imports.preferNoStd for alloc ignored when "extern crate std" is present

[kristoff3r]

When a crate contains extern crate std; rust-analyzer always want to import e.g. String and other alloc imports from std, even when preferNoStd is set and/or the crate is #![no_std]. For imports from core it seems to suggest both, but with core first.

I discovered this while working on a bevy crate that has extern crate std behind a feature flag, but it seems to be a problem regardless of the feature flag.

rust-analyzer version: rust-analyzer version: 0.4.2281-standalone

rustc version: rustc 1.84.0 (9fc6b4312 2025-01-07)

editor or extension: VScode v0.4.2281 (pre-release)

relevant settings:
settings.json:

{
  "rust-analyzer.imports.preferNoStd": true
}

code snippet to reproduce:

#![no_std]

extern crate alloc;

extern crate std;

// ctrl+. on string only suggests std::string::String
pub fn foo() -> String {}