From a52ce7379aa69cffdcf796093398ea84ad7e1921 Mon Sep 17 00:00:00 2001
From: Robert Reif <reif@FX6840>
Date: Thu, 10 Sep 2020 14:47:59 -0400
Subject: [PATCH] fix #9886 (Hang in TemplateSimplifier
 (gcc/gcc/testsuite/g++.dg/cpp0x/decltype34.C))

---
 lib/templatesimplifier.cpp    |  2 +-
 test/testsimplifytemplate.cpp | 19 +++++++++++++++++++
 2 files changed, 20 insertions(+), 1 deletion(-)

diff --git a/lib/templatesimplifier.cpp b/lib/templatesimplifier.cpp
index 0dab6b681..f87f94114 100644
--- a/lib/templatesimplifier.cpp
+++ b/lib/templatesimplifier.cpp
@@ -1127,7 +1127,7 @@ void TemplateSimplifier::useDefaultArgumentValues(TokenAndName &declaration)
                         (from->strAt(1) == ">" || (from->previous()->isName() &&
                                                    typeParameterNames.find(from->strAt(-1)) == typeParameterNames.end())))
                         ++indentlevel;
-                    else if (from->str() == ">" && (links.empty() || links.top()->str() == "<"))
+                    else if (from->str() == ">" && (links.empty() || links.top()->str() == "<" || indentlevel))
                         --indentlevel;
                     auto entry = typeParameterNames.find(from->str());
                     if (entry != typeParameterNames.end() && entry->second < instantiationArgs.size()) {
diff --git a/test/testsimplifytemplate.cpp b/test/testsimplifytemplate.cpp
index b42a4ddfa..d84211abc 100644
--- a/test/testsimplifytemplate.cpp
+++ b/test/testsimplifytemplate.cpp
@@ -198,6 +198,7 @@ private:
         TEST_CASE(template156);
         TEST_CASE(template157); // #9854
         TEST_CASE(template158); // daca crash
+        TEST_CASE(template159); // #9886
         TEST_CASE(template_specialization_1);  // #7868 - template specialization template <typename T> struct S<C<T>> {..};
         TEST_CASE(template_specialization_2);  // #7868 - template specialization template <typename T> struct S<C<T>> {..};
         TEST_CASE(template_enum);  // #6299 Syntax error in complex enum declaration (including template)
@@ -4018,6 +4019,24 @@ private:
         tok(code); // don't crash
     }
 
+    void template159() {  // #9886
+        const char code[] = "struct impl { template <class T> static T create(); };\n"
+                            "template<class T, class U, class = decltype(impl::create<T>()->impl::create<U>())>\n"
+                            "struct tester{};\n"
+                            "tester<impl*, int> ti;\n"
+                            "template<class T, class U, class = decltype(impl::create<T>()->impl::create<U>())>\n"
+                            "int test() { return 0; }\n"
+                            "int i = test<impl*, int>();";
+        const char exp[]  = "struct impl { template < class T > static T create ( ) ; } ; "
+                            "struct tester<impl*,int,decltype(impl::create<impl*>().impl::create<int>())> ; "
+                            "tester<impl*,int,decltype(impl::create<impl*>().impl::create<int>())> ti ; "
+                            "int test<impl*,int,decltype(impl::create<impl*>().impl::create<int>())> ( ) ; "
+                            "int i ; i = test<impl*,int,decltype(impl::create<impl*>().impl::create<int>())> ( ) ; "
+                            "int test<impl*,int,decltype(impl::create<impl*>().impl::create<int>())> ( ) { return 0 ; } "
+                            "struct tester<impl*,int,decltype(impl::create<impl*>().impl::create<int>())> { } ;";
+        ASSERT_EQUALS(exp, tok(code));
+    }
+
     void template_specialization_1() {  // #7868 - template specialization template <typename T> struct S<C<T>> {..};
         const char code[] = "template <typename T> struct C {};\n"
                             "template <typename T> struct S {a};\n"