Make `Visitor::visit_body` take a plain `&Body` #70449

ecstatic-morse · 2020-03-26T23:11:27Z

ReadOnlyBodyAndCache has replaced &Body in many parts of the code base that don't care about basic block predecessors. This includes the MIR Visitor trait, which I suspect resulted in many unnecessary changes in #64736. This reverts part of that PR to reduce the number of places where we need to pass a ReadOnlyBodyAndCache.

In the long term, we should either give ReadOnlyBodyAndCache more ergonomic name and replace all uses of &mir::Body with it at the cost of carrying an extra pointer everywhere, or use it only in places that actually need access to the predecessor cache. Perhaps there is an even nicer alternative.

r? @Nashenas88

eddyb · 2020-03-27T10:05:46Z

src/librustc_mir/borrow_check/borrow_set.rs

@@ -107,7 +107,7 @@ impl LocalsStateAtExit {
            LocalsStateAtExit::AllAreInvalidated
        } else {
            let mut has_storage_dead = HasStorageDead(BitSet::new_empty(body.local_decls.len()));
-            has_storage_dead.visit_body(body);
+            has_storage_dead.visit_body(*body);


Can you use &body instead of *body everywhere? I think it would've already coerced except ReadOnlyBodyAndCache is itself a reference internally so it's not passed by reference.

Although, I'm surprised ReadOnlyBodyAndCache exists, wouldn't &BodyAndCache also do the same thing?

ReadOnlyBodyAndCache can only exist if the cache has already been precomputed. That guarantee doesn't hold with &BodyAndCache. That was the only reason a separate type was used. It would have been a lot easier if I could have just used &BodyAndCache.

See the assert here:

rust/src/librustc/mir/cache.rs

Lines 195 to 198 in a06baa5

assert!(

cache.predecessors.is_some(),

"Cannot construct ReadOnlyBodyAndCache without computed predecessors"

);

And the reason a variant with &Body and &mut Cache doesn't work is that there were some places that required such a struct to be Copy, which doesn't hold with the &mut. Though I can't remember which trait was causing that issue.

eddyb · 2020-03-27T10:06:12Z

cc @oli-obk

Nashenas88 · 2020-03-27T13:20:42Z

src/librustc/mir/visit.rs

+macro_rules! body_type {
+    (mut $tcx:lifetime) => {
        &mut BodyAndCache<$tcx>
    };
-    ($a:lifetime, $tcx:lifetime) => {
-        ReadOnlyBodyAndCache<$a, $tcx>
+    ($tcx:lifetime) => {
+        &Body<$tcx>
    };
 }


So you're having the read-only case not require the cache? I actually hadn't even considered that when I first wrote this. That should actually make this a lot easier to use!

Nashenas88 · 2020-03-27T15:36:51Z

r? @oli-obk

oli-obk · 2020-03-29T11:57:55Z

r=me after a rebase

ecstatic-morse · 2020-03-29T21:20:19Z

@bors r=oli-obk

bors · 2020-03-29T21:20:21Z

📌 Commit 538cdef has been approved by oli-obk

bors · 2020-03-30T02:04:06Z

⌛ Testing commit 538cdef with merge 0afdf43...

bors · 2020-03-30T05:02:08Z

☀️ Test successful - checks-azure
Approved by: oli-obk
Pushing 0afdf43 to master...

rust-highfive · 2020-03-30T05:03:22Z

📣 Toolstate changed by #70449!

Tested on commit 0afdf43.
Direct link to PR: #70449

💔 clippy-driver on windows: test-pass → build-fail (cc @mcarton @oli-obk @Manishearth @flip1995 @yaahc @phansch @llogiq).
💔 clippy-driver on linux: test-pass → build-fail (cc @mcarton @oli-obk @Manishearth @flip1995 @yaahc @phansch @llogiq).

@mcarton

Tested on commit rust-lang/rust@0afdf43. Direct link to PR: <rust-lang/rust#70449> 💔 clippy-driver on windows: test-pass → build-fail (cc @mcarton @oli-obk @Manishearth @flip1995 @yaahc @phansch @llogiq). 💔 clippy-driver on linux: test-pass → build-fail (cc @mcarton @oli-obk @Manishearth @flip1995 @yaahc @phansch @llogiq).

Rustup to rust-lang/rust#70449 cc rust-lang/rust#70449 changelog: none

Changes: ```` rustup rust-lang#70536 Rustup to rust-lang#70449 readme: move "how to run single lint" instructions to "Allowing/denying lints" section. git attribute macros not allowed in submodules Deprecate REPLACE_CONSTS lint Bump itertools ```` Fixes rust-lang#70554

submodules: update clippy from 70b93aa to e170c84 Changes: ```` rustup rust-lang#70536 Rustup to rust-lang#70449 readme: move "how to run single lint" instructions to "Allowing/denying lints" section. git attribute macros not allowed in submodules Deprecate REPLACE_CONSTS lint Bump itertools ```` Fixes rust-lang#70554

Changes: ```` rustup rust-lang/rust#70536 Rustup to rust-lang/rust#70449 readme: move "how to run single lint" instructions to "Allowing/denying lints" section. git attribute macros not allowed in submodules Deprecate REPLACE_CONSTS lint Bump itertools ```` Fixes #70554

rust-highfive assigned Nashenas88 Mar 26, 2020

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

ecstatic-morse changed the title ~~Make Visitor::visit_body take a simple Body~~ Make Visitor::visit_body take a simple &Body Mar 26, 2020

eddyb reviewed Mar 27, 2020

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Nashenas88 reviewed Mar 27, 2020

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rust-highfive assigned oli-obk and unassigned Nashenas88 Mar 27, 2020

Make Visitor::visit_body take a simple Body

b641e9e

ecstatic-morse force-pushed the visit-body branch from d52b4ac to fc480d1 Compare March 29, 2020 18:58

Use & to do deref coercion for ReadOnlyBodyAndCache

538cdef

ecstatic-morse force-pushed the visit-body branch from fc480d1 to 538cdef Compare March 29, 2020 20:30

ecstatic-morse changed the title ~~Make Visitor::visit_body take a simple &Body~~ Make Visitor::visit_body take a plain &Body Mar 29, 2020

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 Mar 29, 2020

bors added the merged-by-bors This PR was explicitly merged by bors. label Mar 30, 2020

bors merged commit 0afdf43 into rust-lang:master Mar 30, 2020

rust-highfive mentioned this pull request Mar 30, 2020

clippy-driver no longer builds after rust-lang/rust#70449 #70554

Closed

bors mentioned this pull request Mar 30, 2020

Add utility to find locals that don't use StorageLive annotations and use it for MaybeStorageLive #70447

Merged

phansch added a commit to phansch/rust-clippy that referenced this pull request Mar 30, 2020

Rustup to rust-lang/rust#70449

68ed6cc

phansch mentioned this pull request Mar 30, 2020

Rustup to https://github.com/rust-lang/rust/pull/70449 rust-lang/rust-clippy#5390

Merged

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

Auto merge of #5390 - phansch:rustupp, r=matthiaskrgr

0254c42

Rustup to rust-lang/rust#70449 cc rust-lang/rust#70449 changelog: none

ecstatic-morse deleted the visit-body branch October 6, 2020 01:42

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Make `Visitor::visit_body` take a plain `&Body` #70449

Make `Visitor::visit_body` take a plain `&Body` #70449

ecstatic-morse commented Mar 26, 2020

eddyb Mar 27, 2020

Nashenas88 Mar 27, 2020

Nashenas88 Mar 27, 2020 •

edited

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Nashenas88 Mar 27, 2020

eddyb commented Mar 27, 2020

Nashenas88 Mar 27, 2020

Nashenas88 commented Mar 27, 2020

oli-obk commented Mar 29, 2020

ecstatic-morse commented Mar 29, 2020

bors commented Mar 29, 2020

bors commented Mar 30, 2020

bors commented Mar 30, 2020

rust-highfive commented Mar 30, 2020

	assert!(
	cache.predecessors.is_some(),
	"Cannot construct ReadOnlyBodyAndCache without computed predecessors"
	);

Make Visitor::visit_body take a plain &Body #70449

Make Visitor::visit_body take a plain &Body #70449

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ecstatic-morse commented Mar 26, 2020

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rust-highfive commented Mar 30, 2020

Make `Visitor::visit_body` take a plain `&Body` #70449

Make `Visitor::visit_body` take a plain `&Body` #70449

Nashenas88 Mar 27, 2020 •

edited

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