OpenE2K
/
rust
2
0
Fork 0
Code Issues Pull Requests Projects Releases Wiki Activity

Auto merge of #52242 - ashtneoi:suggest-ref-mut, r=pnkfelix 

NLL: Suggest `ref mut` and `&mut self`

Fixes #51244. Supersedes #51249, I think.

Under the old lexical lifetimes, the compiler provided helpful suggestions about adding `mut` when you tried to mutate a variable bound as `&self` or (explicit) `ref`. NLL doesn't have those suggestions yet. This pull request adds them.

I didn't bother making the help text exactly the same as without NLL, but I can if that's important.

(Originally this was supposed to be part of #51612, but I got bogged down trying to fit everything in one PR.)
This commit is contained in:
bors 2018-07-13 17:08:39 +00:00
parent bce32b532d 1ed861910f
commit fe29a4cda5
17 changed files with 239 additions and 60 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

13
src/librustc_borrowck/borrowck/mod.rs
View File

@ -39,6 +39,7 @@ use rustc::middle::free_region::RegionRelations;
use rustc::ty::{self, Ty, TyCtxt};
use rustc::ty::query::Providers;
use rustc_mir::util::borrowck_errors::{BorrowckErrors, Origin};
use rustc_mir::util::suggest_ref_mut;
use rustc::util::nodemap::FxHashSet;
use std::cell::RefCell;
@ -1206,15 +1207,15 @@ impl<'a, 'tcx> BorrowckCtxt<'a, 'tcx> {
self.note_immutable_local(db, error_node_id, node_id)
}
Some(ImmutabilityBlame::LocalDeref(node_id)) => {
let let_span = self.tcx.hir.span(node_id);
match self.local_binding_mode(node_id) {
ty::BindByReference(..) => {
let snippet = self.tcx.sess.codemap().span_to_snippet(let_span);
if let Ok(snippet) = snippet {
db.span_label(
let let_span = self.tcx.hir.span(node_id);
let suggestion = suggest_ref_mut(self.tcx, let_span);
if let Some((let_span, replace_str)) = suggestion {
db.span_suggestion(
let_span,
format!("consider changing this to `{}`",
snippet.replace("ref ", "ref mut "))
"use a mutable reference instead",
replace_str,
);
}
}

88
src/librustc_mir/borrow_check/mod.rs
View File

@ -44,6 +44,7 @@ use dataflow::{EverInitializedPlaces, MovingOutStatements};
use dataflow::{MaybeInitializedPlaces, MaybeUninitializedPlaces};
use util::borrowck_errors::{BorrowckErrors, Origin};
use util::collect_writes::FindAssignments;
use util::suggest_ref_mut;
use self::borrow_set::{BorrowData, BorrowSet};
use self::flows::Flows;
@ -1837,17 +1838,41 @@ impl<'cx, 'gcx, 'tcx> MirBorrowckCtxt<'cx, 'gcx, 'tcx> {
Place::Projection(box Projection {
base: Place::Local(local),
elem: ProjectionElem::Deref,
}) if self.mir.local_decls[*local].is_nonref_binding() =>
{
let (err_help_span, suggested_code) =
find_place_to_suggest_ampmut(self.tcx, self.mir, *local);
err.span_suggestion(
err_help_span,
"consider changing this to be a mutable reference",
suggested_code,
);
}) if self.mir.local_decls[*local].is_user_variable.is_some() => {
let local_decl = &self.mir.local_decls[*local];
let suggestion = match local_decl.is_user_variable.as_ref().unwrap() {
ClearCrossCrate::Set(mir::BindingForm::ImplicitSelf) => {
Some(suggest_ampmut_self(local_decl))
},
ClearCrossCrate::Set(mir::BindingForm::Var(mir::VarBindingForm {
binding_mode: ty::BindingMode::BindByValue(_),
opt_ty_info,
..
})) => Some(suggest_ampmut(
self.tcx,
self.mir,
*local,
local_decl,
*opt_ty_info,
)),
ClearCrossCrate::Set(mir::BindingForm::Var(mir::VarBindingForm {
binding_mode: ty::BindingMode::BindByReference(_),
..
})) => suggest_ref_mut(self.tcx, local_decl.source_info.span),
ClearCrossCrate::Clear => bug!("saw cleared local state"),
};
if let Some((err_help_span, suggested_code)) = suggestion {
err.span_suggestion(
err_help_span,
"consider changing this to be a mutable reference",
suggested_code,
);
}
if let Some(name) = local_decl.name {
err.span_label(
span,
@ -1874,13 +1899,16 @@ impl<'cx, 'gcx, 'tcx> MirBorrowckCtxt<'cx, 'gcx, 'tcx> {
err.emit();
return true;
// Returns the span to highlight and the associated text to
// present when suggesting that the user use an `&mut`.
//
fn suggest_ampmut_self<'cx, 'gcx, 'tcx>(
local_decl: &mir::LocalDecl<'tcx>,
) -> (Span, String) {
(local_decl.source_info.span, "&mut self".to_string())
}
// When we want to suggest a user change a local variable to be a `&mut`, there
// are three potential "obvious" things to highlight:
//
// let ident [: Type] [= RightHandSideExresssion];
// let ident [: Type] [= RightHandSideExpression];
// ^^^^^ ^^^^ ^^^^^^^^^^^^^^^^^^^^^^^
// (1.) (2.) (3.)
//
@ -1889,48 +1917,44 @@ impl<'cx, 'gcx, 'tcx> MirBorrowckCtxt<'cx, 'gcx, 'tcx> {
// for example, if the RHS is present and the Type is not, then the type is going to
// be inferred *from* the RHS, which means we should highlight that (and suggest
// that they borrow the RHS mutably).
fn find_place_to_suggest_ampmut<'cx, 'gcx, 'tcx>(
//
// This implementation attempts to emulate AST-borrowck prioritization
// by trying (3.), then (2.) and finally falling back on (1.).
fn suggest_ampmut<'cx, 'gcx, 'tcx>(
tcx: TyCtxt<'cx, 'gcx, 'tcx>,
mir: &Mir<'tcx>,
local: Local,
local_decl: &mir::LocalDecl<'tcx>,
opt_ty_info: Option<Span>,
) -> (Span, String) {
// This implementation attempts to emulate AST-borrowck prioritization
// by trying (3.), then (2.) and finally falling back on (1.).
let locations = mir.find_assignments(local);
if locations.len() > 0 {
let assignment_rhs_span = mir.source_info(locations[0]).span;
let snippet = tcx.sess.codemap().span_to_snippet(assignment_rhs_span);
if let Ok(src) = snippet {
// pnkfelix inherited code; believes intention is
// highlighted text will always be `&<expr>` and
// thus can transform to `&mut` by slicing off
// first ASCII character and prepending "&mut ".
if src.starts_with('&') {
let borrowed_expr = src[1..].to_string();
return (assignment_rhs_span, format!("&mut {}", borrowed_expr));
return (
assignment_rhs_span,
format!("&mut {}", borrowed_expr),
);
}
}
}
let local_decl = &mir.local_decls[local];
let highlight_span = match local_decl.is_user_variable {
let highlight_span = match opt_ty_info {
// if this is a variable binding with an explicit type,
// try to highlight that for the suggestion.
Some(ClearCrossCrate::Set(mir::BindingForm::Var(mir::VarBindingForm {
opt_ty_info: Some(ty_span),
..
}))) => ty_span,
Some(ClearCrossCrate::Clear) => bug!("saw cleared local state"),
Some(ty_span) => ty_span,
// otherwise, just highlight the span associated with
// the (MIR) LocalDecl.
_ => local_decl.source_info.span,
None => local_decl.source_info.span,
};
let ty_mut = local_decl.ty.builtin_deref(true).unwrap();
assert_eq!(ty_mut.mutbl, hir::MutImmutable);
return (highlight_span, format!("&mut {}", ty_mut.ty));
(highlight_span, format!("&mut {}", ty_mut.ty))
}
}

2
src/librustc_mir/lib.rs
View File

@ -33,6 +33,7 @@ Rust MIR: a lowered representation of Rust. Also: an experiment!
#![feature(never_type)]
#![feature(specialization)]
#![feature(try_trait)]
#![feature(unicode_internals)]
#![recursion_limit="256"]
@ -56,6 +57,7 @@ extern crate rustc_target;
extern crate log_settings;
extern crate rustc_apfloat;
extern crate byteorder;
extern crate core;
mod diagnostics;

20
src/librustc_mir/util/mod.rs
View File

@ -8,6 +8,10 @@
// option. This file may not be copied, modified, or distributed
// except according to those terms.
use core::unicode::property::Pattern_White_Space;
use rustc::ty;
use syntax_pos::Span;
pub mod borrowck_errors;
pub mod elaborate_drops;
pub mod def_use;
@ -23,3 +27,19 @@ pub use self::alignment::is_disaligned;
pub use self::pretty::{dump_enabled, dump_mir, write_mir_pretty, PassWhere};
pub use self::graphviz::{write_mir_graphviz};
pub use self::graphviz::write_node_label as write_graphviz_node_label;
/// If possible, suggest replacing `ref` with `ref mut`.
pub fn suggest_ref_mut<'cx, 'gcx, 'tcx>(
tcx: ty::TyCtxt<'cx, 'gcx, 'tcx>,
pattern_span: Span,
) -> Option<(Span, String)> {
let hi_src = tcx.sess.codemap().span_to_snippet(pattern_span).unwrap();
if hi_src.starts_with("ref")
&& hi_src["ref".len()..].starts_with(Pattern_White_Space)
{
let replacement = format!("ref mut{}", &hi_src["ref".len()..]);
Some((pattern_span, replacement))
} else {
None
}
}

2
src/test/ui/did_you_mean/issue-38147-1.nll.stderr
View File

@ -2,7 +2,7 @@ error[E0596]: cannot borrow immutable item `*self.s` as mutable
--> $DIR/issue-38147-1.rs:27:9
|
LL | fn f(&self) {
| ----- help: consider changing this to be a mutable reference: `&mut Foo<'_>`
| ----- help: consider changing this to be a mutable reference: `&mut self`
LL | self.s.push('x'); //~ ERROR cannot borrow data mutably
| ^^^^^^ `self` is a `&` reference, so the data it refers to cannot be borrowed as mutable

6
src/test/ui/did_you_mean/issue-39544.nll.stderr
View File

@ -10,7 +10,7 @@ error[E0596]: cannot borrow immutable item `self.x` as mutable
--> $DIR/issue-39544.rs:26:17
|
LL | fn foo<'z>(&'z self) {
| -------- help: consider changing this to be a mutable reference: `&mut Z`
| -------- help: consider changing this to be a mutable reference: `&mut self`
LL | let _ = &mut self.x; //~ ERROR cannot borrow
| ^^^^^^^^^^^ `self` is a `&` reference, so the data it refers to cannot be borrowed as mutable
@ -18,7 +18,7 @@ error[E0596]: cannot borrow immutable item `self.x` as mutable
--> $DIR/issue-39544.rs:30:17
|
LL | fn foo1(&self, other: &Z) {
| ----- help: consider changing this to be a mutable reference: `&mut Z`
| ----- help: consider changing this to be a mutable reference: `&mut self`
LL | let _ = &mut self.x; //~ ERROR cannot borrow
| ^^^^^^^^^^^ `self` is a `&` reference, so the data it refers to cannot be borrowed as mutable
@ -35,7 +35,7 @@ error[E0596]: cannot borrow immutable item `self.x` as mutable
--> $DIR/issue-39544.rs:35:17
|
LL | fn foo2<'a>(&'a self, other: &Z) {
| -------- help: consider changing this to be a mutable reference: `&mut Z`
| -------- help: consider changing this to be a mutable reference: `&mut self`
LL | let _ = &mut self.x; //~ ERROR cannot borrow
| ^^^^^^^^^^^ `self` is a `&` reference, so the data it refers to cannot be borrowed as mutable

17
src/test/ui/nll/issue-51244.rs Normal file
View File

@ -0,0 +1,17 @@
// Copyright 2018 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)]
fn main() {
let ref my_ref @ _ = 0;
*my_ref = 0;
//~^ ERROR cannot assign to `*my_ref` which is behind a `&` reference [E0594]
}

11
src/test/ui/nll/issue-51244.stderr Normal file
View File

@ -0,0 +1,11 @@
error[E0594]: cannot assign to `*my_ref` which is behind a `&` reference
--> $DIR/issue-51244.rs:15:5
|
LL | let ref my_ref @ _ = 0;
| -------------- help: consider changing this to be a mutable reference: `ref mut my_ref @ _`
LL | *my_ref = 0;
| ^^^^^^^^^^^ `my_ref` is a `&` reference, so the data it refers to cannot be written
error: aborting due to previous error
For more information about this error, try `rustc --explain E0594`.

6
src/test/ui/rfc-2005-default-binding-mode/enum.nll.stderr
View File

@ -2,19 +2,19 @@ error[E0594]: cannot assign to `*x` which is behind a `&` reference
--> $DIR/enum.rs:19:5
|
LL | *x += 1; //~ ERROR cannot assign to immutable
| ^^^^^^^ cannot assign
| ^^^^^^^ `x` is a `&` reference, so the data it refers to cannot be written
error[E0594]: cannot assign to `*x` which is behind a `&` reference
--> $DIR/enum.rs:23:9
|
LL | *x += 1; //~ ERROR cannot assign to immutable
| ^^^^^^^ cannot assign
| ^^^^^^^ `x` is a `&` reference, so the data it refers to cannot be written
error[E0594]: cannot assign to `*x` which is behind a `&` reference
--> $DIR/enum.rs:29:9
|
LL | *x += 1; //~ ERROR cannot assign to immutable
| ^^^^^^^ cannot assign
| ^^^^^^^ `x` is a `&` reference, so the data it refers to cannot be written
error: aborting due to 3 previous errors

6
src/test/ui/rfc-2005-default-binding-mode/enum.stderr
View File

@ -1,24 +1,18 @@
error[E0594]: cannot assign to immutable borrowed content `*x`
--> $DIR/enum.rs:19:5
|
LL | let Wrap(x) = &Wrap(3);
| - consider changing this to `x`
LL | *x += 1; //~ ERROR cannot assign to immutable
| ^^^^^^^ cannot borrow as mutable
error[E0594]: cannot assign to immutable borrowed content `*x`
--> $DIR/enum.rs:23:9
|
LL | if let Some(x) = &Some(3) {
| - consider changing this to `x`
LL | *x += 1; //~ ERROR cannot assign to immutable
| ^^^^^^^ cannot borrow as mutable
error[E0594]: cannot assign to immutable borrowed content `*x`
--> $DIR/enum.rs:29:9
|
LL | while let Some(x) = &Some(3) {
| - consider changing this to `x`
LL | *x += 1; //~ ERROR cannot assign to immutable
| ^^^^^^^ cannot borrow as mutable

6
src/test/ui/rfc-2005-default-binding-mode/explicit-mut.nll.stderr
View File

@ -2,19 +2,19 @@ error[E0594]: cannot assign to `*n` which is behind a `&` reference
--> $DIR/explicit-mut.rs:17:13
|
LL | *n += 1; //~ ERROR cannot assign to immutable
| ^^^^^^^ cannot assign
| ^^^^^^^ `n` is a `&` reference, so the data it refers to cannot be written
error[E0594]: cannot assign to `*n` which is behind a `&` reference
--> $DIR/explicit-mut.rs:25:13
|
LL | *n += 1; //~ ERROR cannot assign to immutable
| ^^^^^^^ cannot assign
| ^^^^^^^ `n` is a `&` reference, so the data it refers to cannot be written
error[E0594]: cannot assign to `*n` which is behind a `&` reference
--> $DIR/explicit-mut.rs:33:13
|
LL | *n += 1; //~ ERROR cannot assign to immutable
| ^^^^^^^ cannot assign
| ^^^^^^^ `n` is a `&` reference, so the data it refers to cannot be written
error: aborting due to 3 previous errors

6
src/test/ui/rfc-2005-default-binding-mode/explicit-mut.stderr
View File

@ -1,24 +1,18 @@
error[E0594]: cannot assign to immutable borrowed content `*n`
--> $DIR/explicit-mut.rs:17:13
|
LL | Some(n) => {
| - consider changing this to `n`
LL | *n += 1; //~ ERROR cannot assign to immutable
| ^^^^^^^ cannot borrow as mutable
error[E0594]: cannot assign to immutable borrowed content `*n`
--> $DIR/explicit-mut.rs:25:13
|
LL | Some(n) => {
| - consider changing this to `n`
LL | *n += 1; //~ ERROR cannot assign to immutable
| ^^^^^^^ cannot borrow as mutable
error[E0594]: cannot assign to immutable borrowed content `*n`
--> $DIR/explicit-mut.rs:33:13
|
LL | Some(n) => {
| - consider changing this to `n`
LL | *n += 1; //~ ERROR cannot assign to immutable
| ^^^^^^^ cannot borrow as mutable

11
src/test/ui/suggestions/issue-51244.nll.stderr Normal file
View File

@ -0,0 +1,11 @@
error[E0594]: cannot assign to `*my_ref` which is behind a `&` reference
--> $DIR/issue-51244.rs:13:5
|
LL | let ref my_ref @ _ = 0;
| -------------- help: consider changing this to be a mutable reference: `ref mut my_ref @ _`
LL | *my_ref = 0; //~ ERROR cannot assign to immutable borrowed content `*my_ref` [E0594]
| ^^^^^^^^^^^ `my_ref` is a `&` reference, so the data it refers to cannot be written
error: aborting due to previous error
For more information about this error, try `rustc --explain E0594`.

14
src/test/ui/suggestions/issue-51244.rs Normal file
View File

@ -0,0 +1,14 @@
// Copyright 2018 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.
fn main() {
let ref my_ref @ _ = 0;
*my_ref = 0; //~ ERROR cannot assign to immutable borrowed content `*my_ref` [E0594]
}

11
src/test/ui/suggestions/issue-51244.stderr Normal file
View File

@ -0,0 +1,11 @@
error[E0594]: cannot assign to immutable borrowed content `*my_ref`
--> $DIR/issue-51244.rs:13:5
|
LL | let ref my_ref @ _ = 0;
| -------------- help: use a mutable reference instead: `ref mut my_ref @ _`
LL | *my_ref = 0; //~ ERROR cannot assign to immutable borrowed content `*my_ref` [E0594]
| ^^^^^^^^^^^ cannot borrow as mutable
error: aborting due to previous error
For more information about this error, try `rustc --explain E0594`.

42
src/test/ui/suggestions/suggest-ref-mut.rs Normal file
View File

@ -0,0 +1,42 @@
// Copyright 2018 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)]
struct X(usize);
impl X {
fn zap(&self) {
//~^ HELP
//~| SUGGESTION &mut self
self.0 = 32;
//~^ ERROR
}
}
fn main() {
let ref foo = 16;
//~^ HELP
//~| SUGGESTION ref mut foo
*foo = 32;
//~^ ERROR
if let Some(ref bar) = Some(16) {
//~^ HELP
//~| SUGGESTION ref mut bar
*bar = 32;
//~^ ERROR
}
match 16 {
ref quo => { *quo = 32; },
//~^ ERROR
//~| HELP
//~| SUGGESTION ref mut quo
}
}

38
src/test/ui/suggestions/suggest-ref-mut.stderr Normal file
View File

@ -0,0 +1,38 @@
error[E0594]: cannot assign to `self.0` which is behind a `&` reference
--> $DIR/suggest-ref-mut.rs:19:9
|
LL | fn zap(&self) {
| ----- help: consider changing this to be a mutable reference: `&mut self`
...
LL | self.0 = 32;
| ^^^^^^^^^^^ `self` is a `&` reference, so the data it refers to cannot be written
error[E0594]: cannot assign to `*foo` which is behind a `&` reference
--> $DIR/suggest-ref-mut.rs:28:5
|
LL | let ref foo = 16;
| ------- help: consider changing this to be a mutable reference: `ref mut foo`
...
LL | *foo = 32;
| ^^^^^^^^^ `foo` is a `&` reference, so the data it refers to cannot be written
error[E0594]: cannot assign to `*bar` which is behind a `&` reference
--> $DIR/suggest-ref-mut.rs:33:9
|
LL | if let Some(ref bar) = Some(16) {
| ------- help: consider changing this to be a mutable reference: `ref mut bar`
...
LL | *bar = 32;
| ^^^^^^^^^ `bar` is a `&` reference, so the data it refers to cannot be written
error[E0594]: cannot assign to `*quo` which is behind a `&` reference
--> $DIR/suggest-ref-mut.rs:37:22
|
LL | ref quo => { *quo = 32; },
| ------- ^^^^^^^^^ `quo` is a `&` reference, so the data it refers to cannot be written
| |
| help: consider changing this to be a mutable reference: `ref mut quo`
error: aborting due to 4 previous errors
For more information about this error, try `rustc --explain E0594`.