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