rustc: simpler ParameterEnvironment and free regions. #41914

eddyb · 2017-05-11T15:36:40Z

The commits describe the slow transformation but the highlights are:

ReEarlyBound is considered free, with a scope based on the item that defined the lifetime parameter, and the root body of the RegionMaps in use, removing the need for free_substs
liberate_late_bound_regions and implicit_region_bound moved to typeck
CodeExtent not interned at all now - ideally it would be 2 u32 but it's small anyway

Future work building up on this could include:

ParameterEnvironment becoming just the result of predicates_of
- interning makes my "parent chain" scheme unnecessary
implicit_region_bound could be retrieved from RegionMaps
renaming CodeExtent to Scope
- generalizing "call site" to "use site" or something better to include constants
renaming RegionMaps to ScopeTree and its API to talk about "parents" explicitly

rust-highfive · 2017-05-11T15:36:51Z

r? @pnkfelix

(rust_highfive has picked a reviewer for you, use r? to override)

nikomatsakis · 2017-05-11T16:55:27Z

r? @nikomatsakis

nikomatsakis

OK, this looks pretty nice. I left two small nits.

nikomatsakis · 2017-05-11T17:34:03Z

src/librustc/middle/region.rs

+            body
+        })
+        .unwrap_or_else(|| {
+            let root = tcx.hir.as_local_node_id(fr.scope).unwrap();


I can't really follow what's going on here; maybe add a comment or two for what kinds of rust code falls into which case here?

This is explained on root_parent but do note this is not the final version of that function.
Let me know on the final functions where it seems unclear.

nikomatsakis · 2017-05-11T18:13:36Z

src/librustc/infer/region_inference/mod.rs

@@ -213,6 +215,7 @@ pub struct RegionVarBindings<'a, 'gcx: 'a+'tcx, 'tcx: 'a> {
    // record the fact that `'a <= 'b` is implied by the fn signature,
    // and then ignore the constraint when solving equations. This is
    // a bit of a hack but seems to work.
+    early_bound_givens: RefCell<FxHashSet<(ty::EarlyBoundRegion, ty::RegionVid)>>,


maybe combine these by changing the type to RefCell<FxHashSet<(ty::Region<'tcx>, ty::RegionVid)>>, where the region is either an early-bound or free?

I was wondering if that would be more expensive but I doubt it now. Will do.

nikomatsakis · 2017-05-11T18:23:44Z

I see that the librustc_driver unit tests are failing. I do hate those. I've been wanting to refactor them in such a way that we can encode the same scenarios in .rs files, but it's kind of difficult. I'm tempted to just tell you to delete them -- I'm not sure to what extent we have complete coverage of those scenarios elsewhere though (specifically some of the LUB tests).

arielb1 · 2017-05-11T19:28:37Z

CodeExtent was interned as a u32 once upon a time. Not sure why that changed.

arielb1 · 2017-05-11T19:36:31Z

src/librustc/middle/region.rs

+            }
+            _ => fr.scope
+        };
+        assert_eq!(param_owner, fr.scope);


Why can't you use fr.scope directly?

I wanted to have no regressions from lifetime parameters not defined on the scope leaking into e.g. the signature of a closure.

nikomatsakis · 2017-05-11T20:01:19Z

@arielb1

CodeExtent was interned as a u32 once upon a time. Not sure why that changed.

I changed that to a pointer because there were various contexts that needed to be able to access the data without having enough context to get a region-maps (note that there is now more than one region-maps). But passing by value is probably even better. (Also, in the meantime, we've started to intern Regions, so I don't think that the size matters so much anymore anyway.)

nikomatsakis · 2017-05-12T13:47:24Z

src/librustc/middle/region.rs

+
+        let param_owner_id = tcx.hir.as_local_node_id(param_owner).unwrap();
+        let body_id = tcx.hir.maybe_body_owned_by(param_owner_id).unwrap_or_else(|| {
+            // The lifetime was defined on node that doesn't own a body,


👍 nice comment

nikomatsakis · 2017-05-12T13:52:45Z

@bors r+

bors · 2017-05-12T13:52:46Z

📌 Commit 788e70e has been approved by nikomatsakis

Rollup of 15 pull requests - Successful merges: #41820, #41843, #41847, #41860, #41896, #41912, #41916, #41918, #41919, #41921, #41923, #41934, #41940, #41942, #41943 - Failed merges: #41914

bors · 2017-05-13T14:03:03Z

☔ The latest upstream changes (presumably #41965) made this pull request unmergeable. Please resolve the merge conflicts.

eddyb · 2017-05-13T14:43:51Z

@bors r=nikomatsakis

bors · 2017-05-13T14:43:52Z

📌 Commit 6da4123 has been approved by nikomatsakis

eddyb · 2017-05-13T17:04:40Z

@bors p=1000 (separate for perf. I wish we had a guaranteed to keep PRs out of rollups)

bors · 2017-05-13T17:56:16Z

⌛ Testing commit 6da4123 with merge 826d8f3...

rustc: simpler ParameterEnvironment and free regions. The commits describe the slow transformation but the highlights are: * `ReEarlyBound` is considered free, with a scope based on the item that defined the lifetime parameter, and the root body of the `RegionMaps` in use, removing the need for `free_substs` * `liberate_late_bound_regions` and `implicit_region_bound` moved to typeck * `CodeExtent` not interned at all now - ideally it would be 2 `u32` but it's small anyway Future work building up on this could include: * `ParameterEnvironment` becoming just the result of `predicates_of` * interning makes my "parent chain" scheme unnecessary * `implicit_region_bound` could be retrieved from `RegionMaps` * renaming `CodeExtent` to `Scope` * generalizing "call site" to "use site" or something better to include constants * renaming `RegionMaps` to `ScopeTree` and its API to talk about "parents" explicitly

bors · 2017-05-13T20:19:20Z

☀️ Test successful - status-appveyor, status-travis
Approved by: nikomatsakis
Pushing 826d8f3 to master...

rust-highfive assigned pnkfelix May 11, 2017

rust-highfive assigned nikomatsakis and unassigned pnkfelix May 11, 2017

nikomatsakis requested changes May 11, 2017

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arielb1 reviewed May 11, 2017

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eddyb force-pushed the region-refactor branch from 457e481 to bb37801 Compare May 11, 2017 21:57

alexcrichton added the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label May 11, 2017

eddyb force-pushed the region-refactor branch from bb37801 to 33c653e Compare May 12, 2017 08:57

eddyb mentioned this pull request May 12, 2017

Lifetime scope note messages have off-by-one column numbers. #41938

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eddyb force-pushed the region-refactor branch from 33c653e to 788e70e Compare May 12, 2017 11:05

nikomatsakis reviewed May 12, 2017

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nikomatsakis approved these changes May 12, 2017

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Mark-Simulacrum mentioned this pull request May 12, 2017

Rollup of 15 pull requests #41954

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eddyb added 7 commits May 13, 2017 17:42

rustc: uniformly compute ParameterEnvironment's "free outlive scope".

bd8246b

rustc: use call_site_extent for closure environment free regions.

9809fe0

rustc_mir: remove unnecessary drop scope for constants.

72aab7a

rustc: use DefId instead of CodeExtent for FreeRegion's scope.

6d4c214

rustc: move liberate_late_bound_regions to rustc_typeck.

74c6788

rustc_typeck: do not leak late-bound lifetimes from bounds to closures.

dbae169

rustc: treat ReEarlyBound as free without replacing it with ReFree.

2da080e

eddyb added 3 commits May 13, 2017 17:42

rustc: remove redundant fn_id's from CodeExtentData.

da8b6e2

rustc: stop interning CodeExtent, it's small enough.

ea1c6df

rustc: don't keep a second reference to the HIR map in middle::region.

6da4123

eddyb force-pushed the region-refactor branch from 788e70e to 6da4123 Compare May 13, 2017 14:43

bors merged commit 6da4123 into rust-lang:master May 13, 2017

eddyb deleted the region-refactor branch May 14, 2017 02:58

Mark-Simulacrum mentioned this pull request Jun 6, 2017

Rust 1.19 regression, treebitmap 0.2.2 #42467

Closed

dtolnay mentioned this pull request Jan 28, 2018

Rust compiler panics when trying to reference impl-ed constants with Self #47814

Closed

rustc: simpler ParameterEnvironment and free regions. #41914

rustc: simpler ParameterEnvironment and free regions. #41914

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