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Rollup merge of rust-lang#81158 - 1000teslas:issue-80313-fix, r=Aaron…
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Point to span of upvar making closure FnMut

For rust-lang#80313.
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Dylan-DPC authored Jan 27, 2021
2 parents bd8896c + 26b4baf commit 37c692f
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Showing 13 changed files with 152 additions and 4 deletions.
Original file line number Diff line number Diff line change
@@ -1,9 +1,12 @@
use rustc_hir as hir;
use rustc_hir::Node;
use rustc_index::vec::Idx;
use rustc_middle::mir::{self, ClearCrossCrate, Local, LocalDecl, LocalInfo, Location};
use rustc_middle::mir::{Mutability, Place, PlaceRef, ProjectionElem};
use rustc_middle::ty::{self, Ty, TyCtxt};
use rustc_middle::{
hir::place::PlaceBase,
mir::{self, ClearCrossCrate, Local, LocalDecl, LocalInfo, Location},
};
use rustc_span::source_map::DesugaringKind;
use rustc_span::symbol::{kw, Symbol};
use rustc_span::Span;
Expand Down Expand Up @@ -241,6 +244,10 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
format!("mut {}", self.local_names[local].unwrap()),
Applicability::MachineApplicable,
);
let tcx = self.infcx.tcx;
if let ty::Closure(id, _) = the_place_err.ty(self.body, tcx).ty.kind() {
self.show_mutating_upvar(tcx, id, the_place_err, &mut err);
}
}

// Also suggest adding mut for upvars
Expand Down Expand Up @@ -271,6 +278,14 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
);
}
}

let tcx = self.infcx.tcx;
if let ty::Ref(_, ty, Mutability::Mut) = the_place_err.ty(self.body, tcx).ty.kind()
{
if let ty::Closure(id, _) = ty.kind() {
self.show_mutating_upvar(tcx, id, the_place_err, &mut err);
}
}
}

// complete hack to approximate old AST-borrowck
Expand Down Expand Up @@ -463,6 +478,45 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
err.buffer(&mut self.errors_buffer);
}

// point to span of upvar making closure call require mutable borrow
fn show_mutating_upvar(
&self,
tcx: TyCtxt<'_>,
id: &hir::def_id::DefId,
the_place_err: PlaceRef<'tcx>,
err: &mut DiagnosticBuilder<'_>,
) {
let id = id.expect_local();
let tables = tcx.typeck(id);
let hir_id = tcx.hir().local_def_id_to_hir_id(id);
let (span, place) = &tables.closure_kind_origins()[hir_id];
let reason = if let PlaceBase::Upvar(upvar_id) = place.base {
let upvar = ty::place_to_string_for_capture(tcx, place);
match tables.upvar_capture(upvar_id) {
ty::UpvarCapture::ByRef(ty::UpvarBorrow {
kind: ty::BorrowKind::MutBorrow,
..
}) => {
format!("mutable borrow of `{}`", upvar)
}
ty::UpvarCapture::ByValue(_) => {
format!("possible mutation of `{}`", upvar)
}
_ => bug!("upvar `{}` borrowed, but not mutably", upvar),
}
} else {
bug!("not an upvar")
};
err.span_label(
*span,
format!(
"calling `{}` requires mutable binding due to {}",
self.describe_place(the_place_err).unwrap(),
reason
),
);
}

/// Targeted error when encountering an `FnMut` closure where an `Fn` closure was expected.
fn expected_fn_found_fn_mut_call(&self, err: &mut DiagnosticBuilder<'_>, sp: Span, act: &str) {
err.span_label(sp, format!("cannot {}", act));
Expand Down
4 changes: 3 additions & 1 deletion src/test/ui/borrowck/borrow-raw-address-of-mutability.stderr
Original file line number Diff line number Diff line change
Expand Up @@ -20,7 +20,9 @@ error[E0596]: cannot borrow `f` as mutable, as it is not declared as mutable
|
LL | let f = || {
| - help: consider changing this to be mutable: `mut f`
...
LL | let y = &raw mut x;
| - calling `f` requires mutable binding due to mutable borrow of `x`
LL | };
LL | f();
| ^ cannot borrow as mutable

Expand Down
7 changes: 7 additions & 0 deletions src/test/ui/closures/issue-80313-mutable-borrow-in-closure.rs
Original file line number Diff line number Diff line change
@@ -0,0 +1,7 @@
fn main() {
let mut my_var = false;
let callback = || {
&mut my_var;
};
callback(); //~ ERROR E0596
}
14 changes: 14 additions & 0 deletions src/test/ui/closures/issue-80313-mutable-borrow-in-closure.stderr
Original file line number Diff line number Diff line change
@@ -0,0 +1,14 @@
error[E0596]: cannot borrow `callback` as mutable, as it is not declared as mutable
--> $DIR/issue-80313-mutable-borrow-in-closure.rs:6:5
|
LL | let callback = || {
| -------- help: consider changing this to be mutable: `mut callback`
LL | &mut my_var;
| ------ calling `callback` requires mutable binding due to mutable borrow of `my_var`
LL | };
LL | callback();
| ^^^^^^^^ cannot borrow as mutable

error: aborting due to previous error

For more information about this error, try `rustc --explain E0596`.
Original file line number Diff line number Diff line change
@@ -0,0 +1,7 @@
fn main() {
let mut my_var = false;
let callback = move || {
&mut my_var;
};
callback(); //~ ERROR E0596
}
Original file line number Diff line number Diff line change
@@ -0,0 +1,14 @@
error[E0596]: cannot borrow `callback` as mutable, as it is not declared as mutable
--> $DIR/issue-80313-mutable-borrow-in-move-closure.rs:6:5
|
LL | let callback = move || {
| -------- help: consider changing this to be mutable: `mut callback`
LL | &mut my_var;
| ------ calling `callback` requires mutable binding due to possible mutation of `my_var`
LL | };
LL | callback();
| ^^^^^^^^ cannot borrow as mutable

error: aborting due to previous error

For more information about this error, try `rustc --explain E0596`.
7 changes: 7 additions & 0 deletions src/test/ui/closures/issue-80313-mutation-in-closure.rs
Original file line number Diff line number Diff line change
@@ -0,0 +1,7 @@
fn main() {
let mut my_var = false;
let callback = || {
my_var = true;
};
callback(); //~ ERROR E0596
}
14 changes: 14 additions & 0 deletions src/test/ui/closures/issue-80313-mutation-in-closure.stderr
Original file line number Diff line number Diff line change
@@ -0,0 +1,14 @@
error[E0596]: cannot borrow `callback` as mutable, as it is not declared as mutable
--> $DIR/issue-80313-mutation-in-closure.rs:6:5
|
LL | let callback = || {
| -------- help: consider changing this to be mutable: `mut callback`
LL | my_var = true;
| ------ calling `callback` requires mutable binding due to mutable borrow of `my_var`
LL | };
LL | callback();
| ^^^^^^^^ cannot borrow as mutable

error: aborting due to previous error

For more information about this error, try `rustc --explain E0596`.
7 changes: 7 additions & 0 deletions src/test/ui/closures/issue-80313-mutation-in-move-closure.rs
Original file line number Diff line number Diff line change
@@ -0,0 +1,7 @@
fn main() {
let mut my_var = false;
let callback = move || {
my_var = true;
};
callback(); //~ ERROR E0596
}
14 changes: 14 additions & 0 deletions src/test/ui/closures/issue-80313-mutation-in-move-closure.stderr
Original file line number Diff line number Diff line change
@@ -0,0 +1,14 @@
error[E0596]: cannot borrow `callback` as mutable, as it is not declared as mutable
--> $DIR/issue-80313-mutation-in-move-closure.rs:6:5
|
LL | let callback = move || {
| -------- help: consider changing this to be mutable: `mut callback`
LL | my_var = true;
| ------ calling `callback` requires mutable binding due to possible mutation of `my_var`
LL | };
LL | callback();
| ^^^^^^^^ cannot borrow as mutable

error: aborting due to previous error

For more information about this error, try `rustc --explain E0596`.
Original file line number Diff line number Diff line change
Expand Up @@ -3,6 +3,8 @@ error[E0596]: cannot borrow `tick1` as mutable, as it is not declared as mutable
|
LL | let tick1 = || {
| ----- help: consider changing this to be mutable: `mut tick1`
LL | counter += 1;
| ------- calling `tick1` requires mutable binding due to mutable borrow of `counter`
...
LL | tick1();
| ^^^^^ cannot borrow as mutable
Expand All @@ -12,6 +14,8 @@ error[E0596]: cannot borrow `tick2` as mutable, as it is not declared as mutable
|
LL | let tick2 = || {
| ----- help: consider changing this to be mutable: `mut tick2`
LL | tick1();
| ----- calling `tick2` requires mutable binding due to mutable borrow of `tick1`
...
LL | tick2();
| ^^^^^ cannot borrow as mutable
Expand Down
Original file line number Diff line number Diff line change
Expand Up @@ -2,7 +2,9 @@ error[E0596]: cannot borrow `tick` as mutable, as it is not declared as mutable
--> $DIR/unboxed-closures-infer-fnmut-missing-mut.rs:7:5
|
LL | let tick = || counter += 1;
| ---- help: consider changing this to be mutable: `mut tick`
| ---- ------- calling `tick` requires mutable binding due to mutable borrow of `counter`
| |
| help: consider changing this to be mutable: `mut tick`
LL | tick();
| ^^^^ cannot borrow as mutable

Expand Down
Original file line number Diff line number Diff line change
Expand Up @@ -2,7 +2,9 @@ error[E0596]: cannot borrow `tick` as mutable, as it is not declared as mutable
--> $DIR/unboxed-closures-infer-fnmut-move-missing-mut.rs:7:5
|
LL | let tick = move || counter += 1;
| ---- help: consider changing this to be mutable: `mut tick`
| ---- ------- calling `tick` requires mutable binding due to possible mutation of `counter`
| |
| help: consider changing this to be mutable: `mut tick`
LL | tick();
| ^^^^ cannot borrow as mutable

Expand Down

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