diff --git a/compiler/rustc_mir/src/borrow_check/diagnostics/mutability_errors.rs b/compiler/rustc_mir/src/borrow_check/diagnostics/mutability_errors.rs
index e1af6fc07cf8f..73196c732f5bb 100644
--- a/compiler/rustc_mir/src/borrow_check/diagnostics/mutability_errors.rs
+++ b/compiler/rustc_mir/src/borrow_check/diagnostics/mutability_errors.rs
@@ -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;
@@ -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
@@ -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
@@ -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));
diff --git a/src/test/ui/borrowck/borrow-raw-address-of-mutability.stderr b/src/test/ui/borrowck/borrow-raw-address-of-mutability.stderr
index 44dde0fd80b0d..ea74fb966846f 100644
--- a/src/test/ui/borrowck/borrow-raw-address-of-mutability.stderr
+++ b/src/test/ui/borrowck/borrow-raw-address-of-mutability.stderr
@@ -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
diff --git a/src/test/ui/closures/issue-80313-mutable-borrow-in-closure.rs b/src/test/ui/closures/issue-80313-mutable-borrow-in-closure.rs
new file mode 100644
index 0000000000000..ff210ae06a3bd
--- /dev/null
+++ b/src/test/ui/closures/issue-80313-mutable-borrow-in-closure.rs
@@ -0,0 +1,7 @@
+fn main() {
+ let mut my_var = false;
+ let callback = || {
+ &mut my_var;
+ };
+ callback(); //~ ERROR E0596
+}
diff --git a/src/test/ui/closures/issue-80313-mutable-borrow-in-closure.stderr b/src/test/ui/closures/issue-80313-mutable-borrow-in-closure.stderr
new file mode 100644
index 0000000000000..bf9e1febdbba4
--- /dev/null
+++ b/src/test/ui/closures/issue-80313-mutable-borrow-in-closure.stderr
@@ -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`.
diff --git a/src/test/ui/closures/issue-80313-mutable-borrow-in-move-closure.rs b/src/test/ui/closures/issue-80313-mutable-borrow-in-move-closure.rs
new file mode 100644
index 0000000000000..8f2d8a676302c
--- /dev/null
+++ b/src/test/ui/closures/issue-80313-mutable-borrow-in-move-closure.rs
@@ -0,0 +1,7 @@
+fn main() {
+ let mut my_var = false;
+ let callback = move || {
+ &mut my_var;
+ };
+ callback(); //~ ERROR E0596
+}
diff --git a/src/test/ui/closures/issue-80313-mutable-borrow-in-move-closure.stderr b/src/test/ui/closures/issue-80313-mutable-borrow-in-move-closure.stderr
new file mode 100644
index 0000000000000..b67cec6a609f0
--- /dev/null
+++ b/src/test/ui/closures/issue-80313-mutable-borrow-in-move-closure.stderr
@@ -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`.
diff --git a/src/test/ui/closures/issue-80313-mutation-in-closure.rs b/src/test/ui/closures/issue-80313-mutation-in-closure.rs
new file mode 100644
index 0000000000000..e082ea562ef22
--- /dev/null
+++ b/src/test/ui/closures/issue-80313-mutation-in-closure.rs
@@ -0,0 +1,7 @@
+fn main() {
+ let mut my_var = false;
+ let callback = || {
+ my_var = true;
+ };
+ callback(); //~ ERROR E0596
+}
diff --git a/src/test/ui/closures/issue-80313-mutation-in-closure.stderr b/src/test/ui/closures/issue-80313-mutation-in-closure.stderr
new file mode 100644
index 0000000000000..6e98549f6b84f
--- /dev/null
+++ b/src/test/ui/closures/issue-80313-mutation-in-closure.stderr
@@ -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`.
diff --git a/src/test/ui/closures/issue-80313-mutation-in-move-closure.rs b/src/test/ui/closures/issue-80313-mutation-in-move-closure.rs
new file mode 100644
index 0000000000000..f66bf4e062831
--- /dev/null
+++ b/src/test/ui/closures/issue-80313-mutation-in-move-closure.rs
@@ -0,0 +1,7 @@
+fn main() {
+ let mut my_var = false;
+ let callback = move || {
+ my_var = true;
+ };
+ callback(); //~ ERROR E0596
+}
diff --git a/src/test/ui/closures/issue-80313-mutation-in-move-closure.stderr b/src/test/ui/closures/issue-80313-mutation-in-move-closure.stderr
new file mode 100644
index 0000000000000..edd55422a0bd4
--- /dev/null
+++ b/src/test/ui/closures/issue-80313-mutation-in-move-closure.stderr
@@ -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`.
diff --git a/src/test/ui/unboxed-closures/unboxed-closures-infer-fnmut-calling-fnmut-no-mut.stderr b/src/test/ui/unboxed-closures/unboxed-closures-infer-fnmut-calling-fnmut-no-mut.stderr
index 5dea424596e9c..a0ed56d4bcf7b 100644
--- a/src/test/ui/unboxed-closures/unboxed-closures-infer-fnmut-calling-fnmut-no-mut.stderr
+++ b/src/test/ui/unboxed-closures/unboxed-closures-infer-fnmut-calling-fnmut-no-mut.stderr
@@ -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
@@ -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
diff --git a/src/test/ui/unboxed-closures/unboxed-closures-infer-fnmut-missing-mut.stderr b/src/test/ui/unboxed-closures/unboxed-closures-infer-fnmut-missing-mut.stderr
index eb398628846dd..27d23e3fa044b 100644
--- a/src/test/ui/unboxed-closures/unboxed-closures-infer-fnmut-missing-mut.stderr
+++ b/src/test/ui/unboxed-closures/unboxed-closures-infer-fnmut-missing-mut.stderr
@@ -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
diff --git a/src/test/ui/unboxed-closures/unboxed-closures-infer-fnmut-move-missing-mut.stderr b/src/test/ui/unboxed-closures/unboxed-closures-infer-fnmut-move-missing-mut.stderr
index b9d76d9a752ce..c00f986c397a7 100644
--- a/src/test/ui/unboxed-closures/unboxed-closures-infer-fnmut-move-missing-mut.stderr
+++ b/src/test/ui/unboxed-closures/unboxed-closures-infer-fnmut-move-missing-mut.stderr
@@ -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