Add an InfiniteLoop variant to EvalErrorKind

Author: ecstatic-morse

src/librustc/ich/impls_ty.rs

@@ -549,7 +549,8 @@ for ::mir::interpret::EvalErrorKind<'gcx, O> {
             RemainderByZero |
             DivisionByZero |
             GeneratorResumedAfterReturn |
-            GeneratorResumedAfterPanic => {}
+            GeneratorResumedAfterPanic |
+            InfiniteLoop => {}
             ReferencedConstant(ref err) => err.hash_stable(hcx, hasher),
             MachineError(ref err) => err.hash_stable(hcx, hasher),
             FunctionPointerTyMismatch(a, b) => {

src/librustc/mir/interpret/error.rs

@@ -264,6 +264,7 @@ pub enum EvalErrorKind<'tcx, O> {
     ReferencedConstant(Lrc<ConstEvalErr<'tcx>>),
     GeneratorResumedAfterReturn,
     GeneratorResumedAfterPanic,
+    InfiniteLoop,
 }
 
 pub type EvalResult<'tcx, T = ()> = Result<T, EvalError<'tcx>>;
@@ -398,6 +399,7 @@ impl<'tcx, O> EvalErrorKind<'tcx, O> {
             RemainderByZero => "attempt to calculate the remainder with a divisor of zero",
             GeneratorResumedAfterReturn => "generator resumed after completion",
             GeneratorResumedAfterPanic => "generator resumed after panicking",
+            InfiniteLoop => "program will never terminate",
         }
     }
 }

src/librustc/ty/structural_impls.rs

@@ -587,6 +587,7 @@ impl<'a, 'tcx, O: Lift<'tcx>> Lift<'tcx> for interpret::EvalErrorKind<'a, O> {
             RemainderByZero => RemainderByZero,
             GeneratorResumedAfterReturn => GeneratorResumedAfterReturn,
             GeneratorResumedAfterPanic => GeneratorResumedAfterPanic,
+            InfiniteLoop => InfiniteLoop,
         })
     }
 }

src/librustc_mir/interpret/eval_context.rs

@@ -180,7 +180,7 @@ impl<'a, 'mir, 'tcx, M> InfiniteLoopDetector<'a, 'mir, 'tcx, M>
         machine: &M,
         stack: &Vec<Frame<'mir, 'tcx>>,
         memory: &Memory<'a, 'mir, 'tcx, M>,
-    ) -> Result<(), (/*TODO*/)> {
+    ) -> EvalResult<'_, ()> {
         let snapshot = (machine, stack, memory);
 
         let mut fx = FxHasher::default();
@@ -197,8 +197,8 @@ impl<'a, 'mir, 'tcx, M> InfiniteLoopDetector<'a, 'mir, 'tcx, M>
             return Ok(())
         }
 
-        // Second cycle,
-        Err(())
+        // Second cycle
+        Err(EvalErrorKind::InfiniteLoop.into())
     }
 }