MIR-borrowck: Adding notes to E0506 #44811

zilbuz · Sep 24, 2017

This PR adds notes to the MIR borrowck error E0506.

rust-highfive · Sep 24, 2017

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GuillaumeGomez · Sep 24, 2017

Could you please add a test for this change? Take a look at how they're done in src/test/compile-fail.

zilbuz · Sep 24, 2017

There is a test for E0506 (https://github.com/rust-lang/rust/blob/master/src/test/compile-fail/E0506.rs), but it doesn't test this message because the compiler uses the AST borrowck instead of the MIR borrowck. I manually checked that the messages were the same though. I assumed that the tests for MIR borrowck would be added on a later PR (@pnkfelix ?). Or maybe you're asking for a different kind of test ?

KiChjang · Sep 24, 2017

We could actually use a UI test for this, but it's not feasible right now because we can't properly display lvalues in the MIR borrowck.

pnkfelix · Sep 25, 2017

In principle we could add a test, by telling the test infrastructure to pass the necessary -Z flags.

In particular, you can do // compile-flags: -Z emit-end-regions -Z borrowck-mir at the top of the file. (You can find other tests that pass other such flags in src/test/compile-fail/)

(I assume that the UI tests accept the same compile-flags comment.)

Whether its a good idea to put in tests for MIR-borrowck at this stage... it probably is worth it, just to make sure we don't regress. But maybe they should go into their own sub-directory or something, just to keep them isolated from "real tests" of current functionality.

pnkfelix · Sep 25, 2017

(After discussion in rust-impl-period/WG-compiler-nll, we decided that we will try the approach of extending the existing tests under compile-fail/ via the // revisions: ... system so that we can keep a single test file and list different sets of expected error messages based on whether or not we are passing -Z borrowck-mir.)

bors · Sep 26, 2017

☔️ The latest upstream changes (presumably #44736) made this pull request unmergeable. Please resolve the merge conflicts.

zilbuz · Sep 26, 2017

Alright I edited the tests on compile-fail that raise E0506. I omitted the tests that triggers ICE as other issues are supposed to fix them.

arielb1 · Sep 27, 2017

Nice. I suppose we'll also want to add "borrow ends here" when we start supporting these, which should be soon.

@bors r+

bors · Sep 27, 2017

📌 Commit b683538 has been approved by arielb1

arielb1 · Sep 27, 2017

arielb1 reviewed Sep 27, 2017

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arielb1 · Sep 27, 2017

src/librustc_mir/borrow_check.rs

@@ -975,10 +975,19 @@ impl<'c, 'b, 'a: 'b+'c, 'gcx, 'tcx: 'a> MirBorrowckCtxt<'c, 'b, 'a, 'gcx, 'tcx>
        err.emit();
    }

-    fn report_illegal_mutation_of_borrowed(&mut self, _: Context, (lvalue, span): (&Lvalue, Span)) {
+    fn report_illegal_mutation_of_borrowed(&mut self,


I think this should be moved to borrowck_errors actually, but that could be done in another commit.

You mean like @mikhail-m1 has done in #44882 ?

Done here: #44922

pnkfelix · Sep 27, 2017

pnkfelix reviewed Sep 27, 2017

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pnkfelix · Sep 27, 2017

src/test/compile-fail/coerce-overloaded-autoderef.rs

 }

 fn double_borrow2<T>(x: &mut Box<T>) {
    borrow2(x, x);
-    //~^ ERROR cannot borrow `*x` as immutable because it is also borrowed as mutable
+    //[ast]~^ ERROR cannot borrow `*x` as immutable because it is also borrowed as mutable
+    //[mir]~^^ ERROR cannot borrow `*x` as immutable because it is also borrowed as mutable (Ast)


the ~^^ here could just be ~|

No, it seems that when using revisions, the comments of the revision not currently compiled aren't processed. If I use ~|, I have the following error :
compile-fail\coerce-overloaded-autoderef.rs' panicked at 'encountered //~| without preceding //~^ line.', src\libcore\option.rs:839:4

pnkfelix · Sep 27, 2017

pnkfelix reviewed Sep 27, 2017

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pnkfelix · Sep 27, 2017

src/test/compile-fail/coerce-overloaded-autoderef.rs

 }

 fn double_mut_borrow2<T>(x: &mut Box<T>) {
    borrow_mut2(x, x);
-    //~^ ERROR cannot borrow `*x` as mutable more than once at a time
+    //[ast]~^ ERROR cannot borrow `*x` as mutable more than once at a time
+    //[mir]~^^ ERROR cannot borrow `*x` as mutable more than once at a time (Ast)


the ~^^ here could just be ~|

Cf. #44811 (comment)

pnkfelix · Sep 27, 2017

pnkfelix reviewed Sep 27, 2017

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pnkfelix · Sep 27, 2017

src/test/compile-fail/coerce-overloaded-autoderef.rs

 }

 fn double_imm_borrow(x: &mut Box<i32>) {
    let y = borrow(x);
    let z = borrow(x);
    **x += 1;
-    //~^ ERROR cannot assign to `**x` because it is borrowed
+    //[ast]~^ ERROR cannot assign to `**x` because it is borrowed
+    //[mir]~^^ ERROR cannot assign to `**x` because it is borrowed (Ast)


the ~^^ here could just be ~|

Cf. #44811 (comment)

pnkfelix · Sep 27, 2017

pnkfelix reviewed Sep 27, 2017

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pnkfelix · Sep 27, 2017

src/test/compile-fail/coerce-overloaded-autoderef.rs

@@ -17,24 +20,32 @@ fn borrow2<T>(_: &mut T, _: &T) {}
 fn double_mut_borrow<T>(x: &mut Box<T>) {
    let y = borrow_mut(x);
    let z = borrow_mut(x);
-    //~^ ERROR cannot borrow `*x` as mutable more than once at a time
+    //[ast]~^ ERROR cannot borrow `*x` as mutable more than once at a time
+    //[mir]~^^ ERROR cannot borrow `*x` as mutable more than once at a time (Ast)


the ~^^ here could just be ~|

Cf. #44811 (comment)

pnkfelix · Sep 27, 2017

pnkfelix reviewed Sep 27, 2017

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pnkfelix · Sep 27, 2017

src/test/compile-fail/borrowck/borrowck-overloaded-index-and-overloaded-deref.rs

@@ -39,7 +42,9 @@ fn main() {
    let mut v = MyVec { x: MyPtr { x: Foo { f: 22 } } };
    let i = &v[0].f;
    v = MyVec { x: MyPtr { x: Foo { f: 23 } } };
-    //~^ ERROR cannot assign to `v`
+    //[ast]~^ ERROR cannot assign to `v`
+    //[mir]~^^ ERROR cannot assign to `v` because it is borrowed (Ast)


the ~^^ here could just be ~|

Cf. #44811 (comment)

bors · Sep 29, 2017

⌛️ Testing commit b683538 with merge a379780...

bors · Sep 29, 2017

☀️ Test successful - status-appveyor, status-travis
Approved by: arielb1
Pushing a379780 to master...

rust-highfive assigned arielb1 Sep 24, 2017

carols10cents added the S-waiting-on-author label Sep 25, 2017

pnkfelix referenced this pull request Sep 25, 2017
Merged
Add span label to E0384 for MIR borrowck #44806

zilbuz force-pushed the zilbuz:issue-44596/E0506 branch from 09f85ed to b683538 Sep 26, 2017

bors added a commit that referenced this pull request Sep 29, 2017

Auto merge of #44811 - zilbuz:issue-44596/E0506, r=arielb1
MIR-borrowck: Adding notes to E0506 This PR adds notes to the MIR borrowck error E0506. Part of #44596

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KiChjang commented Sep 24, 2017 •

edited

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bors merged commit `b683538` into rust-lang:master Sep 29, 2017
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