Support cfg features generated by build scripts

[AlyoshaVasilieva]

Environment

• IntelliJ Rust plugin version: 0.2.110.5742-193-dev
• Rust toolchain version: 1.39 stable
• IDE name and version: IntelliJ IDEA 2019.3 beta 2
• Operating system: Windows 10 x64

Problem description

Ctrl-clicking function in specific circumstance takes me to wrong function. Experimental macro expansion engine is enabled.

Steps to reproduce

Cargo.toml:

[package]
name = "bug-repro"
version = "0.1.0"
authors = ["Alyosha Vasilieva <1284317+AlyoshaVasilieva@users.noreply.github.com>"]
edition = "2018"

[dependencies]
indexmap = "=1.3.0"
digest = "=0.8.1"

main.rs:

use indexmap::map::IndexMap;

fn main() {
    let mut map = IndexMap::new();
    map.insert("key", "value");
}

IndexMap::new is highlighted as error with "Unresolved reference: `new`".

Ctrl-clicking IndexMap, despite being highlighted red, correctly takes me to its declaration.

Ctrl-clicking new incorrectly takes me to the new function inside impl<D: Input + FixedOutput + Reset + Clone + Default> Digest for D, part of the digest crate.

Compilation works and gives no warnings or errors.

[artemmukhin]

This issue is caused by the fact that indexmap uses custom has_std cfg option (which is actually populated by build.rs via the autocfg crate).

The declarations of IndexMap look like this:

#[cfg(has_std)]
pub struct IndexMap<K, V, S = RandomState> { ... }
#[cfg(not(has_std))]
pub struct IndexMap<K, V, S> { ... }

Currently, IntelliJ Rust only supports some standard cfg options (for more information #4488), so has_std option isn't evaluated. That's why both declarations of IndexMap is used during name resolution.

[Undin]

Now there is a way to collect info about generated items including generated cfg option while project refresh action. Under the hood, it uses cargo check so it may significantly increase refresh time (especially, in the first time when it has to compile all dependencies).
It's disabled by default for now. To turn it on, enable org.rust.cargo.evaluate.build.scripts option in Experimental Features dialog. The dialog can be found via Help | Find Action