Account for trait alias when looking for defid

[tesuji]

I hit the crash on the expect call when running clippy on rustc libcore.
Hopefully this will fix it.
changelog: none

[phansch]

Do you think it would be a lot of work to extract a minimal test case? It would be nice to have a test for this

[tesuji]

Do clippy have a way to log the file it is processing? I think this would help extract a testcase.
Or just merge this and test again on libcore I think.

[ghost]

Just apply the changes locally and test with your local copy.

cd "<project_dir>"
cargo build --manifest-path "<local_clippy>/Cargo.toml"
cargo run --manifest-path "<local_clippy>/Cargo.toml" --bin cargo-clippy

[tesuji]

Thanks @mikerite. I cannot manage to find a testcase for this but binary
buillt with this patch fixes the crash when running on libcore.

[ghost]

I can confirm that the bug is where we look up the AsRef or AsMut traits. libcore is probably one of the few crates where these don't exist. It wouldn't be easy to make a test case for this. You'd have to build something without using core.

--

Edit: Realized my fix was the same as this pull request.

[flip1995]

#![no_core] isn't a thing yet, is it?

EDIT: rust-lang/rust#29639 Nope It is! 🎉

// ignore-windows
// ignore-macos

#![feature(no_core, lang_items, start)]
#![no_core]

#[link(name = "c")]
extern {}

#[lang = "sized"]
pub trait Sized {}
#[lang = "copy"]
pub trait Copy {}
#[lang = "freeze"]
pub unsafe trait Freeze {}

#[lang = "start"]
#[start]
fn start(_argc: isize, _argv: *const *const u8) -> isize {
    0
}

This compiles and does not have libcore. Can you try to create a test case with this?

[flip1995]

The example code, that I posted, already passes the test, without your change. You have to adapt this code, so that it matches

rust-clippy/clippy_lints/src/methods/mod.rs

Lines 1074 to 1086 in b8e5e6f

	if_chain! {
	if let hir::ImplItemKind::Method(ref sig, id) = impl_item.node;
	if let Some(first_arg) = iter_input_pats(&sig.decl, cx.tcx.hir().body(id)).next();
	if let hir::ItemKind::Impl(_, _, _, _, None, _, _) = item.node;
	let method_def_id = cx.tcx.hir().local_def_id(impl_item.hir_id);
	let method_sig = cx.tcx.fn_sig(method_def_id);
	let method_sig = cx.tcx.erase_late_bound_regions(&method_sig);
	let first_arg_ty = &method_sig.inputs().iter().next();
	// check conventions w.r.t. conversion method names and predicates
	if let Some(first_arg_ty) = first_arg_ty;

rust-clippy/clippy_lints/src/methods/mod.rs

Lines 1103 to 1107 in b8e5e6f

	if let Some((ref conv, self_kinds)) = &CONVENTIONS
	.iter()
	.find(|(ref conv, _)| conv.check(&name))
	{
	if !self_kinds.iter().any(|k| k.matches(cx, ty, first_arg_ty)) {

Where the last line in the second snippet should fail at the matches call

---

IIUC This should just be an impl of e.g. a to_ method, taking &self as it's first argument.

[flip1995]

I added it myself. Thanks for your fix!

@bors r+

[bors]

📌 Commit 475a142 has been approved by flip1995

[bors]

⌛ Testing commit 475a142 with merge 9c148c8...

[flip1995]

Fun fact: If you add the & to self in a no_core crate, rustc complains that

error[E0658]: `&A` cannot be used as the type of `self` without the `arbitrary_self_types` feature
  --> tests/ui/def_id_nocore.rs:26:19
   |
26 |     pub fn as_ref(&self) -> &'static str {
   |                   ^^^^^
   |
   = note: for more information, see https://github.com/rust-lang/rust/issues/44874
   = help: add `#![feature(arbitrary_self_types)]` to the crate attributes to enable
   = help: consider changing to `self`, `&self`, `&mut self`, `self: Box<Self>`, `self: Rc<Self>`, `self: Arc<Self>`, or `self: Pin<P>` (where P is one of the previous types except `Self`)

I don't think, that we need to adapt the warning though 😄

[bors]

💔 Test failed - status-appveyor

[flip1995]

@bors r+

[bors]

📌 Commit c222e7e has been approved by flip1995

[bors]

⌛ Testing commit c222e7e with merge f760088...

[bors]

☀️ Test successful - checks-travis, status-appveyor
Approved by: flip1995
Pushing f760088 to master...