PCH: fix a crash caused by a circular deserialization dependency

We started by trying to deserialize decltype(func-param) in a trailing return
type, which causes the function parameter decl to be deserialized, which pulls
in the function decl, which pulls the function type, which pulls the same
decltype() in the return type, and then we crashed.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@197644 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Serialization/ASTReaderDecl.cpp b/lib/Serialization/ASTReaderDecl.cpp
index 70fb062b2c59c5bab1912da1f5134e0a0bbf27ea..c2e286814bcabb699258f379b35f5dacda78c7c8 100644 (file)
--- a/lib/Serialization/ASTReaderDecl.cpp
+++ b/lib/Serialization/ASTReaderDecl.cpp
@@ -356,11 +356,14 @@ void ASTDeclReader::Visit(Decl *D) {
 }
 
 void ASTDeclReader::VisitDecl(Decl *D) {
-  if (D->isTemplateParameter()) {
+  if (D->isTemplateParameter() || D->isTemplateParameterPack() ||
+      isa<ParmVarDecl>(D)) {
     // We don't want to deserialize the DeclContext of a template
-    // parameter immediately, because the template parameter might be
-    // used in the formulation of its DeclContext. Use the translation
-    // unit DeclContext as a placeholder.
+    // parameter or of a parameter of a function template immediately.   These
+    // entities might be used in the formulation of its DeclContext (for
+    // example, a function parameter can be used in decltype() in trailing
+    // return type of the function).  Use the translation unit DeclContext as a
+    // placeholder.
     GlobalDeclID SemaDCIDForTemplateParmDecl = ReadDeclID(Record, Idx);
     GlobalDeclID LexicalDCIDForTemplateParmDecl = ReadDeclID(Record, Idx);
     Reader.addPendingDeclContextInfo(D,

diff --git a/test/PCH/cxx-templates.h b/test/PCH/cxx-templates.h
index 992f478e33e6e6d0e079f39f714032704113a145..c4a84472769144bcea52c748f82ec3e86154ebd3 100644 (file)
--- a/test/PCH/cxx-templates.h
+++ b/test/PCH/cxx-templates.h
@@ -311,3 +311,50 @@ namespace local_extern {
     return sizeof(arr);
   }
 }
+
+namespace rdar15468709a {
+  template<typename> struct decay {};
+
+  template<typename FooParamTy> auto foo(FooParamTy fooParam) -> decltype(fooParam);
+  template<typename BarParamTy> auto bar(BarParamTy barParam) -> decay<decltype(barParam)>;
+
+  struct B {};
+
+  void crash() {
+    B some;
+    bar(some);
+  }
+}
+
+namespace rdar15468709b {
+  template<typename> struct decay {};
+
+  template<typename... Foos> int returnsInt(Foos... foos);
+
+  template<typename... FooParamTy> auto foo(FooParamTy... fooParam) -> decltype(returnsInt(fooParam...));
+  template<typename... BarParamTy> auto bar(BarParamTy... barParam) -> decay<decltype(returnsInt(barParam...))>;
+
+  struct B {};
+
+  void crash() {
+    B some;
+    bar(some);
+  }
+}
+
+namespace rdar15468709c {
+  template<typename> struct decay {};
+
+  template<class... Foos> int returnsInt(Foos... foos);
+
+  template<typename FooParamTy> void foo(FooParamTy fooParam) { decltype(fooParam) a; }
+  template<typename BarParamTy> auto bar(BarParamTy barParam) -> decay<decltype(barParam)>;
+
+  struct B {};
+
+  void crash() {
+    B some;
+    bar(some);
+  }
+}
+