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also check let arms and nested patterns for mutable borrows

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This commit is contained in:
Niko Matsakis 2018-06-01 09:41:44 -04:00
parent 577a5b2703
commit a667049c33
5 changed files with 211 additions and 5 deletions
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16
src/librustc/middle/mem_categorization.rs
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@ -936,16 +936,32 @@ impl<'a, 'gcx, 'tcx> MemCategorizationContext<'a, 'gcx, 'tcx> {
span: Span,
expr_ty: Ty<'tcx>)
-> cmt_<'tcx> {
debug!(
"cat_rvalue_node(id={:?}, span={:?}, expr_ty={:?})",
id,
span,
expr_ty,
);
let hir_id = self.tcx.hir.node_to_hir_id(id);
let promotable = self.rvalue_promotable_map.as_ref().map(|m| m.contains(&hir_id.local_id))
.unwrap_or(false);
debug!(
"cat_rvalue_node: promotable = {:?}",
promotable,
);
// Always promote `[T; 0]` (even when e.g. borrowed mutably).
let promotable = match expr_ty.sty {
ty::TyArray(_, len) if len.assert_usize(self.tcx) == Some(0) => true,
_ => promotable,
};
debug!(
"cat_rvalue_node: promotable = {:?} (2)",
promotable,
);
// Compute maximum lifetime of this rvalue. This is 'static if
// we can promote to a constant, otherwise equal to enclosing temp
// lifetime.

39
src/librustc_passes/rvalue_promotion.rs
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@ -150,6 +150,23 @@ impl<'a, 'gcx> CheckCrateVisitor<'a, 'gcx> {
span.allows_unstable();
}
}
/// While the `ExprUseVisitor` walks, we will identify which
/// expressions are borrowed, and insert their ids into this
/// table. Actually, we insert the "borrow-id", which is normally
/// the id of the expession being borrowed: but in the case of
/// `ref mut` borrows, the `id` of the pattern is
/// inserted. Therefore later we remove that entry from the table
/// and transfer it over to the value being matched. This will
/// then prevent said value from being promoted.
fn remove_mut_rvalue_borrow(&mut self, pat: &hir::Pat) -> bool {
let mut any_removed = false;
pat.walk(|p| {
any_removed |= self.mut_rvalue_borrows.remove(&p.id);
true
});
any_removed
}
}
impl<'a, 'tcx> Visitor<'tcx> for CheckCrateVisitor<'a, 'tcx> {
@ -200,9 +217,15 @@ impl<'a, 'tcx> Visitor<'tcx> for CheckCrateVisitor<'a, 'tcx> {
fn visit_stmt(&mut self, stmt: &'tcx hir::Stmt) {
match stmt.node {
hir::StmtDecl(ref decl, _) => {
match decl.node {
hir::DeclLocal(_) => {
match &decl.node {
hir::DeclLocal(local) => {
self.promotable = false;
if self.remove_mut_rvalue_borrow(&local.pat) {
if let Some(init) = &local.init {
self.mut_rvalue_borrows.insert(init.id);
}
}
}
// Item statements are allowed
hir::DeclItem(_) => {}
@ -229,9 +252,7 @@ impl<'a, 'tcx> Visitor<'tcx> for CheckCrateVisitor<'a, 'tcx> {
// patterns and set that on the discriminator.
let mut mut_borrow = false;
for pat in arms.iter().flat_map(|arm| &arm.pats) {
if self.mut_rvalue_borrows.remove(&pat.id) {
mut_borrow = true;
}
mut_borrow = self.remove_mut_rvalue_borrow(pat);
}
if mut_borrow {
self.mut_rvalue_borrows.insert(discr.id);
@ -498,6 +519,14 @@ impl<'a, 'gcx, 'tcx> euv::Delegate<'tcx> for CheckCrateVisitor<'a, 'gcx> {
_loan_region: ty::Region<'tcx>,
bk: ty::BorrowKind,
loan_cause: euv::LoanCause) {
debug!(
"borrow(borrow_id={:?}, cmt={:?}, bk={:?}, loan_cause={:?})",
borrow_id,
cmt,
bk,
loan_cause,
);
// Kind of hacky, but we allow Unsafe coercions in constants.
// These occur when we convert a &T or *T to a *U, as well as
// when making a thin pointer (e.g., `*T`) into a fat pointer

63
src/test/ui/borrowck/promote-ref-mut-in-let-issue-46557.nll.stderr Normal file
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@ -0,0 +1,63 @@
error[E0597]: borrowed value does not live long enough
--> $DIR/promote-ref-mut-in-let-issue-46557.rs:15:21
|
LL | fn gimme_static_mut_let() -> &'static mut u32 {
| _______________________________________________-
LL | | let ref mut x = 1234543; //~ ERROR
| | ^^^^^^^ temporary value does not live long enough
LL | | x
LL | | }
| | -
| | |
| |_temporary value only lives until here
| borrow later used here
error[E0597]: borrowed value does not live long enough
--> $DIR/promote-ref-mut-in-let-issue-46557.rs:20:25
|
LL | fn gimme_static_mut_let_nested() -> &'static mut u32 {
| ______________________________________________________-
LL | | let (ref mut x, ) = (1234543, ); //~ ERROR
| | ^^^^^^^^^^^ temporary value does not live long enough
LL | | x
LL | | }
| | -
| | |
| |_temporary value only lives until here
| borrow later used here
error[E0597]: borrowed value does not live long enough
--> $DIR/promote-ref-mut-in-let-issue-46557.rs:25:11
|
LL | match 1234543 {
| ^^^^^^^ temporary value does not live long enough
...
LL | }
| - temporary value only lives until here
|
= note: borrowed value must be valid for the static lifetime...
error[E0597]: borrowed value does not live long enough
--> $DIR/promote-ref-mut-in-let-issue-46557.rs:31:11
|
LL | match (123443,) {
| ^^^^^^^^^ temporary value does not live long enough
...
LL | }
| - temporary value only lives until here
|
= note: borrowed value must be valid for the static lifetime...
error[E0597]: borrowed value does not live long enough
--> $DIR/promote-ref-mut-in-let-issue-46557.rs:37:10
|
LL | &mut 1234543 //~ ERROR
| ^^^^^^^ temporary value does not live long enough
LL | }
| - temporary value only lives until here
|
= note: borrowed value must be valid for the static lifetime...
error: aborting due to 5 previous errors
For more information about this error, try `rustc --explain E0597`.

41
src/test/ui/borrowck/promote-ref-mut-in-let-issue-46557.rs Normal file
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@ -0,0 +1,41 @@
// Copyright 2014 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.
// Test that we fail to promote the constant here which has a `ref
// mut` borrow.
fn gimme_static_mut_let() -> &'static mut u32 {
let ref mut x = 1234543; //~ ERROR
x
}
fn gimme_static_mut_let_nested() -> &'static mut u32 {
let (ref mut x, ) = (1234543, ); //~ ERROR
x
}
fn gimme_static_mut_match() -> &'static mut u32 {
match 1234543 {
ref mut x => x //~ ERROR
}
}
fn gimme_static_mut_match_nested() -> &'static mut u32 {
match (123443,) {
(ref mut x,) => x, //~ ERROR
}
}
fn gimme_static_mut_ampersand() -> &'static mut u32 {
&mut 1234543 //~ ERROR
}
fn main() {
}

57
src/test/ui/borrowck/promote-ref-mut-in-let-issue-46557.stderr Normal file
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@ -0,0 +1,57 @@
error[E0597]: borrowed value does not live long enough
--> $DIR/promote-ref-mut-in-let-issue-46557.rs:15:9
|
LL | let ref mut x = 1234543; //~ ERROR
| ^^^^^^^^^ temporary value does not live long enough
LL | x
LL | }
| - temporary value only lives until here
|
= note: borrowed value must be valid for the static lifetime...
error[E0597]: borrowed value does not live long enough
--> $DIR/promote-ref-mut-in-let-issue-46557.rs:20:10
|
LL | let (ref mut x, ) = (1234543, ); //~ ERROR
| ^^^^^^^^^ borrowed value does not live long enough
LL | x
LL | }
| - borrowed value only lives until here
|
= note: borrowed value must be valid for the static lifetime...
error[E0597]: borrowed value does not live long enough
--> $DIR/promote-ref-mut-in-let-issue-46557.rs:26:9
|
LL | ref mut x => x //~ ERROR
| ^^^^^^^^^ temporary value does not live long enough
LL | }
LL | }
| - temporary value only lives until here
|
= note: borrowed value must be valid for the static lifetime...
error[E0597]: borrowed value does not live long enough
--> $DIR/promote-ref-mut-in-let-issue-46557.rs:32:10
|
LL | (ref mut x,) => x, //~ ERROR
| ^^^^^^^^^ borrowed value does not live long enough
LL | }
LL | }
| - borrowed value only lives until here
|
= note: borrowed value must be valid for the static lifetime...
error[E0597]: borrowed value does not live long enough
--> $DIR/promote-ref-mut-in-let-issue-46557.rs:37:10
|
LL | &mut 1234543 //~ ERROR
| ^^^^^^^ temporary value does not live long enough
LL | }
| - temporary value only lives until here
|
= note: borrowed value must be valid for the static lifetime...
error: aborting due to 5 previous errors
For more information about this error, try `rustc --explain E0597`.