Prefer expr_or_init over manual init detection

Urgau · Urgau · commit e577dcdd4dd0 · 2023-09-27T15:09:30.000+02:00
diff --git a/compiler/rustc_lint/src/lib.rs b/compiler/rustc_lint/src/lib.rs
@@ -200,7 +200,7 @@ late_lint_methods!(
             BoxPointers: BoxPointers,
             PathStatements: PathStatements,
             LetUnderscore: LetUnderscore,
-            InvalidReferenceCasting: InvalidReferenceCasting::default(),
+            InvalidReferenceCasting: InvalidReferenceCasting,
             // Depends on referenced function signatures in expressions
             UnusedResults: UnusedResults,
             NonUpperCaseGlobals: NonUpperCaseGlobals,
diff --git a/compiler/rustc_lint/src/reference_casting.rs b/compiler/rustc_lint/src/reference_casting.rs
@@ -1,8 +1,7 @@
 use rustc_ast::Mutability;
-use rustc_data_structures::fx::FxHashMap;
-use rustc_hir::{def::Res, Expr, ExprKind, HirId, Local, QPath, StmtKind, UnOp};
+use rustc_hir::{Expr, ExprKind, UnOp};
 use rustc_middle::ty::{self, TypeAndMut};
-use rustc_span::{sym, Span};
+use rustc_span::sym;
 
 use crate::{lints::InvalidReferenceCastingDiag, LateContext, LateLintPass, LintContext};
 
@@ -34,38 +33,18 @@ declare_lint! {
     "casts of `&T` to `&mut T` without interior mutability"
 }
 
-#[derive(Default)]
-pub struct InvalidReferenceCasting {
-    casted: FxHashMap<HirId, Span>,
-}
-
-impl_lint_pass!(InvalidReferenceCasting => [INVALID_REFERENCE_CASTING]);
+declare_lint_pass!(InvalidReferenceCasting => [INVALID_REFERENCE_CASTING]);
 
 impl<'tcx> LateLintPass<'tcx> for InvalidReferenceCasting {
-    fn check_stmt(&mut self, cx: &LateContext<'tcx>, stmt: &'tcx rustc_hir::Stmt<'tcx>) {
-        let StmtKind::Local(local) = stmt.kind else {
-            return;
-        };
-        let Local { init: Some(init), els: None, .. } = local else {
-            return;
-        };
-
-        if is_cast_from_const_to_mut(cx, init) {
-            self.casted.insert(local.pat.hir_id, init.span);
-        }
-    }
-
     fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'tcx>) {
         let Some((is_assignment, e)) = is_operation_we_care_about(cx, expr) else {
             return;
         };
 
-        let orig_cast = if is_cast_from_const_to_mut(cx, e) {
-            None
-        } else if let ExprKind::Path(QPath::Resolved(_, path)) = e.kind
-            && let Res::Local(hir_id) = &path.res
-            && let Some(orig_cast) = self.casted.get(hir_id) {
-            Some(*orig_cast)
+        let init = cx.expr_or_init(e);
+
+        let orig_cast = if is_cast_from_const_to_mut(cx, init) {
+            if init.span != e.span { Some(init.span) } else { None }
         } else {
             return;
         };
diff --git a/tests/ui/lint/reference_casting.rs b/tests/ui/lint/reference_casting.rs
@@ -47,9 +47,19 @@ unsafe fn ref_to_mut() {
     let deferred = (std::ptr::from_ref(num) as *const i32 as *const i32).cast_mut() as *mut i32;
     let _num = &mut *deferred;
     //~^ ERROR casting `&T` to `&mut T` is undefined behavior
+    let deferred_rebind = deferred;
+    let _num = &mut *deferred_rebind;
+    //~^ ERROR casting `&T` to `&mut T` is undefined behavior
     let _num = &mut *(num as *const _ as usize as *mut i32);
     //~^ ERROR casting `&T` to `&mut T` is undefined behavior
 
+    static NUM: &'static i32 = &2;
+    let num = NUM as *const i32 as *mut i32;
+    let num = num;
+    let num = num;
+    let _num = &mut *num;
+    //~^ ERROR casting `&T` to `&mut T` is undefined behavior
+
     unsafe fn generic_ref_cast_mut<T>(this: &T) -> &mut T {
         &mut *((this as *const _) as *mut _)
         //~^ ERROR casting `&T` to `&mut T` is undefined behavior
@@ -94,6 +104,9 @@ unsafe fn assign_to_ref() {
     let value = num as *const i32 as *mut i32;
     *value = 1;
     //~^ ERROR assigning to `&T` is undefined behavior
+    let value_rebind = value;
+    *value_rebind = 1;
+    //~^ ERROR assigning to `&T` is undefined behavior
     *(num as *const i32).cast::<i32>().cast_mut() = 2;
     //~^ ERROR assigning to `&T` is undefined behavior
     *(num as *const _ as usize as *mut i32) = 2;
diff --git a/tests/ui/lint/reference_casting.stderr b/tests/ui/lint/reference_casting.stderr
@@ -112,95 +112,117 @@ LL |     let _num = &mut *deferred;
    = note: for more information, visit <https://doc.rust-lang.org/book/ch15-05-interior-mutability.html>
 
 error: casting `&T` to `&mut T` is undefined behavior, even if the reference is unused, consider instead using an `UnsafeCell`
-  --> $DIR/reference_casting.rs:50:16
+  --> $DIR/reference_casting.rs:51:16
+   |
+LL |     let deferred = (std::ptr::from_ref(num) as *const i32 as *const i32).cast_mut() as *mut i32;
+   |                    ---------------------------------------------------------------------------- casting happend here
+...
+LL |     let _num = &mut *deferred_rebind;
+   |                ^^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: for more information, visit <https://doc.rust-lang.org/book/ch15-05-interior-mutability.html>
+
+error: casting `&T` to `&mut T` is undefined behavior, even if the reference is unused, consider instead using an `UnsafeCell`
+  --> $DIR/reference_casting.rs:53:16
    |
 LL |     let _num = &mut *(num as *const _ as usize as *mut i32);
    |                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
    = note: for more information, visit <https://doc.rust-lang.org/book/ch15-05-interior-mutability.html>
 
 error: casting `&T` to `&mut T` is undefined behavior, even if the reference is unused, consider instead using an `UnsafeCell`
-  --> $DIR/reference_casting.rs:54:9
+  --> $DIR/reference_casting.rs:60:16
+   |
+LL |     let num = NUM as *const i32 as *mut i32;
+   |               ----------------------------- casting happend here
+...
+LL |     let _num = &mut *num;
+   |                ^^^^^^^^^
+   |
+   = note: for more information, visit <https://doc.rust-lang.org/book/ch15-05-interior-mutability.html>
+
+error: casting `&T` to `&mut T` is undefined behavior, even if the reference is unused, consider instead using an `UnsafeCell`
+  --> $DIR/reference_casting.rs:64:9
    |
 LL |         &mut *((this as *const _) as *mut _)
    |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
    = note: for more information, visit <https://doc.rust-lang.org/book/ch15-05-interior-mutability.html>
 
 error: casting `&T` to `&mut T` is undefined behavior, even if the reference is unused, consider instead using an `UnsafeCell`
-  --> $DIR/reference_casting.rs:59:18
+  --> $DIR/reference_casting.rs:69:18
    |
 LL |         unsafe { &mut *std::cell::UnsafeCell::raw_get(x as *const _ as *const _) }
    |                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
    = note: for more information, visit <https://doc.rust-lang.org/book/ch15-05-interior-mutability.html>
 
 error: casting `&T` to `&mut T` is undefined behavior, even if the reference is unused, consider instead using an `UnsafeCell`
-  --> $DIR/reference_casting.rs:64:18
+  --> $DIR/reference_casting.rs:74:18
    |
 LL |         unsafe { &mut *std::cell::UnsafeCell::raw_get(x as *const _ as *const _) }
    |                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
    = note: for more information, visit <https://doc.rust-lang.org/book/ch15-05-interior-mutability.html>
 
 error: assigning to `&T` is undefined behavior, consider using an `UnsafeCell`
-  --> $DIR/reference_casting.rs:74:5
+  --> $DIR/reference_casting.rs:84:5
    |
 LL |     *(a as *const _ as *mut _) = String::from("Replaced");
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
    = note: for more information, visit <https://doc.rust-lang.org/book/ch15-05-interior-mutability.html>
 
 error: assigning to `&T` is undefined behavior, consider using an `UnsafeCell`
-  --> $DIR/reference_casting.rs:76:5
+  --> $DIR/reference_casting.rs:86:5
    |
 LL |     *(a as *const _ as *mut String) += " world";
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
    = note: for more information, visit <https://doc.rust-lang.org/book/ch15-05-interior-mutability.html>
 
 error: assigning to `&T` is undefined behavior, consider using an `UnsafeCell`
-  --> $DIR/reference_casting.rs:78:5
+  --> $DIR/reference_casting.rs:88:5
    |
 LL |     *std::ptr::from_ref(num).cast_mut() += 1;
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
    = note: for more information, visit <https://doc.rust-lang.org/book/ch15-05-interior-mutability.html>
 
 error: assigning to `&T` is undefined behavior, consider using an `UnsafeCell`
-  --> $DIR/reference_casting.rs:80:5
+  --> $DIR/reference_casting.rs:90:5
    |
 LL |     *std::ptr::from_ref({ num }).cast_mut() += 1;
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
    = note: for more information, visit <https://doc.rust-lang.org/book/ch15-05-interior-mutability.html>
 
 error: assigning to `&T` is undefined behavior, consider using an `UnsafeCell`
-  --> $DIR/reference_casting.rs:82:5
+  --> $DIR/reference_casting.rs:92:5
    |
 LL |     *{ std::ptr::from_ref(num) }.cast_mut() += 1;
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
    = note: for more information, visit <https://doc.rust-lang.org/book/ch15-05-interior-mutability.html>
 
 error: assigning to `&T` is undefined behavior, consider using an `UnsafeCell`
-  --> $DIR/reference_casting.rs:84:5
+  --> $DIR/reference_casting.rs:94:5
    |
 LL |     *(std::ptr::from_ref({ num }) as *mut i32) += 1;
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
    = note: for more information, visit <https://doc.rust-lang.org/book/ch15-05-interior-mutability.html>
 
 error: assigning to `&T` is undefined behavior, consider using an `UnsafeCell`
-  --> $DIR/reference_casting.rs:86:5
+  --> $DIR/reference_casting.rs:96:5
    |
 LL |     *std::mem::transmute::<_, *mut i32>(num) += 1;
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
    = note: for more information, visit <https://doc.rust-lang.org/book/ch15-05-interior-mutability.html>
 
 error: assigning to `&T` is undefined behavior, consider using an `UnsafeCell`
-  --> $DIR/reference_casting.rs:88:5
+  --> $DIR/reference_casting.rs:98:5
    |
 LL | /     std::ptr::write(
 LL | |
@@ -212,7 +234,7 @@ LL | |     );
    = note: for more information, visit <https://doc.rust-lang.org/book/ch15-05-interior-mutability.html>
 
 error: assigning to `&T` is undefined behavior, consider using an `UnsafeCell`
-  --> $DIR/reference_casting.rs:95:5
+  --> $DIR/reference_casting.rs:105:5
    |
 LL |     let value = num as *const i32 as *mut i32;
    |                 ----------------------------- casting happend here
@@ -222,23 +244,34 @@ LL |     *value = 1;
    = note: for more information, visit <https://doc.rust-lang.org/book/ch15-05-interior-mutability.html>
 
 error: assigning to `&T` is undefined behavior, consider using an `UnsafeCell`
-  --> $DIR/reference_casting.rs:97:5
+  --> $DIR/reference_casting.rs:108:5
+   |
+LL |     let value = num as *const i32 as *mut i32;
+   |                 ----------------------------- casting happend here
+...
+LL |     *value_rebind = 1;
+   |     ^^^^^^^^^^^^^^^^^
+   |
+   = note: for more information, visit <https://doc.rust-lang.org/book/ch15-05-interior-mutability.html>
+
+error: assigning to `&T` is undefined behavior, consider using an `UnsafeCell`
+  --> $DIR/reference_casting.rs:110:5
    |
 LL |     *(num as *const i32).cast::<i32>().cast_mut() = 2;
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
    = note: for more information, visit <https://doc.rust-lang.org/book/ch15-05-interior-mutability.html>
 
 error: assigning to `&T` is undefined behavior, consider using an `UnsafeCell`
-  --> $DIR/reference_casting.rs:99:5
+  --> $DIR/reference_casting.rs:112:5
    |
 LL |     *(num as *const _ as usize as *mut i32) = 2;
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
    = note: for more information, visit <https://doc.rust-lang.org/book/ch15-05-interior-mutability.html>
 
 error: assigning to `&T` is undefined behavior, consider using an `UnsafeCell`
-  --> $DIR/reference_casting.rs:101:5
+  --> $DIR/reference_casting.rs:114:5
    |
 LL |     let value = num as *const i32 as *mut i32;
    |                 ----------------------------- casting happend here
@@ -249,7 +282,7 @@ LL |     std::ptr::write(value, 2);
    = note: for more information, visit <https://doc.rust-lang.org/book/ch15-05-interior-mutability.html>
 
 error: assigning to `&T` is undefined behavior, consider using an `UnsafeCell`
-  --> $DIR/reference_casting.rs:103:5
+  --> $DIR/reference_casting.rs:116:5
    |
 LL |     let value = num as *const i32 as *mut i32;
    |                 ----------------------------- casting happend here
@@ -260,7 +293,7 @@ LL |     std::ptr::write_unaligned(value, 2);
    = note: for more information, visit <https://doc.rust-lang.org/book/ch15-05-interior-mutability.html>
 
 error: assigning to `&T` is undefined behavior, consider using an `UnsafeCell`
-  --> $DIR/reference_casting.rs:105:5
+  --> $DIR/reference_casting.rs:118:5
    |
 LL |     let value = num as *const i32 as *mut i32;
    |                 ----------------------------- casting happend here
@@ -271,12 +304,12 @@ LL |     std::ptr::write_volatile(value, 2);
    = note: for more information, visit <https://doc.rust-lang.org/book/ch15-05-interior-mutability.html>
 
 error: assigning to `&T` is undefined behavior, consider using an `UnsafeCell`
-  --> $DIR/reference_casting.rs:109:9
+  --> $DIR/reference_casting.rs:122:9
    |
 LL |         *(this as *const _ as *mut _) = a;
    |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
    = note: for more information, visit <https://doc.rust-lang.org/book/ch15-05-interior-mutability.html>
 
-error: aborting due to 32 previous errors
+error: aborting due to 35 previous errors
 
