int x, int y) { return x + y; }
+  int foo() {
+    std::function<int(int,int)> ignore_args = [] { return add(2, 2); }
+    return ignore_args(3, 3);
+  }
+
+which will *not* compile, since the lambda does not contain an ``operator()`` that
+that accepts 2 arguments. With permissive parameter list, it instead generates
+
+.. code-block:: c++
+
+  int add(int x, int y) { return x + y; }
+  int foo() {
+    std::function<int(int,int)> ignore_args = [](auto&&...) { return add(2, 2); }
+    return ignore_args(3, 3);
+  }
+
+which is correct.
+  
+This check requires using C++14 or higher to run.

clang-tools-extra/test/clang-tidy/checkers/modernize-avoid-bind-permissive-parameter-list.cpp

+// RUN: %check_clang_tidy -std=c++14-or-later %s modernize-avoid-bind %t -- \
+// RUN:   -config="{CheckOptions: [ \
+// RUN:     {key: modernize-avoid-bind.PermissiveParameterList, value: 1}]}" --
+
+namespace std {
+inline namespace impl {
+template <class Fp, class... Arguments>
+class bind_rt {};
+
+template <class Fp, class... Arguments>
+bind_rt<Fp, Arguments...> bind(Fp &&, Arguments &&...);
+} // namespace impl
+
+template <typename T>
+T ref(T &t);
+} // namespace std
+
+int add(int x, int y) { return x + y; }
+
+// Let's fake a minimal std::function-like facility.
+namespace std {
+template <typename _Tp>
+_Tp declval();
+
+template <typename _Functor, typename... _ArgTypes>
+struct __res {
+  template <typename... _Args>
+  static decltype(declval<_Functor>()(_Args()...)) _S_test(int);
+
+  template <typename...>
+  static void _S_test(...);
+
+  using type = decltype(_S_test<_ArgTypes...>(0));
+};
+
+template <typename>
+struct function;
+
+template <typename... _ArgTypes>
+struct function<void(_ArgTypes...)> {
+  template <typename _Functor,
+            typename = typename __res<_Functor, _ArgTypes...>::type>
+  function(_Functor) {}
+};
+} // namespace std
+
+struct placeholder {};
+placeholder _1;
+
+void testLiteralParameters() {
+  auto AAA = std::bind(add, 2, 2);
+  // CHECK-MESSAGES: :[[@LINE-1]]:14: warning: prefer a lambda to std::bind [modernize-avoid-bind]
+  // CHECK-FIXES: auto AAA = [](auto && ...) { return add(2, 2); };
+
+  auto BBB = std::bind(add, _1, 2);
+  // CHECK-MESSAGES: :[[@LINE-1]]:14: warning: prefer a lambda to std::bind [modernize-avoid-bind]
+  // CHECK-FIXES: auto BBB = [](auto && PH1, auto && ...) { return add(PH1, 2); };
+}

clang-tools-extra/test/clang-tidy/checkers/modernize-avoid-bind.cpp

 // RUN: %check_clang_tidy -std=c++14-or-later %s modernize-avoid-bind %t
 
 namespace std {
 inline namespace impl {
 template <class Fp, class... Arguments>
 class bind_rt {};
 
 template <class Fp, class... Arguments>
 bind_rt<Fp, Arguments...> bind(Fp &&, Arguments &&...);
 }
+
+template <typename T>
+T ref(T &t);
 }
 
-int add(int x, int y) { return x + y; }
+namespace boost {
+template <class Fp, class... Arguments>
+class bind_rt {};
 
-void f() {
-  auto clj = std::bind(add, 2, 2);
-  // CHECK-MESSAGES: :[[@LINE-1]]:14: warning: prefer a lambda to std::bind [modernize-avoid-bind]
-  // CHECK-FIXES: auto clj = [] { return add(2, 2); };
-}
+template <class Fp, class... Arguments>
+bind_rt<Fp, Arguments...> bind(const Fp &, Arguments...);
 
-void g() {
-  int x = 2;
-  int y = 2;
-  auto clj = std::bind(add, x, y);
-  // CHECK-MESSAGES: :[[@LINE-1]]:14: warning: prefer a lambda to std::bind
-  // CHECK-FIXES: auto clj = [=] { return add(x, y); };
+template <class T>
+struct reference_wrapper {
+  explicit reference_wrapper(T &t) {}
+};
+
+template <class T>
+reference_wrapper<T> const ref(T &t) {
+  return reference_wrapper<T>(t);
 }
 
-struct placeholder {};
-placeholder _1;
-placeholder _2;
+} // namespace boost
 
-void h() {
-  int x = 2;
-  auto clj = std::bind(add, x, _1);
-  // CHECK-MESSAGES: :[[@LINE-1]]:14: warning: prefer a lambda to std::bind
-  // CHECK-FIXES: auto clj = [=](auto && arg1) { return add(x, arg1); };
-}
+namespace C {
+int add(int x, int y) { return x + y; }
+} // namespace C
 
-struct A;
-struct B;
-bool ABTest(const A &, const B &);
+struct Foo {
+  static int add(int x, int y) { return x + y; }
+};
 
-void i() {
-  auto BATest = std::bind(ABTest, _2, _1);
-  // CHECK-MESSAGES: :[[@LINE-1]]:17: warning: prefer a lambda to std::bind
-  // CHECK-FIXES: auto BATest = [](auto && arg1, auto && arg2) { return ABTest(arg2, arg1); };
-}
+struct D {
+  D() = default;
+  void operator()(int x, int y) const {}
 
-void j() {
-  auto clj = std::bind(add, 2, 2, 2);
-  // CHECK-MESSAGES: :[[@LINE-1]]:14: warning: prefer a lambda to std::bind
-  // No fix is applied for argument mismatches.
-  // CHECK-FIXES: auto clj = std::bind(add, 2, 2, 2);
-}
+  void MemberFunction(int x) {}
 
-void k() {
-  auto clj = std::bind(add, _1, _1);
-  // CHECK-MESSAGES: :[[@LINE-1]]:14: warning: prefer a lambda to std::bind
-  // No fix is applied for reused placeholders.
-  // CHECK-FIXES: auto clj = std::bind(add, _1, _1);
-}
+  static D *create();
+};
 
-void m() {
-  auto clj = std::bind(add, 1, add(2, 5));
-  // CHECK-MESSAGES: :[[@LINE-1]]:14: warning: prefer a lambda to std::bind
-  // No fix is applied for nested calls.
-  // CHECK-FIXES: auto clj = std::bind(add, 1, add(2, 5));
-}
+struct F {
+  F(int x) {}
+  ~F() {}
 
-namespace C {
-  int add(int x, int y){ return x + y; }
-}
+  int get() { return 42; }
+};
 
-void n() {
-  auto clj = std::bind(C::add, 1, 1);
-  // CHECK-MESSAGES: :[[@LINE-1]]:14: warning: prefer a lambda to std::bind
-  // CHECK-FIXES: auto clj = [] { return C::add(1, 1); };
-}
+void UseF(F);
+
+struct placeholder {};
+placeholder _1;
+placeholder _2;
+
+int add(int x, int y) { return x + y; }
+int addThree(int x, int y, int z) { return x + y + z; }
 
 // Let's fake a minimal std::function-like facility.
 namespace std {
 template <typename _Tp>
 _Tp declval();
 
 template <typename _Functor, typename... _ArgTypes>
 struct __res {

 void UseThing(Thing *);
 
 struct Callback {
   Callback();
   Callback(std::function<void()>);
   void Reset(std::function<void()>);
 };
 
-void test(Thing *t) {
+int GlobalVariable = 42;
+
+struct TestCaptureByValueStruct {
+  int MemberVariable;
+  static int StaticMemberVariable;
+  F MemberStruct;
+
+  void testCaptureByValue(int Param, F f) {
+    int x = 3;
+    int y = 4;
+    auto AAA = std::bind(add, x, y);
+    // CHECK-MESSAGES: :[[@LINE-1]]:16: warning: prefer a lambda to std::bind [modernize-avoid-bind]
+    // CHECK-FIXES: auto AAA = [x, y] { return add(x, y); };
+
+    // When the captured variable is repeated, it should only appear in the capture list once.
+    auto BBB = std::bind(add, x, x);
+    // CHECK-MESSAGES: :[[@LINE-1]]:16: warning: prefer a lambda to std::bind [modernize-avoid-bind]
+    // CHECK-FIXES: auto BBB = [x] { return add(x, x); };
+
+    int LocalVariable;
+    // Global variables shouldn't be captured at all, and members should be captured through this.
+    auto CCC = std::bind(add, MemberVariable, GlobalVariable);
+    // CHECK-MESSAGES: :[[@LINE-1]]:16: warning: prefer a lambda to std::bind [modernize-avoid-bind]
+    // CHECK-FIXES: auto CCC = [this] { return add(MemberVariable, GlobalVariable); };
+
+    // Static member variables shouldn't be captured, but locals should
+    auto DDD = std::bind(add, TestCaptureByValueStruct::StaticMemberVariable, LocalVariable);
+    // CHECK-MESSAGES: :[[@LINE-1]]:16: warning: prefer a lambda to std::bind [modernize-avoid-bind]
+    // CHECK-FIXES: auto DDD = [LocalVariable] { return add(TestCaptureByValueStruct::StaticMemberVariable, LocalVariable); };
+
+    auto EEE = std::bind(add, Param, Param);
+    // CHECK-MESSAGES: :[[@LINE-1]]:16: warning: prefer a lambda to std::bind [modernize-avoid-bind]
+    // CHECK-FIXES: auto EEE = [Param] { return add(Param, Param); };
+
+    // The signature of boost::bind() is different, and causes
+    // CXXBindTemporaryExprs to be created in certain cases.  So let's test
+    // those here.
+    auto FFF = boost::bind(UseF, f);
+    // CHECK-MESSAGES: :[[@LINE-1]]:16: warning: prefer a lambda to boost::bind [modernize-avoid-bind]
+    // CHECK-FIXES: auto FFF = [f] { return UseF(f); };
+
+    auto GGG = boost::bind(UseF, MemberStruct);
+    // CHECK-MESSAGES: :[[@LINE-1]]:16: warning: prefer a lambda to boost::bind [modernize-avoid-bind]
+    // CHECK-FIXES: auto GGG = [this] { return UseF(MemberStruct); };
+  }
+};
+
+void testLiteralParameters() {
+  auto AAA = std::bind(add, 2, 2);
+  // CHECK-MESSAGES: :[[@LINE-1]]:14: warning: prefer a lambda to std::bind [modernize-avoid-bind]
+  // CHECK-FIXES: auto AAA = [] { return add(2, 2); };
+
+  auto BBB = std::bind(addThree, 2, 3, 4);
+  // CHECK-MESSAGES: :[[@LINE-1]]:14: warning: prefer a lambda to std::bind [modernize-avoid-bind]
+  // CHECK-FIXES: auto BBB = [] { return addThree(2, 3, 4); };
+}
+
+void testCaptureByReference() {
+  int x = 2;
+  int y = 2;
+  auto AAA = std::bind(add, std::ref(x), std::ref(y));
+  // CHECK-MESSAGES: :[[@LINE-1]]:14: warning: prefer a lambda to std::bind
+  // CHECK-FIXES: auto AAA = [&x, &y] { return add(x, y); };
+
+  auto BBB = std::bind(add, std::ref(x), y);
+  // CHECK-MESSAGES: :[[@LINE-1]]:14: warning: prefer a lambda to std::bind
+  // CHECK-FIXES: auto BBB = [&x, y] { return add(x, y); };
+
+  auto CCC = std::bind(add, y, std::ref(x));
+  // CHECK-MESSAGES: :[[@LINE-1]]:14: warning: prefer a lambda to std::bind
+  // CHECK-FIXES: auto CCC = [y, &x] { return add(y, x); };
+
+  // Make sure it works with boost::ref() too which has slightly different
+  // semantics.
+  auto DDD = boost::bind(add, boost::ref(x), boost::ref(y));
+  // CHECK-MESSAGES: :[[@LINE-1]]:14: warning: prefer a lambda to boost::bind
+  // CHECK-FIXES: auto DDD = [&x, &y] { return add(x, y); };
+
+  auto EEE = boost::bind(add, boost::ref(x), y);
+  // CHECK-MESSAGES: :[[@LINE-1]]:14: warning: prefer a lambda to boost::bind
+  // CHECK-FIXES: auto EEE = [&x, y] { return add(x, y); };
+
+  auto FFF = boost::bind(add, y, boost::ref(x));
+  // CHECK-MESSAGES: :[[@LINE-1]]:14: warning: prefer a lambda to boost::bind
+  // CHECK-FIXES: auto FFF = [y, &x] { return add(y, x); };
+}
+
+void testCaptureByInitExpression() {
+  int x = 42;
+  auto AAA = std::bind(add, x, F(x).get());
+  // CHECK-MESSAGES: :[[@LINE-1]]:14: warning: prefer a lambda to std::bind
+  // CHECK-FIXES: auto AAA = [x, capture0 = F(x).get()] { return add(x, capture0); };
+}
+
+void testFunctionObjects() {
+  D d;
+  D *e = nullptr;
+  auto AAA = std::bind(d, 1, 2);
+  // CHECK-MESSAGES: :[[@LINE-1]]:14: warning: prefer a lambda to std::bind
+  // CHECK-FIXES: auto AAA = [d] { return d(1, 2); }
+
+  auto BBB = std::bind(*e, 1, 2);
+  // CHECK-MESSAGES: :[[@LINE-1]]:14: warning: prefer a lambda to std::bind
+  // CHECK-FIXES: auto BBB = [e] { return (*e)(1, 2); }
+
+  auto CCC = std::bind(D{}, 1, 2);
+  // CHECK-MESSAGES: :[[@LINE-1]]:14: warning: prefer a lambda to std::bind
+  // CHECK-FIXES: auto CCC = [] { return D{}(1, 2); }
+
+  auto DDD = std::bind(D(), 1, 2);
+  // CHECK-MESSAGES: :[[@LINE-1]]:14: warning: prefer a lambda to std::bind
+  // CHECK-FIXES: auto DDD = [] { return D()(1, 2); }
+
+  auto EEE = std::bind(*D::create(), 1, 2);
+  // CHECK-MESSAGES: :[[@LINE-1]]:14: warning: prefer a lambda to std::bind
+  // CHECK-FIXES: auto EEE = [Func = *D::create()] { return Func(1, 2); };
+}
+
+void testPlaceholders() {
+  int x = 2;
+  auto AAA = std::bind(add, x, _1);
+  // CHECK-MESSAGES: :[[@LINE-1]]:14: warning: prefer a lambda to std::bind
+  // CHECK-FIXES: auto AAA = [x](auto && PH1) { return add(x, PH1); };
+
+  auto BBB = std::bind(add, _2, _1);
+  // CHECK-MESSAGES: :[[@LINE-1]]:14: warning: prefer a lambda to std::bind
+  // CHECK-FIXES: auto BBB = [](auto && PH1, auto && PH2) { return add(PH2, PH1); };
+
+  // No fix is applied for reused placeholders.
+  auto CCC = std::bind(add, _1, _1);
+  // CHECK-MESSAGES: :[[@LINE-1]]:14: warning: prefer a lambda to std::bind
+  // CHECK-FIXES: auto CCC = std::bind(add, _1, _1);
+
+  // When a placeholder is skipped, we always add skipped ones to the lambda as
+  // unnamed parameters.
+  auto DDD = std::bind(add, _2, 1);
+  // CHECK-MESSAGES: :[[@LINE-1]]:14: warning: prefer a lambda to std::bind
+  // CHECK-FIXES: auto DDD = [](auto &&, auto && PH2) { return add(PH2, 1); };
+}
+
+void testGlobalFunctions() {
+  auto AAA = std::bind(C::add, 1, 1);
+  // CHECK-MESSAGES: :[[@LINE-1]]:14: warning: prefer a lambda to std::bind
+  // CHECK-FIXES: auto AAA = [] { return C::add(1, 1); };
+
+  auto BBB = std::bind(Foo::add, 1, 1);
+  // CHECK-MESSAGES: :[[@LINE-1]]:14: warning: prefer a lambda to std::bind
+  // CHECK-FIXES: auto BBB = [] { return Foo::add(1, 1); };
+
+  // The & should get removed inside of the lambda body.
+  auto CCC = std::bind(&C::add, 1, 1);
+  // CHECK-MESSAGES: :[[@LINE-1]]:14: warning: prefer a lambda to std::bind
+  // CHECK-FIXES: auto CCC = [] { return C::add(1, 1); };
+
+  auto DDD = std::bind(&Foo::add, 1, 1);
+  // CHECK-MESSAGES: :[[@LINE-1]]:14: warning: prefer a lambda to std::bind
+  // CHECK-FIXES: auto DDD = [] { return Foo::add(1, 1); };
+
+  auto EEE = std::bind(&add, 1, 1);
+  // CHECK-MESSAGES: :[[@LINE-1]]:14: warning: prefer a lambda to std::bind
+  // CHECK-FIXES: auto EEE = [] { return add(1, 1); };
+}
+
+void testCapturedSubexpressions() {
+  int x = 3;
+  int y = 3;
+
+  auto AAA = std::bind(add, 1, add(2, 5));
+  // CHECK-MESSAGES: :[[@LINE-1]]:14: warning: prefer a lambda to std::bind
+  // Results of nested calls are captured by value.
+  // CHECK-FIXES: auto AAA = [capture0 = add(2, 5)] { return add(1, capture0); };
+
+  auto BBB = std::bind(add, x, add(y, 5));
+  // CHECK-MESSAGES: :[[@LINE-1]]:14: warning: prefer a lambda to std::bind
+  // Results of nested calls are captured by value.
+  // CHECK-FIXES: auto BBB = [x, capture0 = add(y, 5)] { return add(x, capture0); };
+}
+
+struct E {
+  void MemberFunction(int x) {}
+
+  void testMemberFunctions() {
+    D *d;
+    D dd;
+    auto AAA = std::bind(&D::MemberFunction, d, 1);
+    // CHECK-MESSAGES: :[[@LINE-1]]:16: warning: prefer a lambda to std::bind
+    // CHECK-FIXES: auto AAA = [d] { d->MemberFunction(1); };
+
+    auto BBB = std::bind(&D::MemberFunction, &dd, 1);
+    // CHECK-MESSAGES: :[[@LINE-1]]:16: warning: prefer a lambda to std::bind
+    // CHECK-FIXES: auto BBB = [ObjectPtr = &dd] { ObjectPtr->MemberFunction(1); };
+
+    auto CCC = std::bind(&E::MemberFunction, this, 1);
+    // CHECK-MESSAGES: :[[@LINE-1]]:16: warning: prefer a lambda to std::bind
+    // CHECK-FIXES: auto CCC = [this] { MemberFunction(1); };
+
+    // Test what happens when the object pointer is itself a placeholder.
+    auto DDD = std::bind(&D::MemberFunction, _1, 1);
+    // CHECK-MESSAGES: :[[@LINE-1]]:16: warning: prefer a lambda to std::bind
+    // CHECK-FIXES: auto DDD = [](auto && PH1) { PH1->MemberFunction(1); };
+  }
+};
+
+void testStdFunction(Thing *t) {
   Callback cb;
   if (t)
     cb.Reset(std::bind(UseThing, t));
   // CHECK-MESSAGES: :[[@LINE-1]]:14: warning: prefer a lambda to std::bind
-  // CHECK-FIXES: cb.Reset([=] { return UseThing(t); });
+  // CHECK-FIXES: cb.Reset([t] { return UseThing(t); });
 }