False positive: "Cannot borrow immutable local variable as mutable"

[pwlodarczyk92]

Environment

• Intellij-Rust plugin version: 0.2.0.2422-182-nightly
• Rust toolchain version: rustc 1.30.0-nightly (cb6d2dfa8 2018-09-16)
• IDE name and version: IntelliJ IDEA Ultimate 2018.2.3
• Operating system: Ubuntu 16.04 LTS

Problem description

Mutably borrowing field from immutably bound mutable struct reference is incorrectly reported as an error.

Steps to reproduce

fn main() {
    let mut x = (0, 0);
    let y = &mut x;
    let _z = &mut y.0;
}

Cannot borrow immutable local variable y.0 as mutable