Removes references to initialized variable from the following completions:
int x = ^;
Handles only the trivial cases where the variable name is completed
immediately at the start of initializer or assignment, more complicated
cases aren't covered, e.g. these completions still contain 'x':
// More complicated expressions. int x = foo(^); int x = 10 + ^; // Other kinds of initialization. int x{^}; int x(^); // Constructor initializers. struct Foo { Foo() : x(^) {} int x; };
We should address those in the future, but they are outside of the scope of
this initial change.