From cbc865defd0b897ec9befafd4a1895bce58e3cf4 Mon Sep 17 00:00:00 2001 From: Santiago Pastorino Date: Tue, 20 Nov 2018 15:26:01 -0300 Subject: [PATCH 1/3] Use successor_within_block helper --- src/librustc_mir/borrow_check/nll/explain_borrow/find_use.rs | 5 +---- 1 file changed, 1 insertion(+), 4 deletions(-) diff --git a/src/librustc_mir/borrow_check/nll/explain_borrow/find_use.rs b/src/librustc_mir/borrow_check/nll/explain_borrow/find_use.rs index c5aaf5b811e..7d6385752c3 100644 --- a/src/librustc_mir/borrow_check/nll/explain_borrow/find_use.rs +++ b/src/librustc_mir/borrow_check/nll/explain_borrow/find_use.rs @@ -65,10 +65,7 @@ impl<'cx, 'gcx, 'tcx> UseFinder<'cx, 'gcx, 'tcx> { None => { if p.statement_index < block_data.statements.len() { - queue.push_back(Location { - statement_index: p.statement_index + 1, - ..p - }); + queue.push_back(p.successor_within_block()); } else { queue.extend( block_data From 801c3f060fc3bf25a730d89aa0b80da4493f3584 Mon Sep 17 00:00:00 2001 From: Santiago Pastorino Date: Tue, 20 Nov 2018 17:48:16 -0300 Subject: [PATCH 2/3] Fix erroneous loop diagnostic in nll This commit fixes the logic of detecting when a use happen in a later iteration of where a borrow was defined Fixes #53773 --- .../borrow_check/nll/explain_borrow/mod.rs | 179 ++++++++++++------ .../borrowck-for-loop-head-linkage.nll.stderr | 4 +- .../borrowck-lend-flow-loop.nll.stderr | 4 +- ...ck-mut-borrow-linear-errors.ast.nll.stderr | 4 +- ...rrowck-mut-borrow-linear-errors.mir.stderr | 4 +- .../mut-borrow-outside-loop.nll.stderr | 2 +- ...ssue-52126-assign-op-invariance.nll.stderr | 2 +- src/test/ui/nll/issue-53773.rs | 49 +++++ src/test/ui/nll/issue-53773.stderr | 16 ++ .../borrowck-issue-49631.nll.stderr | 2 +- ...egions-escape-loop-via-variable.nll.stderr | 2 +- .../regions-escape-loop-via-vec.nll.stderr | 8 +- .../ui/vec/vec-mut-iter-borrow.nll.stderr | 2 +- 13 files changed, 205 insertions(+), 73 deletions(-) create mode 100644 src/test/ui/nll/issue-53773.rs create mode 100644 src/test/ui/nll/issue-53773.stderr diff --git a/src/librustc_mir/borrow_check/nll/explain_borrow/mod.rs b/src/librustc_mir/borrow_check/nll/explain_borrow/mod.rs index a6a6962bb15..86cab6cbfb2 100644 --- a/src/librustc_mir/borrow_check/nll/explain_borrow/mod.rs +++ b/src/librustc_mir/borrow_check/nll/explain_borrow/mod.rs @@ -1,3 +1,5 @@ +use std::collections::VecDeque; + use crate::borrow_check::borrow_set::BorrowData; use crate::borrow_check::error_reporting::UseSpans; use crate::borrow_check::nll::ConstraintDescription; @@ -9,6 +11,7 @@ use rustc::mir::{ Place, Projection, ProjectionElem, Rvalue, Statement, StatementKind, TerminatorKind }; +use rustc_data_structures::fx::FxHashSet; use rustc_errors::DiagnosticBuilder; use syntax_pos::Span; @@ -220,7 +223,8 @@ impl<'cx, 'gcx, 'tcx> MirBorrowckCtxt<'cx, 'gcx, 'tcx> { let spans = self.move_spans(&Place::Local(local), location) .or_else(|| self.borrow_spans(span, location)); - if self.is_borrow_location_in_loop(context.loc) { + let borrow_location = context.loc; + if self.is_use_in_later_iteration_of_loop(borrow_location, location) { let later_use = self.later_use_kind(borrow, spans, location); BorrowExplanation::UsedLaterInLoop(later_use.0, later_use.1) } else { @@ -285,76 +289,139 @@ impl<'cx, 'gcx, 'tcx> MirBorrowckCtxt<'cx, 'gcx, 'tcx> { } } - /// Checks if a borrow location is within a loop. - fn is_borrow_location_in_loop( + /// true if `borrow_location` can reach `use_location` by going through a loop and + /// `use_location` is also inside of that loop + fn is_use_in_later_iteration_of_loop( &self, borrow_location: Location, + use_location: Location, ) -> bool { - let mut visited_locations = Vec::new(); - let mut pending_locations = vec![ borrow_location ]; - debug!("is_in_loop: borrow_location={:?}", borrow_location); + let back_edge = self.reach_through_backedge(borrow_location, use_location); + back_edge.map_or(false, |back_edge| { + self.can_reach_head_of_loop(use_location, back_edge) + }) + } - while let Some(location) = pending_locations.pop() { - debug!("is_in_loop: location={:?} pending_locations={:?} visited_locations={:?}", - location, pending_locations, visited_locations); - if location == borrow_location && visited_locations.contains(&borrow_location) { - // We've managed to return to where we started (and this isn't the start of the - // search). - debug!("is_in_loop: found!"); - return true; + /// Returns the outmost back edge if `from` location can reach `to` location passing through + /// that back edge + fn reach_through_backedge(&self, from: Location, to: Location) -> Option { + let mut visited_locations = FxHashSet::default(); + let mut pending_locations = VecDeque::new(); + visited_locations.insert(from); + pending_locations.push_back(from); + debug!("reach_through_backedge: from={:?} to={:?}", from, to,); + + let mut outmost_back_edge = None; + while let Some(location) = pending_locations.pop_front() { + debug!( + "reach_through_backedge: location={:?} outmost_back_edge={:?} + pending_locations={:?} visited_locations={:?}", + location, outmost_back_edge, pending_locations, visited_locations + ); + + if location == to && outmost_back_edge.is_some() { + // We've managed to reach the use location + debug!("reach_through_backedge: found!"); + return outmost_back_edge; } - // Skip locations we've been. - if visited_locations.contains(&location) { continue; } - let block = &self.mir.basic_blocks()[location.block]; - if location.statement_index == block.statements.len() { - // Add start location of the next blocks to pending locations. - match block.terminator().kind { - TerminatorKind::Goto { target } => { - pending_locations.push(target.start_location()); - }, - TerminatorKind::SwitchInt { ref targets, .. } => { - pending_locations.extend( - targets.into_iter().map(|target| target.start_location())); - }, - TerminatorKind::Drop { target, unwind, .. } | - TerminatorKind::DropAndReplace { target, unwind, .. } | - TerminatorKind::Assert { target, cleanup: unwind, .. } | - TerminatorKind::Yield { resume: target, drop: unwind, .. } | - TerminatorKind::FalseUnwind { real_target: target, unwind, .. } => { - pending_locations.push(target.start_location()); - if let Some(unwind) = unwind { - pending_locations.push(unwind.start_location()); - } - }, - TerminatorKind::Call { ref destination, cleanup, .. } => { - if let Some((_, destination)) = destination { - pending_locations.push(destination.start_location()); - } - if let Some(cleanup) = cleanup { - pending_locations.push(cleanup.start_location()); - } - }, - TerminatorKind::FalseEdges { real_target, ref imaginary_targets, .. } => { - pending_locations.push(real_target.start_location()); - pending_locations.extend( - imaginary_targets.into_iter().map(|target| target.start_location())); - }, - _ => {}, + + if location.statement_index < block.statements.len() { + let successor = location.successor_within_block(); + if visited_locations.insert(successor) { + pending_locations.push_back(successor); } } else { - // Add the next statement to pending locations. - pending_locations.push(location.successor_within_block()); - } + pending_locations.extend( + block + .terminator() + .successors() + .map(|bb| Location { + statement_index: 0, + block: *bb, + }) + .filter(|s| visited_locations.insert(*s)) + .map(|s| { + if self.is_back_edge(location, s) { + match outmost_back_edge { + None => { + outmost_back_edge = Some(location); + } - // Keep track of where we have visited. - visited_locations.push(location); + Some(back_edge) + if location.dominates(back_edge, &self.dominators) => + { + outmost_back_edge = Some(location); + } + + Some(_) => {} + } + } + + s + }), + ); + } + } + + None + } + + /// true if `from` location can reach `loop_head` location and `loop_head` dominates all the + /// intermediate nodes + fn can_reach_head_of_loop(&self, from: Location, loop_head: Location) -> bool { + self.find_loop_head_dfs(from, loop_head, &mut FxHashSet::default()) + } + + fn find_loop_head_dfs( + &self, + from: Location, + loop_head: Location, + visited_locations: &mut FxHashSet, + ) -> bool { + visited_locations.insert(from); + + if from == loop_head { + return true; + } + + if loop_head.dominates(from, &self.dominators) { + let block = &self.mir.basic_blocks()[from.block]; + + if from.statement_index < block.statements.len() { + let successor = from.successor_within_block(); + + if !visited_locations.contains(&successor) + && self.find_loop_head_dfs(successor, loop_head, visited_locations) + { + return true; + } + } else { + for bb in block.terminator().successors() { + let successor = Location { + statement_index: 0, + block: *bb, + }; + + if !visited_locations.contains(&successor) + && self.find_loop_head_dfs(successor, loop_head, visited_locations) + { + return true; + } + } + } } false } + /// True if an edge `source -> target` is a backedge -- in other words, if the target + /// dominates the source. + fn is_back_edge(&self, source: Location, target: Location) -> bool { + target.dominates(source, &self.mir.dominators()) + } + /// Determine how the borrow was later used. fn later_use_kind( &self, diff --git a/src/test/ui/borrowck/borrowck-for-loop-head-linkage.nll.stderr b/src/test/ui/borrowck/borrowck-for-loop-head-linkage.nll.stderr index c0549c91e33..32ca24ba6ec 100644 --- a/src/test/ui/borrowck/borrowck-for-loop-head-linkage.nll.stderr +++ b/src/test/ui/borrowck/borrowck-for-loop-head-linkage.nll.stderr @@ -5,7 +5,7 @@ LL | for &x in &vector { | ------- | | | immutable borrow occurs here - | immutable borrow used here, in later iteration of loop + | immutable borrow later used here LL | let cap = vector.capacity(); LL | vector.extend(repeat(0)); //~ ERROR cannot borrow | ^^^^^^^^^^^^^^^^^^^^^^^^ mutable borrow occurs here @@ -17,7 +17,7 @@ LL | for &x in &vector { | ------- | | | immutable borrow occurs here - | immutable borrow used here, in later iteration of loop + | immutable borrow later used here ... LL | vector[1] = 5; //~ ERROR cannot borrow | ^^^^^^ mutable borrow occurs here diff --git a/src/test/ui/borrowck/borrowck-lend-flow-loop.nll.stderr b/src/test/ui/borrowck/borrowck-lend-flow-loop.nll.stderr index 19de3582c88..396fd6ffa0c 100644 --- a/src/test/ui/borrowck/borrowck-lend-flow-loop.nll.stderr +++ b/src/test/ui/borrowck/borrowck-lend-flow-loop.nll.stderr @@ -8,13 +8,13 @@ LL | borrow(&*v); //[ast]~ ERROR cannot borrow | ^^^ immutable borrow occurs here ... LL | *x = box 5; - | -- mutable borrow used here, in later iteration of loop + | -- mutable borrow later used here error[E0502]: cannot borrow `*v` as immutable because it is also borrowed as mutable --> $DIR/borrowck-lend-flow-loop.rs:109:16 | LL | **x += 1; - | -------- mutable borrow used here, in later iteration of loop + | -------- mutable borrow later used here LL | borrow(&*v); //[ast]~ ERROR cannot borrow | ^^^ immutable borrow occurs here ... diff --git a/src/test/ui/borrowck/borrowck-mut-borrow-linear-errors.ast.nll.stderr b/src/test/ui/borrowck/borrowck-mut-borrow-linear-errors.ast.nll.stderr index 806c3a623bc..0f077765336 100644 --- a/src/test/ui/borrowck/borrowck-mut-borrow-linear-errors.ast.nll.stderr +++ b/src/test/ui/borrowck/borrowck-mut-borrow-linear-errors.ast.nll.stderr @@ -4,7 +4,7 @@ error[E0499]: cannot borrow `x` as mutable more than once at a time LL | 1 => { addr.push(&mut x); } //[ast]~ ERROR [E0499] | ---- ^^^^^^ second mutable borrow occurs here | | - | first borrow used here, in later iteration of loop + | first borrow later used here ... LL | _ => { addr.push(&mut x); } //[ast]~ ERROR [E0499] | ------ first mutable borrow occurs here @@ -13,7 +13,7 @@ error[E0499]: cannot borrow `x` as mutable more than once at a time --> $DIR/borrowck-mut-borrow-linear-errors.rs:15:30 | LL | 1 => { addr.push(&mut x); } //[ast]~ ERROR [E0499] - | ---- first borrow used here, in later iteration of loop + | ---- first borrow later used here LL | //[mir]~^ ERROR [E0499] LL | 2 => { addr.push(&mut x); } //[ast]~ ERROR [E0499] | ^^^^^^ second mutable borrow occurs here diff --git a/src/test/ui/borrowck/borrowck-mut-borrow-linear-errors.mir.stderr b/src/test/ui/borrowck/borrowck-mut-borrow-linear-errors.mir.stderr index 806c3a623bc..0f077765336 100644 --- a/src/test/ui/borrowck/borrowck-mut-borrow-linear-errors.mir.stderr +++ b/src/test/ui/borrowck/borrowck-mut-borrow-linear-errors.mir.stderr @@ -4,7 +4,7 @@ error[E0499]: cannot borrow `x` as mutable more than once at a time LL | 1 => { addr.push(&mut x); } //[ast]~ ERROR [E0499] | ---- ^^^^^^ second mutable borrow occurs here | | - | first borrow used here, in later iteration of loop + | first borrow later used here ... LL | _ => { addr.push(&mut x); } //[ast]~ ERROR [E0499] | ------ first mutable borrow occurs here @@ -13,7 +13,7 @@ error[E0499]: cannot borrow `x` as mutable more than once at a time --> $DIR/borrowck-mut-borrow-linear-errors.rs:15:30 | LL | 1 => { addr.push(&mut x); } //[ast]~ ERROR [E0499] - | ---- first borrow used here, in later iteration of loop + | ---- first borrow later used here LL | //[mir]~^ ERROR [E0499] LL | 2 => { addr.push(&mut x); } //[ast]~ ERROR [E0499] | ^^^^^^ second mutable borrow occurs here diff --git a/src/test/ui/borrowck/mut-borrow-outside-loop.nll.stderr b/src/test/ui/borrowck/mut-borrow-outside-loop.nll.stderr index 7e183116c46..9b20fc02319 100644 --- a/src/test/ui/borrowck/mut-borrow-outside-loop.nll.stderr +++ b/src/test/ui/borrowck/mut-borrow-outside-loop.nll.stderr @@ -17,7 +17,7 @@ LL | let inner_second = &mut inner_void; //~ ERROR cannot borrow | ^^^^^^^^^^^^^^^ second mutable borrow occurs here LL | inner_second.use_mut(); LL | inner_first.use_mut(); - | ----------- first borrow used here, in later iteration of loop + | ----------- first borrow later used here error: aborting due to 2 previous errors diff --git a/src/test/ui/issues/issue-52126-assign-op-invariance.nll.stderr b/src/test/ui/issues/issue-52126-assign-op-invariance.nll.stderr index 8332cf1b3a3..d231f621e59 100644 --- a/src/test/ui/issues/issue-52126-assign-op-invariance.nll.stderr +++ b/src/test/ui/issues/issue-52126-assign-op-invariance.nll.stderr @@ -5,7 +5,7 @@ LL | let v: Vec<&str> = line.split_whitespace().collect(); | ^^^^ borrowed value does not live long enough ... LL | acc += cnt2; - | --- borrow used here, in later iteration of loop + | --- borrow later used here ... LL | } | - `line` dropped here while still borrowed diff --git a/src/test/ui/nll/issue-53773.rs b/src/test/ui/nll/issue-53773.rs new file mode 100644 index 00000000000..62e1631dcf3 --- /dev/null +++ b/src/test/ui/nll/issue-53773.rs @@ -0,0 +1,49 @@ +#![feature(nll)] + +struct Archive; +struct ArchiveIterator<'a> { + x: &'a Archive, +} +struct ArchiveChild<'a> { + x: &'a Archive, +} + +struct A { + raw: &'static mut Archive, +} +struct Iter<'a> { + raw: &'a mut ArchiveIterator<'a>, +} +struct C<'a> { + raw: &'a mut ArchiveChild<'a>, +} + +impl A { + pub fn iter(&self) -> Iter<'_> { + panic!() + } +} +impl Drop for A { + fn drop(&mut self) {} +} +impl<'a> Drop for C<'a> { + fn drop(&mut self) {} +} + +impl<'a> Iterator for Iter<'a> { + type Item = C<'a>; + fn next(&mut self) -> Option> { + panic!() + } +} + +fn error(archive: &A) { + let mut members: Vec<&mut ArchiveChild<'_>> = vec![]; + for child in archive.iter() { + members.push(child.raw); + //~^ ERROR borrow may still be in use when destructor runs [E0713] + } + members.len(); +} + +fn main() {} diff --git a/src/test/ui/nll/issue-53773.stderr b/src/test/ui/nll/issue-53773.stderr new file mode 100644 index 00000000000..92a9946068c --- /dev/null +++ b/src/test/ui/nll/issue-53773.stderr @@ -0,0 +1,16 @@ +error[E0713]: borrow may still be in use when destructor runs + --> $DIR/issue-53773.rs:43:22 + | +LL | members.push(child.raw); + | ^^^^^^^^^ +LL | //~^ ERROR borrow may still be in use when destructor runs [E0713] +LL | } + | - here, drop of `child` needs exclusive access to `*child.raw`, because the type `C<'_>` implements the `Drop` trait +LL | members.len(); + | ------- borrow later used here + | + = note: consider using a `let` binding to create a longer lived value + +error: aborting due to previous error + +For more information about this error, try `rustc --explain E0713`. diff --git a/src/test/ui/rfc-2005-default-binding-mode/borrowck-issue-49631.nll.stderr b/src/test/ui/rfc-2005-default-binding-mode/borrowck-issue-49631.nll.stderr index 9e242712b9e..3a6f66ca4da 100644 --- a/src/test/ui/rfc-2005-default-binding-mode/borrowck-issue-49631.nll.stderr +++ b/src/test/ui/rfc-2005-default-binding-mode/borrowck-issue-49631.nll.stderr @@ -7,7 +7,7 @@ LL | foo.mutate(); | ^^^^^^^^^^^^ mutable borrow occurs here LL | //~^ ERROR cannot borrow `foo` as mutable LL | println!("foo={:?}", *string); - | ------- immutable borrow used here, in later iteration of loop + | ------- immutable borrow later used here error: aborting due to previous error diff --git a/src/test/ui/span/regions-escape-loop-via-variable.nll.stderr b/src/test/ui/span/regions-escape-loop-via-variable.nll.stderr index 841e3c48414..42df6685297 100644 --- a/src/test/ui/span/regions-escape-loop-via-variable.nll.stderr +++ b/src/test/ui/span/regions-escape-loop-via-variable.nll.stderr @@ -2,7 +2,7 @@ error[E0597]: `x` does not live long enough --> $DIR/regions-escape-loop-via-variable.rs:11:13 | LL | let x = 1 + *p; - | -- borrow used here, in later iteration of loop + | -- borrow later used here LL | p = &x; | ^^ borrowed value does not live long enough LL | } diff --git a/src/test/ui/span/regions-escape-loop-via-vec.nll.stderr b/src/test/ui/span/regions-escape-loop-via-vec.nll.stderr index ea64828fedd..e07fb727782 100644 --- a/src/test/ui/span/regions-escape-loop-via-vec.nll.stderr +++ b/src/test/ui/span/regions-escape-loop-via-vec.nll.stderr @@ -7,7 +7,7 @@ LL | while x < 10 { //~ ERROR cannot use `x` because it was mutably borrowed | ^ use of borrowed `x` LL | let mut z = x; //~ ERROR cannot use `x` because it was mutably borrowed LL | _y.push(&mut z); - | -- borrow used here, in later iteration of loop + | -- borrow later used here error[E0503]: cannot use `x` because it was mutably borrowed --> $DIR/regions-escape-loop-via-vec.rs:6:21 @@ -18,7 +18,7 @@ LL | while x < 10 { //~ ERROR cannot use `x` because it was mutably borrowed LL | let mut z = x; //~ ERROR cannot use `x` because it was mutably borrowed | ^ use of borrowed `x` LL | _y.push(&mut z); - | -- borrow used here, in later iteration of loop + | -- borrow later used here error[E0597]: `z` does not live long enough --> $DIR/regions-escape-loop-via-vec.rs:7:17 @@ -26,7 +26,7 @@ error[E0597]: `z` does not live long enough LL | _y.push(&mut z); | -- ^^^^^^ borrowed value does not live long enough | | - | borrow used here, in later iteration of loop + | borrow later used here ... LL | } | - `z` dropped here while still borrowed @@ -38,7 +38,7 @@ LL | let mut _y = vec![&mut x]; | ------ borrow of `x` occurs here ... LL | _y.push(&mut z); - | -- borrow used here, in later iteration of loop + | -- borrow later used here LL | //~^ ERROR `z` does not live long enough LL | x += 1; //~ ERROR cannot assign | ^^^^^^ use of borrowed `x` diff --git a/src/test/ui/vec/vec-mut-iter-borrow.nll.stderr b/src/test/ui/vec/vec-mut-iter-borrow.nll.stderr index 73cddd8d680..c77be26f019 100644 --- a/src/test/ui/vec/vec-mut-iter-borrow.nll.stderr +++ b/src/test/ui/vec/vec-mut-iter-borrow.nll.stderr @@ -5,7 +5,7 @@ LL | for x in &mut xs { | ------- | | | first mutable borrow occurs here - | first borrow used here, in later iteration of loop + | first borrow later used here LL | xs.push(1) //~ ERROR cannot borrow `xs` | ^^ second mutable borrow occurs here From a12982cdc2fee3d892015ee981a2f98481f831f0 Mon Sep 17 00:00:00 2001 From: Santiago Pastorino Date: Wed, 20 Feb 2019 12:15:27 -0300 Subject: [PATCH 3/3] Run rustfmt --- .../borrow_check/nll/explain_borrow/mod.rs | 268 ++++++++++-------- 1 file changed, 153 insertions(+), 115 deletions(-) diff --git a/src/librustc_mir/borrow_check/nll/explain_borrow/mod.rs b/src/librustc_mir/borrow_check/nll/explain_borrow/mod.rs index 86cab6cbfb2..8ea249959dd 100644 --- a/src/librustc_mir/borrow_check/nll/explain_borrow/mod.rs +++ b/src/librustc_mir/borrow_check/nll/explain_borrow/mod.rs @@ -2,15 +2,14 @@ use std::collections::VecDeque; use crate::borrow_check::borrow_set::BorrowData; use crate::borrow_check::error_reporting::UseSpans; -use crate::borrow_check::nll::ConstraintDescription; use crate::borrow_check::nll::region_infer::{Cause, RegionName}; +use crate::borrow_check::nll::ConstraintDescription; use crate::borrow_check::{Context, MirBorrowckCtxt, WriteKind}; -use rustc::ty::{self, TyCtxt}; use rustc::mir::{ - CastKind, ConstraintCategory, FakeReadCause, Local, Location, Mir, Operand, - Place, Projection, ProjectionElem, Rvalue, Statement, StatementKind, - TerminatorKind + CastKind, ConstraintCategory, FakeReadCause, Local, Location, Mir, Operand, Place, Projection, + ProjectionElem, Rvalue, Statement, StatementKind, TerminatorKind, }; +use rustc::ty::{self, TyCtxt}; use rustc_data_structures::fx::FxHashSet; use rustc_errors::DiagnosticBuilder; use syntax_pos::Span; @@ -63,50 +62,58 @@ impl BorrowExplanation { let message = match later_use_kind { LaterUseKind::TraitCapture => "borrow later captured here by trait object", LaterUseKind::ClosureCapture => "borrow later captured here by closure", - LaterUseKind::Call => "borrow later used by call", + LaterUseKind::Call => "borrow later used by call", LaterUseKind::FakeLetRead => "borrow later stored here", LaterUseKind::Other => "borrow later used here", }; err.span_label(var_or_use_span, format!("{}{}", borrow_desc, message)); - }, + } BorrowExplanation::UsedLaterInLoop(later_use_kind, var_or_use_span) => { let message = match later_use_kind { - LaterUseKind::TraitCapture => - "borrow captured here by trait object, in later iteration of loop", - LaterUseKind::ClosureCapture => - "borrow captured here by closure, in later iteration of loop", - LaterUseKind::Call => "borrow used by call, in later iteration of loop", + LaterUseKind::TraitCapture => { + "borrow captured here by trait object, in later iteration of loop" + } + LaterUseKind::ClosureCapture => { + "borrow captured here by closure, in later iteration of loop" + } + LaterUseKind::Call => "borrow used by call, in later iteration of loop", LaterUseKind::FakeLetRead => "borrow later stored here", LaterUseKind::Other => "borrow used here, in later iteration of loop", }; err.span_label(var_or_use_span, format!("{}{}", borrow_desc, message)); - }, - BorrowExplanation::UsedLaterWhenDropped { drop_loc, dropped_local, - should_note_order } => - { + } + BorrowExplanation::UsedLaterWhenDropped { + drop_loc, + dropped_local, + should_note_order, + } => { let local_decl = &mir.local_decls[dropped_local]; let (dtor_desc, type_desc) = match local_decl.ty.sty { // If type is an ADT that implements Drop, then // simplify output by reporting just the ADT name. - ty::Adt(adt, _substs) if adt.has_dtor(tcx) && !adt.is_box() => - ("`Drop` code", format!("type `{}`", tcx.item_path_str(adt.did))), + ty::Adt(adt, _substs) if adt.has_dtor(tcx) && !adt.is_box() => ( + "`Drop` code", + format!("type `{}`", tcx.item_path_str(adt.did)), + ), // Otherwise, just report the whole type (and use // the intentionally fuzzy phrase "destructor") - ty::Closure(..) => - ("destructor", "closure".to_owned()), - ty::Generator(..) => - ("destructor", "generator".to_owned()), + ty::Closure(..) => ("destructor", "closure".to_owned()), + ty::Generator(..) => ("destructor", "generator".to_owned()), _ => ("destructor", format!("type `{}`", local_decl.ty)), }; match local_decl.name { Some(local_name) => { - let message = - format!("{B}borrow might be used here, when `{LOC}` is dropped \ - and runs the {DTOR} for {TYPE}", - B=borrow_desc, LOC=local_name, TYPE=type_desc, DTOR=dtor_desc); + let message = format!( + "{B}borrow might be used here, when `{LOC}` is dropped \ + and runs the {DTOR} for {TYPE}", + B = borrow_desc, + LOC = local_name, + TYPE = type_desc, + DTOR = dtor_desc + ); err.span_label(mir.source_info(drop_loc).span, message); if should_note_order { @@ -117,15 +124,22 @@ impl BorrowExplanation { } } None => { - err.span_label(local_decl.source_info.span, - format!("a temporary with access to the {B}borrow \ - is created here ...", - B=borrow_desc)); - let message = - format!("... and the {B}borrow might be used here, \ - when that temporary is dropped \ - and runs the {DTOR} for {TYPE}", - B=borrow_desc, TYPE=type_desc, DTOR=dtor_desc); + err.span_label( + local_decl.source_info.span, + format!( + "a temporary with access to the {B}borrow \ + is created here ...", + B = borrow_desc + ), + ); + let message = format!( + "... and the {B}borrow might be used here, \ + when that temporary is dropped \ + and runs the {DTOR} for {TYPE}", + B = borrow_desc, + TYPE = type_desc, + DTOR = dtor_desc + ); err.span_label(mir.source_info(drop_loc).span, message); if let Some(info) = &local_decl.is_block_tail { @@ -149,7 +163,7 @@ impl BorrowExplanation { } } } - }, + } BorrowExplanation::MustBeValidFor { category, span, @@ -160,18 +174,28 @@ impl BorrowExplanation { region_name.highlight_region_name(err); if let Some(desc) = opt_place_desc { - err.span_label(span, format!( - "{}requires that `{}` is borrowed for `{}`", - category.description(), desc, region_name, - )); + err.span_label( + span, + format!( + "{}requires that `{}` is borrowed for `{}`", + category.description(), + desc, + region_name, + ), + ); } else { - err.span_label(span, format!( - "{}requires that {}borrow lasts for `{}`", - category.description(), borrow_desc, region_name, - )); + err.span_label( + span, + format!( + "{}requires that {}borrow lasts for `{}`", + category.description(), + borrow_desc, + region_name, + ), + ); }; - }, - _ => {}, + } + _ => {} } } } @@ -217,10 +241,11 @@ impl<'cx, 'gcx, 'tcx> MirBorrowckCtxt<'cx, 'gcx, 'tcx> { region_sub ); - match find_use::find(mir, regioncx, tcx, region_sub, context.loc) { + match find_use::find(mir, regioncx, tcx, region_sub, context.loc) { Some(Cause::LiveVar(local, location)) => { let span = mir.source_info(location).span; - let spans = self.move_spans(&Place::Local(local), location) + let spans = self + .move_spans(&Place::Local(local), location) .or_else(|| self.borrow_spans(span, location)); let borrow_location = context.loc; @@ -236,55 +261,56 @@ impl<'cx, 'gcx, 'tcx> MirBorrowckCtxt<'cx, 'gcx, 'tcx> { } } - Some(Cause::DropVar(local, location)) => { - let mut should_note_order = false; - if mir.local_decls[local].name.is_some() { - if let Some((WriteKind::StorageDeadOrDrop, place)) = kind_place { - if let Place::Local(borrowed_local) = place { - let dropped_local_scope = mir.local_decls[local].visibility_scope; - let borrowed_local_scope = - mir.local_decls[*borrowed_local].visibility_scope; + Some(Cause::DropVar(local, location)) => { + let mut should_note_order = false; + if mir.local_decls[local].name.is_some() { + if let Some((WriteKind::StorageDeadOrDrop, place)) = kind_place { + if let Place::Local(borrowed_local) = place { + let dropped_local_scope = mir.local_decls[local].visibility_scope; + let borrowed_local_scope = + mir.local_decls[*borrowed_local].visibility_scope; - if mir.is_sub_scope(borrowed_local_scope, dropped_local_scope) - && local != *borrowed_local - { - should_note_order = true; - } - } - } - } + if mir.is_sub_scope(borrowed_local_scope, dropped_local_scope) + && local != *borrowed_local + { + should_note_order = true; + } + } + } + } - BorrowExplanation::UsedLaterWhenDropped { - drop_loc: location, - dropped_local: local, - should_note_order, - } + BorrowExplanation::UsedLaterWhenDropped { + drop_loc: location, + dropped_local: local, + should_note_order, + } } - None => if let Some(region) = regioncx.to_error_region_vid(borrow_region_vid) { - let (category, from_closure, span, region_name) = self - .nonlexical_regioncx - .free_region_constraint_info( - self.mir, - self.mir_def_id, - self.infcx, - borrow_region_vid, - region, - ); - if let Some(region_name) = region_name { - let opt_place_desc = self.describe_place(&borrow.borrowed_place); - BorrowExplanation::MustBeValidFor { - category, - from_closure, - span, - region_name, - opt_place_desc, + None => { + if let Some(region) = regioncx.to_error_region_vid(borrow_region_vid) { + let (category, from_closure, span, region_name) = + self.nonlexical_regioncx.free_region_constraint_info( + self.mir, + self.mir_def_id, + self.infcx, + borrow_region_vid, + region, + ); + if let Some(region_name) = region_name { + let opt_place_desc = self.describe_place(&borrow.borrowed_place); + BorrowExplanation::MustBeValidFor { + category, + from_closure, + span, + region_name, + opt_place_desc, + } + } else { + BorrowExplanation::Unexplained } } else { BorrowExplanation::Unexplained } - } else { - BorrowExplanation::Unexplained } } } @@ -427,27 +453,31 @@ impl<'cx, 'gcx, 'tcx> MirBorrowckCtxt<'cx, 'gcx, 'tcx> { &self, borrow: &BorrowData<'tcx>, use_spans: UseSpans, - location: Location + location: Location, ) -> (LaterUseKind, Span) { match use_spans { UseSpans::ClosureUse { var_span, .. } => { // Used in a closure. (LaterUseKind::ClosureCapture, var_span) - }, + } UseSpans::OtherUse(span) => { let block = &self.mir.basic_blocks()[location.block]; let kind = if let Some(&Statement { kind: StatementKind::FakeRead(FakeReadCause::ForLet, _), .. - }) = block.statements.get(location.statement_index) { + }) = block.statements.get(location.statement_index) + { LaterUseKind::FakeLetRead } else if self.was_captured_by_trait_object(borrow) { LaterUseKind::TraitCapture } else if location.statement_index == block.statements.len() { if let TerminatorKind::Call { - ref func, from_hir_call: true, .. - } = block.terminator().kind { + ref func, + from_hir_call: true, + .. + } = block.terminator().kind + { // Just point to the function, to reduce the chance of overlapping spans. let function_span = match func { Operand::Constant(c) => c.span, @@ -458,7 +488,7 @@ impl<'cx, 'gcx, 'tcx> MirBorrowckCtxt<'cx, 'gcx, 'tcx> { } else { span } - }, + } _ => span, }; return (LaterUseKind::Call, function_span); @@ -482,7 +512,10 @@ impl<'cx, 'gcx, 'tcx> MirBorrowckCtxt<'cx, 'gcx, 'tcx> { let location = borrow.reserve_location; let block = &self.mir[location.block]; let stmt = block.statements.get(location.statement_index); - debug!("was_captured_by_trait_object: location={:?} stmt={:?}", location, stmt); + debug!( + "was_captured_by_trait_object: location={:?} stmt={:?}", + location, stmt + ); // We make a `queue` vector that has the locations we want to visit. As of writing, this // will only ever have one item at any given time, but by using a vector, we can pop from @@ -491,13 +524,17 @@ impl<'cx, 'gcx, 'tcx> MirBorrowckCtxt<'cx, 'gcx, 'tcx> { let mut target = if let Some(&Statement { kind: StatementKind::Assign(Place::Local(local), _), .. - }) = stmt { + }) = stmt + { local } else { return false; }; - debug!("was_captured_by_trait: target={:?} queue={:?}", target, queue); + debug!( + "was_captured_by_trait: target={:?} queue={:?}", + target, queue + ); while let Some(current_location) = queue.pop() { debug!("was_captured_by_trait: target={:?}", target); let block = &self.mir[current_location.block]; @@ -508,55 +545,55 @@ impl<'cx, 'gcx, 'tcx> MirBorrowckCtxt<'cx, 'gcx, 'tcx> { debug!("was_captured_by_trait_object: stmt={:?}", stmt); // The only kind of statement that we care about is assignments... - if let StatementKind::Assign( - place, - box rvalue, - ) = &stmt.kind { + if let StatementKind::Assign(place, box rvalue) = &stmt.kind { let into = match place { Place::Local(into) => into, Place::Projection(box Projection { base: Place::Local(into), elem: ProjectionElem::Deref, }) => into, - _ => { + _ => { // Continue at the next location. queue.push(current_location.successor_within_block()); continue; - }, + } }; match rvalue { // If we see a use, we should check whether it is our data, and if so // update the place that we're looking for to that new place. Rvalue::Use(operand) => match operand { - Operand::Copy(Place::Local(from)) | - Operand::Move(Place::Local(from)) if *from == target => { + Operand::Copy(Place::Local(from)) + | Operand::Move(Place::Local(from)) + if *from == target => + { target = *into; - }, - _ => {}, + } + _ => {} }, // If we see a unsized cast, then if it is our data we should check // whether it is being cast to a trait object. Rvalue::Cast(CastKind::Unsize, operand, ty) => match operand { - Operand::Copy(Place::Local(from)) | - Operand::Move(Place::Local(from)) if *from == target => { + Operand::Copy(Place::Local(from)) + | Operand::Move(Place::Local(from)) + if *from == target => + { debug!("was_captured_by_trait_object: ty={:?}", ty); // Check the type for a trait object. return match ty.sty { // `&dyn Trait` ty::TyKind::Ref(_, ty, _) if ty.is_trait() => true, // `Box` - _ if ty.is_box() && ty.boxed_ty().is_trait() => - true, + _ if ty.is_box() && ty.boxed_ty().is_trait() => true, // `dyn Trait` _ if ty.is_trait() => true, // Anything else. _ => false, }; - }, + } _ => return false, }, - _ => {}, + _ => {} } } @@ -571,7 +608,8 @@ impl<'cx, 'gcx, 'tcx> MirBorrowckCtxt<'cx, 'gcx, 'tcx> { destination: Some((Place::Local(dest), block)), args, .. - } = &terminator.kind { + } = &terminator.kind + { debug!( "was_captured_by_trait_object: target={:?} dest={:?} args={:?}", target, dest, args