Index: clang/lib/Parse/ParseStmt.cpp
===================================================================
--- clang/lib/Parse/ParseStmt.cpp
+++ clang/lib/Parse/ParseStmt.cpp
@@ -163,6 +163,30 @@
 };
 }
 
+static bool IsUnknownTypedefName(Parser &P) {
+  if (P.getCurToken().isNot(tok::identifier))
+    return false;
+
+  // Handle things like "unknown *bar;" as declaration for better
+  // diagnostics. Also it leads to creation of invalid declaration
+  // node in AST for such cases which is good for AST consumers.
+  switch (P.NextToken().getKind()) {
+  default:
+    return false;
+  case tok::kw___attribute:
+  case tok::kw_const:
+  case tok::kw_volatile:
+  case tok::star:
+  case tok::identifier:
+    return !P.getLangOpts().ObjC;
+  case tok::amp:
+  case tok::ampamp:
+  case tok::kw___declspec:
+  case tok::l_square:
+    return P.getLangOpts().CPlusPlus;
+  }
+}
+
 StmtResult Parser::ParseStatementOrDeclarationAfterAttributes(
     StmtVector &Stmts, ParsedStmtContext StmtCtx,
     SourceLocation *TrailingElseLoc, ParsedAttributes &CXX11Attrs,
@@ -236,7 +260,7 @@
          (StmtCtx & ParsedStmtContext::AllowDeclarationsInC) !=
              ParsedStmtContext()) &&
         ((GNUAttributeLoc.isValid() && !(HaveAttrs && AllAttrsAreStmtAttrs)) ||
-         isDeclarationStatement())) {
+         isDeclarationStatement() || IsUnknownTypedefName(*this))) {
       SourceLocation DeclStart = Tok.getLocation(), DeclEnd;
       DeclGroupPtrTy Decl;
       if (GNUAttributeLoc.isValid()) {
Index: clang/test/AST/ast-dump-invalid.c
===================================================================
--- /dev/null
+++ clang/test/AST/ast-dump-invalid.c
@@ -0,0 +1,14 @@
+// RUN: not %clang_cc1 -triple x86_64-unknown-unknown -frecovery-ast -fno-recovery-ast-type -ast-dump %s | FileCheck -strict-whitespace %s
+
+void test1() {
+  unknown_t a;
+  // CHECK:      VarDecl{{.*}} invalid a 'int'
+  unknown_t *b;
+  // CHECK:      VarDecl{{.*}} invalid b 'int *'
+  unknown_t const *c;
+  // CHECK:      VarDecl{{.*}} invalid c 'const int *'
+  unknown_t volatile *d;
+  // CHECK:      VarDecl{{.*}} invalid d 'volatile int *'
+  unknown_t __attribute__ ((aligned (16))) f;
+  // CHECK:      VarDecl{{.*}} invalid f 'int'
+}
Index: clang/test/AST/ast-dump-recovery.c
===================================================================
--- clang/test/AST/ast-dump-recovery.c
+++ clang/test/AST/ast-dump-recovery.c
@@ -98,3 +98,11 @@
   // CHECK-NEXT: `-RecoveryExpr {{.*}} '<dependent type>'
   ext(undef_var);
 }
+
+void RecoverToAnInvalidDecl() {
+  Unknown* foo; // invalid decl
+  foo;
+  // Verify that RecoveryExpr has an inner DeclRefExpr.
+  // CHECK:      RecoveryExpr {{.*}} '<dependent type>' contains-errors lvalue
+  // CHECK-NEXT: `-DeclRefExpr {{.*}} 'foo' 'int *'
+}
Index: clang/test/Driver/types.c
===================================================================
--- clang/test/Driver/types.c
+++ clang/test/Driver/types.c
@@ -20,5 +20,5 @@
   __uint128_t t;
 }
 
-// CHECK: error: use of undeclared identifier '__int128_t'
-// CHECK: error: use of undeclared identifier '__uint128_t'
+// CHECK: error: unknown type name '__int128_t'
+// CHECK: error: unknown type name '__uint128_t'
Index: clang/test/Parser/CompoundStmtScope.c
===================================================================
--- clang/test/Parser/CompoundStmtScope.c
+++ clang/test/Parser/CompoundStmtScope.c
@@ -4,5 +4,5 @@
   {
     typedef float X;
   }
-  X Y;  // expected-error {{use of undeclared identifier}}
+  X Y;  // expected-error {{unknown type name 'X'}}
 }
Index: clang/test/Parser/opencl-atomics-cl20.cl
===================================================================
--- clang/test/Parser/opencl-atomics-cl20.cl
+++ clang/test/Parser/opencl-atomics-cl20.cl
@@ -17,10 +17,10 @@
   atomic_float f;
   atomic_flag fl;
 #if !defined(LANG_VER_OK)
-// expected-error@-5 {{use of undeclared identifier 'atomic_int'}}
-// expected-error@-5 {{use of undeclared identifier 'atomic_uint'}}
-// expected-error@-5 {{use of undeclared identifier 'atomic_float'}}
-// expected-error@-5 {{use of undeclared identifier 'atomic_flag'}}
+// expected-error@-5 {{unknown type name 'atomic_int'}}
+// expected-error@-5 {{unknown type name 'atomic_uint'}}
+// expected-error@-5 {{unknown type name 'atomic_float'}}
+// expected-error@-5 {{unknown type name 'atomic_flag'}}
 #endif
 
 // Optional types
@@ -35,28 +35,26 @@
 // one of the extensions is not supported. Here we check with
 // `cl_khr_int64_base_atomics` only.
 #if !defined(LANG_VER_OK) || !defined(cl_khr_int64_base_atomics)
-// expected-error@-11 {{use of undeclared identifier 'atomic_long'}}
-// expected-error@-11 {{use of undeclared identifier 'atomic_ulong'}}
-// expected-error@-11 {{use of undeclared identifier 'atomic_double'}}
-#if defined(LANG_VER_OK)
-// expected-error@-15 {{expected ';' after expression}}
-// expected-error@-16 {{use of undeclared identifier 'l'}}
-// expected-error@-16 {{expected ';' after expression}}
-// expected-error@-17 {{use of undeclared identifier 'ul'}}
-#endif
+// expected-error@-11 {{unknown type name 'atomic_long'}}
+// expected-error@-11 {{unknown type name 'atomic_ulong'}}
+// expected-error@-11 {{unknown type name 'atomic_double'}}
 #if !defined(LANG_VER_OK) || defined(__SPIR64__)
-// expected-error@-18 {{use of undeclared identifier 'atomic_size_t'}}
-// expected-error@-16 {{use of undeclared identifier 'atomic_ptrdiff_t'}}
-#if !defined(LANG_VER_OK)
-// expected-error@-20 {{use of undeclared identifier 'atomic_intptr_t'}}
-// expected-error@-20 {{use of undeclared identifier 'atomic_uintptr_t'}}
+// expected-error@-12 {{unknown type name 'atomic_size_t'}}
+// expected-error@-12 {{unknown type name 'atomic_intptr_t'}}
+#if !defined(LANG_VER_OK) && defined(__SPIR64__)
+// expected-error@-14 {{unknown type name 'atomic_intptr_t'; did you mean 'atomic_int'?}}
+// expected-note@* {{'atomic_int' declared here}}
+// expected-error@-16 {{unknown type name 'atomic_uintptr_t'}}
+// expected-error@-16 {{unknown type name 'atomic_ptrdiff_t'}}
 #else
-// expected-error@-24 {{expected ';' after expression}}
-// expected-error@-25 {{use of undeclared identifier 's'}}
-// expected-error@-25 {{unknown type name 'atomic_intptr_t'; did you mean 'atomic_int'?}}
+#if defined(LANG_VER_OK)
 // expected-note@* {{'atomic_int' declared here}}
-// expected-error@-26 {{unknown type name 'atomic_uintptr_t'; did you mean 'atomic_uint'?}}
+// expected-error@-20 {{unknown type name 'atomic_uintptr_t'; did you mean 'atomic_uint'?}}
 // expected-note@* {{'atomic_uint' declared here}}
+#else
+// expected-error@-23 {{unknown type name 'atomic_uintptr_t'}}
+#endif
+// expected-error@-24 {{unknown type name 'atomic_ptrdiff_t'}}
 #endif
 #endif
 #endif
Index: clang/test/Parser/recovery.c
===================================================================
--- clang/test/Parser/recovery.c
+++ clang/test/Parser/recovery.c
@@ -10,8 +10,8 @@
 // Testcase derived from PR2692
 static void f (char * (*g) (char **, int), char **p, ...) {
   char *s;
-  va_list v;                              // expected-error {{identifier}}
-  s = g (p, __builtin_va_arg(v, int));    // expected-error {{identifier}}
+  va_list v;                              // expected-error {{unknown type name 'va_list'}}
+  s = g (p, __builtin_va_arg(v, int));
 }
 
 
@@ -99,3 +99,12 @@
   x = VALUE3 // expected-error{{expected ';' after expression}}
   x = VALUE4(0) // expected-error{{expected ';' after expression}}
 }
+
+void test3(void) {
+  unknown_t a; // expected-error {{unknown type name 'unknown_t'}}
+  unknown_t *b; // expected-error {{unknown type name 'unknown_t'}}
+  unknown_t const *c; // expected-error {{unknown type name 'unknown_t'}}
+  unknown_t volatile *d; // expected-error {{unknown type name 'unknown_t'}}
+  unknown_t __attribute__ ((aligned (16))) f; // expected-error {{unknown type name 'unknown_t'}}
+  int g = unknown_t * a; // expected-error {{use of undeclared identifier 'unknown_t'}}
+}
Index: clang/test/SemaOpenCL/intel-subgroup-avc-ext-types.cl
===================================================================
--- clang/test/SemaOpenCL/intel-subgroup-avc-ext-types.cl
+++ clang/test/SemaOpenCL/intel-subgroup-avc-ext-types.cl
@@ -46,19 +46,19 @@
 // expected-error@-14 {{initializing '__private intel_sub_group_avc_ime_single_reference_streamin_t' with an expression of incompatible type '__private char'}}
 // expected-error@-14 {{initializing '__private intel_sub_group_avc_ime_dual_reference_streamin_t' with an expression of incompatible type 'int'}}
 #else
-// expected-error@-28 {{use of undeclared identifier 'intel_sub_group_avc_mce_payload_t'}}
-// expected-error@-28 {{use of undeclared identifier 'intel_sub_group_avc_ime_payload_t'}}
-// expected-error@-28 {{use of undeclared identifier 'intel_sub_group_avc_ref_payload_t'}}
-// expected-error@-28 {{use of undeclared identifier 'intel_sub_group_avc_sic_payload_t'}}
-// expected-error@-28 {{use of undeclared identifier 'intel_sub_group_avc_mce_result_t'}}
-// expected-error@-28 {{use of undeclared identifier 'intel_sub_group_avc_ime_result_t'}}
-// expected-error@-28 {{use of undeclared identifier 'intel_sub_group_avc_ref_result_t'}}
-// expected-error@-28 {{use of undeclared identifier 'intel_sub_group_avc_sic_result_t'}}
-// expected-error@-28 {{use of undeclared identifier 'intel_sub_group_avc_ime_result_single_reference_streamout_t'}}
-// expected-error@-28 {{use of undeclared identifier 'intel_sub_group_avc_ime_result_dual_reference_streamout_t'}}
-// expected-error@-28 {{use of undeclared identifier 'intel_sub_group_avc_ime_dual_reference_streamin_t'}}
-// expected-error@-28 {{use of undeclared identifier 'intel_sub_group_avc_ime_single_reference_streamin_t'}}
-// expected-error@-28 {{use of undeclared identifier 'intel_sub_group_avc_ime_dual_reference_streamin_t'}}
+// expected-error@-28 {{unknown type name 'intel_sub_group_avc_mce_payload_t'}}
+// expected-error@-28 {{unknown type name 'intel_sub_group_avc_ime_payload_t'}}
+// expected-error@-28 {{unknown type name 'intel_sub_group_avc_ref_payload_t'}}
+// expected-error@-28 {{unknown type name 'intel_sub_group_avc_sic_payload_t'}}
+// expected-error@-28 {{unknown type name 'intel_sub_group_avc_mce_result_t'}}
+// expected-error@-28 {{unknown type name 'intel_sub_group_avc_ime_result_t'}}
+// expected-error@-28 {{unknown type name 'intel_sub_group_avc_ref_result_t'}}
+// expected-error@-28 {{unknown type name 'intel_sub_group_avc_sic_result_t'}}
+// expected-error@-28 {{unknown type name 'intel_sub_group_avc_ime_result_single_reference_streamout_t'}}
+// expected-error@-28 {{unknown type name 'intel_sub_group_avc_ime_result_dual_reference_streamout_t'}}
+// expected-error@-28 {{unknown type name 'intel_sub_group_avc_ime_dual_reference_streamin_t'}}
+// expected-error@-28 {{unknown type name 'intel_sub_group_avc_ime_single_reference_streamin_t'}}
+// expected-error@-28 {{unknown type name 'intel_sub_group_avc_ime_dual_reference_streamin_t'}}
 #endif
 }
 
@@ -75,13 +75,12 @@
 // expected-error@-5 {{initializing '__private intel_sub_group_avc_ref_payload_t' with an expression of incompatible type '__private intel_sub_group_avc_ime_payload_t'}}
 // expected-error@-3 {{assigning to '__private intel_sub_group_avc_sic_result_t' from incompatible type '__private intel_sub_group_avc_ime_result_t'}}
 #else
-// expected-error@-11 {{use of undeclared identifier 'intel_sub_group_avc_mce_payload_t'}}
-// expected-error@-11 {{use of undeclared identifier 'intel_sub_group_avc_mce_payload_t'}}
-// expected-error@-11 {{use of undeclared identifier 'intel_sub_group_avc_ime_payload_t'}}
-// expected-error@-11 {{use of undeclared identifier 'intel_sub_group_avc_ref_payload_t'}}
-// expected-error@-11 {{use of undeclared identifier 'intel_sub_group_avc_sic_result_t'}}
-// expected-error@-11 {{use of undeclared identifier 'intel_sub_group_avc_ime_result_t'}}
-// expected-error@-11 {{use of undeclared identifier 'result_sic'}} expected-error@-11 {{use of undeclared identifier 'result_ime'}}
+// expected-error@-11 {{unknown type name 'intel_sub_group_avc_mce_payload_t'}}
+// expected-error@-11 {{unknown type name 'intel_sub_group_avc_mce_payload_t'}}
+// expected-error@-11 {{unknown type name 'intel_sub_group_avc_ime_payload_t'}}
+// expected-error@-11 {{unknown type name 'intel_sub_group_avc_ref_payload_t'}}
+// expected-error@-11 {{unknown type name 'intel_sub_group_avc_sic_result_t'}}
+// expected-error@-11 {{unknown type name 'intel_sub_group_avc_ime_result_t'}}
 #endif
 }
 
Index: clang/test/SemaOpenCL/invalid-device-enqueue-types-cl3.0.cl
===================================================================
--- clang/test/SemaOpenCL/invalid-device-enqueue-types-cl3.0.cl
+++ clang/test/SemaOpenCL/invalid-device-enqueue-types-cl3.0.cl
@@ -5,8 +5,8 @@
   clk_event_t e;
   queue_t q;
 #ifndef __opencl_c_device_enqueue
-// expected-error@-3 {{use of undeclared identifier 'clk_event_t'}}
-// expected-error@-3 {{use of undeclared identifier 'queue_t'}}
+// expected-error@-3 {{unknown type name 'clk_event_t'}}
+// expected-error@-3 {{unknown type name 'queue_t'}}
 #else
 // expected-no-diagnostics
 #endif
Index: clang/test/SemaOpenCL/invalid-pipes-cl1.2.cl
===================================================================
--- clang/test/SemaOpenCL/invalid-pipes-cl1.2.cl
+++ clang/test/SemaOpenCL/invalid-pipes-cl1.2.cl
@@ -26,10 +26,5 @@
 #endif
 
 void bar(void) {
- reserve_id_t r;
-#if defined(__OPENCL_C_VERSION__)
-// expected-error@-2 {{use of undeclared identifier 'reserve_id_t'}}
-#else
-// expected-error@-4 {{unknown type name 'reserve_id_t'}}
-#endif
+ reserve_id_t r; // expected-error {{unknown type name 'reserve_id_t'}}
 }