Rollup merge of #45927 - sinkuu:mir-borrowck-closure, r=estebank

MIR-borrowck: fix diagnostics for closures

Emit notes for captured variables in the same manner as AST borrowck.

```
error[E0499]: cannot borrow `x` as mutable more than once at a time (Ast)
  --> $DIR/borrowck-closures-two-mut.rs:24:24
   |
23 |     let c1 = to_fn_mut(|| x = 4);
   |                        -- - previous borrow occurs due to use of `x` in closure
   |                        |
   |                        first mutable borrow occurs here
24 |     let c2 = to_fn_mut(|| x = 5); //~ ERROR cannot borrow `x` as mutable more than once
   |                        ^^ - borrow occurs due to use of `x` in closure
   |                        |
   |                        second mutable borrow occurs here
25 | }
   | - first borrow ends here

error[E0499]: cannot borrow `x` as mutable more than once at a time (Mir)
  --> $DIR/borrowck-closures-two-mut.rs:24:24
   |
23 |     let c1 = to_fn_mut(|| x = 4);
   |                        -- - previous borrow occurs due to use of `x` in closure
   |                        |
   |                        first mutable borrow occurs here
24 |     let c2 = to_fn_mut(|| x = 5); //~ ERROR cannot borrow `x` as mutable more than once
   |                        ^^ - borrow occurs due to use of `x` in closure
   |                        |
   |                        second mutable borrow occurs here
25 | }
   | - first borrow ends here
```

Fixes #45362.
This commit is contained in:
kennytm 2017-11-13 17:09:45 +08:00 committed by GitHub
commit 574dff9052
5 changed files with 303 additions and 9 deletions

View File

@ -1949,7 +1949,7 @@ impl ForeignItem_ {
}
/// A free variable referred to in a function.
#[derive(Copy, Clone, RustcEncodable, RustcDecodable)]
#[derive(Debug, Copy, Clone, RustcEncodable, RustcDecodable)]
pub struct Freevar {
/// The variable being accessed free.
pub def: Def,

View File

@ -267,10 +267,10 @@ impl<'tcx> Mir<'tcx> {
let block = &self[location.block];
let stmts = &block.statements;
let idx = location.statement_index;
if location.statement_index < stmts.len() {
if idx < stmts.len() {
&stmts[idx].source_info
} else {
assert!(location.statement_index == stmts.len());
assert!(idx == stmts.len());
&block.terminator().source_info
}
}

View File

@ -1169,8 +1169,72 @@ impl<'c, 'b, 'a: 'b+'c, 'gcx, 'tcx: 'a> MirBorrowckCtxt<'c, 'b, 'a, 'gcx, 'tcx>
err.emit();
}
/// Finds the span of arguments of a closure (within `maybe_closure_span`) and its usage of
/// the local assigned at `location`.
/// This is done by searching in statements succeeding `location`
/// and originating from `maybe_closure_span`.
fn find_closure_span(
&self,
maybe_closure_span: Span,
location: Location,
) -> Option<(Span, Span)> {
use rustc::hir::ExprClosure;
use rustc::mir::AggregateKind;
let local = if let StatementKind::Assign(Lvalue::Local(local), _) =
self.mir[location.block].statements[location.statement_index].kind
{
local
} else {
return None;
};
for stmt in &self.mir[location.block].statements[location.statement_index + 1..] {
if maybe_closure_span != stmt.source_info.span {
break;
}
if let StatementKind::Assign(_, Rvalue::Aggregate(ref kind, ref lvs)) = stmt.kind {
if let AggregateKind::Closure(def_id, _) = **kind {
debug!("find_closure_span: found closure {:?}", lvs);
return if let Some(node_id) = self.tcx.hir.as_local_node_id(def_id) {
let args_span = if let ExprClosure(_, _, _, span, _) =
self.tcx.hir.expect_expr(node_id).node
{
span
} else {
return None;
};
self.tcx
.with_freevars(node_id, |freevars| {
for (v, lv) in freevars.iter().zip(lvs) {
if let Operand::Consume(Lvalue::Local(l)) = *lv {
if local == l {
debug!(
"find_closure_span: found captured local {:?}",
l
);
return Some(v.span);
}
}
}
None
})
.map(|var_span| (args_span, var_span))
} else {
None
};
}
}
}
None
}
fn report_conflicting_borrow(&mut self,
_context: Context,
context: Context,
common_prefix: &Lvalue,
(lvalue, span): (&Lvalue, Span),
gen_borrow_kind: BorrowKind,
@ -1183,38 +1247,60 @@ impl<'c, 'b, 'a: 'b+'c, 'gcx, 'tcx: 'a> MirBorrowckCtxt<'c, 'b, 'a, 'gcx, 'tcx>
let issued_span = self.retrieve_borrow_span(issued_borrow);
let new_closure_span = self.find_closure_span(span, context.loc);
let span = new_closure_span.map(|(args, _)| args).unwrap_or(span);
let old_closure_span = self.find_closure_span(issued_span, issued_borrow.location);
let issued_span = old_closure_span.map(|(args, _)| args).unwrap_or(issued_span);
let desc_lvalue = self.describe_lvalue(lvalue);
// FIXME: supply non-"" `opt_via` when appropriate
let mut err = match (gen_borrow_kind, "immutable", "mutable",
issued_borrow.kind, "immutable", "mutable") {
(BorrowKind::Shared, lft, _, BorrowKind::Mut, _, rgt) |
(BorrowKind::Mut, _, lft, BorrowKind::Shared, rgt, _) =>
self.tcx.cannot_reborrow_already_borrowed(
span, &self.describe_lvalue(lvalue), "", lft, issued_span,
span, &desc_lvalue, "", lft, issued_span,
"it", rgt, "", end_issued_loan_span, Origin::Mir),
(BorrowKind::Mut, _, _, BorrowKind::Mut, _, _) =>
self.tcx.cannot_mutably_borrow_multiply(
span, &self.describe_lvalue(lvalue), "", issued_span,
span, &desc_lvalue, "", issued_span,
"", end_issued_loan_span, Origin::Mir),
(BorrowKind::Unique, _, _, BorrowKind::Unique, _, _) =>
self.tcx.cannot_uniquely_borrow_by_two_closures(
span, &self.describe_lvalue(lvalue), issued_span,
span, &desc_lvalue, issued_span,
end_issued_loan_span, Origin::Mir),
(BorrowKind::Unique, _, _, _, _, _) =>
self.tcx.cannot_uniquely_borrow_by_one_closure(
span, &self.describe_lvalue(lvalue), "",
span, &desc_lvalue, "",
issued_span, "it", "", end_issued_loan_span, Origin::Mir),
(_, _, _, BorrowKind::Unique, _, _) =>
self.tcx.cannot_reborrow_already_uniquely_borrowed(
span, &self.describe_lvalue(lvalue), "it", "",
span, &desc_lvalue, "it", "",
issued_span, "", end_issued_loan_span, Origin::Mir),
(BorrowKind::Shared, _, _, BorrowKind::Shared, _, _) =>
unreachable!(),
};
if let Some((_, var_span)) = old_closure_span {
err.span_label(
var_span,
format!("previous borrow occurs due to use of `{}` in closure", desc_lvalue),
);
}
if let Some((_, var_span)) = new_closure_span {
err.span_label(
var_span,
format!("borrow occurs due to use of `{}` in closure", desc_lvalue),
);
}
err.emit();
}

View File

@ -0,0 +1,62 @@
// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.
// Tests that two closures cannot simultaneously have mutable
// access to the variable, whether that mutable access be used
// for direct assignment or for taking mutable ref. Issue #6801.
// compile-flags: -Z emit-end-regions -Z borrowck-mir
#![feature(box_syntax)]
fn to_fn_mut<F: FnMut()>(f: F) -> F { f }
fn a() {
let mut x = 3;
let c1 = to_fn_mut(|| x = 4);
let c2 = to_fn_mut(|| x = 5); //~ ERROR cannot borrow `x` as mutable more than once
}
fn set(x: &mut isize) {
*x = 4;
}
fn b() {
let mut x = 3;
let c1 = to_fn_mut(|| set(&mut x));
let c2 = to_fn_mut(|| set(&mut x)); //~ ERROR cannot borrow `x` as mutable more than once
}
fn c() {
let mut x = 3;
let c1 = to_fn_mut(|| x = 5);
let c2 = to_fn_mut(|| set(&mut x)); //~ ERROR cannot borrow `x` as mutable more than once
}
fn d() {
let mut x = 3;
let c1 = to_fn_mut(|| x = 5);
let c2 = to_fn_mut(|| { let _y = to_fn_mut(|| set(&mut x)); }); // (nested closure)
//~^ ERROR cannot borrow `x` as mutable more than once
}
fn g() {
struct Foo {
f: Box<isize>
}
let mut x: Box<_> = box Foo { f: box 3 };
let c1 = to_fn_mut(|| set(&mut *x.f));
let c2 = to_fn_mut(|| set(&mut *x.f));
//~^ ERROR cannot borrow `x` as mutable more than once
}
fn main() {
}

View File

@ -0,0 +1,146 @@
error[E0499]: cannot borrow `x` as mutable more than once at a time (Ast)
--> $DIR/borrowck-closures-two-mut.rs:24:24
|
23 | let c1 = to_fn_mut(|| x = 4);
| -- - previous borrow occurs due to use of `x` in closure
| |
| first mutable borrow occurs here
24 | let c2 = to_fn_mut(|| x = 5); //~ ERROR cannot borrow `x` as mutable more than once
| ^^ - borrow occurs due to use of `x` in closure
| |
| second mutable borrow occurs here
25 | }
| - first borrow ends here
error[E0499]: cannot borrow `x` as mutable more than once at a time (Ast)
--> $DIR/borrowck-closures-two-mut.rs:34:24
|
33 | let c1 = to_fn_mut(|| set(&mut x));
| -- - previous borrow occurs due to use of `x` in closure
| |
| first mutable borrow occurs here
34 | let c2 = to_fn_mut(|| set(&mut x)); //~ ERROR cannot borrow `x` as mutable more than once
| ^^ - borrow occurs due to use of `x` in closure
| |
| second mutable borrow occurs here
35 | }
| - first borrow ends here
error[E0499]: cannot borrow `x` as mutable more than once at a time (Ast)
--> $DIR/borrowck-closures-two-mut.rs:40:24
|
39 | let c1 = to_fn_mut(|| x = 5);
| -- - previous borrow occurs due to use of `x` in closure
| |
| first mutable borrow occurs here
40 | let c2 = to_fn_mut(|| set(&mut x)); //~ ERROR cannot borrow `x` as mutable more than once
| ^^ - borrow occurs due to use of `x` in closure
| |
| second mutable borrow occurs here
41 | }
| - first borrow ends here
error[E0499]: cannot borrow `x` as mutable more than once at a time (Ast)
--> $DIR/borrowck-closures-two-mut.rs:46:24
|
45 | let c1 = to_fn_mut(|| x = 5);
| -- - previous borrow occurs due to use of `x` in closure
| |
| first mutable borrow occurs here
46 | let c2 = to_fn_mut(|| { let _y = to_fn_mut(|| set(&mut x)); }); // (nested closure)
| ^^ - borrow occurs due to use of `x` in closure
| |
| second mutable borrow occurs here
47 | //~^ ERROR cannot borrow `x` as mutable more than once
48 | }
| - first borrow ends here
error[E0499]: cannot borrow `x` as mutable more than once at a time (Ast)
--> $DIR/borrowck-closures-two-mut.rs:57:24
|
56 | let c1 = to_fn_mut(|| set(&mut *x.f));
| -- - previous borrow occurs due to use of `x` in closure
| |
| first mutable borrow occurs here
57 | let c2 = to_fn_mut(|| set(&mut *x.f));
| ^^ - borrow occurs due to use of `x` in closure
| |
| second mutable borrow occurs here
58 | //~^ ERROR cannot borrow `x` as mutable more than once
59 | }
| - first borrow ends here
error[E0499]: cannot borrow `x` as mutable more than once at a time (Mir)
--> $DIR/borrowck-closures-two-mut.rs:24:24
|
23 | let c1 = to_fn_mut(|| x = 4);
| -- - previous borrow occurs due to use of `x` in closure
| |
| first mutable borrow occurs here
24 | let c2 = to_fn_mut(|| x = 5); //~ ERROR cannot borrow `x` as mutable more than once
| ^^ - borrow occurs due to use of `x` in closure
| |
| second mutable borrow occurs here
25 | }
| - first borrow ends here
error[E0499]: cannot borrow `x` as mutable more than once at a time (Mir)
--> $DIR/borrowck-closures-two-mut.rs:34:24
|
33 | let c1 = to_fn_mut(|| set(&mut x));
| -- - previous borrow occurs due to use of `x` in closure
| |
| first mutable borrow occurs here
34 | let c2 = to_fn_mut(|| set(&mut x)); //~ ERROR cannot borrow `x` as mutable more than once
| ^^ - borrow occurs due to use of `x` in closure
| |
| second mutable borrow occurs here
35 | }
| - first borrow ends here
error[E0499]: cannot borrow `x` as mutable more than once at a time (Mir)
--> $DIR/borrowck-closures-two-mut.rs:40:24
|
39 | let c1 = to_fn_mut(|| x = 5);
| -- - previous borrow occurs due to use of `x` in closure
| |
| first mutable borrow occurs here
40 | let c2 = to_fn_mut(|| set(&mut x)); //~ ERROR cannot borrow `x` as mutable more than once
| ^^ - borrow occurs due to use of `x` in closure
| |
| second mutable borrow occurs here
41 | }
| - first borrow ends here
error[E0499]: cannot borrow `x` as mutable more than once at a time (Mir)
--> $DIR/borrowck-closures-two-mut.rs:46:24
|
45 | let c1 = to_fn_mut(|| x = 5);
| -- - previous borrow occurs due to use of `x` in closure
| |
| first mutable borrow occurs here
46 | let c2 = to_fn_mut(|| { let _y = to_fn_mut(|| set(&mut x)); }); // (nested closure)
| ^^ - borrow occurs due to use of `x` in closure
| |
| second mutable borrow occurs here
47 | //~^ ERROR cannot borrow `x` as mutable more than once
48 | }
| - first borrow ends here
error[E0499]: cannot borrow `x` as mutable more than once at a time (Mir)
--> $DIR/borrowck-closures-two-mut.rs:57:24
|
56 | let c1 = to_fn_mut(|| set(&mut *x.f));
| -- - previous borrow occurs due to use of `x` in closure
| |
| first mutable borrow occurs here
57 | let c2 = to_fn_mut(|| set(&mut *x.f));
| ^^ - borrow occurs due to use of `x` in closure
| |
| second mutable borrow occurs here
58 | //~^ ERROR cannot borrow `x` as mutable more than once
59 | }
| - first borrow ends here
error: aborting due to 10 previous errors