Rollup merge of #80133 - Aaron1011:fix/const-mut-deref, r=estebank

Suppress `CONST_ITEM_MUTATION` lint if a dereference occurs anywhere

Fixes #79971

2 files changed, 16 insertions, 8 deletions

diff --git a/src/test/ui/lint/lint-const-item-mutation.rs b/src/test/ui/lint/lint-const-item-mutation.rs
index ef55f31593b..4bf5e0a9e21 100644
--- a/src/test/ui/lint/lint-const-item-mutation.rs
+++ b/src/test/ui/lint/lint-const-item-mutation.rs
@@ -30,6 +30,8 @@ const MUTABLE: Mutable = Mutable { msg: "" };
 const MUTABLE2: Mutable2 = Mutable2 { msg: "", other: String::new() };
 const VEC: Vec<i32> = Vec::new();
 const PTR: *mut () = 1 as *mut _;
+const PTR_TO_ARRAY: *mut [u32; 4] = 0x12345678 as _;
+const ARRAY_OF_PTR: [*mut u32; 1] = [1 as *mut _];
 
 fn main() {
     ARRAY[0] = 5; //~ WARN attempting to modify
@@ -55,4 +57,10 @@ fn main() {
     // Test that we don't warn when converting a raw pointer
     // into a mutable reference
     unsafe { &mut *PTR };
+
+    // Test that we don't warn when there's a dereference involved.
+    // If we ever 'leave' the const via a deference, we're going
+    // to end up modifying something other than the temporary
+    unsafe { (*PTR_TO_ARRAY)[0] = 1 };
+    unsafe { *ARRAY_OF_PTR[0] = 25; }
 }
diff --git a/src/test/ui/lint/lint-const-item-mutation.stderr b/src/test/ui/lint/lint-const-item-mutation.stderr
index ae95abc72f3..74505eeb987 100644
--- a/src/test/ui/lint/lint-const-item-mutation.stderr
+++ b/src/test/ui/lint/lint-const-item-mutation.stderr
@@ -1,5 +1,5 @@
 warning: attempting to modify a `const` item
-  --> $DIR/lint-const-item-mutation.rs:35:5
+  --> $DIR/lint-const-item-mutation.rs:37:5
    |
 LL |     ARRAY[0] = 5;
    |     ^^^^^^^^^^^^
@@ -13,7 +13,7 @@ LL | const ARRAY: [u8; 1] = [25];
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 warning: attempting to modify a `const` item
-  --> $DIR/lint-const-item-mutation.rs:36:5
+  --> $DIR/lint-const-item-mutation.rs:38:5
    |
 LL |     MY_STRUCT.field = false;
    |     ^^^^^^^^^^^^^^^^^^^^^^^
@@ -26,7 +26,7 @@ LL | const MY_STRUCT: MyStruct = MyStruct { field: true, inner_array: ['a'], raw
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 warning: attempting to modify a `const` item
-  --> $DIR/lint-const-item-mutation.rs:37:5
+  --> $DIR/lint-const-item-mutation.rs:39:5
    |
 LL |     MY_STRUCT.inner_array[0] = 'b';
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -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
-  --> $DIR/lint-const-item-mutation.rs:38:5
+  --> $DIR/lint-const-item-mutation.rs:40:5
    |
 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
-  --> $DIR/lint-const-item-mutation.rs:39:5
+  --> $DIR/lint-const-item-mutation.rs:41:5
    |
 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
-  --> $DIR/lint-const-item-mutation.rs:40:5
+  --> $DIR/lint-const-item-mutation.rs:42:5
    |
 LL |     (&mut MY_STRUCT).use_mut();
    |     ^^^^^^^^^^^^^^^^
@@ -86,7 +86,7 @@ LL | const MY_STRUCT: MyStruct = MyStruct { field: true, inner_array: ['a'], raw
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 warning: attempting to modify a `const` item
-  --> $DIR/lint-const-item-mutation.rs:52:5
+  --> $DIR/lint-const-item-mutation.rs:54:5
    |
 LL |     MUTABLE2.msg = "wow";
    |     ^^^^^^^^^^^^^^^^^^^^
@@ -99,7 +99,7 @@ LL | const MUTABLE2: Mutable2 = Mutable2 { msg: "", other: String::new() };
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 warning: taking a mutable reference to a `const` item
-  --> $DIR/lint-const-item-mutation.rs:53:5
+  --> $DIR/lint-const-item-mutation.rs:55:5
    |
 LL |     VEC.push(0);
    |     ^^^^^^^^^^^