src/test/ui/consts/trait_specialization.rs

   1 // ignore-wasm32-bare which doesn't support `std::process:exit()`
   2 // compile-flags: -Zmir-opt-level=3
   3 // run-pass
   4
   5 // Tests that specialization does not cause optimizations running on polymorphic MIR to resolve
   6 // to a `default` implementation.
   7
   8 #![feature(specialization)] //~ WARN the feature `specialization` is incomplete
   9
  10 trait Marker {}
  11
  12 trait SpecializedTrait {
  13     const CONST_BOOL: bool;
  14     const CONST_STR: &'static str;
  15     fn method() -> &'static str;
  16 }
  17 impl <T> SpecializedTrait for T {
  18     default const CONST_BOOL: bool = false;
  19     default const CONST_STR: &'static str = "in default impl";
  20     #[inline(always)]
  21     default fn method() -> &'static str {
  22         "in default impl"
  23     }
  24 }
  25 impl <T: Marker> SpecializedTrait for T {
  26     const CONST_BOOL: bool = true;
  27     const CONST_STR: &'static str = "in specialized impl";
  28     fn method() -> &'static str {
  29         "in specialized impl"
  30     }
  31 }
  32
  33 fn const_bool<T>() -> &'static str {
  34     if <T as SpecializedTrait>::CONST_BOOL {
  35         "in specialized impl"
  36     } else {
  37         "in default impl"
  38     }
  39 }
  40 fn const_str<T>() -> &'static str {
  41     <T as SpecializedTrait>::CONST_STR
  42 }
  43 fn run_method<T>() -> &'static str {
  44     <T as SpecializedTrait>::method()
  45 }
  46
  47 struct TypeA;
  48 impl Marker for TypeA {}
  49 struct TypeB;
  50
  51 #[inline(never)]
  52 fn exit_if_not_eq(left: &str, right: &str) {
  53     if left != right {
  54         std::process::exit(1);
  55     }
  56 }
  57
  58 pub fn main() {
  59     exit_if_not_eq("in specialized impl", const_bool::<TypeA>());
  60     exit_if_not_eq("in default impl", const_bool::<TypeB>());
  61     exit_if_not_eq("in specialized impl", const_str::<TypeA>());
  62     exit_if_not_eq("in default impl", const_str::<TypeB>());
  63     exit_if_not_eq("in specialized impl", run_method::<TypeA>());
  64     exit_if_not_eq("in default impl", run_method::<TypeB>());
  65 }