Lazily load the ContextDecl for a lambda's DefinitionData, to fix a

deserialization cycle caused by the ContextDecl recursively importing members
of the lambda's closure type.

llvm-svn: 279694

clang/test/Modules/lambda-context.cpp

@@ -0,0 +1,22 @@
+// RUN: %clang_cc1 -fmodules -std=c++11 -emit-pch -o %t %s
+// RUN: %clang_cc1 -fmodules -std=c++11 -include-pch %t %s -verify
+//
+// This test checks for a bug in the deserialization code that was only
+// reachable with modules enabled, but actually building and using modules is
+// not necessary in order to trigger it, so we just use PCH here to make the
+// test simpler.
+
+#ifndef HEADER_INCLUDED
+#define HEADER_INCLUDED
+
+struct X { template <typename T> X(T) {} };
+struct Y { Y(X x = [] {}); };
+
+#else
+
+// This triggers us to load the specialization of X::X for Y's lambda. That
+// lambda's context decl must not be loaded as a result of loading the lambda,
+// as that would hit a deserialization cycle.
+X x = [] {}; // expected-no-diagnostics
+
+#endif