From 987c2f590fade75245e32807ee83c31483e02d8a Mon Sep 17 00:00:00 2001
From: Manuel Klimek <klimek@google.com>
Date: Tue, 4 Dec 2012 13:40:29 +0000
Subject: [PATCH] Fixes crash in isDerivedFrom for recursive templates.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@169262 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/ASTMatchers/ASTMatchFinder.cpp        |  7 ++++++-
 unittests/ASTMatchers/ASTMatchersTest.cpp | 11 +++++++++++
 2 files changed, 17 insertions(+), 1 deletion(-)

diff --git a/lib/ASTMatchers/ASTMatchFinder.cpp b/lib/ASTMatchers/ASTMatchFinder.cpp
index c13cf4a277..7f89550573 100644
--- a/lib/ASTMatchers/ASTMatchFinder.cpp
+++ b/lib/ASTMatchers/ASTMatchFinder.cpp
@@ -605,7 +605,12 @@ bool MatchASTVisitor::classIsDerivedFrom(const CXXRecordDecl *Declaration,
       ClassDecl = TypeNode->getAsCXXRecordDecl();
     }
     assert(ClassDecl != NULL);
-    assert(ClassDecl != Declaration);
+    if (ClassDecl == Declaration) {
+      // This can happen for recursive template definitions; if the
+      // current declaration did not match, we can safely return false.
+      assert(TemplateType);
+      return false;
+    }
     if (Base.matches(*ClassDecl, this, Builder))
       return true;
     if (classIsDerivedFrom(ClassDecl, Base, Builder))
diff --git a/unittests/ASTMatchers/ASTMatchersTest.cpp b/unittests/ASTMatchers/ASTMatchersTest.cpp
index f3d377b771..f640dff16f 100644
--- a/unittests/ASTMatchers/ASTMatchersTest.cpp
+++ b/unittests/ASTMatchers/ASTMatchersTest.cpp
@@ -232,6 +232,17 @@ TEST(DeclarationMatcher, ClassIsDerived) {
       "template <> class Z<void> {};"
       "template <typename T> class Z : public Z<void>, public X {};",
       ZIsDerivedFromX));
+  EXPECT_TRUE(
+      notMatches("template<int> struct X;"
+                 "template<int i> struct X : public X<i-1> {};",
+                 recordDecl(isDerivedFrom(recordDecl(hasName("Some"))))));
+  EXPECT_TRUE(matches(
+      "struct A {};"
+      "template<int> struct X;"
+      "template<int i> struct X : public X<i-1> {};"
+      "template<> struct X<0> : public A {};"
+      "struct B : public X<42> {};",
+      recordDecl(hasName("B"), isDerivedFrom(recordDecl(hasName("A"))))));
 
   // FIXME: Once we have better matchers for template type matching,
   // get rid of the Variable(...) matching and match the right template
-- 
2.40.0