nordic-dev.net/rust
nordic-dev.net/rust
2
0
Fork 0
mirror of https://github.com/rust-lang/rust.git synced 2025-04-29 03:27:44 +00:00
Code Issues Packages Projects Releases Wiki Activity

Rollup merge of #78865 - Aaron1011:fix/const-item-mut-reborrow, r=varkor

Browse Source 
Don't fire `CONST_ITEM_MUTATION` lint when borrowing a deref

Fixes #78819

This extends the check for dereferences added in PR #77324
to cover mutable borrows, as well as direct writes. If we're operating
on a dereference of a `const` item, we shouldn't be firing the lint.
This commit is contained in:
Mara Bos 2020-11-08 13:36:33 +01:00 committed by GitHub
commit 91759b2de5
No known key found for this signature in database
GPG Key ID: 4AEE18F83AFDEB23
3 changed files with 47 additions and 33 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

51
compiler/rustc_mir/src/transform/check_const_item_mutation.rs
View File

@ -61,22 +61,35 @@ impl<'a, 'tcx> ConstMutationChecker<'a, 'tcx> {
fn lint_const_item_usage( fn lint_const_item_usage(
&self, &self,
place: &Place<'tcx>,
const_item: DefId, const_item: DefId,
location: Location, location: Location,
decorate: impl for<'b> FnOnce(LintDiagnosticBuilder<'b>) -> DiagnosticBuilder<'b>, decorate: impl for<'b> FnOnce(LintDiagnosticBuilder<'b>) -> DiagnosticBuilder<'b>,
) { ) {
let source_info = self.body.source_info(location); // Don't lint on borrowing/assigning to a dereference
let lint_root = self.body.source_scopes[source_info.scope] // e.g:
.local_data //
.as_ref() // `unsafe { *FOO = 0; *BAR.field = 1; }`
.assert_crate_local() // `unsafe { &mut *FOO }`
.lint_root; if !matches!(place.projection.last(), Some(PlaceElem::Deref)) {
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| { self.tcx.struct_span_lint_hir(
decorate(lint) CONST_ITEM_MUTATION,
.span_note(self.tcx.def_span(const_item), "`const` item defined here") lint_root,
.emit() source_info.span,
}); |lint| {
decorate(lint)
.span_note(self.tcx.def_span(const_item), "`const` item defined here")
.emit()
},
);
}
} }
} }
@ -88,15 +101,11 @@ impl<'a, 'tcx> Visitor<'tcx> for ConstMutationChecker<'a, 'tcx> {
// so emitting a lint would be redundant. // so emitting a lint would be redundant.
if !lhs.projection.is_empty() { if !lhs.projection.is_empty() {
if let Some(def_id) = self.is_const_item_without_destructor(lhs.local) { if let Some(def_id) = self.is_const_item_without_destructor(lhs.local) {
// Don't lint on writes through a pointer self.lint_const_item_usage(&lhs, def_id, loc, |lint| {
// (e.g. `unsafe { *FOO = 0; *BAR.field = 1; }`) let mut lint = lint.build("attempting to modify a `const` item");
if !matches!(lhs.projection.last(), Some(PlaceElem::Deref)) { lint.note("each usage of a `const` item creates a new temporary; the original `const` item will not be modified");
self.lint_const_item_usage(def_id, loc, |lint| { 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: // We are looking for MIR of the form:
@ -127,7 +136,7 @@ impl<'a, 'tcx> Visitor<'tcx> for ConstMutationChecker<'a, 'tcx> {
}); });
let lint_loc = let lint_loc =
if method_did.is_some() { self.body.terminator_loc(loc.block) } else { loc }; if method_did.is_some() { self.body.terminator_loc(loc.block) } else { loc };
self.lint_const_item_usage(def_id, lint_loc, |lint| { self.lint_const_item_usage(place, def_id, lint_loc, |lint| {
let mut lint = lint.build("taking a mutable reference to a `const` item"); let mut lint = lint.build("taking a mutable reference to a `const` item");
lint lint
.note("each usage of a `const` item creates a new temporary") .note("each usage of a `const` item creates a new temporary")

5
src/test/ui/lint/lint-const-item-mutation.rs
View File

@ -29,6 +29,7 @@ const RAW_PTR: *mut u8 = 1 as *mut u8;
const MUTABLE: Mutable = Mutable { msg: "" }; const MUTABLE: Mutable = Mutable { msg: "" };
const MUTABLE2: Mutable2 = Mutable2 { msg: "", other: String::new() }; const MUTABLE2: Mutable2 = Mutable2 { msg: "", other: String::new() };
const VEC: Vec<i32> = Vec::new(); const VEC: Vec<i32> = Vec::new();
const PTR: *mut () = 1 as *mut _;
fn main() { fn main() {
ARRAY[0] = 5; //~ WARN attempting to modify ARRAY[0] = 5; //~ WARN attempting to modify
@ -50,4 +51,8 @@ fn main() {
MUTABLE.msg = "wow"; // no warning, because Drop observes the mutation MUTABLE.msg = "wow"; // no warning, because Drop observes the mutation
MUTABLE2.msg = "wow"; //~ WARN attempting to modify MUTABLE2.msg = "wow"; //~ WARN attempting to modify
VEC.push(0); //~ WARN taking a mutable reference to a `const` item VEC.push(0); //~ WARN taking a mutable reference to a `const` item
// Test that we don't warn when converting a raw pointer
// into a mutable reference
unsafe { &mut *PTR };
} }

24
src/test/ui/lint/lint-const-item-mutation.stderr
View File

@ -1,11 +1,11 @@
warning: attempting to modify a `const` item warning: attempting to modify a `const` item
--> $DIR/lint-const-item-mutation.rs:34:5 --> $DIR/lint-const-item-mutation.rs:35:5
| |
LL | ARRAY[0] = 5; LL | ARRAY[0] = 5;
| ^^^^^^^^^^^^ | ^^^^^^^^^^^^
| |
= note: `#[warn(const_item_mutation)]` on by default = 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: each usage of a `const` item creates a new temporary; the original `const` item will not be modified
note: `const` item defined here note: `const` item defined here
--> $DIR/lint-const-item-mutation.rs:26:1 --> $DIR/lint-const-item-mutation.rs:26:1
| |
@ -13,12 +13,12 @@ LL | const ARRAY: [u8; 1] = [25];
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
warning: attempting to modify a `const` item warning: attempting to modify a `const` item
--> $DIR/lint-const-item-mutation.rs:35:5 --> $DIR/lint-const-item-mutation.rs:36:5
| |
LL | MY_STRUCT.field = false; 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: each usage of a `const` item creates a new temporary; the original `const` item will not be modified
note: `const` item defined here note: `const` item defined here
--> $DIR/lint-const-item-mutation.rs:27:1 --> $DIR/lint-const-item-mutation.rs:27:1
| |
@ -26,12 +26,12 @@ LL | const MY_STRUCT: MyStruct = MyStruct { field: true, inner_array: ['a'], raw
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
warning: attempting to modify a `const` item warning: attempting to modify a `const` item
--> $DIR/lint-const-item-mutation.rs:36:5 --> $DIR/lint-const-item-mutation.rs:37:5
| |
LL | MY_STRUCT.inner_array[0] = 'b'; 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: each usage of a `const` item creates a new temporary; the original `const` item will not be modified
note: `const` item defined here note: `const` item defined here
--> $DIR/lint-const-item-mutation.rs:27:1 --> $DIR/lint-const-item-mutation.rs:27:1
| |
@ -39,7 +39,7 @@ LL | const MY_STRUCT: MyStruct = MyStruct { field: true, inner_array: ['a'], raw
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
warning: taking a mutable reference to a `const` item warning: taking a mutable reference to a `const` item
--> $DIR/lint-const-item-mutation.rs:37:5 --> $DIR/lint-const-item-mutation.rs:38:5
| |
LL | MY_STRUCT.use_mut(); LL | MY_STRUCT.use_mut();
| ^^^^^^^^^^^^^^^^^^^ | ^^^^^^^^^^^^^^^^^^^
@ -58,7 +58,7 @@ LL | const MY_STRUCT: MyStruct = MyStruct { field: true, inner_array: ['a'], raw
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
warning: taking a mutable reference to a `const` item warning: taking a mutable reference to a `const` item
--> $DIR/lint-const-item-mutation.rs:38:5 --> $DIR/lint-const-item-mutation.rs:39:5
| |
LL | &mut MY_STRUCT; LL | &mut MY_STRUCT;
| ^^^^^^^^^^^^^^ | ^^^^^^^^^^^^^^
@ -72,7 +72,7 @@ LL | const MY_STRUCT: MyStruct = MyStruct { field: true, inner_array: ['a'], raw
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
warning: taking a mutable reference to a `const` item warning: taking a mutable reference to a `const` item
--> $DIR/lint-const-item-mutation.rs:39:5 --> $DIR/lint-const-item-mutation.rs:40:5
| |
LL | (&mut MY_STRUCT).use_mut(); LL | (&mut MY_STRUCT).use_mut();
| ^^^^^^^^^^^^^^^^ | ^^^^^^^^^^^^^^^^
@ -86,12 +86,12 @@ LL | const MY_STRUCT: MyStruct = MyStruct { field: true, inner_array: ['a'], raw
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
warning: attempting to modify a `const` item warning: attempting to modify a `const` item
--> $DIR/lint-const-item-mutation.rs:51:5 --> $DIR/lint-const-item-mutation.rs:52:5
| |
LL | MUTABLE2.msg = "wow"; LL | MUTABLE2.msg = "wow";
| ^^^^^^^^^^^^^^^^^^^^ | ^^^^^^^^^^^^^^^^^^^^
| |
= note: each usage of a `const` item creates a new temporary - the original `const` item will not be modified = note: each usage of a `const` item creates a new temporary; the original `const` item will not be modified
note: `const` item defined here note: `const` item defined here
--> $DIR/lint-const-item-mutation.rs:30:1 --> $DIR/lint-const-item-mutation.rs:30:1
| |
@ -99,7 +99,7 @@ LL | const MUTABLE2: Mutable2 = Mutable2 { msg: "", other: String::new() };
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
warning: taking a mutable reference to a `const` item warning: taking a mutable reference to a `const` item
--> $DIR/lint-const-item-mutation.rs:52:5 --> $DIR/lint-const-item-mutation.rs:53:5
| |
LL | VEC.push(0); LL | VEC.push(0);
| ^^^^^^^^^^^ | ^^^^^^^^^^^