C++: Limit template instantiation depth

A recursive template generates infinite expansions.

Consider the following example:

template <class R1>
struct Base
{
};

template<typename R>
struct Derived :
  Base<
    typename Derived<typename Base<R>::type>::type,
    typename Derived<typename Base<R>::type>::type
  >::type
{};

R is instantiated as Base<R>::type, which causes another
instantiation of R into Base<Base<R>> etc...

This is not a solution, but a workaround.

Task-number: QTCREATORBUG-15141
Change-Id: Ib04f70275e07919e2cb6c7fb61a2045bd52f4a7d
Reviewed-by: Nikolai Kosjar <nikolai.kosjar@theqtcompany.com>

src/libs/cplusplus/LookupContext.cpp

@@ -1549,6 +1549,7 @@ CreateBindings::CreateBindings(Document::Ptr thisDocument, const Snapshot &snaps
     : _snapshot(snapshot)
     , _control(QSharedPointer<Control>(new Control))
     , _expandTemplates(false)
+    , _depth(0)
 {
     _globalNamespace = allocLookupScope(/*parent = */ 0, /*name = */ 0);
     _currentLookupScope = _globalNamespace;
@@ -1978,8 +1979,13 @@ void CreateBindings::initializeSubst(Clone &cloner,
 {
     const unsigned argumentCountOfSpecialization = specialization->templateParameterCount();
 
+    if (_depth > 15)
+        return;
+
+    ++_depth;
     for (unsigned i = 0; i < argumentCountOfSpecialization; ++i)
         resolveTemplateArgument(cloner, subst, origin, specialization, instantiation, i);
+    --_depth;
 }
 
 } // namespace CPlusPlus

src/libs/cplusplus/LookupContext.h

@@ -209,6 +209,7 @@ private:
     LookupScope *_globalNamespace;
     LookupScope *_currentLookupScope;
     bool _expandTemplates;
+    int _depth;
 };
 
 class CPLUSPLUS_EXPORT LookupContext