// Copyright 2012 The Rust Project Developers. See the COPYRIGHT // file at the top-level directory of this distribution and at // http://rust-lang.org/COPYRIGHT. // // Licensed under the Apache License, Version 2.0 or the MIT license // , at your // option. This file may not be copied, modified, or distributed // except according to those terms. struct point { x: int, y: int } fn a() { let mut p = point {x: 3, y: 4}; let _q = &p; //~ NOTE loan of mutable local variable granted here // This assignment is illegal because the field x is not // inherently mutable; since `p` was made immutable, `p.x` is now // immutable. Otherwise the type of &_q.x (&int) would be wrong. p.x = 5; //~ ERROR assigning to mutable field prohibited due to outstanding loan } fn c() { // this is sort of the opposite. We take a loan to the interior of `p` // and then try to overwrite `p` as a whole. let mut p = point {x: 3, y: 4}; let _q = &p.y; //~ NOTE loan of mutable local variable granted here p = point {x: 5, y: 7};//~ ERROR assigning to mutable local variable prohibited due to outstanding loan copy p; } fn d() { // just for completeness's sake, the easy case, where we take the // address of a subcomponent and then modify that subcomponent: let mut p = point {x: 3, y: 4}; let _q = &p.y; //~ NOTE loan of mutable field granted here p.y = 5; //~ ERROR assigning to mutable field prohibited due to outstanding loan copy p; } fn main() { }