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Track unused mutable variables across closures

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This commit is contained in:
Keith Yeung 2018-03-02 20:42:37 -08:00
parent 3e423d0586
commit 5a2b590ec0
7 changed files with 189 additions and 49 deletions
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5
src/librustc/ich/impls_mir.rs
View file

@ -563,6 +563,11 @@ impl<'a, 'gcx> HashStable<StableHashingContext<'a>> for mir::Literal<'gcx> {
impl_stable_hash_for!(struct mir::Location { block, statement_index });
impl_stable_hash_for!(struct mir::BorrowCheckResult<'tcx> {
closure_requirements,
used_mut_upvars
});
impl_stable_hash_for!(struct mir::ClosureRegionRequirements<'tcx> {
num_external_vids,
outlives_requirements

7
src/librustc/mir/mod.rs
View file

@ -21,6 +21,7 @@ use rustc_data_structures::indexed_vec::{IndexVec, Idx};
use rustc_data_structures::control_flow_graph::dominators::{Dominators, dominators};
use rustc_data_structures::control_flow_graph::{GraphPredecessors, GraphSuccessors};
use rustc_data_structures::control_flow_graph::ControlFlowGraph;
use rustc_data_structures::small_vec::SmallVec;
use rustc_serialize as serialize;
use hir::def::CtorKind;
use hir::def_id::DefId;
@ -2043,6 +2044,12 @@ pub struct GeneratorLayout<'tcx> {
pub fields: Vec<LocalDecl<'tcx>>,
}
#[derive(Clone, Debug, RustcEncodable, RustcDecodable)]
pub struct BorrowCheckResult<'gcx> {
pub closure_requirements: Option<ClosureRegionRequirements<'gcx>>,
pub used_mut_upvars: SmallVec<[Field; 8]>,
}
/// After we borrow check a closure, we are left with various
/// requirements that we have inferred between the free regions that
/// appear in the closure's signature or on its field types. These

2
src/librustc/ty/maps/mod.rs
View file

@ -211,7 +211,7 @@ define_maps! { <'tcx>
/// Borrow checks the function body. If this is a closure, returns
/// additional requirements that the closure's creator must verify.
[] fn mir_borrowck: MirBorrowCheck(DefId) -> Option<mir::ClosureRegionRequirements<'tcx>>,
[] fn mir_borrowck: MirBorrowCheck(DefId) -> mir::BorrowCheckResult<'tcx>,
/// Gets a complete map from all types to their inherent impls.
/// Not meant to be used directly outside of coherence.

103
src/librustc_mir/borrow_check/mod.rs
View file

@ -18,15 +18,16 @@ use rustc::infer::InferCtxt;
use rustc::ty::{self, ParamEnv, TyCtxt};
use rustc::ty::maps::Providers;
use rustc::lint::builtin::UNUSED_MUT;
use rustc::mir::{AssertMessage, BasicBlock, BorrowKind, ClearCrossCrate, Local};
use rustc::mir::{Location, Place, Mir, Mutability, Operand, Projection, ProjectionElem};
use rustc::mir::{Rvalue, Field, Statement, StatementKind, Terminator, TerminatorKind};
use rustc::mir::ClosureRegionRequirements;
use rustc::mir::{AssertMessage, AggregateKind, BasicBlock, BorrowCheckResult, BorrowKind};
use rustc::mir::{ClearCrossCrate, Local, Location, Place, Mir, Mutability, Operand};
use rustc::mir::{Projection, ProjectionElem, Rvalue, Field, Statement, StatementKind};
use rustc::mir::{Terminator, TerminatorKind};
use rustc_data_structures::control_flow_graph::dominators::Dominators;
use rustc_data_structures::fx::FxHashSet;
use rustc_data_structures::indexed_set::IdxSetBuf;
use rustc_data_structures::indexed_vec::Idx;
use rustc_data_structures::small_vec::SmallVec;
use std::rc::Rc;
@ -70,12 +71,15 @@ pub fn provide(providers: &mut Providers) {
fn mir_borrowck<'a, 'tcx>(
tcx: TyCtxt<'a, 'tcx, 'tcx>,
def_id: DefId,
) -> Option<ClosureRegionRequirements<'tcx>> {
) -> BorrowCheckResult<'tcx> {
let input_mir = tcx.mir_validated(def_id);
debug!("run query mir_borrowck: {}", tcx.item_path_str(def_id));
if !tcx.has_attr(def_id, "rustc_mir_borrowck") && !tcx.use_mir_borrowck() {
return None;
return BorrowCheckResult {
closure_requirements: None,
used_mut_upvars: SmallVec::new(),
};
}
let opt_closure_req = tcx.infer_ctxt().enter(|infcx| {
@ -91,7 +95,7 @@ fn do_mir_borrowck<'a, 'gcx, 'tcx>(
infcx: &InferCtxt<'a, 'gcx, 'tcx>,
input_mir: &Mir<'gcx>,
def_id: DefId,
) -> Option<ClosureRegionRequirements<'gcx>> {
) -> BorrowCheckResult<'gcx> {
let tcx = infcx.tcx;
let attributes = tcx.get_attrs(def_id);
let param_env = tcx.param_env(def_id);
@ -239,6 +243,7 @@ fn do_mir_borrowck<'a, 'gcx, 'tcx>(
moved_error_reported: FxHashSet(),
nonlexical_regioncx: opt_regioncx,
used_mut: FxHashSet(),
used_mut_upvars: SmallVec::new(),
nonlexical_cause_info: None,
borrow_set,
dominators,
@ -254,7 +259,28 @@ fn do_mir_borrowck<'a, 'gcx, 'tcx>(
mbcx.analyze_results(&mut state); // entry point for DataflowResultsConsumer
opt_closure_req
debug!("mbcx.used_mut: {:?}", mbcx.used_mut);
for local in mbcx.mir.mut_vars_iter().filter(|local| !mbcx.used_mut.contains(local)) {
if let ClearCrossCrate::Set(ref vsi) = mbcx.mir.visibility_scope_info {
let source_info = mbcx.mir.local_decls[local].source_info;
let mut_span = tcx.sess.codemap().span_until_non_whitespace(source_info.span);
tcx.struct_span_lint_node(
UNUSED_MUT,
vsi[source_info.scope].lint_root,
source_info.span,
"variable does not need to be mutable"
)
.span_suggestion_short(mut_span, "remove this `mut`", "".to_owned())
.emit();
}
}
BorrowCheckResult {
closure_requirements: opt_closure_req,
used_mut_upvars: mbcx.used_mut_upvars,
}
}
#[allow(dead_code)]
@ -292,6 +318,9 @@ pub struct MirBorrowckCtxt<'cx, 'gcx: 'tcx, 'tcx: 'cx> {
/// This field keeps track of all the local variables that are declared mut and are mutated.
/// Used for the warning issued by an unused mutable local variable.
used_mut: FxHashSet<Local>,
/// If the function we're checking is a closure, then we'll need to report back the list of
/// mutable upvars that have been used. This field keeps track of them.
used_mut_upvars: SmallVec<[Field; 8]>,
/// Non-lexical region inference context, if NLL is enabled. This
/// contains the results from region inference and lets us e.g.
/// find out which CFG points are contained in each borrow region.
@ -439,22 +468,6 @@ impl<'cx, 'gcx, 'tcx> DataflowResultsConsumer<'cx, 'tcx> for MirBorrowckCtxt<'cx
self.check_activations(location, span, flow_state);
for local in self.mir.mut_vars_iter().filter(|local| !self.used_mut.contains(local)) {
if let ClearCrossCrate::Set(ref vsi) = self.mir.visibility_scope_info {
let source_info = self.mir.local_decls[local].source_info;
let mut_span = self.tcx.sess.codemap().span_until_non_whitespace(source_info.span);
self.tcx.struct_span_lint_node(
UNUSED_MUT,
vsi[source_info.scope].lint_root,
source_info.span,
"variable does not need to be mutable"
)
.span_suggestion_short(mut_span, "remove this `mut`", "".to_owned())
.emit();
}
}
match term.kind {
TerminatorKind::SwitchInt {
ref discr,
@ -1118,9 +1131,33 @@ impl<'cx, 'gcx, 'tcx> MirBorrowckCtxt<'cx, 'gcx, 'tcx> {
// `NullOp::Box`?
}
Rvalue::Aggregate(ref _aggregate_kind, ref operands) => for operand in operands {
self.consume_operand(context, (operand, span), flow_state);
},
Rvalue::Aggregate(ref aggregate_kind, ref operands) => {
// We need to report back the list of mutable upvars that were
// moved into the closure and subsequently used by the closure,
// in order to populate our used_mut set.
if let AggregateKind::Closure(def_id, _) = &**aggregate_kind {
let BorrowCheckResult { used_mut_upvars, .. } = self.tcx.mir_borrowck(*def_id);
for field in used_mut_upvars {
match operands[field.index()] {
Operand::Move(Place::Local(local)) => {
self.used_mut.insert(local);
}
Operand::Move(Place::Projection(ref proj)) => {
if let Some(field) = self.is_upvar_field_projection(&proj.base) {
self.used_mut_upvars.push(field);
}
}
Operand::Move(Place::Static(..)) |
Operand::Copy(..) |
Operand::Constant(..) => {}
}
}
}
for operand in operands {
self.consume_operand(context, (operand, span), flow_state);
}
}
}
}
@ -1652,8 +1689,16 @@ impl<'cx, 'gcx, 'tcx> MirBorrowckCtxt<'cx, 'gcx, 'tcx> {
err.emit();
},
Reservation(WriteKind::Mutate) | Write(WriteKind::Mutate) => {
if let Place::Local(local) = *place {
self.used_mut.insert(local);
match place {
Place::Local(local) => {
self.used_mut.insert(*local);
}
Place::Projection(ref proj) => {
if let Some(field) = self.is_upvar_field_projection(&proj.base) {
self.used_mut_upvars.push(field);
}
}
Place::Static(..) => {}
}
if let Err(place_err) = self.is_mutable(place, is_local_mutation_allowed) {
error_reported = true;

4
src/librustc_mir/borrow_check/nll/type_check/mod.rs
View file

@ -1426,7 +1426,9 @@ impl<'a, 'gcx, 'tcx> TypeChecker<'a, 'gcx, 'tcx> {
// these extra requirements are basically like where
// clauses on the struct.
AggregateKind::Closure(def_id, substs) => {
if let Some(closure_region_requirements) = tcx.mir_borrowck(*def_id) {
if let Some(closure_region_requirements) =
tcx.mir_borrowck(*def_id).closure_requirements
{
closure_region_requirements.apply_requirements(
self.infcx,
self.body_id,

61
src/test/compile-fail/lint-unused-mut-variables.rs
View file

@ -8,6 +8,9 @@
// option. This file may not be copied, modified, or distributed
// except according to those terms.
// revisions: lexical nll
#![cfg_attr(nll, feature(nll))]
// Exercise the unused_mut attribute in some positive and negative cases
#![allow(unused_assignments)]
@ -18,15 +21,22 @@
fn main() {
// negative cases
let mut a = 3; //~ ERROR: variable does not need to be mutable
let mut a = 2; //~ ERROR: variable does not need to be mutable
let mut b = 3; //~ ERROR: variable does not need to be mutable
let mut a = vec![3]; //~ ERROR: variable does not need to be mutable
let (mut a, b) = (1, 2); //~ ERROR: variable does not need to be mutable
let mut a; //~ ERROR: variable does not need to be mutable
let mut a = 3; //[lexical]~ ERROR: variable does not need to be mutable
//[nll]~^ ERROR: variable does not need to be mutable
let mut a = 2; //[lexical]~ ERROR: variable does not need to be mutable
//[nll]~^ ERROR: variable does not need to be mutable
let mut b = 3; //[lexical]~ ERROR: variable does not need to be mutable
//[nll]~^ ERROR: variable does not need to be mutable
let mut a = vec![3]; //[lexical]~ ERROR: variable does not need to be mutable
//[nll]~^ ERROR: variable does not need to be mutable
let (mut a, b) = (1, 2); //[lexical]~ ERROR: variable does not need to be mutable
//[nll]~^ ERROR: variable does not need to be mutable
let mut a; //[lexical]~ ERROR: variable does not need to be mutable
//[nll]~^ ERROR: variable does not need to be mutable
a = 3;
let mut b; //~ ERROR: variable does not need to be mutable
let mut b; //[lexical]~ ERROR: variable does not need to be mutable
//[nll]~^ ERROR: variable does not need to be mutable
if true {
b = 3;
} else {
@ -34,37 +44,45 @@ fn main() {
}
match 30 {
mut x => {} //~ ERROR: variable does not need to be mutable
mut x => {} //[lexical]~ ERROR: variable does not need to be mutable
//[nll]~^ ERROR: variable does not need to be mutable
}
match (30, 2) {
(mut x, 1) | //~ ERROR: variable does not need to be mutable
(mut x, 1) | //[lexical]~ ERROR: variable does not need to be mutable
//[nll]~^ ERROR: variable does not need to be mutable
(mut x, 2) |
(mut x, 3) => {
}
_ => {}
}
let x = |mut y: isize| 10; //~ ERROR: variable does not need to be mutable
fn what(mut foo: isize) {} //~ ERROR: variable does not need to be mutable
let x = |mut y: isize| 10; //[lexical]~ ERROR: variable does not need to be mutable
//[nll]~^ ERROR: variable does not need to be mutable
fn what(mut foo: isize) {} //[lexical]~ ERROR: variable does not need to be mutable
//[nll]~^ ERROR: variable does not need to be mutable
let mut a = &mut 5; //~ ERROR: variable does not need to be mutable
let mut a = &mut 5; //[lexical]~ ERROR: variable does not need to be mutable
//[nll]~^ ERROR: variable does not need to be mutable
*a = 4;
let mut a = 5;
let mut b = (&mut a,);
*b.0 = 4; //~^ ERROR: variable does not need to be mutable
let mut b = (&mut a,); //[lexical]~ ERROR: variable does not need to be mutable
*b.0 = 4; //[nll]~^ ERROR: variable does not need to be mutable
let mut x = &mut 1; //~ ERROR: variable does not need to be mutable
let mut x = &mut 1; //[lexical]~ ERROR: variable does not need to be mutable
//[nll]~^ ERROR: variable does not need to be mutable
let mut f = || {
*x += 1;
};
f();
fn mut_ref_arg(mut arg : &mut [u8]) -> &mut [u8] {
&mut arg[..] //~^ ERROR: variable does not need to be mutable
&mut arg[..] //[lexical]~^ ERROR: variable does not need to be mutable
//[nll]~^^ ERROR: variable does not need to be mutable
}
let mut v : &mut Vec<()> = &mut vec![]; //~ ERROR: variable does not need to be mutable
let mut v : &mut Vec<()> = &mut vec![]; //[lexical]~ ERROR: variable does not need to be mutable
//[nll]~^ ERROR: variable does not need to be mutable
v.push(());
// positive cases
@ -76,6 +94,12 @@ fn main() {
callback(|| {
a.push(3);
});
let mut a = Vec::new();
callback(|| {
callback(|| {
a.push(3);
});
});
let (mut a, b) = (1, 2);
a = 34;
@ -116,5 +140,6 @@ fn foo(mut a: isize) {
fn bar() {
#[allow(unused_mut)]
let mut a = 3;
let mut b = vec![2]; //~ ERROR: variable does not need to be mutable
let mut b = vec![2]; //[lexical]~ ERROR: variable does not need to be mutable
//[nll]~^ ERROR: variable does not need to be mutable
}

56
src/test/run-pass/borrowck/borrowck-unused-mut-locals.rs Normal file
View file

@ -0,0 +1,56 @@
// Copyright 2015 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.
#![feature(nll)]
#![deny(unused_mut)]
#[derive(Debug)]
struct A {}
fn init_a() -> A {
A {}
}
#[derive(Debug)]
struct B<'a> {
ed: &'a mut A,
}
fn init_b<'a>(ed: &'a mut A) -> B<'a> {
B { ed }
}
#[derive(Debug)]
struct C<'a> {
pd: &'a mut B<'a>,
}
fn init_c<'a>(pd: &'a mut B<'a>) -> C<'a> {
C { pd }
}
#[derive(Debug)]
struct D<'a> {
sd: &'a mut C<'a>,
}
fn init_d<'a>(sd: &'a mut C<'a>) -> D<'a> {
D { sd }
}
fn main() {
let mut a = init_a();
let mut b = init_b(&mut a);
let mut c = init_c(&mut b);
let d = init_d(&mut c);
println!("{:?}", d)
}