diff --git a/clang/lib/Sema/SemaDecl.cpp b/clang/lib/Sema/SemaDecl.cpp
index 65330dbbdecb..30ec0c4e4bce 100644
--- a/clang/lib/Sema/SemaDecl.cpp
+++ b/clang/lib/Sema/SemaDecl.cpp
@@ -7176,12 +7176,7 @@ Sema::ActOnFunctionDeclarator(Scope *S, Declarator &D, DeclContext *DC,
       if (!NewFD->isInvalidDecl() && NewFD->isMSVCRTEntryPoint())
         CheckMSVCRTEntryPoint(NewFD);
 
-      if (NewFD->isInvalidDecl()) {
-        // If this is a class member, mark the class invalid immediately.
-        // This avoids some consistency errors later.
-        if (CXXMethodDecl* methodDecl = dyn_cast<CXXMethodDecl>(NewFD))
-          methodDecl->getParent()->setInvalidDecl();
-      } else
+      if (!NewFD->isInvalidDecl())
         D.setRedeclaration(CheckFunctionDeclaration(S, NewFD, Previous,
                                                     isExplicitSpecialization));
     }
diff --git a/clang/test/SemaCXX/constructor-initializer.cpp b/clang/test/SemaCXX/constructor-initializer.cpp
index 17576328c11b..697f718eabb8 100644
--- a/clang/test/SemaCXX/constructor-initializer.cpp
+++ b/clang/test/SemaCXX/constructor-initializer.cpp
@@ -232,15 +232,14 @@ namespace PR7402 {
 // <rdar://problem/8308215>: don't crash.
 // Lots of questionable recovery here;  errors can change.
 namespace test3 {
-  class A : public std::exception {}; // expected-error {{undeclared identifier}} expected-error {{expected class name}} expected-note 4 {{candidate}}
+  class A : public std::exception {}; // expected-error {{undeclared identifier}} expected-error {{expected class name}} expected-note 2 {{candidate}}
   class B : public A {
   public:
     B(const String& s, int e=0) // expected-error {{unknown type name}} 
       : A(e), m_String(s) , m_ErrorStr(__null) {} // expected-error {{no matching constructor}} expected-error {{does not name}}
     B(const B& e)
       : A(e), m_String(e.m_String), m_ErrorStr(__null) { // expected-error {{does not name}} \
-      // expected-error {{no member named 'm_String' in 'test3::B'}} \
-      // expected-error {{no matching}}
+      // expected-error {{no member named 'm_String' in 'test3::B'}}
     }
   };
 }
diff --git a/clang/test/SemaCXX/pr13394-crash-on-invalid.cpp b/clang/test/SemaCXX/pr13394-crash-on-invalid.cpp
index 42b6508c7132..304ee92f6a8d 100644
--- a/clang/test/SemaCXX/pr13394-crash-on-invalid.cpp
+++ b/clang/test/SemaCXX/pr13394-crash-on-invalid.cpp
@@ -8,12 +8,12 @@ namespace stretch_v1 {
 }
 namespace gatekeeper_v1 {
   namespace gatekeeper_factory_v1 {
-    struct closure_t { // expected-note {{'closure_t' declared here}}
+    struct closure_t { // expected-note {{'closure_t' declared here}} expected-note {{'gatekeeper_factory_v1::closure_t' declared here}}
       gatekeeper_v1::closure_t* create(); // expected-error {{no type named 'closure_t' in namespace 'gatekeeper_v1'; did you mean simply 'closure_t'?}}
     };
   }
   // FIXME: Typo correction should remove the 'gatekeeper_v1::' name specifier
-  gatekeeper_v1::closure_t *x; // expected-error-re {{no type named 'closure_t' in namespace 'gatekeeper_v1'{{$}}}}
+  gatekeeper_v1::closure_t *x; // expected-error {{no type named 'closure_t' in namespace 'gatekeeper_v1'; did you mean 'gatekeeper_factory_v1::closure_t'}}
 }
 
 namespace Foo {
diff --git a/clang/test/SemaCXX/pr18284-crash-on-invalid.cpp b/clang/test/SemaCXX/pr18284-crash-on-invalid.cpp
new file mode 100644
index 000000000000..5b1cb21f4bb6
--- /dev/null
+++ b/clang/test/SemaCXX/pr18284-crash-on-invalid.cpp
@@ -0,0 +1,24 @@
+// RUN: %clang_cc1 -fsyntax-only -verify %s
+// Don't crash (PR18284).
+
+namespace n1 {
+class A { };
+class C { A a; };
+
+A::RunTest() {} // expected-error {{C++ requires a type specifier for all declarations}}
+
+void f() {
+  new C;
+}
+} // namespace n1
+
+namespace n2 {
+class A { };
+class C : public A { };
+
+A::RunTest() {} // expected-error {{C++ requires a type specifier for all declarations}}
+
+void f() {
+  new C;
+}
+} // namespace n2