Visual Studio C++ compiler weird behaviour

T(i_do_not_exist); is an object declaration with the same meaning as T i_do_not_exist;.

N4567 § 6.8[stmt.ambig]p1

There is an ambiguity in the grammar involving expression-statements and declarations: An expression-statement with a function-style explicit type conversion (5.2.3) as its leftmost subexpression can be indistinguishable from a declaration where the first declarator starts with a (. In those cases the statement is a declaration.

§ 8.3[dcl.meaning]p6

In a declaration T D where D has the form

( D1 )

the type of the contained declarator-id is the same as that of the contained declarator-id in the declaration

T D1

Parentheses do not alter the type of the embedded declarator-id, but they can alter the binding of complex declarators.