Extended Description

Given

template <typename T, int I>
struct Value;
template
struct Value<T, 0> {
};
template<typename TContainer, unsigned>
struct InternalMap {
};
template
struct Value<InternalMap<T1, 1>, 0 > {
typedef char Type;
};
template
typename Value<InternalMap<T1, 1>, 0 >::Type property();
void Test_Property() {
property();
}

clang -cc1 crashes with

Impossible TemplateArgument
UNREACHABLE executed at /home/espindola/llvm/llvm/tools/clang/lib/AST/TypeLoc.cpp:326!
0 clang 0x0000000001128702
1 clang 0x0000000001128b93
2 libpthread.so.0 0x00007f7150fe5fe0
3 libc.so.6 0x00007f7150442935 gsignal + 53
4 libc.so.6 0x00007f71504440e8 abort + 328
5 clang 0x00000000010fb009 llvm::llvm_unreachable_internal(char const*, char const*, unsigned int) + 457
6 clang 0x0000000001d30041 clang::TemplateSpecializationTypeLoc::initializeArgLocs(clang::ASTContext&, unsigned int, clang::TemplateArgument const*, clang::TemplateArgumentLocInfo*, clang::SourceLocation) + 417