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Michael-F-Bryan opened this issue Mar 15, 2018 · 6 comments
Open

Document common manipulations and operations #91

Michael-F-Bryan opened this issue Mar 15, 2018 · 6 comments
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A-contributor-onboarding Area: contributor on-boarding advice (e.g. for new contributors) A-examples Area: examples C-enhancement Category: enhancement E-help-wanted Call for participation: extra help is wanted E-medium Difficulty: might require some prior knowledge or code reading T-compiler Relevant to compiler team

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@Michael-F-Bryan
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Michael-F-Bryan commented Mar 15, 2018 •
edited by mark-i-m
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While playing around using rustc internals as a library I found it was pretty difficult to discover how to do a bunch of "common" operations. We might be able to improve discoverability by documenting these in an appendix.

Off the top of my head, it'd be nice to know how to:

  • Get the fully qualified name of a type given its HIR representation and location (e.g. c_char -> libc::c_char or std::os::raw::c_char, depending on context)
  • Get a Path for a given Item
  • Find the DefId of a function or struct declaration
  • How to pretty-print a function declaration

Feel free to add other "common" questions or shortcuts in the comments and I'll update this list accordingly.

CC: #74
@Michael-F-Bryan
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I'd be happy to write this up but I'll probably need a little guidance because I only know how to do the second thing (find DefId) at the moment.

@mark-i-m
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I don't even know enough to know what is a common operation, but something like that would definitely be helpful. Something like a cookbook appendix...

@Michael-F-Bryan
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To be honest, I was planning to use it as more of a "post questions here if Michael can't figure out how to do something seemingly simple" kind of thing.

For example, I know we do name resolution before rustc_driver fires the after_analysis callback, yet for the life of me I can't figure out how to get the fully qualified name for all a type. For context, I need to convert something like fn inc(a: c_int) -> c_int into fn inc(a: ::std::os::raw::c_int) -> ::std::os::raw::c_int.

@mark-i-m mark-i-m added E-help-wanted Call for participation: extra help is wanted E-medium Difficulty: might require some prior knowledge or code reading labels Mar 16, 2018
@mark-i-m
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mark-i-m commented Jun 4, 2018

How to get a string from a Span (e.g. for printing errors)... Use codemap.span_to_snippet(span)

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mark-i-m commented Jun 7, 2020

How to get the parent of a defid (e.g. the module of an item): https://rust-lang.zulipchat.com/#narrow/stream/182449-t-compiler.2Fhelp/topic/How.20do.20I.20get.20the.20module.20that.20an.20Item.20belongs.20to.3F

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mark-i-m commented Jun 7, 2020

How to get an Item from a DefId: https://rust-lang.zulipchat.com/#narrow/stream/182449-t-compiler.2Fhelp/topic/How.20do.20I.20get.20an.20Item.20from.20a.20DefId.3F

Also, would be good to talk about def_kind

@jieyouxu jieyouxu added A-contributor-onboarding Area: contributor on-boarding advice (e.g. for new contributors) T-compiler Relevant to compiler team C-enhancement Category: enhancement A-examples Area: examples labels Nov 4, 2024
github-actions bot pushed a commit that referenced this issue Apr 19, 2025
@matthiaskrgr
Rollup merge of #139967 - jieyouxu:auxiliary, r=wesleywiser
1234dc2 
Introduce and use specialized `//@ ignore-auxiliary` for test support files instead of using `//@ ignore-test`

### Summary

Add a semantically meaningful directive for ignoring test *auxiliary* files. This is for auxiliary files that *participate* in actual tests but should not be built by `compiletest` (i.e. these files are involved through `mod xxx;` or `include!()` or `#[path = "xxx"]`, etc.).

### Motivation

A specialized directive like `//@ ignore-auxiliary` makes it way easier to audit disabled tests via `//@ ignore-test`.
  - These support files cannot use the canonical `auxiliary/` dir because they participate in module resolution or are included, or their relative paths can be important for test intention otherwise.

Follow-up to:
- #139705
- #139783
- #139740

See also discussions in:

- [#t-compiler > Directive name for non-test aux files?](https://rust-lang.zulipchat.com/#narrow/channel/131828-t-compiler/topic/Directive.20name.20for.20non-test.20aux.20files.3F/with/512773817)
- [#t-compiler > Handling disabled `//@ ignore-test` tests](https://rust-lang.zulipchat.com/#narrow/channel/131828-t-compiler/topic/Handling.20disabled.20.60.2F.2F.40.20ignore-test.60.20tests/with/512005974)
- [#t-compiler/meetings > [steering] 2025-04-11 Dealing with disabled tests](https://rust-lang.zulipchat.com/#narrow/channel/238009-t-compiler.2Fmeetings/topic/.5Bsteering.5D.202025-04-11.20Dealing.20with.20disabled.20tests/with/511717981)

### Remarks on remaining unconditionally disabled tests under `tests/`

After this PR, against commit 79a272c6402, only **14** remaining test files are disabled through `//@ ignore-test`:

<details>
<summary>Remaining `//@ ignore-test` files under `tests/`</summary>

```
tests/debuginfo/drop-locations.rs
4://@ ignore-test (broken, see #128971)

tests/rustdoc/macro-document-private-duplicate.rs
1://@ ignore-test (fails spuriously, see issue #89228)

tests/rustdoc/inline_cross/assoc-const-equality.rs
3://@ ignore-test (FIXME: #125092)

tests/ui/match/issue-27021.rs
7://@ ignore-test (#54987)

tests/ui/match/issue-26996.rs
7://@ ignore-test (#54987)

tests/ui/issues/issue-49298.rs
9://@ ignore-test (#54987)

tests/ui/issues/issue-59756.rs
2://@ ignore-test (rustfix needs multiple suggestions)

tests/ui/precondition-checks/write.rs
5://@ ignore-test (unimplemented)

tests/ui/precondition-checks/read.rs
5://@ ignore-test (unimplemented)

tests/ui/precondition-checks/write_bytes.rs
5://@ ignore-test (unimplemented)

tests/ui/explicit-tail-calls/drop-order.rs
2://@ ignore-test: tail calls are not implemented in rustc_codegen_ssa yet, so this causes 🧊

tests/ui/panics/panic-short-backtrace-windows-x86_64.rs
3://@ ignore-test (#92000)

tests/ui/json/json-bom-plus-crlf-multifile-aux.rs
3://@ ignore-test Not a test. Used by other tests

tests/ui/traits/next-solver/object-soundness-requires-generalization.rs
2://@ ignore-test (see #114196)
```
</details>

Of these, most are either **unimplemented**, or **spurious**, or **known-broken**. The outstanding one is `tests/ui/json/json-bom-plus-crlf-multifile-aux.rs` which I did not want to touch in *this* PR -- that aux file has load-bearing BOM and carriage returns and byte offset matters. I think those test files that require special encoding / BOM probably are better off as `run-make` tests. See #139968 for that aux file.

### Review advice

- Best reviewed commit-by-commit.
- The directive name diverged from the most voted `//@ auxiliary` because I think that's easy to confuse with `//@ aux-{crate,dir}`.

r? compiler
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