when the expression in decltype does not result in a simple type the entire expression is shown as type instead of the deduced one

Reproducible: Always

Steps to Reproduce:
1. open a c++ file
2. paste simple code sample:
struct N { int a; };
struct M { N z; };
decltype(M::z) i;
3. hover over i

Actual Results:  
tooltip says type of i is decltype(M::z)

Expected Results:  
tooltip should say type of i is N

code completion works for the wrongly showed type

a second sample of code for something more complex:
#include <vector>
decltype(std::declval<std::vector<char>>().begin()) x;