reassign-ref-mut

Author: Kivooeo

tests/ui/pattern/move-ref-patterns/pattern-ref-bindings-reassignment.rs

@@ -1,16 +1,24 @@
-// Tests how we behave when the user attempts to mutate an immutable
-// binding that was introduced by either `ref` or `ref mut`
-// patterns.
-//
-// Such bindings cannot be made mutable via the mere addition of the
-// `mut` keyword, and thus we want to check that the compiler does not
-// suggest doing so.
+//! Tests how we behave when the user attempts to mutate an immutable
+//! binding that was introduced by either `ref` or `ref mut`
+//! patterns.
+//!
+//! Such bindings cannot be made mutable via the mere addition of the
+//! `mut` keyword, and thus we want to check that the compiler does not
+//! suggest doing so.
 
 fn main() {
     let (mut one_two, mut three_four) = ((1, 2), (3, 4));
+
+    // Bind via pattern:
+    // - `a` as immutable reference (`ref`)
+    // - `b` as mutable reference (`ref mut`)
     let &mut (ref a, ref mut b) = &mut one_two;
+
+    // Attempt to reassign immutable `ref`-bound variable
     a = &three_four.0;
-    //~^ ERROR cannot assign twice to immutable variable `a` [E0384]
+    //~^ ERROR cannot assign twice to immutable variable `a`
+
+    // Attempt to reassign mutable `ref mut`-bound variable
     b = &mut three_four.1;
-    //~^ ERROR cannot assign twice to immutable variable `b` [E0384]
+    //~^ ERROR cannot assign twice to immutable variable `b`
 }

tests/ui/pattern/move-ref-patterns/pattern-ref-bindings-reassignment.stderr

@@ -1,13 +1,14 @@
 error[E0384]: cannot assign twice to immutable variable `a`
-  --> $DIR/reassign-ref-mut.rs:12:5
+  --> $DIR/pattern-ref-bindings-reassignment.rs:18:5
    |
 LL |     let &mut (ref a, ref mut b) = &mut one_two;
    |               ----- first assignment to `a`
+...
 LL |     a = &three_four.0;
    |     ^^^^^^^^^^^^^^^^^ cannot assign twice to immutable variable
 
 error[E0384]: cannot assign twice to immutable variable `b`
-  --> $DIR/reassign-ref-mut.rs:14:5
+  --> $DIR/pattern-ref-bindings-reassignment.rs:22:5
    |
 LL |     let &mut (ref a, ref mut b) = &mut one_two;
    |                      --------- first assignment to `b`