This scenario has the Crystal compiler generate bad code

Depending on various tweaks, either a stack overflow or segfault occurs.

It seems to be caused by the compiler inferring types for methods combined with generic types and/or polymorphism.

src/spectator/expectations/value_expectation.cr

@@ -2,8 +2,9 @@ require "./expectation"
 
 module Spectator::Expectations
   # Expectation that operates on values.
-  # There is a primary "actual" value that the SUT produced.
-  # A matcher is used on that value to determine whether it satisfies some criteria.
+  # There are two values - the actual and expected.
+  # The actual value is what the SUT returned.
+  # The expected value is what the test wants to see.
   class ValueExpectation(ActualType) < Expectation
     # Creates the expectation.
     # The `matched` flag should be true if the matcher is satisfied with the partial.

test.cr

@@ -0,0 +1,8 @@
+require "./src/spectator"
+
+Spectator.describe String do
+  let(x) { 7 }
+  it "a" { expect(x).to(eq(nil)) }
+  it "b" { expect(x.odd?).to(be_true) }
+  it "c" { expect(x).to(eq(42)) }
+end