Index: clang/include/clang/Sema/Sema.h
===================================================================
--- clang/include/clang/Sema/Sema.h
+++ clang/include/clang/Sema/Sema.h
@@ -2902,9 +2902,11 @@
       SkipBodyInfo *SkipBody = nullptr);
   Decl *ActOnStartOfFunctionDef(Scope *S, Declarator &D,
                                 MultiTemplateParamsArg TemplateParamLists,
-                                SkipBodyInfo *SkipBody = nullptr);
+                                SkipBodyInfo *SkipBody = nullptr,
+                                bool FnDeleted = false);
   Decl *ActOnStartOfFunctionDef(Scope *S, Decl *D,
-                                SkipBodyInfo *SkipBody = nullptr);
+                                SkipBodyInfo *SkipBody = nullptr,
+                                bool FnDeleted = false);
   void ActOnStartTrailingRequiresClause(Scope *S, Declarator &D);
   ExprResult ActOnFinishTrailingRequiresClause(ExprResult ConstraintExpr);
   ExprResult ActOnRequiresClause(ExprResult ConstraintExpr);
Index: clang/lib/Parse/Parser.cpp
===================================================================
--- clang/lib/Parse/Parser.cpp
+++ clang/lib/Parse/Parser.cpp
@@ -1302,11 +1302,13 @@
   // Tell the actions module that we have entered a function definition with the
   // specified Declarator for the function.
   Sema::SkipBodyInfo SkipBody;
+  bool Delete =
+      Tok.is(tok::equal) && NextToken().is(tok::kw_delete) ? true : false;
   Decl *Res = Actions.ActOnStartOfFunctionDef(getCurScope(), D,
                                               TemplateInfo.TemplateParams
                                                   ? *TemplateInfo.TemplateParams
                                                   : MultiTemplateParamsArg(),
-                                              &SkipBody);
+                                              &SkipBody, Delete);
 
   if (SkipBody.ShouldSkip) {
     SkipFunctionBody();
@@ -1332,7 +1334,6 @@
   if (TryConsumeToken(tok::equal)) {
     assert(getLangOpts().CPlusPlus && "Only C++ function definitions have '='");
 
-    bool Delete = false;
     SourceLocation KWLoc;
     if (TryConsumeToken(tok::kw_delete, KWLoc)) {
       Diag(KWLoc, getLangOpts().CPlusPlus11
Index: clang/lib/Sema/SemaDecl.cpp
===================================================================
--- clang/lib/Sema/SemaDecl.cpp
+++ clang/lib/Sema/SemaDecl.cpp
@@ -14185,7 +14185,7 @@
 Decl *
 Sema::ActOnStartOfFunctionDef(Scope *FnBodyScope, Declarator &D,
                               MultiTemplateParamsArg TemplateParameterLists,
-                              SkipBodyInfo *SkipBody) {
+                              SkipBodyInfo *SkipBody, bool FnDeleted) {
   assert(getCurFunctionDecl() == nullptr && "Function parsing confused");
   assert(D.isFunctionDeclarator() && "Not a function declarator!");
   Scope *ParentScope = FnBodyScope->getParent();
@@ -14204,7 +14204,7 @@
 
   D.setFunctionDefinitionKind(FunctionDefinitionKind::Definition);
   Decl *DP = HandleDeclarator(ParentScope, D, TemplateParameterLists);
-  Decl *Dcl = ActOnStartOfFunctionDef(FnBodyScope, DP, SkipBody);
+  Decl *Dcl = ActOnStartOfFunctionDef(FnBodyScope, DP, SkipBody, FnDeleted);
 
   if (!Bases.empty())
     ActOnFinishedFunctionDefinitionInOpenMPDeclareVariantScope(Dcl, Bases);
@@ -14380,7 +14380,7 @@
 }
 
 Decl *Sema::ActOnStartOfFunctionDef(Scope *FnBodyScope, Decl *D,
-                                    SkipBodyInfo *SkipBody) {
+                                    SkipBodyInfo *SkipBody, bool FnDeleted) {
   if (!D) {
     // Parsing the function declaration failed in some way. Push on a fake scope
     // anyway so we can try to parse the function body.
@@ -14470,10 +14470,11 @@
   }
 
   // The return type of a function definition must be complete
-  // (C99 6.9.1p3, C++ [dcl.fct]p6).
+  // unless the function is deleted
+  // (C99 6.9.1p3, C++ [dcl.fct.def.general]p2).
   QualType ResultType = FD->getReturnType();
   if (!ResultType->isDependentType() && !ResultType->isVoidType() &&
-      !FD->isInvalidDecl() &&
+      !FD->isInvalidDecl() && !FnDeleted &&
       RequireCompleteType(FD->getLocation(), ResultType,
                           diag::err_func_def_incomplete_result))
     FD->setInvalidDecl();
@@ -14482,8 +14483,9 @@
     PushDeclContext(FnBodyScope, FD);
 
   // Check the validity of our function parameters
-  CheckParmsForFunctionDef(FD->parameters(),
-                           /*CheckParameterNames=*/true);
+  if (!FnDeleted)
+    CheckParmsForFunctionDef(FD->parameters(),
+                             /*CheckParameterNames=*/true);
 
   // Add non-parameter declarations already in the function to the current
   // scope.
Index: clang/test/CXX/dcl.decl/dcl.fct.def/dcl.fct.def.general/p2.cpp
===================================================================
--- /dev/null
+++ clang/test/CXX/dcl.decl/dcl.fct.def/dcl.fct.def.general/p2.cpp
@@ -0,0 +1,12 @@
+// RUN: %clang_cc1 -fsyntax-only -verify %s
+
+struct Incomplete;                 // expected-note 4{{forward declaration of 'Incomplete'}}
+Incomplete f(Incomplete) = delete; // well-formed
+Incomplete g(Incomplete) {}        // expected-error{{incomplete result type 'Incomplete' in function definition}}\
+// expected-error{{variable has incomplete type 'Incomplete'}}
+
+struct C {
+  Incomplete f(Incomplete) = delete; // well-formed
+  Incomplete g(Incomplete) {}        // expected-error{{incomplete result type 'Incomplete' in function definition}}\
+  // expected-error{{variable has incomplete type 'Incomplete'}}
+};