Tracking Issue: Bugs introduced by Rustup #3905

This is a tracking issue for the bugs introduced by #3905. This is only a summary, more debugging attempts can be found in the PR:

FP identity_conversion on read_dir()?: Fixed Make most macro checks also check for desugarings #4082

Summary: This FP happens, because the code is expanded to HIR code, which includes a line containing From::from(err). This gets linted, but shouldn't. Previously it got expanded to the same HIR code, but didn't get linted.

Minimal example:

use std::path::Path;
use std::fs;

fn main() {
    let path = Path::new(".");
    for _ in fs::read_dir(path)? {}
}

Missing suggestion on explicit_iter_loop

Summary: Even though span_lint_and_sugg is used, no suggestion is displayed, but also no error or ICE. This problem came up once before on something completely unrelated: #3582 (comment). (This could be a problem in rustc, in the suggestion emitting code.)

Minimal example:

#[warn(clippy::explicit_iter_loop)]
fn main() {
    let v = vec![1];
    for _ in v.iter() { }
}

FN into_iter_on_array when into_iter() is called in the for-loop head

Summary: The problem is, that the into_iter MethodCall in the expanded HIR code is seen as macro expanded code, so that is_macro returns true for the span of the MethodCall expression. The HIR expanded code didn't change recently, so something must have changed in rustc, determining if an expression comes from a macro expansion.

Minimal example:

fn main() {
    for _ in [1, 2, 3].into_iter() {}
}

This is not an issue anymore, since the changes have been rolled back, or?

Only the libtest changes were rolled back

Regression tests are in #3936

@flip1995

Citing @estebank from #3944 (comment): (identity_conversion bug)

@flip1995 I believe we can get around that by touching https://github.com/rust-lang/rust/blob/9217fe0e2f04d61dd29c9aaebee2c993705e1d26/src/librustc/hir/lowering.rs#L4667-L4774

We can mark any of the mentioned spans with CompilerDesugaringKind::QuestionMark as a reason, we just need to identify which span it should be (or mark all of them, which should be fine, depending on how that mark is used elsewhere).

Auto merge of #4089 - flip1995:id_conv_reg_test, r=Manishearth

I would have found this problem quicker if it was mentioned in the Lints: Known problems

identity_conversion is fixed in the latest version. a5bcaf5

Everything listed here got fixed. Verified in #3936

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Tracking Issue: Bugs introduced by Rustup #3905 #3913

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Tracking Issue: Bugs introduced by Rustup #3905 #3913

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phansch commented on Apr 10, 2019

Manishearth commented on Apr 10, 2019

flip1995 commented on Apr 10, 2019

flip1995 commented on Apr 16, 2019

ReinierMaas commented on Jun 13, 2019

flip1995 commented on Jun 14, 2019

flip1995 commented on Jun 14, 2019

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