src/test/ui/polymorphization/const_parameters/closures.rs

   1 // build-fail
   2 // compile-flags:-Zpolymorphize=on
   3 #![feature(generic_const_exprs, rustc_attrs)]
   4 //~^ WARN the feature `generic_const_exprs` is incomplete
   5
   6 // This test checks that the polymorphization analysis correctly detects unused const
   7 // parameters in closures.
   8
   9 // Function doesn't have any generic parameters to be unused.
  10 #[rustc_polymorphize_error]
  11 pub fn no_parameters() {
  12     let _ = || {};
  13 }
  14
  15 // Function has an unused generic parameter in parent and closure.
  16 #[rustc_polymorphize_error]
  17 pub fn unused<const T: usize>() -> usize {
  18     //~^ ERROR item has unused generic parameters
  19     let add_one = |x: usize| x + 1;
  20     //~^ ERROR item has unused generic parameters
  21     add_one(3)
  22 }
  23
  24 // Function has an unused generic parameter in closure, but not in parent.
  25 #[rustc_polymorphize_error]
  26 pub fn used_parent<const T: usize>() -> usize {
  27     let x: usize = T;
  28     let add_one = |x: usize| x + 1;
  29     //~^ ERROR item has unused generic parameters
  30     x + add_one(3)
  31 }
  32
  33 // Function uses generic parameter in value of a binding in closure.
  34 #[rustc_polymorphize_error]
  35 pub fn used_binding<const T: usize>() -> usize {
  36     let x = || {
  37         let y: usize = T;
  38         y
  39     };
  40
  41     x()
  42 }
  43
  44 // Closure uses a value as an upvar, which used the generic parameter.
  45 #[rustc_polymorphize_error]
  46 pub fn unused_upvar<const T: usize>() -> usize {
  47     let x: usize = T;
  48     let y = || x;
  49     //~^ ERROR item has unused generic parameters
  50     y()
  51 }
  52
  53 // Closure uses generic parameter in substitutions to another function.
  54 #[rustc_polymorphize_error]
  55 pub fn used_substs<const T: usize>() -> usize {
  56     let x = || unused::<T>();
  57     x()
  58 }
  59
  60 fn main() {
  61     no_parameters();
  62     let _ = unused::<1>();
  63     let _ = used_parent::<1>();
  64     let _ = used_binding::<1>();
  65     let _ = unused_upvar::<1>();
  66     let _ = used_substs::<1>();
  67 }