Track type information for IR expressions

[gsomix]

For now pointer member access operator (#129) works only for lvalues, but not rvalues. E.g. this sample doesn't compile:

foo x;
(&x)->x = 42; // error

In #129 to find members by identifier we relied on GetValueType: unit -> TypeReference method implemented for all lvalues. I propose to extend this approach and track type information for all IR expressions:

foo x;
// `x` is lvalue expression of type `foo`
// `(&x)` is rvalue expression of type `foo*`
// `(&x)->x` is lvalue expression of type `int`
(&x)->x = 42; // works!
(42)->x = 42; // error: "Int32" has no member named "x"

• Fix parser for expressions in parentheses
• Implement GetConstantType for constants
• Implement GetExpessionType for address-of operator (&) expression
• Implement GetExpressionType for other unary expressions
• Implement GetExpessionType for binary operator expressions See Implement usual arithmetic conversions #136
• Implement GetExpressionType for other expressions
• Fix pointer member access operator
• Tests, tests, tests!
• Add sample

[ForNeVeR]

In general, I approve this plan. There are some small issues, though.

[ForNeVeR]

Thanks!

[gsomix]

Thanks for the review!