"Fallout": Slightly different errors are generated in this edge case.

src/test/compile-fail/borrowck-closures-mut-of-imm.rs

@@ -24,6 +24,7 @@ fn a(x: &int) {
     //~^ ERROR cannot borrow
     let c2 = || set(&mut *x);
     //~^ ERROR cannot borrow
+    //~| ERROR closure requires unique access
 }
 
 fn main() {

src/test/compile-fail/issue-17551.rs

@@ -13,6 +13,6 @@
 struct B<T>;
 
 fn main() {
-    let foo = B; //~ ERROR unable to infer enough type information
-    let closure = |:| foo;
+    let foo = B;
+    let closure = |:| foo; //~ ERROR unable to infer enough type information
 }