1 files changed, 133 insertions, 0 deletions
diff --git a/clang-tools-extra/clang-tidy/bugprone/MoveForwardingReferenceCheck.cpp b/clang-tools-extra/clang-tidy/bugprone/MoveForwardingReferenceCheck.cpp
new file mode 100644
index 00000000000..516ee193033
--- /dev/null
+++ b/clang-tools-extra/clang-tidy/bugprone/MoveForwardingReferenceCheck.cpp
@@ -0,0 +1,133 @@
+//===--- MoveForwardingReferenceCheck.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 "MoveForwardingReferenceCheck.h"
+#include "clang/Lex/Lexer.h"
+#include "llvm/Support/raw_ostream.h"
+
+#include <algorithm>
+
+using namespace clang::ast_matchers;
+
+namespace clang {
+namespace tidy {
+namespace bugprone {
+
+static void replaceMoveWithForward(const UnresolvedLookupExpr *Callee,
+                                   const ParmVarDecl *ParmVar,
+                                   const TemplateTypeParmDecl *TypeParmDecl,
+                                   DiagnosticBuilder &Diag,
+                                   const ASTContext &Context) {
+  const SourceManager &SM = Context.getSourceManager();
+  const LangOptions &LangOpts = Context.getLangOpts();
+
+  CharSourceRange CallRange =
+      Lexer::makeFileCharRange(CharSourceRange::getTokenRange(
+                                   Callee->getLocStart(), Callee->getLocEnd()),
+                               SM, LangOpts);
+
+  if (CallRange.isValid()) {
+    const std::string TypeName =
+        TypeParmDecl->getIdentifier()
+            ? TypeParmDecl->getName().str()
+            : (llvm::Twine("decltype(") + ParmVar->getName() + ")").str();
+
+    const std::string ForwardName =
+        (llvm::Twine("forward<") + TypeName + ">").str();
+
+    // Create a replacement only if we see a "standard" way of calling
+    // std::move(). This will hopefully prevent erroneous replacements if the
+    // code does unusual things (e.g. create an alias for std::move() in
+    // another namespace).
+    NestedNameSpecifier *NNS = Callee->getQualifier();
+    if (!NNS) {
+      // Called as "move" (i.e. presumably the code had a "using std::move;").
+      // We still conservatively put a "std::" in front of the forward because
+      // we don't know whether the code also had a "using std::forward;".
+      Diag << FixItHint::CreateReplacement(CallRange, "std::" + ForwardName);
+    } else if (const NamespaceDecl *Namespace = NNS->getAsNamespace()) {
+      if (Namespace->getName() == "std") {
+        if (!NNS->getPrefix()) {
+          // Called as "std::move".
+          Diag << FixItHint::CreateReplacement(CallRange,
+                                               "std::" + ForwardName);
+        } else if (NNS->getPrefix()->getKind() == NestedNameSpecifier::Global) {
+          // Called as "::std::move".
+          Diag << FixItHint::CreateReplacement(CallRange,
+                                               "::std::" + ForwardName);
+        }
+      }
+    }
+  }
+}
+
+void MoveForwardingReferenceCheck::registerMatchers(MatchFinder *Finder) {
+  if (!getLangOpts().CPlusPlus11)
+    return;
+
+  // Matches a ParmVarDecl for a forwarding reference, i.e. a non-const rvalue
+  // reference of a function template parameter type.
+  auto ForwardingReferenceParmMatcher =
+      parmVarDecl(
+          hasType(qualType(rValueReferenceType(),
+                           references(templateTypeParmType(hasDeclaration(
+                               templateTypeParmDecl().bind("type-parm-decl")))),
+                           unless(references(qualType(isConstQualified()))))))
+          .bind("parm-var");
+
+  Finder->addMatcher(
+      callExpr(callee(unresolvedLookupExpr(
+                          hasAnyDeclaration(namedDecl(
+                              hasUnderlyingDecl(hasName("::std::move")))))
+                          .bind("lookup")),
+               argumentCountIs(1),
+               hasArgument(0, ignoringParenImpCasts(declRefExpr(
+                                  to(ForwardingReferenceParmMatcher)))))
+          .bind("call-move"),
+      this);
+}
+
+void MoveForwardingReferenceCheck::check(
+    const MatchFinder::MatchResult &Result) {
+  const auto *CallMove = Result.Nodes.getNodeAs<CallExpr>("call-move");
+  const auto *UnresolvedLookup =
+      Result.Nodes.getNodeAs<UnresolvedLookupExpr>("lookup");
+  const auto *ParmVar = Result.Nodes.getNodeAs<ParmVarDecl>("parm-var");
+  const auto *TypeParmDecl =
+      Result.Nodes.getNodeAs<TemplateTypeParmDecl>("type-parm-decl");
+
+  // Get the FunctionDecl and FunctionTemplateDecl containing the function
+  // parameter.
+  const auto *FuncForParam = dyn_cast<FunctionDecl>(ParmVar->getDeclContext());
+  if (!FuncForParam)
+    return;
+  const FunctionTemplateDecl *FuncTemplate =
+      FuncForParam->getDescribedFunctionTemplate();
+  if (!FuncTemplate)
+    return;
+
+  // Check that the template type parameter belongs to the same function
+  // template as the function parameter of that type. (This implies that type
+  // deduction will happen on the type.)
+  const TemplateParameterList *Params = FuncTemplate->getTemplateParameters();
+  if (!std::count(Params->begin(), Params->end(), TypeParmDecl))
+    return;
+
+  auto Diag = diag(CallMove->getExprLoc(),
+                   "forwarding reference passed to std::move(), which may "
+                   "unexpectedly cause lvalues to be moved; use "
+                   "std::forward() instead");
+
+  replaceMoveWithForward(UnresolvedLookup, ParmVar, TypeParmDecl, Diag,
+                         *Result.Context);
+}
+
+} // namespace bugprone
+} // namespace tidy
+} // namespace clang