Add test of const item mutation with Drop impl

Author: dtolnay

src/test/ui/lint/lint-const-item-mutation.rs

@@ -9,9 +9,19 @@ impl MyStruct {
     fn use_mut(&mut self) {}
 }
 
+struct Mutable {
+    msg: &'static str,
+}
+impl Drop for Mutable {
+    fn drop(&mut self) {
+        println!("{}", self.msg);
+    }
+}
+
 const ARRAY: [u8; 1] = [25];
 const MY_STRUCT: MyStruct = MyStruct { field: true, inner_array: ['a'], raw_ptr: 2 as *mut u8 };
 const RAW_PTR: *mut u8 = 1 as *mut u8;
+const MUTABLE: Mutable = Mutable { msg: "" };
 
 fn main() {
     ARRAY[0] = 5; //~ WARN attempting to modify
@@ -29,4 +39,6 @@ fn main() {
         *RAW_PTR = 0;
         *MY_STRUCT.raw_ptr = 0;
     }
+
+    MUTABLE.msg = "wow"; // no warning, because Drop observes the mutation
 }

src/test/ui/lint/lint-const-item-mutation.stderr

@@ -1,45 +1,45 @@
 warning: attempting to modify a `const` item
-  --> $DIR/lint-const-item-mutation.rs:17:5
+  --> $DIR/lint-const-item-mutation.rs:27:5
    |
 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:12:1
+  --> $DIR/lint-const-item-mutation.rs:21:1
    |
 LL | const ARRAY: [u8; 1] = [25];
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 warning: attempting to modify a `const` item
-  --> $DIR/lint-const-item-mutation.rs:18:5
+  --> $DIR/lint-const-item-mutation.rs:28:5
    |
 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:13:1
+  --> $DIR/lint-const-item-mutation.rs:22:1
    |
 LL | const MY_STRUCT: MyStruct = MyStruct { field: true, inner_array: ['a'], raw_ptr: 2 as *mut u8 };
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 warning: attempting to modify a `const` item
-  --> $DIR/lint-const-item-mutation.rs:19:5
+  --> $DIR/lint-const-item-mutation.rs:29:5
    |
 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:13:1
+  --> $DIR/lint-const-item-mutation.rs:22:1
    |
 LL | const MY_STRUCT: MyStruct = MyStruct { field: true, inner_array: ['a'], raw_ptr: 2 as *mut u8 };
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 warning: taking a mutable reference to a `const` item
-  --> $DIR/lint-const-item-mutation.rs:20:5
+  --> $DIR/lint-const-item-mutation.rs:30:5
    |
 LL |     MY_STRUCT.use_mut();
    |     ^^^^^^^^^^^^^^^^^^^
@@ -52,35 +52,35 @@ note: mutable reference created due to call to this method
 LL |     fn use_mut(&mut self) {}
    |     ^^^^^^^^^^^^^^^^^^^^^
 note: `const` item defined here
-  --> $DIR/lint-const-item-mutation.rs:13:1
+  --> $DIR/lint-const-item-mutation.rs:22:1
    |
 LL | const MY_STRUCT: MyStruct = MyStruct { field: true, inner_array: ['a'], raw_ptr: 2 as *mut u8 };
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 warning: taking a mutable reference to a `const` item
-  --> $DIR/lint-const-item-mutation.rs:21:5
+  --> $DIR/lint-const-item-mutation.rs:31:5
    |
 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:13:1
+  --> $DIR/lint-const-item-mutation.rs:22:1
    |
 LL | const MY_STRUCT: MyStruct = MyStruct { field: true, inner_array: ['a'], raw_ptr: 2 as *mut u8 };
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 warning: taking a mutable reference to a `const` item
-  --> $DIR/lint-const-item-mutation.rs:22:5
+  --> $DIR/lint-const-item-mutation.rs:32:5
    |
 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:13:1
+  --> $DIR/lint-const-item-mutation.rs:22:1
    |
 LL | const MY_STRUCT: MyStruct = MyStruct { field: true, inner_array: ['a'], raw_ptr: 2 as *mut u8 };
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^