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Make migrate mode work at item level granularity
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matthewjasper committed Mar 2, 2019
1 parent 0ea2271 commit 2742b23
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Showing 7 changed files with 127 additions and 25 deletions.
8 changes: 6 additions & 2 deletions src/librustc/middle/expr_use_visitor.rs
Original file line number Diff line number Diff line change
Expand Up @@ -82,6 +82,9 @@ pub trait Delegate<'tcx> {
assignment_span: Span,
assignee_cmt: &mc::cmt_<'tcx>,
mode: MutateMode);

// A nested closure or generator - only one layer deep.
fn nested_body(&mut self, _body_id: hir::BodyId) {}
}

#[derive(Copy, Clone, PartialEq, Debug)]
Expand Down Expand Up @@ -531,8 +534,9 @@ impl<'a, 'gcx, 'tcx> ExprUseVisitor<'a, 'gcx, 'tcx> {
self.consume_expr(&base);
}

hir::ExprKind::Closure(.., fn_decl_span, _) => {
self.walk_captures(expr, fn_decl_span)
hir::ExprKind::Closure(_, _, body_id, fn_decl_span, _) => {
self.delegate.nested_body(body_id);
self.walk_captures(expr, fn_decl_span);
}

hir::ExprKind::Box(ref base) => {
Expand Down
16 changes: 16 additions & 0 deletions src/librustc_borrowck/borrowck/check_loans.rs
Original file line number Diff line number Diff line change
Expand Up @@ -177,6 +177,22 @@ impl<'a, 'tcx> euv::Delegate<'tcx> for CheckLoanCtxt<'a, 'tcx> {
}

fn decl_without_init(&mut self, _id: hir::HirId, _span: Span) { }

fn nested_body(&mut self, body_id: hir::BodyId) {
// rust-lang/rust#58776: MIR and AST borrow check disagree on where
// certain closure errors are reported. As such migrate borrowck has to
// operate at the level of items, rather than bodies. Check if the
// contained closure had any errors and set `signalled_any_error` if it
// has.
let bccx = self.bccx;
if bccx.tcx.migrate_borrowck() {
if let SignalledError::NoErrorsSeen = bccx.signalled_any_error.get() {
let closure_def_id = bccx.tcx.hir().body_owner_def_id(body_id);

bccx.signalled_any_error.set(bccx.tcx.borrowck(closure_def_id).signalled_any_error);
}
}
}
}

pub fn check_loans<'a, 'b, 'c, 'tcx>(bccx: &BorrowckCtxt<'a, 'tcx>,
Expand Down
28 changes: 5 additions & 23 deletions src/librustc_mir/borrow_check/mod.rs
Original file line number Diff line number Diff line change
Expand Up @@ -329,30 +329,12 @@ fn do_mir_borrowck<'a, 'gcx, 'tcx>(
// When borrowck=migrate, check if AST-borrowck would
// error on the given code.

// rust-lang/rust#55492: loop over parents to ensure that
// errors that AST-borrowck only detects in some parent of
// a closure still allows NLL to signal an error.
let mut curr_def_id = def_id;
let signalled_any_error = loop {
match tcx.borrowck(curr_def_id).signalled_any_error {
SignalledError::NoErrorsSeen => {
// keep traversing (and borrow-checking) parents
}
SignalledError::SawSomeError => {
// stop search here
break SignalledError::SawSomeError;
}
}

if tcx.is_closure(curr_def_id) {
curr_def_id = tcx.parent_def_id(curr_def_id)
.expect("a closure must have a parent_def_id");
} else {
break SignalledError::NoErrorsSeen;
}
};
// rust-lang/rust#55492, rust-lang/rust#58776 check the base def id
// for errors. AST borrowck is responsible for aggregating
// `signalled_any_error` from all of the nested closures here.
let base_def_id = tcx.closure_base_def_id(def_id);

match signalled_any_error {
match tcx.borrowck(base_def_id).signalled_any_error {
SignalledError::NoErrorsSeen => {
// if AST-borrowck signalled no errors, then
// downgrade all the buffered MIR-borrowck errors
Expand Down
Original file line number Diff line number Diff line change
@@ -0,0 +1,15 @@
error[E0597]: `**greeting` does not live long enough
--> $DIR/issue-58776-borrowck-scans-children.rs:10:24
|
LL | let res = (|| (|| &greeting)())();
| -- ^^^^^^^^ - borrowed value only lives until here
| | |
| | borrowed value does not live long enough
| capture occurs here
...
LL | }
| - borrowed value needs to live until here

error: aborting due to previous error

For more information about this error, try `rustc --explain E0597`.
Original file line number Diff line number Diff line change
@@ -0,0 +1,32 @@
error[E0506]: cannot assign to `greeting` because it is borrowed
--> $DIR/issue-58776-borrowck-scans-children.rs:13:5
|
LL | let res = (|| (|| &greeting)())();
| -- -------- borrow occurs due to use in closure
| |
| borrow of `greeting` occurs here
...
LL | greeting = "DEALLOCATED".to_string();
| ^^^^^^^^ assignment to borrowed `greeting` occurs here
...
LL | println!("thread result: {:?}", res);
| --- borrow later used here

error[E0505]: cannot move out of `greeting` because it is borrowed
--> $DIR/issue-58776-borrowck-scans-children.rs:16:10
|
LL | let res = (|| (|| &greeting)())();
| -- -------- borrow occurs due to use in closure
| |
| borrow of `greeting` occurs here
...
LL | drop(greeting);
| ^^^^^^^^ move out of `greeting` occurs here
...
LL | println!("thread result: {:?}", res);
| --- borrow later used here

error: aborting due to 2 previous errors

Some errors occurred: E0505, E0506.
For more information about an error, try `rustc --explain E0505`.
Original file line number Diff line number Diff line change
@@ -0,0 +1,32 @@
error[E0506]: cannot assign to `greeting` because it is borrowed
--> $DIR/issue-58776-borrowck-scans-children.rs:13:5
|
LL | let res = (|| (|| &greeting)())();
| -- -------- borrow occurs due to use in closure
| |
| borrow of `greeting` occurs here
...
LL | greeting = "DEALLOCATED".to_string();
| ^^^^^^^^ assignment to borrowed `greeting` occurs here
...
LL | println!("thread result: {:?}", res);
| --- borrow later used here

error[E0505]: cannot move out of `greeting` because it is borrowed
--> $DIR/issue-58776-borrowck-scans-children.rs:16:10
|
LL | let res = (|| (|| &greeting)())();
| -- -------- borrow occurs due to use in closure
| |
| borrow of `greeting` occurs here
...
LL | drop(greeting);
| ^^^^^^^^ move out of `greeting` occurs here
...
LL | println!("thread result: {:?}", res);
| --- borrow later used here

error: aborting due to 2 previous errors

Some errors occurred: E0505, E0506.
For more information about an error, try `rustc --explain E0505`.
21 changes: 21 additions & 0 deletions src/test/ui/borrowck/issue-58776-borrowck-scans-children.rs
Original file line number Diff line number Diff line change
@@ -0,0 +1,21 @@
// ignore-compare-mode-nll

// revisions: ast migrate nll

//[migrate]compile-flags: -Z borrowck=migrate
#![cfg_attr(nll, feature(nll))]

fn main() {
let mut greeting = "Hello world!".to_string();
let res = (|| (|| &greeting)())();
//[ast]~^ ERROR does not live long enough

greeting = "DEALLOCATED".to_string();
//[migrate]~^ ERROR cannot assign
//[nll]~^^ ERROR cannot assign
drop(greeting);
//[migrate]~^ ERROR cannot move
//[nll]~^^ ERROR cannot move

println!("thread result: {:?}", res);
}

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