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MIR borrowck: print lvalues in error messages in the same way that the AST borrowck - #44985

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zilbuz:issue-44974
Oct 12, 2017
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MIR borrowck: print lvalues in error messages in the same way that the AST borrowck#44985
bors merged 12 commits into
rust-lang:masterfrom
zilbuz:issue-44974

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@zilbuz

@zilbuzzilbuz commented Oct 2, 2017•
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Fix#44974

  • Print fields with .name rather than .<num>
  • Autoderef values if followed by a field or an index
  • Output [..] when borrowing inside a slice

@rust-highfive

rust-highfive commented Oct 2, 2017

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r? @pnkfelix

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

@zilbuz

zilbuz commented Oct 2, 2017

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I'd like some feedback on this PR. I can't think of any example that trigger the messages marked debug!() in my diff of borrow_check.rs. Can someone give me some example ?

@pnkfelix

pnkfelix commented Oct 2, 2017

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@zilbuz I'm about to hit the sack, but if you use the following input code, I think you should see some examples of some of the cases you are wondering about:

#![feature(slice_patterns)]fnmain(){#[derive(Debug)]enumE<X>{A(X),B{x:X}}#[derive(Debug)]structS<'a,X:'a,Y>{x:&'a[X],y:(Y,Y),};let e = E::A(3);match e {E::A(ref ax) => println!("e.ax: {:?}", ax),E::B{x:ref bx } => println!("e.bx: {:?}", bx),}let s = S{x:&[1,2,3,],y:(999,998)};match s {S{x:&[ref x0,ref xn..],y:(ref y0,ref y1)} => {println!("s.x0: {:?} s.xn: {:?}", x0, xn);println!("s.y0: {:?}, s.y1: {:?}", y0, y1);}
_ => panic!("other case"),}}

@aidanhsaidanhs added the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Oct 5, 2017
zilbuz added 12 commits October 6, 2017 17:44
@zilbuz
mir-borrowck: print values in error messages in the same way that the…
aa78919
… AST borrowck
- Print fields with `.name` rather than `.<num>`
- Autoderef values if followed by a field or an index
@zilbuz
mir-borrowck: Add tests for describe_lvalue()
ff8ea69
@zilbuz
mir-borrowck: Fix existing tests
7bdf177
@zilbuz
mir-borrowck: Panic when trying to print a field access on a non-box …
456e12e
…type that is neither Adt nor tuple
@zilbuz
mir-borrowck: Autoderef values followed by a constant index, and fix …
ef2f42d
…reported lvalue for constant index
Previously the constant index was reported as `[x of y]` or `[-x of y]` where
`x` was the offset and `y` the minimum length of the slice. The minus sign
wasn't in the right case since for `&[_, x, .., _, _]`, the error reported was
`[-1 of 4]`, and for `&[_, _, .., x, _]`, the error reported was `[2 of 4]`.
This commit fixes the sign so that the indexes 1 and -2 are reported, and
remove the ` of y` part of the message to make it more succinct.
@zilbuz
mir-borrowck: Replace all constant index and sublices output with `[.…
0241ea4
….]` to match the AST borrowck output
@zilbuz
mir-borrowck: Implement end-user output for field of downcast projection
f35c4e3
@zilbuz
mir-borrowck: Implement end-user output for field of field projection
ce3b2e7
@zilbuz
mir-borrowck: Implement end-user output for field of index projection
9ce2f3a
@zilbuz
mir-borrowck: Implement end-user output for field of reference, point…
ca5dc86
…er and array
@zilbuz
mir-borrowck: Append _ or .. depending on the context if a local …
8b8cdd9
…variable hasn't a name
@zilbuz
mir-borrowck: Implement end-user output for field of subslice and sli…
e32e81c
…ce type
@zilbuzzilbuz changed the title [WIP] MIR borrowck: print lvalues in error messages in the same way that the AST borrowckMIR borrowck: print lvalues in error messages in the same way that the AST borrowckOct 6, 2017
@zilbuz

zilbuz commented Oct 6, 2017

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r? @pnkfelix

The only commit untested is e32e81c. I couldn't find a way to access a field through a subslice. I'd have to be able to do something like [1..3].x or xn @ [F { x }..] in a match maybe...

pnkfelix
pnkfelix reviewed Oct 9, 2017
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Comment threadsrc/test/compile-fail/borrowck/borrowck-describe-lvalue.rs
// Static and field from struct
unsafe {
let _x = sfoo.x();
sfoo.x; //[mir]~ ERROR cannot use `sfoo.x` because it was mutably borrowed (Mir)

@pnkfelixpnkfelixOct 9, 2017

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oh interesting...

(I think this represents a bug in MIR-borrowck. But fixing that is orthogonal to this PR in any case.)

@pnkfelixpnkfelixOct 9, 2017

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(likewise for all the other cases below that are paths based off of static variables)

@pnkfelixpnkfelixOct 9, 2017

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Filed as #45129

@pnkfelix

pnkfelix commented Oct 9, 2017

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@bors r+

thanks for all the work here @zilbuz !

@bors

bors commented Oct 9, 2017

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📌 Commit e32e81c has been approved by pnkfelix

@pnkfelixpnkfelix mentioned this pull request Oct 9, 2017
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@bors

bors commented Oct 10, 2017

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⌛ Testing commit e32e81c with merge fd85391dbaf891fda53943b00e97cd609d3186c2...

@bors

bors commented Oct 10, 2017

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💔 Test failed - status-travis

@kennytm

kennytm commented Oct 11, 2017

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@bors retry

@bors

bors commented Oct 12, 2017

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⌛ Testing commit e32e81c with merge d274114...

bors added a commit that referenced this pull request Oct 12, 2017
@bors
Auto merge of#44985- zilbuz:issue-44974, r=pnkfelix
d274114
MIR borrowck: print lvalues in error messages in the same way that the AST borrowck
Fix#44974
- Print fields with `.name` rather than `.<num>`
- Autoderef values if followed by a field or an index
- Output `[..]` when borrowing inside a slice
@bors

bors commented Oct 12, 2017

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☀️ Test successful - status-appveyor, status-travis
Approved by: pnkfelix
Pushing d274114 to master...

@bors
bors merged commit e32e81c into rust-lang:masterOct 12, 2017
@zilbuz
zilbuz deleted the issue-44974 branch March 1, 2018 13:34
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