src/test/ui/never_type/diverging-fallback-control-flow.rs

   1 // run-pass
   2
   3 #![allow(dead_code)]
   4 #![allow(unused_assignments)]
   5 #![allow(unused_variables)]
   6 #![allow(unreachable_code)]
   7
   8 // Test various cases where we permit an unconstrained variable
   9 // to fallback based on control-flow.
  10 //
  11 // These represent current behavior, but are pretty dubious.  I would
  12 // like to revisit these and potentially change them. --nmatsakis
  13
  14 #![feature(never_type, never_type_fallback)]
  15
  16 trait BadDefault {
  17     fn default() -> Self;
  18 }
  19
  20 impl BadDefault for u32 {
  21     fn default() -> Self {
  22         0
  23     }
  24 }
  25
  26 impl BadDefault for ! {
  27     fn default() -> ! {
  28         panic!()
  29     }
  30 }
  31
  32 fn assignment() {
  33     let x;
  34
  35     if true {
  36         x = BadDefault::default();
  37     } else {
  38         x = return;
  39     }
  40 }
  41
  42 fn assignment_rev() {
  43     let x;
  44
  45     if true {
  46         x = return;
  47     } else {
  48         x = BadDefault::default();
  49     }
  50 }
  51
  52 fn if_then_else() {
  53     let _x = if true {
  54         BadDefault::default()
  55     } else {
  56         return;
  57     };
  58 }
  59
  60 fn if_then_else_rev() {
  61     let _x = if true {
  62         return;
  63     } else {
  64         BadDefault::default()
  65     };
  66 }
  67
  68 fn match_arm() {
  69     let _x = match Ok(BadDefault::default()) {
  70         Ok(v) => v,
  71         Err(()) => return,
  72     };
  73 }
  74
  75 fn match_arm_rev() {
  76     let _x = match Ok(BadDefault::default()) {
  77         Err(()) => return,
  78         Ok(v) => v,
  79     };
  80 }
  81
  82 fn loop_break() {
  83     let _x = loop {
  84         if false {
  85             break return;
  86         } else {
  87             break BadDefault::default();
  88         }
  89     };
  90 }
  91
  92 fn loop_break_rev() {
  93     let _x = loop {
  94         if false {
  95             break return;
  96         } else {
  97             break BadDefault::default();
  98         }
  99     };
 100 }
 101
 102 fn main() { }