rustc_lint: only query `typeck_tables_of` when a lint needs it. #73743

eddyb · 2020-06-26T00:46:54Z

This was prompted by @jyn514 running into a situation where rustdoc wants to run the unused_doc lint without triggering type-checking (as an alternative to the "everybody loops" approach - type-checking may error/ICE because of the rustdoc feature of allowing multi-platform docs where the actual bodies of functions may refer to APIs for different platforms).

There was also this comment in the source:

// FIXME: Make this lazy to avoid running the TypeckTables query?

The main effect of this is for lint authors, who now need to use cx.tables() to get &TypeckTables, as opposed to having them always available in cx.tables.

r? @oli-obk or @Manishearth

jyn514 · 2020-06-26T00:51:50Z

This was prompted by @jyn514 running into a situation where rustdoc wants to run the unused_doc lint without triggering type-checking (as an alternative to the "everybody loops" approach - type-checking may error/ICE because of the rustdoc feature of allowing multi-platform docs where the actual bodies of functions may refer to APIs for different platforms).

#73566

Manishearth

Looks good to me!

Manishearth · 2020-06-26T01:06:07Z

Once this lands we should do anoher clippy sync cc @flip1995

Manishearth · 2020-06-26T01:06:43Z

@bors r+

bors · 2020-06-26T01:06:44Z

📌 Commit 0cf4b9d has been approved by Manishearth

Manishearth · 2020-06-26T01:07:22Z

@bors p=1

both because it's a lot of clippy changes and also to unblock rustdoc work

jyn514 · 2020-06-26T01:33:17Z

I rebased #73566 over this and confirmed that I can now run the missing_docs lint without ICEs :)

eddyb · 2020-06-26T01:47:38Z

@bors rollup=never (for perf reasons)

bors · 2020-06-26T06:11:06Z

⌛ Testing commit 0cf4b9d with merge 14e65d5...

bors · 2020-06-26T10:11:35Z

☀️ Test successful - checks-azure
Approved by: Manishearth
Pushing 14e65d5 to master...

eddyb · 2020-06-26T12:41:12Z

(We're discussing the remaining issues with that approach elsewhere, but cx.tables() is invoked because all the lints are running thanks to late_lint_mod - here it seems to be the box_pointers lint that's using cx.tables().
This PR appears to work as intended)

@Manishearth

Rustup cc rust-lang/rust#73743 r? @Manishearth changelog: none

eddyb · 2020-06-26T21:14:23Z

Perf results look mostly neutral.

@Manishearth

Rustup cc rust-lang/rust#73743 r? @Manishearth changelog: none

@Manishearth

Rustup cc rust-lang/rust#73743 r? @Manishearth changelog: none

@Manishearth

Rustup cc rust-lang/rust#73743 r? @Manishearth changelog: none

@eddyb

Don't run `everybody_loops` for rustdoc; instead ignore resolution errors r? @eddyb cc @petrochenkov, @GuillaumeGomez, @Manishearth, @ecstatic-morse, @marmeladema ~~Blocked on rust-lang#73743 Merged. ~~Blocked on crater run.~~ Crater popped up some ICEs ([now fixed](rust-lang#73566 (comment))). See [crater run](https://crater-reports.s3.amazonaws.com/pr-73566/index.html), [ICEs](rust-lang#73566 (comment)). ~~Blocked on rust-lang#74070 so that we don't make typeck_tables_of public when it shouldn't be.~~ Merged. Closes rust-lang#71820, closes rust-lang#71104, closes rust-lang#65863. ## What is the motivation for this change? As seen from a lengthy trail of PRs and issues (rust-lang#73532, rust-lang#73103, rust-lang#71820, rust-lang#71104), `everybody_loops` is causing bugs in rustdoc. The main issue is that it does not preserve the validity of the `DefId` tree, meaning that operations on DefIds may unexpectedly fail when called later. This is blocking intra-doc links (see rust-lang#73101). This PR starts by removing `everybody_loops`, fixing rust-lang#71104 and rust-lang#71820. However, that brings back the bugs seen originally in rust-lang#43348: Since libstd documents items for all platforms, the function bodies sometimes do not type check. Here are the errors from documenting `libstd` with `everybody_loops` disabled and no other changes: ```rust error[E0433]: failed to resolve: could not find `handle` in `sys` --> src/libstd/sys/windows/ext/process.rs:13:27 | 13 | let handle = sys::handle::Handle::new(handle as *mut _); | ^^^^^^ could not find `handle` in `sys` error[E0425]: cannot find function `symlink_inner` in module `sys::fs` --> src/libstd/sys/windows/ext/fs.rs:544:14 | 544 | sys::fs::symlink_inner(src.as_ref(), dst.as_ref(), false) | ^^^^^^^^^^^^^ not found in `sys::fs` error[E0425]: cannot find function `symlink_inner` in module `sys::fs` --> src/libstd/sys/windows/ext/fs.rs:564:14 | 564 | sys::fs::symlink_inner(src.as_ref(), dst.as_ref(), true) | ^^^^^^^^^^^^^ not found in `sys::fs` ``` ## Why does this need changes to `rustc_resolve`? Normally, this could be avoided by simply not calling the `typeck_item_bodies` pass. However, the errors above happen before type checking, in name resolution itself. Since name resolution is intermingled with macro expansion, and rustdoc needs expansion to happen before it knows all items to be documented, there needs to be someway to ignore _resolution_ errors in function bodies. An alternative solution suggested by @petrochenkov was to not run `everybody_loops` on anything containing a nested `DefId`. This would solve some of the immediate issues, but isn't bullet-proof: the following functions still could not be documented if the items in the body failed to resolve: - Functions containing a nested `DefId` (rust-lang#71104) - ~~Functions returning `impl Trait` (rust-lang#43878 These ended up not resolving anyway with this PR. - ~~`const fn`, because `loop {}` in `const fn` is unstable (rust-lang#43636 `const_loop` was just stabilized. This also isn't exactly what rustdoc wants, which is to avoid looking at function bodies in the first place. ## What changes were made? The hack implemented in this PR is to add an option to ignore all resolution errors in function bodies. This is enabled only for rustdoc. Since resolution errors are ignored, the MIR generated will be invalid, as can be seen in the following ICE: ```rust error: internal compiler error: broken MIR in DefId(0:11 ~ doc_cfg[8787]::uses_target_feature[0]) ("return type"): bad type [type error] --> /home/joshua/src/rust/src/test/rustdoc/doc-cfg.rs:51:1 | 51 | / pub unsafe fn uses_target_feature() { 52 | | content::should::be::irrelevant(); 53 | | } | |_^ ``` Fortunately, rustdoc does not need to access MIR in order to generate documentation. Therefore this also removes the call to `analyze()` in `rustdoc::run_core`. This has the side effect of not generating all lints by default. Most lints are safe to ignore (does rustdoc really need to run liveness analysis?) but `missing_docs` in particular is disabled when it should not be. Re-running `missing_docs` specifically does not help, because it causes the typechecking pass to be run, bringing back the errors from rust-lang#24658: ``` error[E0599]: no method named `into_handle` found for struct `sys::unix::pipe::AnonPipe` in the current scope --> src/libstd/sys/windows/ext/process.rs:71:27 | 71 | self.into_inner().into_handle().into_raw() as *mut _ | ^^^^^^^^^^^ method not found in `sys::unix::pipe::AnonPipe` | ``` Because of rust-lang#73743, we only run typeck on demand. So this only causes an issue for functions returning `impl Trait`, which were already special cased by `ReplaceFunctionWithBody`. However, it now considers `async fn f() -> T` to be considered `impl Future<Output = T>`, where before it was considered to have a concrete `T` type. ## How will this affect future changes to rustdoc? - Any new changes to rustdoc will not be able to perform type checking without bringing back resolution errors in function bodies. + As a corollary, any new lints cannot require or perform type checking. In some cases this may require refactoring other parts of the compiler to perform type-checking only on-demand, see for example rust-lang#73743. + As a corollary, rustdoc can never again call `tcx.analysis()` unless this PR is reverted altogether. ## Current status - ~~I am not yet sure how to bring back `missing_docs` without running typeck. @eddyb suggested allowing lints to opt-out of type-checking, which would probably be another rabbit hole.~~ The opt-out was implemented in rust-lang#73743. However, of the rustc lints, now _only_ missing_docs is run and no other lints: rust-lang#73566 (comment). We need a team decision on whether that's an acceptable tradeoff. Note that all rustdoc lints are still run (`intra_doc_link_resolution_failure`, etc). **UPDATE**: This was deemed acceptable in rust-lang#73566 (comment) - ~~The implementation of optional errors in `rustc_resolve` is very brute force, it should probably be moved from `LateResolver` to `Resolver` to avoid duplicating the logic in many places.~~ I'm mostly happy with it now. - This no longer allows errors in `async fn f() -> T`. This caused breakage in 50 crates out of a full crater run, all of which (that I looked at) didn't compile when run with rustc directly. In other words, it used to be that they could not be compiled but could still be documented; now they can't be documented either. This needs a decision from the rustdoc team on whether this is acceptable breakage. **UPDATE**: This was deemed acceptable in rust-lang#73566 (comment) - ~~This makes `fn typeck_tables_of` in `rustc_typeck` public. This is not desired behavior, but needs the changes from rust-lang#74070 in order to be fixed.~~ Reverted.

@eddyb

Don't run `everybody_loops` for rustdoc; instead ignore resolution errors r? @eddyb cc @petrochenkov, @GuillaumeGomez, @Manishearth, @ecstatic-morse, @marmeladema ~~Blocked on rust-lang#73743 Merged. ~~Blocked on crater run.~~ Crater popped up some ICEs ([now fixed](rust-lang#73566 (comment))). See [crater run](https://crater-reports.s3.amazonaws.com/pr-73566/index.html), [ICEs](rust-lang#73566 (comment)). ~~Blocked on rust-lang#74070 so that we don't make typeck_tables_of public when it shouldn't be.~~ Merged. Closes rust-lang#71820, closes rust-lang#71104, closes rust-lang#65863. ## What is the motivation for this change? As seen from a lengthy trail of PRs and issues (rust-lang#73532, rust-lang#73103, rust-lang#71820, rust-lang#71104), `everybody_loops` is causing bugs in rustdoc. The main issue is that it does not preserve the validity of the `DefId` tree, meaning that operations on DefIds may unexpectedly fail when called later. This is blocking intra-doc links (see rust-lang#73101). This PR starts by removing `everybody_loops`, fixing rust-lang#71104 and rust-lang#71820. However, that brings back the bugs seen originally in rust-lang#43348: Since libstd documents items for all platforms, the function bodies sometimes do not type check. Here are the errors from documenting `libstd` with `everybody_loops` disabled and no other changes: ```rust error[E0433]: failed to resolve: could not find `handle` in `sys` --> src/libstd/sys/windows/ext/process.rs:13:27 | 13 | let handle = sys::handle::Handle::new(handle as *mut _); | ^^^^^^ could not find `handle` in `sys` error[E0425]: cannot find function `symlink_inner` in module `sys::fs` --> src/libstd/sys/windows/ext/fs.rs:544:14 | 544 | sys::fs::symlink_inner(src.as_ref(), dst.as_ref(), false) | ^^^^^^^^^^^^^ not found in `sys::fs` error[E0425]: cannot find function `symlink_inner` in module `sys::fs` --> src/libstd/sys/windows/ext/fs.rs:564:14 | 564 | sys::fs::symlink_inner(src.as_ref(), dst.as_ref(), true) | ^^^^^^^^^^^^^ not found in `sys::fs` ``` ## Why does this need changes to `rustc_resolve`? Normally, this could be avoided by simply not calling the `typeck_item_bodies` pass. However, the errors above happen before type checking, in name resolution itself. Since name resolution is intermingled with macro expansion, and rustdoc needs expansion to happen before it knows all items to be documented, there needs to be someway to ignore _resolution_ errors in function bodies. An alternative solution suggested by @petrochenkov was to not run `everybody_loops` on anything containing a nested `DefId`. This would solve some of the immediate issues, but isn't bullet-proof: the following functions still could not be documented if the items in the body failed to resolve: - Functions containing a nested `DefId` (rust-lang#71104) - ~~Functions returning `impl Trait` (rust-lang#43878 These ended up not resolving anyway with this PR. - ~~`const fn`, because `loop {}` in `const fn` is unstable (rust-lang#43636 `const_loop` was just stabilized. This also isn't exactly what rustdoc wants, which is to avoid looking at function bodies in the first place. ## What changes were made? The hack implemented in this PR is to add an option to ignore all resolution errors in function bodies. This is enabled only for rustdoc. Since resolution errors are ignored, the MIR generated will be invalid, as can be seen in the following ICE: ```rust error: internal compiler error: broken MIR in DefId(0:11 ~ doc_cfg[8787]::uses_target_feature[0]) ("return type"): bad type [type error] --> /home/joshua/src/rust/src/test/rustdoc/doc-cfg.rs:51:1 | 51 | / pub unsafe fn uses_target_feature() { 52 | | content::should::be::irrelevant(); 53 | | } | |_^ ``` Fortunately, rustdoc does not need to access MIR in order to generate documentation. Therefore this also removes the call to `analyze()` in `rustdoc::run_core`. This has the side effect of not generating all lints by default. Most lints are safe to ignore (does rustdoc really need to run liveness analysis?) but `missing_docs` in particular is disabled when it should not be. Re-running `missing_docs` specifically does not help, because it causes the typechecking pass to be run, bringing back the errors from rust-lang#24658: ``` error[E0599]: no method named `into_handle` found for struct `sys::unix::pipe::AnonPipe` in the current scope --> src/libstd/sys/windows/ext/process.rs:71:27 | 71 | self.into_inner().into_handle().into_raw() as *mut _ | ^^^^^^^^^^^ method not found in `sys::unix::pipe::AnonPipe` | ``` Because of rust-lang#73743, we only run typeck on demand. So this only causes an issue for functions returning `impl Trait`, which were already special cased by `ReplaceFunctionWithBody`. However, it now considers `async fn f() -> T` to be considered `impl Future<Output = T>`, where before it was considered to have a concrete `T` type. ## How will this affect future changes to rustdoc? - Any new changes to rustdoc will not be able to perform type checking without bringing back resolution errors in function bodies. + As a corollary, any new lints cannot require or perform type checking. In some cases this may require refactoring other parts of the compiler to perform type-checking only on-demand, see for example rust-lang#73743. + As a corollary, rustdoc can never again call `tcx.analysis()` unless this PR is reverted altogether. ## Current status - ~~I am not yet sure how to bring back `missing_docs` without running typeck. @eddyb suggested allowing lints to opt-out of type-checking, which would probably be another rabbit hole.~~ The opt-out was implemented in rust-lang#73743. However, of the rustc lints, now _only_ missing_docs is run and no other lints: rust-lang#73566 (comment). We need a team decision on whether that's an acceptable tradeoff. Note that all rustdoc lints are still run (`intra_doc_link_resolution_failure`, etc). **UPDATE**: This was deemed acceptable in rust-lang#73566 (comment) - ~~The implementation of optional errors in `rustc_resolve` is very brute force, it should probably be moved from `LateResolver` to `Resolver` to avoid duplicating the logic in many places.~~ I'm mostly happy with it now. - This no longer allows errors in `async fn f() -> T`. This caused breakage in 50 crates out of a full crater run, all of which (that I looked at) didn't compile when run with rustc directly. In other words, it used to be that they could not be compiled but could still be documented; now they can't be documented either. This needs a decision from the rustdoc team on whether this is acceptable breakage. **UPDATE**: This was deemed acceptable in rust-lang#73566 (comment) - ~~This makes `fn typeck_tables_of` in `rustc_typeck` public. This is not desired behavior, but needs the changes from rust-lang#74070 in order to be fixed.~~ Reverted.

@eddyb

Don't run `everybody_loops` for rustdoc; instead ignore resolution errors r? @eddyb cc @petrochenkov, @GuillaumeGomez, @Manishearth, @ecstatic-morse, @marmeladema ~~Blocked on rust-lang#73743 Merged. ~~Blocked on crater run.~~ Crater popped up some ICEs ([now fixed](rust-lang#73566 (comment))). See [crater run](https://crater-reports.s3.amazonaws.com/pr-73566/index.html), [ICEs](rust-lang#73566 (comment)). ~~Blocked on rust-lang#74070 so that we don't make typeck_tables_of public when it shouldn't be.~~ Merged. Closes rust-lang#71820, closes rust-lang#71104, closes rust-lang#65863. ## What is the motivation for this change? As seen from a lengthy trail of PRs and issues (rust-lang#73532, rust-lang#73103, rust-lang#71820, rust-lang#71104), `everybody_loops` is causing bugs in rustdoc. The main issue is that it does not preserve the validity of the `DefId` tree, meaning that operations on DefIds may unexpectedly fail when called later. This is blocking intra-doc links (see rust-lang#73101). This PR starts by removing `everybody_loops`, fixing rust-lang#71104 and rust-lang#71820. However, that brings back the bugs seen originally in rust-lang#43348: Since libstd documents items for all platforms, the function bodies sometimes do not type check. Here are the errors from documenting `libstd` with `everybody_loops` disabled and no other changes: ```rust error[E0433]: failed to resolve: could not find `handle` in `sys` --> src/libstd/sys/windows/ext/process.rs:13:27 | 13 | let handle = sys::handle::Handle::new(handle as *mut _); | ^^^^^^ could not find `handle` in `sys` error[E0425]: cannot find function `symlink_inner` in module `sys::fs` --> src/libstd/sys/windows/ext/fs.rs:544:14 | 544 | sys::fs::symlink_inner(src.as_ref(), dst.as_ref(), false) | ^^^^^^^^^^^^^ not found in `sys::fs` error[E0425]: cannot find function `symlink_inner` in module `sys::fs` --> src/libstd/sys/windows/ext/fs.rs:564:14 | 564 | sys::fs::symlink_inner(src.as_ref(), dst.as_ref(), true) | ^^^^^^^^^^^^^ not found in `sys::fs` ``` ## Why does this need changes to `rustc_resolve`? Normally, this could be avoided by simply not calling the `typeck_item_bodies` pass. However, the errors above happen before type checking, in name resolution itself. Since name resolution is intermingled with macro expansion, and rustdoc needs expansion to happen before it knows all items to be documented, there needs to be someway to ignore _resolution_ errors in function bodies. An alternative solution suggested by @petrochenkov was to not run `everybody_loops` on anything containing a nested `DefId`. This would solve some of the immediate issues, but isn't bullet-proof: the following functions still could not be documented if the items in the body failed to resolve: - Functions containing a nested `DefId` (rust-lang#71104) - ~~Functions returning `impl Trait` (rust-lang#43878 These ended up not resolving anyway with this PR. - ~~`const fn`, because `loop {}` in `const fn` is unstable (rust-lang#43636 `const_loop` was just stabilized. This also isn't exactly what rustdoc wants, which is to avoid looking at function bodies in the first place. ## What changes were made? The hack implemented in this PR is to add an option to ignore all resolution errors in function bodies. This is enabled only for rustdoc. Since resolution errors are ignored, the MIR generated will be invalid, as can be seen in the following ICE: ```rust error: internal compiler error: broken MIR in DefId(0:11 ~ doc_cfg[8787]::uses_target_feature[0]) ("return type"): bad type [type error] --> /home/joshua/src/rust/src/test/rustdoc/doc-cfg.rs:51:1 | 51 | / pub unsafe fn uses_target_feature() { 52 | | content::should::be::irrelevant(); 53 | | } | |_^ ``` Fortunately, rustdoc does not need to access MIR in order to generate documentation. Therefore this also removes the call to `analyze()` in `rustdoc::run_core`. This has the side effect of not generating all lints by default. Most lints are safe to ignore (does rustdoc really need to run liveness analysis?) but `missing_docs` in particular is disabled when it should not be. Re-running `missing_docs` specifically does not help, because it causes the typechecking pass to be run, bringing back the errors from rust-lang#24658: ``` error[E0599]: no method named `into_handle` found for struct `sys::unix::pipe::AnonPipe` in the current scope --> src/libstd/sys/windows/ext/process.rs:71:27 | 71 | self.into_inner().into_handle().into_raw() as *mut _ | ^^^^^^^^^^^ method not found in `sys::unix::pipe::AnonPipe` | ``` Because of rust-lang#73743, we only run typeck on demand. So this only causes an issue for functions returning `impl Trait`, which were already special cased by `ReplaceFunctionWithBody`. However, it now considers `async fn f() -> T` to be considered `impl Future<Output = T>`, where before it was considered to have a concrete `T` type. ## How will this affect future changes to rustdoc? - Any new changes to rustdoc will not be able to perform type checking without bringing back resolution errors in function bodies. + As a corollary, any new lints cannot require or perform type checking. In some cases this may require refactoring other parts of the compiler to perform type-checking only on-demand, see for example rust-lang#73743. + As a corollary, rustdoc can never again call `tcx.analysis()` unless this PR is reverted altogether. ## Current status - ~~I am not yet sure how to bring back `missing_docs` without running typeck. @eddyb suggested allowing lints to opt-out of type-checking, which would probably be another rabbit hole.~~ The opt-out was implemented in rust-lang#73743. However, of the rustc lints, now _only_ missing_docs is run and no other lints: rust-lang#73566 (comment). We need a team decision on whether that's an acceptable tradeoff. Note that all rustdoc lints are still run (`intra_doc_link_resolution_failure`, etc). **UPDATE**: This was deemed acceptable in rust-lang#73566 (comment) - ~~The implementation of optional errors in `rustc_resolve` is very brute force, it should probably be moved from `LateResolver` to `Resolver` to avoid duplicating the logic in many places.~~ I'm mostly happy with it now. - This no longer allows errors in `async fn f() -> T`. This caused breakage in 50 crates out of a full crater run, all of which (that I looked at) didn't compile when run with rustc directly. In other words, it used to be that they could not be compiled but could still be documented; now they can't be documented either. This needs a decision from the rustdoc team on whether this is acceptable breakage. **UPDATE**: This was deemed acceptable in rust-lang#73566 (comment) - ~~This makes `fn typeck_tables_of` in `rustc_typeck` public. This is not desired behavior, but needs the changes from rust-lang#74070 in order to be fixed.~~ Reverted.

@eddyb

Don't run `everybody_loops` for rustdoc; instead ignore resolution errors r? @eddyb cc @petrochenkov, @GuillaumeGomez, @Manishearth, @ecstatic-morse, @marmeladema ~~Blocked on rust-lang#73743 Merged. ~~Blocked on crater run.~~ Crater popped up some ICEs ([now fixed](rust-lang#73566 (comment))). See [crater run](https://crater-reports.s3.amazonaws.com/pr-73566/index.html), [ICEs](rust-lang#73566 (comment)). ~~Blocked on rust-lang#74070 so that we don't make typeck_tables_of public when it shouldn't be.~~ Merged. Closes rust-lang#71820, closes rust-lang#71104, closes rust-lang#65863. ## What is the motivation for this change? As seen from a lengthy trail of PRs and issues (rust-lang#73532, rust-lang#73103, rust-lang#71820, rust-lang#71104), `everybody_loops` is causing bugs in rustdoc. The main issue is that it does not preserve the validity of the `DefId` tree, meaning that operations on DefIds may unexpectedly fail when called later. This is blocking intra-doc links (see rust-lang#73101). This PR starts by removing `everybody_loops`, fixing rust-lang#71104 and rust-lang#71820. However, that brings back the bugs seen originally in rust-lang#43348: Since libstd documents items for all platforms, the function bodies sometimes do not type check. Here are the errors from documenting `libstd` with `everybody_loops` disabled and no other changes: ```rust error[E0433]: failed to resolve: could not find `handle` in `sys` --> src/libstd/sys/windows/ext/process.rs:13:27 | 13 | let handle = sys::handle::Handle::new(handle as *mut _); | ^^^^^^ could not find `handle` in `sys` error[E0425]: cannot find function `symlink_inner` in module `sys::fs` --> src/libstd/sys/windows/ext/fs.rs:544:14 | 544 | sys::fs::symlink_inner(src.as_ref(), dst.as_ref(), false) | ^^^^^^^^^^^^^ not found in `sys::fs` error[E0425]: cannot find function `symlink_inner` in module `sys::fs` --> src/libstd/sys/windows/ext/fs.rs:564:14 | 564 | sys::fs::symlink_inner(src.as_ref(), dst.as_ref(), true) | ^^^^^^^^^^^^^ not found in `sys::fs` ``` ## Why does this need changes to `rustc_resolve`? Normally, this could be avoided by simply not calling the `typeck_item_bodies` pass. However, the errors above happen before type checking, in name resolution itself. Since name resolution is intermingled with macro expansion, and rustdoc needs expansion to happen before it knows all items to be documented, there needs to be someway to ignore _resolution_ errors in function bodies. An alternative solution suggested by @petrochenkov was to not run `everybody_loops` on anything containing a nested `DefId`. This would solve some of the immediate issues, but isn't bullet-proof: the following functions still could not be documented if the items in the body failed to resolve: - Functions containing a nested `DefId` (rust-lang#71104) - ~~Functions returning `impl Trait` (rust-lang#43878 These ended up not resolving anyway with this PR. - ~~`const fn`, because `loop {}` in `const fn` is unstable (rust-lang#43636 `const_loop` was just stabilized. This also isn't exactly what rustdoc wants, which is to avoid looking at function bodies in the first place. ## What changes were made? The hack implemented in this PR is to add an option to ignore all resolution errors in function bodies. This is enabled only for rustdoc. Since resolution errors are ignored, the MIR generated will be invalid, as can be seen in the following ICE: ```rust error: internal compiler error: broken MIR in DefId(0:11 ~ doc_cfg[8787]::uses_target_feature[0]) ("return type"): bad type [type error] --> /home/joshua/src/rust/src/test/rustdoc/doc-cfg.rs:51:1 | 51 | / pub unsafe fn uses_target_feature() { 52 | | content::should::be::irrelevant(); 53 | | } | |_^ ``` Fortunately, rustdoc does not need to access MIR in order to generate documentation. Therefore this also removes the call to `analyze()` in `rustdoc::run_core`. This has the side effect of not generating all lints by default. Most lints are safe to ignore (does rustdoc really need to run liveness analysis?) but `missing_docs` in particular is disabled when it should not be. Re-running `missing_docs` specifically does not help, because it causes the typechecking pass to be run, bringing back the errors from rust-lang#24658: ``` error[E0599]: no method named `into_handle` found for struct `sys::unix::pipe::AnonPipe` in the current scope --> src/libstd/sys/windows/ext/process.rs:71:27 | 71 | self.into_inner().into_handle().into_raw() as *mut _ | ^^^^^^^^^^^ method not found in `sys::unix::pipe::AnonPipe` | ``` Because of rust-lang#73743, we only run typeck on demand. So this only causes an issue for functions returning `impl Trait`, which were already special cased by `ReplaceFunctionWithBody`. However, it now considers `async fn f() -> T` to be considered `impl Future<Output = T>`, where before it was considered to have a concrete `T` type. ## How will this affect future changes to rustdoc? - Any new changes to rustdoc will not be able to perform type checking without bringing back resolution errors in function bodies. + As a corollary, any new lints cannot require or perform type checking. In some cases this may require refactoring other parts of the compiler to perform type-checking only on-demand, see for example rust-lang#73743. + As a corollary, rustdoc can never again call `tcx.analysis()` unless this PR is reverted altogether. ## Current status - ~~I am not yet sure how to bring back `missing_docs` without running typeck. @eddyb suggested allowing lints to opt-out of type-checking, which would probably be another rabbit hole.~~ The opt-out was implemented in rust-lang#73743. However, of the rustc lints, now _only_ missing_docs is run and no other lints: rust-lang#73566 (comment). We need a team decision on whether that's an acceptable tradeoff. Note that all rustdoc lints are still run (`intra_doc_link_resolution_failure`, etc). **UPDATE**: This was deemed acceptable in rust-lang#73566 (comment) - ~~The implementation of optional errors in `rustc_resolve` is very brute force, it should probably be moved from `LateResolver` to `Resolver` to avoid duplicating the logic in many places.~~ I'm mostly happy with it now. - This no longer allows errors in `async fn f() -> T`. This caused breakage in 50 crates out of a full crater run, all of which (that I looked at) didn't compile when run with rustc directly. In other words, it used to be that they could not be compiled but could still be documented; now they can't be documented either. This needs a decision from the rustdoc team on whether this is acceptable breakage. **UPDATE**: This was deemed acceptable in rust-lang#73566 (comment) - ~~This makes `fn typeck_tables_of` in `rustc_typeck` public. This is not desired behavior, but needs the changes from rust-lang#74070 in order to be fixed.~~ Reverted.

rustc_lint: only query typeck_tables_of when a lint needs it.

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rust-highfive assigned oli-obk Jun 26, 2020

rust-highfive added the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Jun 26, 2020

jyn514 mentioned this pull request Jun 26, 2020

Don't run everybody_loops for rustdoc; instead ignore resolution errors #73566

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Manishearth approved these changes Jun 26, 2020

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bors added S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Jun 26, 2020

eddyb mentioned this pull request Jun 26, 2020

Remove TypeckTables::empty(None) and make hir_owner non-optional. #73751

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bors added the merged-by-bors This PR was explicitly merged by bors. label Jun 26, 2020

bors merged commit 14e65d5 into rust-lang:master Jun 26, 2020

bors mentioned this pull request Jun 26, 2020

convert higher ranked Predicates to PredicateKind::ForAll #73503

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eddyb deleted the lint-on-demand-typeck-tables branch June 26, 2020 11:16

flip1995 mentioned this pull request Jun 26, 2020

Rustup rust-lang/rust-clippy#5751

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bors added a commit to rust-lang/rust-clippy that referenced this pull request Jun 26, 2020

Auto merge of #5751 - flip1995:rustup, r=Manishearth

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Rustup cc rust-lang/rust#73743 r? @Manishearth changelog: none

bors added a commit to rust-lang/rust-clippy that referenced this pull request Jun 28, 2020

Auto merge of #5751 - flip1995:rustup, r=Manishearth

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Rustup cc rust-lang/rust#73743 r? @Manishearth changelog: none

bors added a commit to rust-lang/rust-clippy that referenced this pull request Jun 30, 2020

Auto merge of #5751 - flip1995:rustup, r=Manishearth,flip1995

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Rustup cc rust-lang/rust#73743 r? @Manishearth changelog: none

bors added a commit to rust-lang/rust-clippy that referenced this pull request Jun 30, 2020

Auto merge of #5751 - flip1995:rustup, r=Manishearth,flip1995

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Rustup cc rust-lang/rust#73743 r? @Manishearth changelog: none

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rustc_lint: only query `typeck_tables_of` when a lint needs it. #73743

rustc_lint: only query `typeck_tables_of` when a lint needs it. #73743

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eddyb commented Jun 26, 2020

rustc_lint: only query typeck_tables_of when a lint needs it. #73743

rustc_lint: only query typeck_tables_of when a lint needs it. #73743

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eddyb commented Jun 26, 2020

rustc_lint: only query `typeck_tables_of` when a lint needs it. #73743

rustc_lint: only query `typeck_tables_of` when a lint needs it. #73743

eddyb commented Jun 26, 2020 •

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