diff --git a/compiler/rustc_middle/src/mir/mod.rs b/compiler/rustc_middle/src/mir/mod.rs
index 1181ba6bbf946..d6d76595f3b9b 100644
--- a/compiler/rustc_middle/src/mir/mod.rs
+++ b/compiler/rustc_middle/src/mir/mod.rs
@@ -899,6 +899,8 @@ pub enum LocalInfo<'tcx> {
User(ClearCrossCrate<BindingForm<'tcx>>),
/// A temporary created that references the static with the given `DefId`.
StaticRef { def_id: DefId, is_thread_local: bool },
+ /// A temporary created that references the const with the given `DefId`
+ ConstRef { def_id: DefId },
}
impl<'tcx> LocalDecl<'tcx> {
diff --git a/compiler/rustc_mir/src/borrow_check/diagnostics/mod.rs b/compiler/rustc_mir/src/borrow_check/diagnostics/mod.rs
index 88ff0271228e0..f51bf7730ea09 100644
--- a/compiler/rustc_mir/src/borrow_check/diagnostics/mod.rs
+++ b/compiler/rustc_mir/src/borrow_check/diagnostics/mod.rs
@@ -804,68 +804,51 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
debug!("move_spans: target_temp = {:?}", target_temp);
if let Some(Terminator {
- kind: TerminatorKind::Call { func, args, fn_span, from_hir_call, .. },
- ..
+ kind: TerminatorKind::Call { fn_span, from_hir_call, .. }, ..
}) = &self.body[location.block].terminator
{
- let mut method_did = None;
- if let Operand::Constant(box Constant { literal: ty::Const { ty, .. }, .. }) = func {
- if let ty::FnDef(def_id, _) = *ty.kind() {
- debug!("move_spans: fn = {:?}", def_id);
- if let Some(ty::AssocItem { fn_has_self_parameter, .. }) =
- self.infcx.tcx.opt_associated_item(def_id)
- {
- if *fn_has_self_parameter {
- method_did = Some(def_id);
- }
- }
- }
- }
+ let method_did = if let Some(method_did) =
+ crate::util::find_self_call(self.infcx.tcx, &self.body, target_temp, location.block)
+ {
+ method_did
+ } else {
+ return normal_ret;
+ };
let tcx = self.infcx.tcx;
- let method_did = if let Some(did) = method_did { did } else { return normal_ret };
-
- if let [Operand::Move(self_place), ..] = **args {
- if self_place.as_local() == Some(target_temp) {
- let parent = tcx.parent(method_did);
- let is_fn_once = parent == tcx.lang_items().fn_once_trait();
- let is_operator = !from_hir_call
- && parent.map_or(false, |p| {
- tcx.lang_items().group(LangItemGroup::Op).contains(&p)
- });
- let fn_call_span = *fn_span;
-
- let self_arg = tcx.fn_arg_names(method_did)[0];
-
- let kind = if is_fn_once {
- FnSelfUseKind::FnOnceCall
- } else if is_operator {
- FnSelfUseKind::Operator { self_arg }
- } else {
- debug!(
- "move_spans: method_did={:?}, fn_call_span={:?}",
- method_did, fn_call_span
- );
- let implicit_into_iter = matches!(
- fn_call_span.desugaring_kind(),
- Some(DesugaringKind::ForLoop(ForLoopLoc::IntoIter))
- );
- FnSelfUseKind::Normal { self_arg, implicit_into_iter }
- };
- return FnSelfUse {
- var_span: stmt.source_info.span,
- fn_call_span,
- fn_span: self
- .infcx
- .tcx
- .sess
- .source_map()
- .guess_head_span(self.infcx.tcx.def_span(method_did)),
- kind,
- };
- }
- }
+ let parent = tcx.parent(method_did);
+ let is_fn_once = parent == tcx.lang_items().fn_once_trait();
+ let is_operator = !from_hir_call
+ && parent.map_or(false, |p| tcx.lang_items().group(LangItemGroup::Op).contains(&p));
+ let fn_call_span = *fn_span;
+
+ let self_arg = tcx.fn_arg_names(method_did)[0];
+
+ let kind = if is_fn_once {
+ FnSelfUseKind::FnOnceCall
+ } else if is_operator {
+ FnSelfUseKind::Operator { self_arg }
+ } else {
+ debug!("move_spans: method_did={:?}, fn_call_span={:?}", method_did, fn_call_span);
+ let implicit_into_iter = matches!(
+ fn_call_span.desugaring_kind(),
+ Some(DesugaringKind::ForLoop(ForLoopLoc::IntoIter))
+ );
+ FnSelfUseKind::Normal { self_arg, implicit_into_iter }
+ };
+
+ return FnSelfUse {
+ var_span: stmt.source_info.span,
+ fn_call_span,
+ fn_span: self
+ .infcx
+ .tcx
+ .sess
+ .source_map()
+ .guess_head_span(self.infcx.tcx.def_span(method_did)),
+ kind,
+ };
}
normal_ret
}
diff --git a/compiler/rustc_mir/src/transform/check_const_item_mutation.rs b/compiler/rustc_mir/src/transform/check_const_item_mutation.rs
new file mode 100644
index 0000000000000..589268e39bda9
--- /dev/null
+++ b/compiler/rustc_mir/src/transform/check_const_item_mutation.rs
@@ -0,0 +1,114 @@
+use rustc_errors::DiagnosticBuilder;
+use rustc_middle::lint::LintDiagnosticBuilder;
+use rustc_middle::mir::visit::Visitor;
+use rustc_middle::mir::*;
+use rustc_middle::ty::TyCtxt;
+use rustc_session::lint::builtin::CONST_ITEM_MUTATION;
+use rustc_span::def_id::DefId;
+
+use crate::transform::{MirPass, MirSource};
+
+pub struct CheckConstItemMutation;
+
+impl<'tcx> MirPass<'tcx> for CheckConstItemMutation {
+ fn run_pass(&self, tcx: TyCtxt<'tcx>, _src: MirSource<'tcx>, body: &mut Body<'tcx>) {
+ let mut checker = ConstMutationChecker { body, tcx, target_local: None };
+ checker.visit_body(&body);
+ }
+}
+
+struct ConstMutationChecker<'a, 'tcx> {
+ body: &'a Body<'tcx>,
+ tcx: TyCtxt<'tcx>,
+ target_local: Option<Local>,
+}
+
+impl<'a, 'tcx> ConstMutationChecker<'a, 'tcx> {
+ fn is_const_item(&self, local: Local) -> Option<DefId> {
+ if let Some(box LocalInfo::ConstRef { def_id }) = self.body.local_decls[local].local_info {
+ Some(def_id)
+ } else {
+ None
+ }
+ }
+ fn lint_const_item_usage(
+ &self,
+ const_item: DefId,
+ location: Location,
+ decorate: impl for<'b> FnOnce(LintDiagnosticBuilder<'b>) -> DiagnosticBuilder<'b>,
+ ) {
+ let source_info = self.body.source_info(location);
+ let lint_root = self.body.source_scopes[source_info.scope]
+ .local_data
+ .as_ref()
+ .assert_crate_local()
+ .lint_root;
+
+ self.tcx.struct_span_lint_hir(CONST_ITEM_MUTATION, lint_root, source_info.span, |lint| {
+ decorate(lint)
+ .span_note(self.tcx.def_span(const_item), "`const` item defined here")
+ .emit()
+ });
+ }
+}
+
+impl<'a, 'tcx> Visitor<'tcx> for ConstMutationChecker<'a, 'tcx> {
+ fn visit_statement(&mut self, stmt: &Statement<'tcx>, loc: Location) {
+ if let StatementKind::Assign(box (lhs, _)) = &stmt.kind {
+ // Check for assignment to fields of a constant
+ // Assigning directly to a constant (e.g. `FOO = true;`) is a hard error,
+ // so emitting a lint would be redundant.
+ if !lhs.projection.is_empty() {
+ if let Some(def_id) = self.is_const_item(lhs.local) {
+ self.lint_const_item_usage(def_id, loc, |lint| {
+ let mut lint = lint.build("attempting to modify a `const` item");
+ lint.note("each usage of a `const` item creates a new temporary - the original `const` item will not be modified");
+ lint
+ })
+ }
+ }
+ // We are looking for MIR of the form:
+ //
+ // ```
+ // _1 = const FOO;
+ // _2 = &mut _1;
+ // method_call(_2, ..)
+ // ```
+ //
+ // Record our current LHS, so that we can detect this
+ // pattern in `visit_rvalue`
+ self.target_local = lhs.as_local();
+ }
+ self.super_statement(stmt, loc);
+ self.target_local = None;
+ }
+ fn visit_rvalue(&mut self, rvalue: &Rvalue<'tcx>, loc: Location) {
+ if let Rvalue::Ref(_, BorrowKind::Mut { .. }, place) = rvalue {
+ let local = place.local;
+ if let Some(def_id) = self.is_const_item(local) {
+ // If this Rvalue is being used as the right-hand side of a
+ // `StatementKind::Assign`, see if it ends up getting used as
+ // the `self` parameter of a method call (as the terminator of our current
+ // BasicBlock). If so, we emit a more specific lint.
+ let method_did = self.target_local.and_then(|target_local| {
+ crate::util::find_self_call(self.tcx, &self.body, target_local, loc.block)
+ });
+ let lint_loc =
+ if method_did.is_some() { self.body.terminator_loc(loc.block) } else { loc };
+ self.lint_const_item_usage(def_id, lint_loc, |lint| {
+ let mut lint = lint.build("taking a mutable reference to a `const` item");
+ lint
+ .note("each usage of a `const` item creates a new temporary")
+ .note("the mutable reference will refer to this temporary, not the original `const` item");
+
+ if let Some(method_did) = method_did {
+ lint.span_note(self.tcx.def_span(method_did), "mutable reference created due to call to this method");
+ }
+
+ lint
+ });
+ }
+ }
+ self.super_rvalue(rvalue, loc);
+ }
+}
diff --git a/compiler/rustc_mir/src/transform/mod.rs b/compiler/rustc_mir/src/transform/mod.rs
index c3a34756122a1..98f93ae6da0fe 100644
--- a/compiler/rustc_mir/src/transform/mod.rs
+++ b/compiler/rustc_mir/src/transform/mod.rs
@@ -16,6 +16,7 @@ use std::borrow::Cow;
pub mod add_call_guards;
pub mod add_moves_for_packed_drops;
pub mod add_retag;
+pub mod check_const_item_mutation;
pub mod check_consts;
pub mod check_packed_ref;
pub mod check_unsafety;
@@ -307,6 +308,7 @@ fn mir_const<'tcx>(
&[&[
// MIR-level lints.
&check_packed_ref::CheckPackedRef,
+ &check_const_item_mutation::CheckConstItemMutation,
// What we need to do constant evaluation.
&simplify::SimplifyCfg::new("initial"),
&rustc_peek::SanityCheck,
diff --git a/compiler/rustc_mir/src/util/find_self_call.rs b/compiler/rustc_mir/src/util/find_self_call.rs
new file mode 100644
index 0000000000000..049b5f01214cf
--- /dev/null
+++ b/compiler/rustc_mir/src/util/find_self_call.rs
@@ -0,0 +1,35 @@
+use rustc_middle::mir::*;
+use rustc_middle::ty::{self, TyCtxt};
+use rustc_span::def_id::DefId;
+
+/// Checks if the specified `local` is used as the `self` prameter of a method call
+/// in the provided `BasicBlock`. If it is, then the `DefId` of the called method is
+/// returned.
+pub fn find_self_call(
+ tcx: TyCtxt<'_>,
+ body: &Body<'_>,
+ local: Local,
+ block: BasicBlock,
+) -> Option<DefId> {
+ debug!("find_self_call(local={:?}): terminator={:?}", local, &body[block].terminator);
+ if let Some(Terminator { kind: TerminatorKind::Call { func, args, .. }, .. }) =
+ &body[block].terminator
+ {
+ debug!("find_self_call: func={:?}", func);
+ if let Operand::Constant(box Constant { literal: ty::Const { ty, .. }, .. }) = func {
+ if let ty::FnDef(def_id, _) = *ty.kind() {
+ if let Some(ty::AssocItem { fn_has_self_parameter: true, .. }) =
+ tcx.opt_associated_item(def_id)
+ {
+ debug!("find_self_call: args={:?}", args);
+ if let [Operand::Move(self_place) | Operand::Copy(self_place), ..] = **args {
+ if self_place.as_local() == Some(local) {
+ return Some(def_id);
+ }
+ }
+ }
+ }
+ }
+ }
+ None
+}
diff --git a/compiler/rustc_mir/src/util/mod.rs b/compiler/rustc_mir/src/util/mod.rs
index ed0fafb1aac16..699f3bcf0146f 100644
--- a/compiler/rustc_mir/src/util/mod.rs
+++ b/compiler/rustc_mir/src/util/mod.rs
@@ -7,12 +7,14 @@ pub mod storage;
mod alignment;
pub mod collect_writes;
+mod find_self_call;
mod graphviz;
pub(crate) mod pretty;
pub(crate) mod spanview;
pub use self::aggregate::expand_aggregate;
pub use self::alignment::is_disaligned;
+pub use self::find_self_call::find_self_call;
pub use self::graphviz::write_node_label as write_graphviz_node_label;
pub use self::graphviz::{graphviz_safe_def_name, write_mir_graphviz};
pub use self::pretty::{dump_enabled, dump_mir, write_mir_pretty, PassWhere};
diff --git a/compiler/rustc_mir_build/src/build/expr/as_constant.rs b/compiler/rustc_mir_build/src/build/expr/as_constant.rs
index 982aefcf6045c..244a70f83b03e 100644
--- a/compiler/rustc_mir_build/src/build/expr/as_constant.rs
+++ b/compiler/rustc_mir_build/src/build/expr/as_constant.rs
@@ -21,7 +21,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
let Expr { ty, temp_lifetime: _, span, kind } = expr;
match kind {
ExprKind::Scope { region_scope: _, lint_level: _, value } => this.as_constant(value),
- ExprKind::Literal { literal, user_ty } => {
+ ExprKind::Literal { literal, user_ty, const_id: _ } => {
let user_ty = user_ty.map(|user_ty| {
this.canonical_user_type_annotations.push(CanonicalUserTypeAnnotation {
span,
diff --git a/compiler/rustc_mir_build/src/build/expr/as_temp.rs b/compiler/rustc_mir_build/src/build/expr/as_temp.rs
index a9cc0cc2f2475..9984b527ffdb4 100644
--- a/compiler/rustc_mir_build/src/build/expr/as_temp.rs
+++ b/compiler/rustc_mir_build/src/build/expr/as_temp.rs
@@ -76,6 +76,9 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
local_decl.local_info =
Some(box LocalInfo::StaticRef { def_id, is_thread_local: true });
}
+ ExprKind::Literal { const_id: Some(def_id), .. } => {
+ local_decl.local_info = Some(box LocalInfo::ConstRef { def_id });
+ }
_ => {}
}
this.local_decls.push(local_decl)
diff --git a/compiler/rustc_mir_build/src/thir/cx/expr.rs b/compiler/rustc_mir_build/src/thir/cx/expr.rs
index e9e49d054b88d..70c7abc265492 100644
--- a/compiler/rustc_mir_build/src/thir/cx/expr.rs
+++ b/compiler/rustc_mir_build/src/thir/cx/expr.rs
@@ -247,6 +247,7 @@ fn make_mirror_unadjusted<'a, 'tcx>(
hir::ExprKind::Lit(ref lit) => ExprKind::Literal {
literal: cx.const_eval_literal(&lit.node, expr_ty, lit.span, false),
user_ty: None,
+ const_id: None,
},
hir::ExprKind::Binary(op, ref lhs, ref rhs) => {
@@ -306,6 +307,7 @@ fn make_mirror_unadjusted<'a, 'tcx>(
ExprKind::Literal {
literal: cx.const_eval_literal(&lit.node, expr_ty, lit.span, true),
user_ty: None,
+ const_id: None,
}
} else {
ExprKind::Unary { op: UnOp::Neg, arg: arg.to_ref() }
@@ -447,6 +449,7 @@ fn make_mirror_unadjusted<'a, 'tcx>(
kind: ExprKind::Literal {
literal: ty::Const::zero_sized(cx.tcx, ty),
user_ty,
+ const_id: None,
},
}
.to_ref(),
@@ -473,6 +476,7 @@ fn make_mirror_unadjusted<'a, 'tcx>(
kind: ExprKind::Literal {
literal: ty::Const::zero_sized(cx.tcx, ty),
user_ty: None,
+ const_id: None,
},
}
.to_ref(),
@@ -585,7 +589,7 @@ fn make_mirror_unadjusted<'a, 'tcx>(
temp_lifetime,
ty: var_ty,
span: expr.span,
- kind: ExprKind::Literal { literal, user_ty: None },
+ kind: ExprKind::Literal { literal, user_ty: None, const_id: None },
}
.to_ref()
};
@@ -714,7 +718,11 @@ fn method_callee<'a, 'tcx>(
temp_lifetime,
ty,
span,
- kind: ExprKind::Literal { literal: ty::Const::zero_sized(cx.tcx(), ty), user_ty },
+ kind: ExprKind::Literal {
+ literal: ty::Const::zero_sized(cx.tcx(), ty),
+ user_ty,
+ const_id: None,
+ },
}
}
@@ -777,6 +785,7 @@ fn convert_path_expr<'a, 'tcx>(
ExprKind::Literal {
literal: ty::Const::zero_sized(cx.tcx, cx.typeck_results().node_type(expr.hir_id)),
user_ty,
+ const_id: None,
}
}
@@ -794,6 +803,7 @@ fn convert_path_expr<'a, 'tcx>(
.tcx
.mk_const(ty::Const { val, ty: cx.typeck_results().node_type(expr.hir_id) }),
user_ty: None,
+ const_id: Some(def_id),
}
}
@@ -810,6 +820,7 @@ fn convert_path_expr<'a, 'tcx>(
ty: cx.typeck_results().node_type(expr.hir_id),
}),
user_ty,
+ const_id: Some(def_id),
}
}
diff --git a/compiler/rustc_mir_build/src/thir/mod.rs b/compiler/rustc_mir_build/src/thir/mod.rs
index 2837bfa040ff7..4d57fd5c64f8d 100644
--- a/compiler/rustc_mir_build/src/thir/mod.rs
+++ b/compiler/rustc_mir_build/src/thir/mod.rs
@@ -273,6 +273,10 @@ crate enum ExprKind<'tcx> {
Literal {
literal: &'tcx Const<'tcx>,
user_ty: Option<Canonical<'tcx, UserType<'tcx>>>,
+ /// The `DefId` of the `const` item this literal
+ /// was produced from, if this is not a user-written
+ /// literal value.
+ const_id: Option<DefId>,
},
/// A literal containing the address of a `static`.
///
diff --git a/compiler/rustc_session/src/lint/builtin.rs b/compiler/rustc_session/src/lint/builtin.rs
index 2db4d2a7f51d9..74b68bfe2a5c3 100644
--- a/compiler/rustc_session/src/lint/builtin.rs
+++ b/compiler/rustc_session/src/lint/builtin.rs
@@ -232,6 +232,12 @@ declare_lint! {
"detects unaligned references to fields of packed structs",
}
+declare_lint! {
+ pub CONST_ITEM_MUTATION,
+ Warn,
+ "detects attempts to mutate a `const` item",
+}
+
declare_lint! {
pub SAFE_PACKED_BORROWS,
Warn,
@@ -572,6 +578,7 @@ declare_lint_pass! {
CONST_ERR,
RENAMED_AND_REMOVED_LINTS,
UNALIGNED_REFERENCES,
+ CONST_ITEM_MUTATION,
SAFE_PACKED_BORROWS,
PATTERNS_IN_FNS_WITHOUT_BODY,
LATE_BOUND_LIFETIME_ARGUMENTS,
diff --git a/src/test/ui/error-codes/E0017.rs b/src/test/ui/error-codes/E0017.rs
index 818dec1207b96..54d3cc54a84d9 100644
--- a/src/test/ui/error-codes/E0017.rs
+++ b/src/test/ui/error-codes/E0017.rs
@@ -3,9 +3,11 @@ const C: i32 = 2;
static mut M: i32 = 3;
const CR: &'static mut i32 = &mut C; //~ ERROR E0764
+ //~| WARN taking a mutable
static STATIC_REF: &'static mut i32 = &mut X; //~ ERROR E0764
//~| ERROR E0019
//~| ERROR cannot borrow
static CONST_REF: &'static mut i32 = &mut C; //~ ERROR E0764
+ //~| WARN taking a mutable
static STATIC_MUT_REF: &'static mut i32 = unsafe { &mut M }; //~ ERROR E0764
fn main() {}
diff --git a/src/test/ui/error-codes/E0017.stderr b/src/test/ui/error-codes/E0017.stderr
index c1d96de1dca7c..40ef6bd97b3b0 100644
--- a/src/test/ui/error-codes/E0017.stderr
+++ b/src/test/ui/error-codes/E0017.stderr
@@ -1,3 +1,18 @@
+warning: taking a mutable reference to a `const` item
+ --> $DIR/E0017.rs:5:30
+ |
+LL | const CR: &'static mut i32 = &mut C;
+ | ^^^^^^
+ |
+ = note: `#[warn(const_item_mutation)]` on by default
+ = note: each usage of a `const` item creates a new temporary
+ = note: the mutable reference will refer to this temporary, not the original `const` item
+note: `const` item defined here
+ --> $DIR/E0017.rs:2:1
+ |
+LL | const C: i32 = 2;
+ | ^^^^^^^^^^^^^^^^^
+
error[E0764]: mutable references are not allowed in constants
--> $DIR/E0017.rs:5:30
|
@@ -5,7 +20,7 @@ LL | const CR: &'static mut i32 = &mut C;
| ^^^^^^ `&mut` is only allowed in `const fn`
error[E0019]: static contains unimplemented expression type
- --> $DIR/E0017.rs:6:39
+ --> $DIR/E0017.rs:7:39
|
LL | static STATIC_REF: &'static mut i32 = &mut X;
| ^^^^^^
@@ -13,30 +28,44 @@ LL | static STATIC_REF: &'static mut i32 = &mut X;
= help: add `#![feature(const_mut_refs)]` to the crate attributes to enable
error[E0764]: mutable references are not allowed in statics
- --> $DIR/E0017.rs:6:39
+ --> $DIR/E0017.rs:7:39
|
LL | static STATIC_REF: &'static mut i32 = &mut X;
| ^^^^^^ `&mut` is only allowed in `const fn`
error[E0596]: cannot borrow immutable static item `X` as mutable
- --> $DIR/E0017.rs:6:39
+ --> $DIR/E0017.rs:7:39
|
LL | static STATIC_REF: &'static mut i32 = &mut X;
| ^^^^^^ cannot borrow as mutable
+warning: taking a mutable reference to a `const` item
+ --> $DIR/E0017.rs:10:38
+ |
+LL | static CONST_REF: &'static mut i32 = &mut C;
+ | ^^^^^^
+ |
+ = note: each usage of a `const` item creates a new temporary
+ = note: the mutable reference will refer to this temporary, not the original `const` item
+note: `const` item defined here
+ --> $DIR/E0017.rs:2:1
+ |
+LL | const C: i32 = 2;
+ | ^^^^^^^^^^^^^^^^^
+
error[E0764]: mutable references are not allowed in statics
- --> $DIR/E0017.rs:9:38
+ --> $DIR/E0017.rs:10:38
|
LL | static CONST_REF: &'static mut i32 = &mut C;
| ^^^^^^ `&mut` is only allowed in `const fn`
error[E0764]: mutable references are not allowed in statics
- --> $DIR/E0017.rs:10:52
+ --> $DIR/E0017.rs:12:52
|
LL | static STATIC_MUT_REF: &'static mut i32 = unsafe { &mut M };
| ^^^^^^ `&mut` is only allowed in `const fn`
-error: aborting due to 6 previous errors
+error: aborting due to 6 previous errors; 2 warnings emitted
Some errors have detailed explanations: E0019, E0596, E0764.
For more information about an error, try `rustc --explain E0019`.
diff --git a/src/test/ui/error-codes/E0388.rs b/src/test/ui/error-codes/E0388.rs
index 13131017c2e07..8ad586bb30f1e 100644
--- a/src/test/ui/error-codes/E0388.rs
+++ b/src/test/ui/error-codes/E0388.rs
@@ -2,9 +2,11 @@ static X: i32 = 1;
const C: i32 = 2;
const CR: &'static mut i32 = &mut C; //~ ERROR E0764
+ //~| WARN taking a mutable
static STATIC_REF: &'static mut i32 = &mut X; //~ ERROR E0019
//~| ERROR cannot borrow
//~| ERROR E0764
static CONST_REF: &'static mut i32 = &mut C; //~ ERROR E0764
+ //~| WARN taking a mutable
fn main() {}
diff --git a/src/test/ui/error-codes/E0388.stderr b/src/test/ui/error-codes/E0388.stderr
index f09100bac43ce..39bc717ceec3e 100644
--- a/src/test/ui/error-codes/E0388.stderr
+++ b/src/test/ui/error-codes/E0388.stderr
@@ -1,3 +1,18 @@
+warning: taking a mutable reference to a `const` item
+ --> $DIR/E0388.rs:4:30
+ |
+LL | const CR: &'static mut i32 = &mut C;
+ | ^^^^^^
+ |
+ = note: `#[warn(const_item_mutation)]` on by default
+ = note: each usage of a `const` item creates a new temporary
+ = note: the mutable reference will refer to this temporary, not the original `const` item
+note: `const` item defined here
+ --> $DIR/E0388.rs:2:1
+ |
+LL | const C: i32 = 2;
+ | ^^^^^^^^^^^^^^^^^
+
error[E0764]: mutable references are not allowed in constants
--> $DIR/E0388.rs:4:30
|
@@ -5,7 +20,7 @@ LL | const CR: &'static mut i32 = &mut C;
| ^^^^^^ `&mut` is only allowed in `const fn`
error[E0019]: static contains unimplemented expression type
- --> $DIR/E0388.rs:5:39
+ --> $DIR/E0388.rs:6:39
|
LL | static STATIC_REF: &'static mut i32 = &mut X;
| ^^^^^^
@@ -13,24 +28,38 @@ LL | static STATIC_REF: &'static mut i32 = &mut X;
= help: add `#![feature(const_mut_refs)]` to the crate attributes to enable
error[E0764]: mutable references are not allowed in statics
- --> $DIR/E0388.rs:5:39
+ --> $DIR/E0388.rs:6:39
|
LL | static STATIC_REF: &'static mut i32 = &mut X;
| ^^^^^^ `&mut` is only allowed in `const fn`
error[E0596]: cannot borrow immutable static item `X` as mutable
- --> $DIR/E0388.rs:5:39
+ --> $DIR/E0388.rs:6:39
|
LL | static STATIC_REF: &'static mut i32 = &mut X;
| ^^^^^^ cannot borrow as mutable
+warning: taking a mutable reference to a `const` item
+ --> $DIR/E0388.rs:9:38
+ |
+LL | static CONST_REF: &'static mut i32 = &mut C;
+ | ^^^^^^
+ |
+ = note: each usage of a `const` item creates a new temporary
+ = note: the mutable reference will refer to this temporary, not the original `const` item
+note: `const` item defined here
+ --> $DIR/E0388.rs:2:1
+ |
+LL | const C: i32 = 2;
+ | ^^^^^^^^^^^^^^^^^
+
error[E0764]: mutable references are not allowed in statics
- --> $DIR/E0388.rs:8:38
+ --> $DIR/E0388.rs:9:38
|
LL | static CONST_REF: &'static mut i32 = &mut C;
| ^^^^^^ `&mut` is only allowed in `const fn`
-error: aborting due to 5 previous errors
+error: aborting due to 5 previous errors; 2 warnings emitted
Some errors have detailed explanations: E0019, E0596, E0764.
For more information about an error, try `rustc --explain E0019`.
diff --git a/src/test/ui/lint/lint-const-item-mutation.rs b/src/test/ui/lint/lint-const-item-mutation.rs
new file mode 100644
index 0000000000000..92d29a7dae475
--- /dev/null
+++ b/src/test/ui/lint/lint-const-item-mutation.rs
@@ -0,0 +1,21 @@
+// check-pass
+
+struct MyStruct {
+ field: bool,
+ inner_array: [char; 1],
+}
+impl MyStruct {
+ fn use_mut(&mut self) {}
+}
+
+const ARRAY: [u8; 1] = [25];
+const MY_STRUCT: MyStruct = MyStruct { field: true, inner_array: ['a'] };
+
+fn main() {
+ ARRAY[0] = 5; //~ WARN attempting to modify
+ MY_STRUCT.field = false; //~ WARN attempting to modify
+ MY_STRUCT.inner_array[0] = 'b'; //~ WARN attempting to modify
+ MY_STRUCT.use_mut(); //~ WARN taking
+ &mut MY_STRUCT; //~ WARN taking
+ (&mut MY_STRUCT).use_mut(); //~ WARN taking
+}
diff --git a/src/test/ui/lint/lint-const-item-mutation.stderr b/src/test/ui/lint/lint-const-item-mutation.stderr
new file mode 100644
index 0000000000000..2d8f2c49744ba
--- /dev/null
+++ b/src/test/ui/lint/lint-const-item-mutation.stderr
@@ -0,0 +1,89 @@
+warning: attempting to modify a `const` item
+ --> $DIR/lint-const-item-mutation.rs:15:5
+ |
+LL | ARRAY[0] = 5;
+ | ^^^^^^^^^^^^
+ |
+ = note: `#[warn(const_item_mutation)]` on by default
+ = note: each usage of a `const` item creates a new temporary - the original `const` item will not be modified
+note: `const` item defined here
+ --> $DIR/lint-const-item-mutation.rs:11:1
+ |
+LL | const ARRAY: [u8; 1] = [25];
+ | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+warning: attempting to modify a `const` item
+ --> $DIR/lint-const-item-mutation.rs:16:5
+ |
+LL | MY_STRUCT.field = false;
+ | ^^^^^^^^^^^^^^^^^^^^^^^
+ |
+ = note: each usage of a `const` item creates a new temporary - the original `const` item will not be modified
+note: `const` item defined here
+ --> $DIR/lint-const-item-mutation.rs:12:1
+ |
+LL | const MY_STRUCT: MyStruct = MyStruct { field: true, inner_array: ['a'] };
+ | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+warning: attempting to modify a `const` item
+ --> $DIR/lint-const-item-mutation.rs:17:5
+ |
+LL | MY_STRUCT.inner_array[0] = 'b';
+ | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+ |
+ = note: each usage of a `const` item creates a new temporary - the original `const` item will not be modified
+note: `const` item defined here
+ --> $DIR/lint-const-item-mutation.rs:12:1
+ |
+LL | const MY_STRUCT: MyStruct = MyStruct { field: true, inner_array: ['a'] };
+ | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+warning: taking a mutable reference to a `const` item
+ --> $DIR/lint-const-item-mutation.rs:18:5
+ |
+LL | MY_STRUCT.use_mut();
+ | ^^^^^^^^^^^^^^^^^^^
+ |
+ = note: each usage of a `const` item creates a new temporary
+ = note: the mutable reference will refer to this temporary, not the original `const` item
+note: mutable reference created due to call to this method
+ --> $DIR/lint-const-item-mutation.rs:8:5
+ |
+LL | fn use_mut(&mut self) {}
+ | ^^^^^^^^^^^^^^^^^^^^^
+note: `const` item defined here
+ --> $DIR/lint-const-item-mutation.rs:12:1
+ |
+LL | const MY_STRUCT: MyStruct = MyStruct { field: true, inner_array: ['a'] };
+ | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+warning: taking a mutable reference to a `const` item
+ --> $DIR/lint-const-item-mutation.rs:19:5
+ |
+LL | &mut MY_STRUCT;
+ | ^^^^^^^^^^^^^^
+ |
+ = note: each usage of a `const` item creates a new temporary
+ = note: the mutable reference will refer to this temporary, not the original `const` item
+note: `const` item defined here
+ --> $DIR/lint-const-item-mutation.rs:12:1
+ |
+LL | const MY_STRUCT: MyStruct = MyStruct { field: true, inner_array: ['a'] };
+ | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+warning: taking a mutable reference to a `const` item
+ --> $DIR/lint-const-item-mutation.rs:20:5
+ |
+LL | (&mut MY_STRUCT).use_mut();
+ | ^^^^^^^^^^^^^^^^
+ |
+ = note: each usage of a `const` item creates a new temporary
+ = note: the mutable reference will refer to this temporary, not the original `const` item
+note: `const` item defined here
+ --> $DIR/lint-const-item-mutation.rs:12:1
+ |
+LL | const MY_STRUCT: MyStruct = MyStruct { field: true, inner_array: ['a'] };
+ | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+warning: 6 warnings emitted
+
diff --git a/src/tools/clippy/clippy_lints/src/temporary_assignment.rs b/src/tools/clippy/clippy_lints/src/temporary_assignment.rs
index 1aeff1baa362e..2b6ddadd4c112 100644
--- a/src/tools/clippy/clippy_lints/src/temporary_assignment.rs
+++ b/src/tools/clippy/clippy_lints/src/temporary_assignment.rs
@@ -1,5 +1,4 @@
use crate::utils::{is_adjusted, span_lint};
-use rustc_hir::def::{DefKind, Res};
use rustc_hir::{Expr, ExprKind};
use rustc_lint::{LateContext, LateLintPass};
use rustc_session::{declare_lint_pass, declare_tool_lint};
@@ -22,10 +21,9 @@ declare_clippy_lint! {
"assignments to temporaries"
}
-fn is_temporary(cx: &LateContext<'_>, expr: &Expr<'_>) -> bool {
+fn is_temporary(_cx: &LateContext<'_>, expr: &Expr<'_>) -> bool {
match &expr.kind {
ExprKind::Struct(..) | ExprKind::Tup(..) => true,
- ExprKind::Path(qpath) => matches!(cx.qpath_res(qpath, expr.hir_id), Res::Def(DefKind::Const, ..)),
_ => false,
}
}
diff --git a/src/tools/clippy/tests/ui/borrow_interior_mutable_const.rs b/src/tools/clippy/tests/ui/borrow_interior_mutable_const.rs
index a414832bcd362..39f8751054850 100644
--- a/src/tools/clippy/tests/ui/borrow_interior_mutable_const.rs
+++ b/src/tools/clippy/tests/ui/borrow_interior_mutable_const.rs
@@ -1,5 +1,6 @@
#![warn(clippy::borrow_interior_mutable_const)]
#![allow(clippy::declare_interior_mutable_const, clippy::ref_in_deref)]
+#![allow(const_item_mutation)]
use std::borrow::Cow;
use std::cell::{Cell, UnsafeCell};
diff --git a/src/tools/clippy/tests/ui/borrow_interior_mutable_const.stderr b/src/tools/clippy/tests/ui/borrow_interior_mutable_const.stderr
index 1e0b3e4d20a52..5800af7e960f4 100644
--- a/src/tools/clippy/tests/ui/borrow_interior_mutable_const.stderr
+++ b/src/tools/clippy/tests/ui/borrow_interior_mutable_const.stderr
@@ -1,5 +1,5 @@
error: a `const` item with interior mutability should not be borrowed
- --> $DIR/borrow_interior_mutable_const.rs:65:5
+ --> $DIR/borrow_interior_mutable_const.rs:66:5
|
LL | ATOMIC.store(1, Ordering::SeqCst); //~ ERROR interior mutability
| ^^^^^^
@@ -8,7 +8,7 @@ LL | ATOMIC.store(1, Ordering::SeqCst); //~ ERROR interior mutability
= help: assign this const to a local or static variable, and use the variable here
error: a `const` item with interior mutability should not be borrowed
- --> $DIR/borrow_interior_mutable_const.rs:66:16
+ --> $DIR/borrow_interior_mutable_const.rs:67:16
|
LL | assert_eq!(ATOMIC.load(Ordering::SeqCst), 5); //~ ERROR interior mutability
| ^^^^^^
@@ -16,7 +16,7 @@ LL | assert_eq!(ATOMIC.load(Ordering::SeqCst), 5); //~ ERROR interior mutabi
= help: assign this const to a local or static variable, and use the variable here
error: a `const` item with interior mutability should not be borrowed
- --> $DIR/borrow_interior_mutable_const.rs:69:22
+ --> $DIR/borrow_interior_mutable_const.rs:70:22
|
LL | let _once_ref = &ONCE_INIT; //~ ERROR interior mutability
| ^^^^^^^^^
@@ -24,7 +24,7 @@ LL | let _once_ref = &ONCE_INIT; //~ ERROR interior mutability
= help: assign this const to a local or static variable, and use the variable here
error: a `const` item with interior mutability should not be borrowed
- --> $DIR/borrow_interior_mutable_const.rs:70:25
+ --> $DIR/borrow_interior_mutable_const.rs:71:25
|
LL | let _once_ref_2 = &&ONCE_INIT; //~ ERROR interior mutability
| ^^^^^^^^^
@@ -32,7 +32,7 @@ LL | let _once_ref_2 = &&ONCE_INIT; //~ ERROR interior mutability
= help: assign this const to a local or static variable, and use the variable here
error: a `const` item with interior mutability should not be borrowed
- --> $DIR/borrow_interior_mutable_const.rs:71:27
+ --> $DIR/borrow_interior_mutable_const.rs:72:27
|
LL | let _once_ref_4 = &&&&ONCE_INIT; //~ ERROR interior mutability
| ^^^^^^^^^
@@ -40,7 +40,7 @@ LL | let _once_ref_4 = &&&&ONCE_INIT; //~ ERROR interior mutability
= help: assign this const to a local or static variable, and use the variable here
error: a `const` item with interior mutability should not be borrowed
- --> $DIR/borrow_interior_mutable_const.rs:72:26
+ --> $DIR/borrow_interior_mutable_const.rs:73:26
|
LL | let _once_mut = &mut ONCE_INIT; //~ ERROR interior mutability
| ^^^^^^^^^
@@ -48,7 +48,7 @@ LL | let _once_mut = &mut ONCE_INIT; //~ ERROR interior mutability
= help: assign this const to a local or static variable, and use the variable here
error: a `const` item with interior mutability should not be borrowed
- --> $DIR/borrow_interior_mutable_const.rs:83:14
+ --> $DIR/borrow_interior_mutable_const.rs:84:14
|
LL | let _ = &ATOMIC_TUPLE; //~ ERROR interior mutability
| ^^^^^^^^^^^^
@@ -56,7 +56,7 @@ LL | let _ = &ATOMIC_TUPLE; //~ ERROR interior mutability
= help: assign this const to a local or static variable, and use the variable here
error: a `const` item with interior mutability should not be borrowed
- --> $DIR/borrow_interior_mutable_const.rs:84:14
+ --> $DIR/borrow_interior_mutable_const.rs:85:14
|
LL | let _ = &ATOMIC_TUPLE.0; //~ ERROR interior mutability
| ^^^^^^^^^^^^
@@ -64,7 +64,7 @@ LL | let _ = &ATOMIC_TUPLE.0; //~ ERROR interior mutability
= help: assign this const to a local or static variable, and use the variable here
error: a `const` item with interior mutability should not be borrowed
- --> $DIR/borrow_interior_mutable_const.rs:85:19
+ --> $DIR/borrow_interior_mutable_const.rs:86:19
|
LL | let _ = &(&&&&ATOMIC_TUPLE).0; //~ ERROR interior mutability
| ^^^^^^^^^^^^
@@ -72,7 +72,7 @@ LL | let _ = &(&&&&ATOMIC_TUPLE).0; //~ ERROR interior mutability
= help: assign this const to a local or static variable, and use the variable here
error: a `const` item with interior mutability should not be borrowed
- --> $DIR/borrow_interior_mutable_const.rs:86:14
+ --> $DIR/borrow_interior_mutable_const.rs:87:14
|
LL | let _ = &ATOMIC_TUPLE.0[0]; //~ ERROR interior mutability
| ^^^^^^^^^^^^
@@ -80,7 +80,7 @@ LL | let _ = &ATOMIC_TUPLE.0[0]; //~ ERROR interior mutability
= help: assign this const to a local or static variable, and use the variable here
error: a `const` item with interior mutability should not be borrowed
- --> $DIR/borrow_interior_mutable_const.rs:87:13
+ --> $DIR/borrow_interior_mutable_const.rs:88:13
|
LL | let _ = ATOMIC_TUPLE.0[0].load(Ordering::SeqCst); //~ ERROR interior mutability
| ^^^^^^^^^^^^
@@ -88,7 +88,7 @@ LL | let _ = ATOMIC_TUPLE.0[0].load(Ordering::SeqCst); //~ ERROR interior mu
= help: assign this const to a local or static variable, and use the variable here
error: a `const` item with interior mutability should not be borrowed
- --> $DIR/borrow_interior_mutable_const.rs:93:13
+ --> $DIR/borrow_interior_mutable_const.rs:94:13
|
LL | let _ = ATOMIC_TUPLE.0[0]; //~ ERROR interior mutability
| ^^^^^^^^^^^^
@@ -96,7 +96,7 @@ LL | let _ = ATOMIC_TUPLE.0[0]; //~ ERROR interior mutability
= help: assign this const to a local or static variable, and use the variable here
error: a `const` item with interior mutability should not be borrowed
- --> $DIR/borrow_interior_mutable_const.rs:98:5
+ --> $DIR/borrow_interior_mutable_const.rs:99:5
|
LL | CELL.set(2); //~ ERROR interior mutability
| ^^^^
@@ -104,7 +104,7 @@ LL | CELL.set(2); //~ ERROR interior mutability
= help: assign this const to a local or static variable, and use the variable here
error: a `const` item with interior mutability should not be borrowed
- --> $DIR/borrow_interior_mutable_const.rs:99:16
+ --> $DIR/borrow_interior_mutable_const.rs:100:16
|
LL | assert_eq!(CELL.get(), 6); //~ ERROR interior mutability
| ^^^^
@@ -112,7 +112,7 @@ LL | assert_eq!(CELL.get(), 6); //~ ERROR interior mutability
= help: assign this const to a local or static variable, and use the variable here
error: a `const` item with interior mutability should not be borrowed
- --> $DIR/borrow_interior_mutable_const.rs:112:5
+ --> $DIR/borrow_interior_mutable_const.rs:113:5
|
LL | u64::ATOMIC.store(5, Ordering::SeqCst); //~ ERROR interior mutability
| ^^^^^^^^^^^
@@ -120,7 +120,7 @@ LL | u64::ATOMIC.store(5, Ordering::SeqCst); //~ ERROR interior mutability
= help: assign this const to a local or static variable, and use the variable here
error: a `const` item with interior mutability should not be borrowed
- --> $DIR/borrow_interior_mutable_const.rs:113:16
+ --> $DIR/borrow_interior_mutable_const.rs:114:16
|
LL | assert_eq!(u64::ATOMIC.load(Ordering::SeqCst), 9); //~ ERROR interior mutability
| ^^^^^^^^^^^
diff --git a/src/tools/clippy/tests/ui/temporary_assignment.rs b/src/tools/clippy/tests/ui/temporary_assignment.rs
index c6c315d5fab5d..d6f56d40c5d4e 100644
--- a/src/tools/clippy/tests/ui/temporary_assignment.rs
+++ b/src/tools/clippy/tests/ui/temporary_assignment.rs
@@ -1,4 +1,5 @@
#![warn(clippy::temporary_assignment)]
+#![allow(const_item_mutation)]
use std::ops::{Deref, DerefMut};
diff --git a/src/tools/clippy/tests/ui/temporary_assignment.stderr b/src/tools/clippy/tests/ui/temporary_assignment.stderr
index 4efe2d4bb6713..4cc32c79f05ce 100644
--- a/src/tools/clippy/tests/ui/temporary_assignment.stderr
+++ b/src/tools/clippy/tests/ui/temporary_assignment.stderr
@@ -1,5 +1,5 @@
error: assignment to temporary
- --> $DIR/temporary_assignment.rs:47:5
+ --> $DIR/temporary_assignment.rs:48:5
|
LL | Struct { field: 0 }.field = 1;
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -7,7 +7,7 @@ LL | Struct { field: 0 }.field = 1;
= note: `-D clippy::temporary-assignment` implied by `-D warnings`
error: assignment to temporary
- --> $DIR/temporary_assignment.rs:48:5
+ --> $DIR/temporary_assignment.rs:49:5
|
LL | / MultiStruct {
LL | | structure: Struct { field: 0 },
@@ -17,40 +17,16 @@ LL | | .field = 1;
| |______________^
error: assignment to temporary
- --> $DIR/temporary_assignment.rs:53:5
+ --> $DIR/temporary_assignment.rs:54:5
|
LL | ArrayStruct { array: [0] }.array[0] = 1;
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
error: assignment to temporary
- --> $DIR/temporary_assignment.rs:54:5
+ --> $DIR/temporary_assignment.rs:55:5
|
LL | (0, 0).0 = 1;
| ^^^^^^^^^^^^
-error: assignment to temporary
- --> $DIR/temporary_assignment.rs:56:5
- |
-LL | A.0 = 2;
- | ^^^^^^^
-
-error: assignment to temporary
- --> $DIR/temporary_assignment.rs:57:5
- |
-LL | B.field = 2;
- | ^^^^^^^^^^^
-
-error: assignment to temporary
- --> $DIR/temporary_assignment.rs:58:5
- |
-LL | C.structure.field = 2;
- | ^^^^^^^^^^^^^^^^^^^^^
-
-error: assignment to temporary
- --> $DIR/temporary_assignment.rs:59:5
- |
-LL | D.array[0] = 2;
- | ^^^^^^^^^^^^^^
-
-error: aborting due to 8 previous errors
+error: aborting due to 4 previous errors