1 files changed, 90 insertions, 0 deletions
diff --git a/clang/lib/Sema/SemaChecking.cpp b/clang/lib/Sema/SemaChecking.cpp
index d14549c9e8c..9fc2bec23b1 100644
--- a/clang/lib/Sema/SemaChecking.cpp
+++ b/clang/lib/Sema/SemaChecking.cpp
@@ -8325,6 +8325,96 @@ void Sema::DiagnoseEmptyLoopBody(const Stmt *S,
   }
 }
 
+//===--- CHECK: Warn on self move with std::move. -------------------------===//
+
+/// DiagnoseSelfMove - Emits a warning if a value is moved to itself.
+void Sema::DiagnoseSelfMove(const Expr *LHSExpr, const Expr *RHSExpr,
+                             SourceLocation OpLoc) {
+
+  if (Diags.isIgnored(diag::warn_sizeof_pointer_expr_memaccess, OpLoc))
+    return;
+
+  if (!ActiveTemplateInstantiations.empty())
+    return;
+
+  // Strip parens and casts away.
+  LHSExpr = LHSExpr->IgnoreParenImpCasts();
+  RHSExpr = RHSExpr->IgnoreParenImpCasts();
+
+  // Check for a call expression
+  const CallExpr *CE = dyn_cast<CallExpr>(RHSExpr);
+  if (!CE || CE->getNumArgs() != 1)
+    return;
+
+  // Check for a call to std::move
+  const FunctionDecl *FD = CE->getDirectCallee();
+  if (!FD || !FD->isInStdNamespace() || !FD->getIdentifier() ||
+      !FD->getIdentifier()->isStr("move"))
+    return;
+
+  // Get argument from std::move
+  RHSExpr = CE->getArg(0);
+
+  const DeclRefExpr *LHSDeclRef = dyn_cast<DeclRefExpr>(LHSExpr);
+  const DeclRefExpr *RHSDeclRef = dyn_cast<DeclRefExpr>(RHSExpr);
+
+  // Two DeclRefExpr's, check that the decls are the same.
+  if (LHSDeclRef && RHSDeclRef) {
+    if (!LHSDeclRef->getDecl() || !RHSDeclRef->getDecl())
+      return;
+    if (LHSDeclRef->getDecl()->getCanonicalDecl() !=
+        RHSDeclRef->getDecl()->getCanonicalDecl())
+      return;
+
+    Diag(OpLoc, diag::warn_self_move) << LHSExpr->getType()
+                                        << LHSExpr->getSourceRange()
+                                        << RHSExpr->getSourceRange();
+    return;
+  }
+
+  // Member variables require a different approach to check for self moves.
+  // MemberExpr's are the same if every nested MemberExpr refers to the same
+  // Decl and that the base Expr's are DeclRefExpr's with the same Decl or
+  // the base Expr's are CXXThisExpr's.
+  const Expr *LHSBase = LHSExpr;
+  const Expr *RHSBase = RHSExpr;
+  const MemberExpr *LHSME = dyn_cast<MemberExpr>(LHSExpr);
+  const MemberExpr *RHSME = dyn_cast<MemberExpr>(RHSExpr);
+  if (!LHSME || !RHSME)
+    return;
+
+  while (LHSME && RHSME) {
+    if (LHSME->getMemberDecl()->getCanonicalDecl() !=
+        RHSME->getMemberDecl()->getCanonicalDecl())
+      return;
+
+    LHSBase = LHSME->getBase();
+    RHSBase = RHSME->getBase();
+    LHSME = dyn_cast<MemberExpr>(LHSBase);
+    RHSME = dyn_cast<MemberExpr>(RHSBase);
+  }
+
+  LHSDeclRef = dyn_cast<DeclRefExpr>(LHSBase);
+  RHSDeclRef = dyn_cast<DeclRefExpr>(RHSBase);
+  if (LHSDeclRef && RHSDeclRef) {
+    if (!LHSDeclRef->getDecl() || !RHSDeclRef->getDecl())
+      return;
+    if (LHSDeclRef->getDecl()->getCanonicalDecl() !=
+        RHSDeclRef->getDecl()->getCanonicalDecl())
+      return;
+
+    Diag(OpLoc, diag::warn_self_move) << LHSExpr->getType()
+                                        << LHSExpr->getSourceRange()
+                                        << RHSExpr->getSourceRange();
+    return;
+  }
+
+  if (isa<CXXThisExpr>(LHSBase) && isa<CXXThisExpr>(RHSBase))
+    Diag(OpLoc, diag::warn_self_move) << LHSExpr->getType()
+                                        << LHSExpr->getSourceRange()
+                                        << RHSExpr->getSourceRange();
+}
+
 //===--- Layout compatibility ----------------------------------------------//
 
 namespace {