From d7421384ecab5271594595cf3ebda3580a6f366a Mon Sep 17 00:00:00 2001
From: Serge Pavlov <sepavloff@gmail.com>
Date: Wed, 10 Jun 2015 19:06:59 +0000
Subject: [PATCH] Do not parse members of incomplete class.

If definition of a class is unknown and out-of-line definition of its
member is encountered, do not parse the member declaration.
This change fixes PR18542.

Differential Revision: http://reviews.llvm.org/D8010


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@239483 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Sema/SemaDecl.cpp            |  6 ++++--
 test/SemaCXX/incomplete-call.cpp | 12 ++++++++++++
 2 files changed, 16 insertions(+), 2 deletions(-)

diff --git a/lib/Sema/SemaDecl.cpp b/lib/Sema/SemaDecl.cpp
index 047958e2fc..1c0eea72dd 100644
--- a/lib/Sema/SemaDecl.cpp
+++ b/lib/Sema/SemaDecl.cpp
@@ -4663,12 +4663,14 @@ NamedDecl *Sema::HandleDeclarator(Scope *S, Declarator &D,
         RequireCompleteDeclContext(D.getCXXScopeSpec(), DC))
       return nullptr;
 
+    // If a class is incomplete, do not parse entities inside it.
     if (isa<CXXRecordDecl>(DC) && !cast<CXXRecordDecl>(DC)->hasDefinition()) {
       Diag(D.getIdentifierLoc(),
            diag::err_member_def_undefined_record)
         << Name << DC << D.getCXXScopeSpec().getRange();
-      D.setInvalidType();
-    } else if (!D.getDeclSpec().isFriendSpecified()) {
+      return nullptr;
+    }
+    if (!D.getDeclSpec().isFriendSpecified()) {
       if (diagnoseQualifiedDeclaration(D.getCXXScopeSpec(), DC,
                                       Name, D.getIdentifierLoc())) {
         if (DC->isRecord())
diff --git a/test/SemaCXX/incomplete-call.cpp b/test/SemaCXX/incomplete-call.cpp
index 69eb03a3ed..6f5169ee8a 100644
--- a/test/SemaCXX/incomplete-call.cpp
+++ b/test/SemaCXX/incomplete-call.cpp
@@ -47,3 +47,15 @@ struct C; // expected-note{{forward declaration}}
 void test_incomplete_object_call(C& c) {
   c(); // expected-error{{incomplete type in call to object of type}}
 }
+
+namespace pr18542 {
+  struct X {
+    int count;
+    template<typename CharT> class basic_istream;
+    template<typename CharT>
+      void basic_istream<CharT>::read() { // expected-error{{out-of-line definition of 'read' from class 'basic_istream<CharT>' without definition}}
+        count = 0;
+      }
+  };
+}
+
-- 
2.40.0