Resolve the prelude import in build_reduced_graph

[LorrensP-2158466]

This pr tries to resolve the prelude import at the build_reduced_graph stage.
Part of batched import resolution in #145108 (cherry picked commit) and maybe needed for #139493.

r? petrochenkov

[petrochenkov]

Could you also add this case to tests?

//@ check-pass #![feature(custom_inner_attributes)] #![rustfmt::skip] fn main() { let _ = todo!(); }

[LorrensP-2158466]

I am currently unable to implement any of your suggestions; it is the prelude import that can not be resolved during build_reduced_graph. Which makes me think that this change doesn't actually do anything useful? At least the prelude import in stdlib keeps failing with every change.

[petrochenkov]

@Voultapher
This change should fix your issues with #139493 and custom inner attributes.
Could you check it when it's ready?

[LorrensP-2158466]

Suggestions worked, however, we can't emit an error when the prelude is already set, I just used a panic for ease of use, and it was triggered when compiling stdlib:

prelude already set: [Segment { ident: prelude#0, id: Some(NodeId(479)), has_generic_args: false, has_lifetime_args: false, args_span: no-location (#0) }, Segment { ident: rust_2021#0, id: Some(NodeId(480)), has_generic_args: false, has_lifetime_args: false, args_span: no-location (#0) }] 

I also can't avoid to only resolve the prelude path when the prelude is not set. Errors like these get emitted:

error[E0433]: failed to resolve: use of undeclared type `String` --> library/std/src/panicking.rs:642:29 | 642 | let mut s = String::new(); | ^^^^^^ use of undeclared type `String` | help: consider importing one of these structs | 12 + use crate::prelude::rust_future::String; | 12 + use alloc::string::String; | error[E0433]: failed to resolve: use of undeclared type `Box` --> library/std/src/panicking.rs:656:13 | 656 | Box::into_raw(Box::new(contents)) | ^^^ use of undeclared type `Box` | help: consider importing one of these structs | 12 + use crate::prelude::rust_future::Box; | 12 + use alloc::boxed::Box; 

@rustbot ready

[petrochenkov]

Okay, I see, in std and in some tests we first apply the prelude import injected implicitly, and then the prelude import written explicitly.
Let's keep it as is then.

[Voultapher]

@petrochenkov I've tested #139493 with this PR and I can confirm it does resolve the problem in question, but I'm also seeing the same UI test failures reported by the CI here.

[Voultapher]

Small addendum, I had hopped that fixing the custom_inner_attributes issue would also resolve the change in errors produced in the where-allowed test since it uses custom_inner_attributes and a top level non prelude macro, but alas the change in errors produced still occurs.

[LorrensP-2158466]

Which tests are you talking about?

[LorrensP-2158466]

I also tried to make CI green, those changes are in the second commit.

@rustbot ready

[petrochenkov]

r=me after fixing typos #145322 (comment) and squashing commits.
@rustbot author

[rustbot]

Reminder, once the PR becomes ready for a review, use @rustbot ready.

[LorrensP-2158466]

@bors2 r=petrochenkov

@rustbot ready

[rust-bors]

@LorrensP-2158466: 🔑 Insufficient privileges: not in review users

[petrochenkov]

@bors r+

[bors]

📌 Commit ff560d3 has been approved by petrochenkov

It is now in the queue for this repository.