type point = { x: int, y: int }; trait methods { fn impurem(); fn blockm(f: fn()); pure fn purem(); } impl foo of methods for point { fn impurem() { } fn blockm(f: fn()) { f() } pure fn purem() { } } fn a() { let mut p = {x: 3, y: 4}; // Here: it's ok to call even though receiver is mutable, because we // can loan it out. p.purem(); p.impurem(); // But in this case we do not honor the loan: do p.blockm { //~ NOTE loan of mutable local variable granted here p.x = 10; //~ ERROR assigning to mutable field prohibited due to outstanding loan } } fn b() { let mut p = {x: 3, y: 4}; // Here I create an outstanding loan and check that we get conflicts: &mut p; //~ NOTE prior loan as mutable granted here //~^ NOTE prior loan as mutable granted here p.purem(); //~ ERROR loan of mutable local variable as immutable conflicts with prior loan p.impurem(); //~ ERROR loan of mutable local variable as immutable conflicts with prior loan } fn c() { // Here the receiver is in aliased memory and hence we cannot // consider it immutable: let q = @mut {x: 3, y: 4}; // ...this is ok for pure fns (*q).purem(); // ...but not impure fns (*q).impurem(); //~ ERROR illegal borrow unless pure: creating immutable alias to aliasable, mutable memory //~^ NOTE impure due to access to impure function } fn main() { }