Treat generators as if they have an arbitrary destructor #49943

pnkfelix · 2018-04-13T15:26:55Z

Conservatively assume dropping a generator touches its upvars, via locals' destructors.

Fix #49918

rust-highfive · 2018-04-13T15:26:58Z

r? @cramertj

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

pnkfelix · 2018-04-13T15:28:00Z

r? @Zoxc

pnkfelix · 2018-04-13T15:30:37Z

(as noted in the comments in code, in principle we could do something smarter here, in terms of recursively analyzing the locals of the generator to see if we can prove e.g. that none of them have destructors. But that is complex and this is simple.)

rust-highfive · 2018-04-13T16:12:34Z

Your PR failed on Travis (raw log). Through arcane magic we have determined that the following fragments from the build log may contain information about the problem.

Click to expand the log.

[00:00:57] configure: rust.quiet-tests     := True
---
[00:42:55] ...............................................................................i....................
[00:43:00] ......................i.............................................................................
[00:43:04] ....................................................................................................
[00:43:08] ....................................................................................................
[00:43:11] ....................................................................................................
[00:43:15] ..........................................................................F.........................
[00:43:21] ....................................................................................................
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[00:43:40] ..................i...........................................................................i.....
[00:43:46] ....................................................................................................
[00:43:52] ........ii..........................................................................................
---
[00:44:03] + error[E0597]: `*cell` does not live long enough
[00:44:03] +   --> $DIR/dropck.rs:19:40
[00:44:03] +    |
[00:44:03] + LL |     let ref_ = Box::leak(Box::new(Some(cell.borrow_mut())));
[00:44:03] +    |                                        ^^^^ borrowed value does not live long enough
[00:44:03] + ...
[00:44:03] + LL | }
[00:44:03] +    | - `*cell` dropped here while still borrowed
[00:44:03] +    |
[00:44:03] +    = note: values in a scope are dropped in the opposite order they are created
[00:44:03] +
[00:44:03] 1 error[E0597]: `ref_` does not live long enough
[00:44:03] 2   --> $DIR/dropck.rs:23:18
[00:44:03] 3    |
[00:44:03]
[00:44:03] 12    |
[00:44:03] 13    = note: values in a scope are dropped in the opposite order they are created
---
[00:44:03] /checkout/src/test/ui/update-references.sh '/checkout/obj/build/x86_64-unknown-linux-gnu/test/ui' 'generator/dropck.rs'
[00:44:03]
[00:44:03] error: 1 errors occurred comparing output.
[00:44:03] status: exit code: 101
[00:44:03] command: "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2/bin/rustc" "/checkout/src/test/ui/generator/dropck.rs" "-L" "/checkout/obj/build/x86_64-unknown-linux-gnu/test/ui" "--target=x86_64-unknown-linux-gnu" "--error-format" "json" "-Zui-testing" "-C" "prefer-dynamic" "-o" "/checkout/obj/build/x86_64-unknown-linux-gnu/test/ui/generator/dropck.stage2-x86_64-unknown-linux-gnu" "-Crpath" "-O" "-Zmiri" "-Zunstable-options" "-Lnative=/checkout/obj/build/x86_64-unknown-linux-gnu/native/rust-test-helpers" "-L" "/checkout/obj/build/x86_64-unknown-linux-gnu/test/ui/generator/dropck.stage2-x86_64-unknown-linux-gnu.aux" "-A" "unused"
[00:44:03] stdout:
[00:44:03] ------------------------------------------
[00:44:03]
[00:44:03] ------------------------------------------
[00:44:03] stderr:
[00:44:03] -----------------------are created","code":null,"level":"note","spans":[],"children":[],"rendered":null}],"rendered":"error[E0597]: `*cell` does not live long enough\n  --> /checkout/src/test/ui/generator/dropck.rs:19:40\n   |\nLL |     let ref_ = Box::leak(Box::new(Some(cell.borrow_mut())));\n   |                                        ^^^^ borrowed value does not live long enough\n...\nLL | }\n   | - `*cell` dropped here while still borrowed\n   |\n   = note: values in a scope are dropped in the opposite order they are created\n\n"}
[00:44:03] {"message":"`ref_` does not live long enough","code":{"code":"E0597","explanation":"\nThis error occurs because a borrow was made inside a variable which has a\ngreater lifetime than the borrowed one.\n\nExample of erroneous code:\n\n```compile_fail,E0597\nstruct Foo<'a> {\n    x: Option<&'a u32>,\n}\n\nlet mut x = Foo { x: None };\nlet y = 0;\nx.x = Some(&y); // error: `y` does not live long enough\n```\n\nIn here, `x` is created before `y` and therefore has a greater lifetime. Always\nkeep in mind that values in a scope are dropped in the opposite order they are\ncreated. So to fix the previous example, just make the `y` lifetime greater than\nthe `x`'s one:\n\n```\nstruct Foo<'a> {\n    x: Option<&'a u32>,\n}\n\nlet y = 0;\nlet mut x = Foo { x: None };\nx.x = Some(&y);\n```\n"},"level":"error","spans":[{"file_name":"/checkout/src/test/ui/generator/dropck.rs","byte_start":832,"byte_end":834,"line_start":21,"line_end":21,"column_start":11,"column_end":13,"is_primary":false,"text":[{"text":"    gen = || {","highlight_start":11,"highlight_end":13}],"label":"capture occurs here","suggested_replacement":null,"expansion":null},{"file_name":"/checkout/src/test/ui/generator/dropck.rs","byte_start":920,"byte_end":924,"line_start":23,"line_end":23,"column_start":18,"column_end":22,"is_primary":true,"text":[{"text":"        let _d = ref_.take(); //~ ERROR `ref_` does not live long enough","highlight_start":18,"highlight_end":22}],"label":"borrowed value does not live long enough","suggested_replacement":null,"expansion":null},{"file_name":"/checkout/src/test/ui/generator/dropck.rs","byte_start":1096,"byte_end":1097,"line_start":28,"line_end":28,"column_start":1,"column_end":2,"is_primary":false,"text":[{"text":"}","highlight_start":1,"highlight_end":2}],"label":"borrowed value dropped before borrower","suggested_replacement":null,"expansion":null}],"children":[{"message":"values in a scope are dropped in the opposite order they are created","code":null,"level":"note","spans":[],"children":[],"rendered":null}],"rendered":"error[E0597]: `ref_` does not live long enough\n  --> /checkout/src/test/ui/generator/dropck.rs:23:18\n   |\nLL |     gen = || {\n   |           -- capture occurs here\nLL |         // but the generator can use it to drop a `Ref<'a, i32>`.\nLL |         let _d = ref_.take(); //~ ERROR `ref_` does not live long enough\n   |                  ^^^^ borrowed value does not live long enough\n...\nLL | }\n   | - borrowed value dropped before borrower\n   |\n   = note: values in a scope are dropped in the opposite order they are created\n\n"}
[00:44:03] {"message":"aborting due to 2 previous errors","code":null,"level":"error","spans":[],"children":[],"rendered":"error: aborting due to 2 previous errors\n\n"}
[00:44:03] {"me-lldb-python" "/usr/bin/python2.7" "--gdb" "/usr/bin/gdb" "--quiet" "--llvm-version" "3.9.1\n" "--system-llvm" "--cc" "" "--cxx" "" "--cflags" "" "--llvm-components" "" "--llvm-cxxflags" "" "--adb-path" "adb" "--adb-test-dir" "/data/tmp/work" "--android-cross-path" "" "--color" "always"
[00:44:03] expected success, got: exit code: 101
[00:44:03]
[00:44:03]
[00:44:03] failed to run: /checkout/obj/build/bootstrap/debug/bootstrap test
[00:44:03] Build completed unsuccessfully in 0:02:16
[00:44:03] make: *** [check] Error 1
[00:44:03] Makefile:58: recipe for target 'check' failed
---
$ dmesg | grep -i kill
[   10.453064] init: failsafe main process (1094) killed by TERM signal

I'm a bot! I can only do what humans tell me to, so if this was not helpful or you have suggestions for improvements, please ping or otherwise contact @TimNN. (Feature Requests)

Zoxc · 2018-04-15T21:46:03Z

This looks correct to me. We model generators as a struct of their upvars with a destructor which may access these upvars. The ui/generator/dropck.rs needs to be updated, and it would also like to see which errors it produces in this PR with NLL enabled.

I'd like someone who knows how dropck works to glance over it though. I'm just going to assume Niko is such a person.

r? @nikomatsakis

Zoxc · 2018-04-15T21:50:12Z

src/librustc_traits/dropck_outlives.rs

-        ty::TyGenerator(def_id, substs, _) => {
-            // Note that the interior types are ignored here.
-            // Any type reachable inside the interior must also be reachable
-            // through the upvars.


This comment should be kept in some form. It serves as justification for why we can get away with only reporting the upvars instead of actually calculating all the types which may get dropped inside.

(okay, addressed this in followup commit)

pnkfelix · 2018-04-16T10:44:56Z

I think the request to see what the output looks like under NLL will be satisfied by the eventual (hopefully soon) landing of PR #49900, so I won't put that change into this PR.

Zoxc · 2018-04-16T17:49:43Z

src/librustc_traits/dropck_outlives.rs

+            // because any side-effects from dropping `_interior` can
+            // only take place through references with lifetimes
+            // derived from lifetimes attached to the upvars, and we
+            // *do* traverse the uvpars here.


Typo, uv-pars. Looks good otherwise.

Zoxc · 2018-04-16T17:52:09Z

@pnkfelix I'd just like you to run the test locally with NLL and post the errors in a comment here.

pnkfelix · 2018-04-19T10:43:47Z

@Zoxc oh okay I can certainly do that.

pnkfelix · 2018-04-19T11:32:29Z

@Zoxc here is the current behavior on ui/generator/dropck.rs with this PR under both AST-borrowck and NLL-borrowck:

AST-borrowck:

% ./build/x86_64-unknown-linux-gnu/stage1/bin/rustc ../src/test/ui/generator/dropck.rs
error[E0597]: `*cell` does not live long enough
  --> ../src/test/ui/generator/dropck.rs:19:40
   |
19 |     let ref_ = Box::leak(Box::new(Some(cell.borrow_mut())));
   |                                        ^^^^ borrowed value does not live long enough
...
29 | }
   | - `*cell` dropped here while still borrowed
   |
   = note: values in a scope are dropped in the opposite order they are created

error[E0597]: `ref_` does not live long enough
  --> ../src/test/ui/generator/dropck.rs:24:18
   |
22 |     gen = || {
   |           -- capture occurs here
23 |         // but the generator can use it to drop a `Ref<'a, i32>`.
24 |         let _d = ref_.take(); //~ ERROR `ref_` does not live long enough
   |                  ^^^^ borrowed value does not live long enough
...
29 | }
   | - borrowed value dropped before borrower
   |
   = note: values in a scope are dropped in the opposite order they are created

error: aborting due to 2 previous errors

For more information about this error, try `rustc --explain E0597`.

NLL (`-Z borrowck=mir`):

% ./build/x86_64-unknown-linux-gnu/stage1/bin/rustc ../src/test/ui/generator/dropck.rs -Z borrowck=mir

error[E0597]: `ref_` does not live long enough
  --> ../src/test/ui/generator/dropck.rs:22:11
   |
22 |       gen = || {
   |  ___________^
23 | |         // but the generator can use it to drop a `Ref<'a, i32>`.
24 | |         let _d = ref_.take(); //~ ERROR `ref_` does not live long enough
25 | |         yield;
26 | |     };
   | |_____^ borrowed value does not live long enough
...
29 |   }
   |   -
   |   |
   |   borrowed value only lives until here
   |   borrow later used here, when `gen` is dropped

error: aborting due to previous error

For more information about this error, try `rustc --explain E0597`.

arielb1 · 2018-04-21T20:56:26Z

There's already a test for this at https://github.com/rust-lang/rust/blob/master/src/test/ui/generator/dropck.rs, that was commented out for some reason. With this PR, that test should give an error.

arielb1 · 2018-04-21T20:58:28Z

src/librustc_traits/dropck_outlives.rs

+            let new_constraints: Vec<ty::subst::Kind<'tcx>> =
+                substs.upvar_tys(def_id, tcx).map(|t| t.into()).collect();
+
+            let mut constraint = substs


https://github.com/rust-lang/rust/pull/45337/files#r145093242
It might be a better idea to treat generators like trait object and have them always be dtorck. If generators are "supposed to be" captured by an impl Trait or trait object, this shouldn't be a problem in practice..

There's no reason to have both outlives and dtorck constraints together, the outlives constraint is always stricter than the is-destruction-safe constraint.

Are you saying @arielb1 that we only need to invoke constraint.outlives.extend(new_contraints), and not also include dtorck_constraint_for_ty?

Sure just return new_constraints as outlives constrains, same as trait objects.

nikomatsakis

r=me with arielb1's comment fixed

shepmaster · 2018-04-30T01:01:05Z

Ping from triage, @pnkfelix ! Will you have time to address the review feedback in the near future?

pnkfelix · 2018-04-30T13:37:51Z

@shepmaster yep, I'll do it either today or tomorrow. (I was out on PTO last week.)

rust-highfive · 2018-04-30T15:26:47Z

The job x86_64-gnu-llvm-3.9 of your PR failed on Travis (raw log). Through arcane magic we have determined that the following fragments from the build log may contain information about the problem.

Click to expand the log.

[00:46:32] ..............................i.....................................................................
[00:46:37] ....................................................................................................
[00:46:41] ....................................................................................................
[00:46:46] ....................................................................................................
[00:46:51] .................................................................................F.F.....F..........
[00:47:04] ....................................................................................................
[00:47:10] ....................................................................................................
[00:47:17] ....................................i...............................................................
[00:47:23] ............i.......................................................................................
---
[00:47:47]  diff of stderr:
[00:47:47] 
[00:47:47] - error: compilation successful
[00:47:47] -   --> $DIR/borrowing.rs:15:1
[00:47:47] + error[E0597]: `a` does not live long enough
[00:47:47] +   --> $DIR/borrowing.rs:18:18
[00:47:47] 3    |
[00:47:47] - LL | / fn main() { #![rustc_error] // rust-lang/rust#49855
[00:47:47] - LL | |     let _b = {
[00:47:47] - LL | |         let a = 3;
[00:47:47] - LL | |         unsafe { (|| yield &a).resume() }
[00:47:47] - ...  |
[00:47:47] - LL | |     };
[00:47:47] - LL | | }
[00:47:47] -    | |_^
[00:47:47] + LL |         unsafe { (|| yield &a).resume() }
[00:47:47] +    |                  |
[00:47:47] +    |                  |
[00:47:47] +    |                  borrowed value does not live long enough
[00:47:47] +    |                  borrow may end up in a temporary, created here
[00:47:47] + LL |         //~^ ERROR: `a` does not live long enough
[00:47:47] + LL |     };
[00:47:47] +    |     -- temporary later dropped here, potentially using the reference
[00:47:47] +    |     |
[00:47:47] +    |     borrowed value only lives until here
[00:47:47] - error: aborting due to previous error
[00:47:47] - error: aborting due to previous error
[00:47:47] + error[E0597]: `a` does not live long enough
[00:47:47] +   --> $DIR/borrowing.rs:24:9
[00:47:47] +    |
[00:47:47] + LL | /         || {
[00:47:47] + LL | |             yield &a
[00:47:47] + LL | |             //~^ ERROR: `a` does not live long enough
[00:47:47] + LL | |         }
[00:47:47] +    | |_________^ borrowed value does not live long enough
[00:47:47] + LL |       };
[00:47:47] +    |       - borrowed value only lives until here
[00:47:47] + LL |   }
[00:47:47] +    |   - borrow later used here, when `_b` is dropped
[00:47:47] + error: aborting due to 2 previous errors
[00:47:47] + 
[00:47:47] + For more information about this error, try `rustc --explain E0597`.
[00:47:47] 15 
[00:47:47] 15 
[00:47:47] 
[00:47:47] 
[00:47:47] The actual stderr differed from the expected stderr.
[00:47:47] Actual stderr saved to /checkout/obj/build/x86_64-unknown-linux-gnu/test/ui/generator/borron here, `x` is created before `y` and therefore has a greater lifetime. Always\nkeep in mind that values in a scope are dropped in the opposite order they are\ncreated. So to fix the previous example, just make the `y` lifetime greater than\nthe `x`'s one:\n\n```\nstruct Foo<'a> {\n    x: Option<&'a u32>,\n}\n\nlet y = 0;\nlet mut x = Foo { x: None };\nx.x = Some(&y);\n```\n"},"level":"error","spans":[{"file_name":"/checkout/src/test/ui/generator/borrowing.rs","byte_start":651,"byte_end":664,"line_start":18,"line_end":18,"column_start":18,"column_end":31,"is_primary":true,"text":[{"text":"        unsafe { (|| yield &a).resume() }","highlight_start":18,"highlight_end":31}],"label":"borrowed value does not live long enough","suggested_replacement":null,"expansion":null},{"file_name":"/checkout/src/test/ui/generator/borrowing.rs","byte_start":730,"byte_end":731,"line_start":20,"line_end":20,"column_start":5,"column_end":6,"is_primary":false,"text":[{"text":"    };","highlight_start":5,"highlight_end":6}],"label":"borrowed value only lives until here","suggested_replacement":null,"expansion":null},{"file_name":"/checkout/src/test/ui/generator/borrowing.rs","byte_start":651,"byte_end":664,"line_start":18,"line_end":18,"column_start":18,"column_end":31,"is_primary":true,"text":[{"text":"        unsafe { (|| yield &a).resume() }","highlight_start":18,"highlight_end":31}],"label":"borrow may end up in a temporary, created here","suggested_replacement":null,"expansion":null},{"file_name":"/checkout/src/test/ui/generator/borrowing.rs","byte_start":731,"byte_end":732,"line_start":20,"line_end":20,"column_start":6,"column_end":7,"is_primary":false,"text":[{"text":"    };","highlight_start":6,"highlight_end":7}],"label":"temporary later dropped here, potentially using the reference","suggested_replacement":null,"expansion":null}],"children":[],"rendered":"error[E0597]: `a` does not live long enough\n  --> /checkout/src/test/ui/generator/borrowing.rs:18:18\n   |\nLL |         unsafe { (|| yield &a).resume() }\n   |                  ^^^^^^^^^^^^^\n   |                  |\n   |                  borrowed value does not live long enough\n   |                  borrow may end up in a temporary, created here\nLL |         //~^ ERROR: `a` does not live long enough\nLL |     };\n   |     -- temporary later dropped here, potentially using the reference\n   |     |\n   |     borrowed value only lives until here\n\n"}
[00:47:47] {"message":"`a` does not live long enough","code":{"code":"E0597","explanation":"\nThis error occurs because a borrow was made inside a variable which has a\ngreater lifetime than the borrowed one.\n\nExample of erroneous code:\n\n```compile_fail,E0597\nstruct Foo<'a> {\n    x: Option<&'a u32>,\n}\n\nlet mut x = Foo { x: None };\nlet y = 0;\nx.x = Some(&y); // error: `y` does not live long enough\n```\n\nIn here, `x` is created before `y` and therefore has a greater lifetime. Always\nkeep in mind that values in a scope are dropped in the opposite order they are\ncreated. So to fix the previous example, just make the `y` lifetime greater than\nthe `x`'s one:\n\n```\nstruct Foo<'a> {\n    x: Option<&'a u32>,\n}\n\nlet y = 0;\nlet mut x = Foo { x: None };\nx.x = Some(&y);\n```\n"},"level":"error","spans":[{"file_name":"/checkout/src/test/ui/generator/borrowing.rs","byte_start":776,"byte_end":865,"line_start":24,"line_end":27,"column_start":9,"column_end":10,"is_primary":true,"text":[{"text":"        || {","highlight_start":9,"highlight_end":13},{"text":"            yield &a","highlight_start":1,"highlight_end":21},{"text":"            //~^ ERROR: `a` does not live long enough","highlight_start":1,"highlight_end":54},{"text":"        }","highlight_start":1,"highlight_end":10}],"label":"borrowed value does not live long enough","suggested_replacement":null,"expansion":null},{"file_name":"/checkout/src/test/ui/generator/borrowing.rs","byte_start":870,"byte_end":871,"line_start":28,"line_end":28,"column_start":5,"column_end":6,"is_primary":false,"text":[{"text":"    };","highlight_start":5,"highlight_end":6}],"label":"borrowed value only lives until here","suggested_replacement":null,"expansion":null},{"file_name":"/checkout/src/test/ui/generator/borrowing.rs","byte_start":873,"byte_end":874,"line_start":29,"line_end":29,"column_start":1,"column_end":2,"is_primary":false,"text":[{"text":"}","highlight_start":1,"highlight_end":2}],"label":"borrow later used here, when `_b` is dropped","suggested_replacement":null,"expansion":null}],"children":[],"rendered":"error[E0597]: `a` does not live long enough\n  --> /checkout/src/test/ui/generator/borrowing.rs:24:9\n   |\nLL | /         || {\nLL | |             yield &a\nLL | |             //~^ ERROR: `a` does not live long enough\nLL | |         }\n   | |_________^ borrowed value does not live long enough\nLL |       };\n   |       - borrowed value only lives until here\nLL |   }\n   |   - borrow later used here, when `_b` is dropped\n\n"}
[00:47:47] {"message":"aborting due to 2 previous errors","code":null,"level":"error","spans":[],"children":[],"rendered":"error: aborting due to 2 previous errors\n\n"}
[00:47:47] {"message":"For more information about this error, try `rustc --explain E0597`.","code":null,"level":"","spans":[],"children":[],"rendered":"For more information about this error, try `rustc --explain E0597`.\n"}
[00:47:47] ------------------------------------------
[00:47:47] 
[00:47:47] thread '[ui (nll)] ui/generator/borrowing.rs' panicked at 'explicit panic', tools/compiletest/src/runtest.rs:2965:9
[00:47:47] note: Run with `RUST_BACKTRACE=1` for a backtrace.
[00:47:47] note: Run with `RUST_BACKTRACE=1` for a backtrace.
[00:47:47] 
[00:47:47] ---- [ui (nll)] ui/generator/dropck.rs stdout ----
[00:47:47]  diff of stderr:
[00:47:47] 
[00:47:47] - error: compilation successful
[00:47:47] -   --> $DIR/dropck.rs:16:1
[00:47:47] + error[E0597]: `ref_` does not live long enough
[00:47:47] +   --> $DIR/dropck.rs:22:11
[00:47:47] 3    |
[00:47:47] - LL | / fn main() { #![rustc_error] // rust-lang/rust#49855
[00:47:47] - LL | |     let (cell, mut gen);
[00:47:47] - LL | |     cell = Box::new(RefCell::new(0));
[00:47:47] - LL | |     let ref_ = Box::leak(Box::new(Some(cell.borrow_mut())));
[00:47:47] - ...  |
[00:47:47] - LL | |     // drops the RefCell and then the Ref, leading to use-after-free
[00:47:47] - LL | | }
[00:47:47] -    | |_^
[00:47:47] + LL |       gen = || {
[00:47:47] +    |  ___________^
[00:47:47] + LL | |         // but the generator can use it to drop a `Ref<'a, i32>`.
[00:47:47] + LL | |         let _d = ref_.take(); //~ ERROR `ref_` does not livestc --explain E0597`.","code":null,"level":"","spans":[],"children":[],"rendered":"For more information about this error, try `rustc --explain E0597`.\n"}
[00:47:47] ------------------------------------------
[00:47:47] 
[00:47:47] thread '[ui (nll)] ui/generator/dropck.rs' panicked at 'explicit panic', tools/compiletest/src/runtest.rs:2965:9
[00:47:47] 
[00:47:47] 
[00:47:47] ---- [ui (nll)] ui/generator/ref-escapes-but-not-over-yield.rs stdout ----
[00:47:47]  diff of stderr:
[00:47:47] 
[00:47:47] 1 error[E0597]: `b` does not live long enough
[00:47:47] 3    |
[00:47:47] 3    |
[00:47:47] - LL |         a = &b;
[00:47:47] -    |             ^^ borrowed value does not live long enough
[00:47:47] - LL |         //~^ ERROR `b` does not live long enough
[00:47:47] - LL |     };
[00:47:47] -    |     - borrowed value only lives until here
[00:47:47] + LL |       let mut b = move || {
[00:47:47] +    |  _________________-
[00:47:47] + LL | |         yield();
[00:47:47] + LL | |         let b = 5;
[00:47:47] + LL | |         a = &b;
[00:47:47] +    | |             ^^ borrowed value does not live long enough
[00:47:47] + LL | |         //~^ ERROR `b` does not live long enough
[00:47:47] + LL | |     };
[00:47:47] +    | |     |
[00:47:47] +    | |     |
[00:47:47] +    | |     borrowed value only lives until here
[00:47:47] +    | |_____temporary later dropped here, potentially using the reference
[00:47:47] +    |       borrow may end up in a temporary, created here
[00:47:47] 10 error: aborting due to previous error
[00:47:47] 11 
[00:47:47] 
[00:47:47] 
[00:47:47] 
[00:47:47] The actual stderr differed from the expected stderr.
[00:47:47] Actual stderr saved to /checkout/obj/build/x86_64-unknown-linux-gnu/test/ui/generator/ref-escapes-but-not-over-yield.nll.stderr
[00:47:47] /checkout/src/test/ui/update-references.sh '/checkout/obj/build/x86_64-unknown-linux-gnu/test/ui' 'generator/ref-escapes-but-not-over-yield.rs'
[00:47:47] 
[00:47:47] error: 1 errors occurred comparing output.
[00:47:47] status: exit code: 101
[00:47:47] status: exit code: 101
[00:47:47] command: "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2/bin/rustc" "/checkout/src/test/ui/generator/ref-escapes-but-not-over-yield.rs" "-L" "/checkout/obj/build/x86_64-unknown-linux-gnu/test/ui" "--target=x86_64-unknown-linux-gnu" "--error-format" "json" "-Zui-testing" "-C" "prefer-dynamic" "-o" "/checkout/obj/build/x86_64-unknown-linux-gnu/test/ui/generator/ref-escapes-but-not-over-yield.stage2-x86_64-unknown-linux-gnu" "-Zborrowck=mir" "-Ztwo-phase-borrows" "-Crpath" "-O" "-Zunstable-options" "-Lnative=/checkout/obj/build/x86_64-unknown-linux-gnu/native/rust-test-helpers" "-L" "/checkout/obj/build/x86_64-unknown-linux-gnu/test/ui/generator/ref-escapes-but-not-over-yield.stage2-x86_64-unknown-linux-gnu.aux" "-A" "unused"
[00:47:47] ------------------------------------------
[00:47:47] 
[00:47:47] ------------------------------------------
[00:47:47] stderr:
[00:47:47] stderr:
[00:47:47] ------------------------------------------
[00:47:47] {"message":"`b` does not live long enough","code":{"code":"E0597","explanation":"\nThis error occurs because a borrow was made inside a variable which has a\ngreater lifetime than the borrowed one.\n\nExample of erroneous code:\n\n```compile_fail,E0597\nstruct Foo<'a> {\n    x: Option<&'a u32>,\n}\n\nlet mut x = Foo { x: None };\nlet y = 0;\nx.x = Some(&y); // error: `y` does not live long enough\n```\n\nIn here, `x` is created before `y` and therefore has a greater lifetime. Always\nkeep in mind that values in a scope are dropped in the opposite order they are\ncreated. So to fix the previous example, just make the `y` lifetime greater than\nthe `x`'s one:\n\n```\nstruct Foo<'a> {\n    x: Option<&'a u32>,\n}\n\nlet y = 0;\nlet mut x = Foo { x: None };\nx.x = Some(&y);\n```\n"},"level":"error","spans":[{"file_name":"/checkout/src/test/ui/generator/ref-escapes-but-not-over-yield.rs","byte_start":882,"byte_end":884,"line_start":24,"line_end":24,"column_start":13,"column_end":15,"is_primary":true,"text":[{"text":"        a = &b;","highlight_start":13,"highlight_end":15}],"label":"borrowed value does not live long enough","suggested_replacement":null,"expansion":null},{"file_name":"/checkout/src/test/ui/generator/ref-escapes-but-not-over-yield.rs","byte_start":939,"byte_end":940,"line_start":26,"line_end":26,"column_start":5,"column_end":6,"is_primary":false,"text":[{"text":"    };","highlight_start":5,"highlight_end":6}],"label":"borrowed value only lives until here","suggested_replacement":null,"expansion":null},{"file_name":"/checkout/src/test/ui/generator/ref-escapes-but-not-over-yield.rs","byte_start":824,"byte_end":940,"line_start":21,"line_end":26,"column_start":17,"column_end":6,"is_primary":false,"text":[{"text":"    let mut b = move |ror: aborting due to previous error\n\n"}
[00:47:47] {"message":"For more information about this error, try `rustc --explain E0597`.","code":null,"level":"","spans":[],"children":[],"rendered":"For more information about this error, try `rustc --explain E0597`.\n"}
[00:47:47] ------------------------------------------
[00:47:47] 
[00:47:47] thread '[ui (nll)] ui/generator/ref-escapes-but-not-over-yield.rs' panicked at 'explicit panic', tools/compiletest/src/runtest.rs:2965:9
[00:47:47] 
---
[00:47:47] test result: FAILED. 1370 passed; 3 failed; 7 ignored; 0 measured; 0 filtered out
[00:47:47] 
[00:47:47] 
[00:47:47] 
[00:47:47] command did not execute successfully: "/checkout/obj/build/x86_64-unknown-linux-gnu/stage0-tools-bin/compiletest" "--compile-lib-path" "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2/lib" "--run-lib-path" "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2/lib/rustlib/x86_64-unknown-linux-gnu/lib" "--rustc-path" "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2/bin/rustc" "--src-base" "/checkout/src/test/ui" "--build-base" "/checkout/obj/build/x86_64-unknown-linux-gnu/test/ui" "--stage-id" "stage2-x86_64-unknown-linux-gnu" "--mode" "ui" "--target" "x86_64-unknown-linux-gnu" "--host" "x86_64-unknown-linux-gnu" "--llvm-filecheck" "/usr/lib/llvm-3.9/bin/FileCheck" "--host-rustcflags" "-Crpath -O -Zunstable-options " "--target-rustcflags" "-Crpath4G  4.0K  7.4G   1% /dev
/dev/sda1        30G  9.8G   19G  35% /
none            4.0K     0  4.0K   0% /sys/fs/cgroup
none            5.0M     0  5.0M   0% /run/lock
none            7.4G     0  7.4G   0% /run/shm
---
60840 ./src/llvm-emscripten/lib
56092 ./obj/build/x86_64-unknown-linux-gnu/stage0/lib/rustlib/x86_64-unknown-linux-gnu/bin
55348 ./obj/build/x86_64-unknown-linux-gnu/stage0-rustc/release
53752 ./obj/build/x86_64-unknown-linux-gnu/stage1-rustc/x86_64-unknown-linux-gnu/release/incremental/syntax-284je5yviillk
53748 ./obj/build/x86_64-unknown-linux-gnu/stage1-rustc/x86_64-unknown-linux-gnu/release/incremental/syntax-284je5yviillk/s-f0lq29bbi9-erx9ij-yefbrhq8bkke
48604 ./obj/build/x86_64-unknown-linux-gnu/stage0/bin
47832 ./obj/build/x86_64-unknown-linux-gnu/stage0-std
46868 ./src/test
46820 ./obj/build/x86_64-unknown-linux-gnu/stage1-std/x86_64-unknown-linux-gnu/release/deps

I'm a bot! I can only do what humans tell me to, so if this was not helpful or you have suggestions for improvements, please ping or otherwise contact @TimNN. (Feature Requests)

…cals' dtors. This is meant to address rust-lang#49918. Review feedback: put back comment justifying skipping interior traversal. Review feedback: dropck generators like trait objects: all their upvars must outlive the generator itself, so just create a DtorckConstraint saying so.

…rules.

pnkfelix · 2018-05-02T11:40:04Z

@bors r=nikomatsakis

bors · 2018-05-02T11:40:05Z

📌 Commit f12d7a5 has been approved by nikomatsakis

bors · 2018-05-02T12:20:38Z

⌛ Testing commit f12d7a5 with merge d40a0b3...

Treat generators as if they have an arbitrary destructor Conservatively assume dropping a generator touches its upvars, via locals' destructors. Fix #49918

bors · 2018-05-02T14:51:54Z

☀️ Test successful - status-appveyor, status-travis
Approved by: nikomatsakis
Pushing d40a0b3 to master...

rust-highfive assigned cramertj Apr 13, 2018

rust-highfive added the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Apr 13, 2018

rust-highfive assigned Zoxc and unassigned cramertj Apr 13, 2018

rust-highfive assigned nikomatsakis and unassigned Zoxc Apr 15, 2018

Zoxc reviewed Apr 15, 2018

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pnkfelix force-pushed the fix-issue-49918 branch from dd63992 to 856637a Compare April 19, 2018 11:25

arielb1 reviewed Apr 21, 2018

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nikomatsakis added S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Apr 25, 2018

pnkfelix added 2 commits May 1, 2018 22:28

Update ui/generator tests to reflect changes from new generator drop …

f12d7a5

…rules.

pnkfelix force-pushed the fix-issue-49918 branch from d71cb04 to f12d7a5 Compare May 1, 2018 21:03

kennytm added the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label May 1, 2018

kennytm removed the S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. label May 1, 2018

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 May 2, 2018

bors added a commit that referenced this pull request May 2, 2018

Auto merge of #49943 - pnkfelix:fix-issue-49918, r=nikomatsakis

d40a0b3

Treat generators as if they have an arbitrary destructor Conservatively assume dropping a generator touches its upvars, via locals' destructors. Fix #49918

bors merged commit f12d7a5 into rust-lang:master May 2, 2018

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Treat generators as if they have an arbitrary destructor #49943

Treat generators as if they have an arbitrary destructor #49943

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Treat generators as if they have an arbitrary destructor #49943

Treat generators as if they have an arbitrary destructor #49943

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AST-borrowck:

NLL (-Z borrowck=mir):

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NLL (`-Z borrowck=mir`):

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