Don't return nil for methods using NoReturn

spec/spectator/mocks/double_spec.cr

@@ -114,6 +114,27 @@ Spectator.describe Spectator::Double do
     end
   end
 
+  context "with a method that uses NoReturn" do
+    Spectator::Double.define(NoReturnDouble) do
+      abstract_stub abstract def oops : NoReturn
+    end
+
+    subject(dbl) { NoReturnDouble.new }
+
+    it "raises a TypeCastError when using a value-based stub" do
+      stub = Spectator::ValueStub.new(:oops, nil).as(Spectator::Stub)
+      dbl._spectator_define_stub(stub)
+      expect { dbl.oops }.to raise_error(TypeCastError, /NoReturn/)
+    end
+
+    it "raises when using an exception stub" do
+      exception = ArgumentError.new("bogus")
+      stub = Spectator::ExceptionStub.new(:oops, exception).as(Spectator::Stub)
+      dbl._spectator_define_stub(stub)
+      expect { dbl.oops }.to raise_error(ArgumentError, "bogus")
+    end
+  end
+
   context "with common object methods" do
     subject(dbl) do
       EmptyDouble.new([

spec/spectator/mocks/mock_spec.cr

@@ -400,6 +400,31 @@ Spectator.describe Spectator::Mock do
         end
       end
     end
+
+    context "with a method that uses NoReturn" do
+      abstract class Thing
+        abstract def oops : NoReturn
+      end
+
+      Spectator::Mock.define_subtype(:class, Thing, MockThing)
+
+      let(mock) { MockThing.new }
+
+      after_each { mock._spectator_clear_stubs }
+
+      it "raises a TypeCastError when using a value-based stub" do
+        stub = Spectator::ValueStub.new(:oops, nil).as(Spectator::Stub)
+        mock._spectator_define_stub(stub)
+        expect { mock.oops }.to raise_error(TypeCastError, /NoReturn/)
+      end
+
+      it "raises when using an exception stub" do
+        exception = ArgumentError.new("bogus")
+        stub = Spectator::ExceptionStub.new(:oops, exception).as(Spectator::Stub)
+        mock._spectator_define_stub(stub)
+        expect { mock.oops }.to raise_error(ArgumentError, "bogus")
+      end
+    end
   end
 
   describe "#inject" do
@@ -719,5 +744,32 @@ Spectator.describe Spectator::Mock do
         end
       end
     end
+
+    context "with a method that uses NoReturn" do
+      struct ::NoReturnThing
+        def oops : NoReturn
+          raise "oops"
+        end
+      end
+
+      Spectator::Mock.inject(:struct, ::NoReturnThing)
+
+      let(mock) { NoReturnThing.new }
+
+      after_each { mock._spectator_clear_stubs }
+
+      it "raises a TypeCastError when using a value-based stub" do
+        stub = Spectator::ValueStub.new(:oops, nil).as(Spectator::Stub)
+        mock._spectator_define_stub(stub)
+        expect { mock.oops }.to raise_error(TypeCastError, /NoReturn/)
+      end
+
+      it "raises when using an exception stub" do
+        exception = ArgumentError.new("bogus")
+        stub = Spectator::ExceptionStub.new(:oops, exception).as(Spectator::Stub)
+        mock._spectator_define_stub(stub)
+        expect { mock.oops }.to raise_error(ArgumentError, "bogus")
+      end
+    end
   end
 end

spec/spectator/mocks/null_double_spec.cr

@@ -90,6 +90,27 @@ Spectator.describe Spectator::NullDouble do
     end
   end
 
+  context "with a method that uses NoReturn" do
+    Spectator::NullDouble.define(NoReturnDouble) do
+      abstract_stub abstract def oops : NoReturn
+    end
+
+    subject(dbl) { NoReturnDouble.new }
+
+    it "raises a TypeCastError when using a value-based stub" do
+      stub = Spectator::ValueStub.new(:oops, nil).as(Spectator::Stub)
+      dbl._spectator_define_stub(stub)
+      expect { dbl.oops }.to raise_error(TypeCastError, /NoReturn/)
+    end
+
+    it "raises when using an exception stub" do
+      exception = ArgumentError.new("bogus")
+      stub = Spectator::ExceptionStub.new(:oops, exception).as(Spectator::Stub)
+      dbl._spectator_define_stub(stub)
+      expect { dbl.oops }.to raise_error(ArgumentError, "bogus")
+    end
+  end
+
   context "with common object methods" do
     subject(dbl) do
       EmptyDouble.new([

src/spectator/mocks/stubbable.cr

@@ -149,7 +149,7 @@ module Spectator
         if %stub = _spectator_find_stub(%call)
           # Cast the stub or return value to the expected type.
           # This is necessary to match the expected return type of the original method.
-          _spectator_cast_stub_value(%stub, %call, typeof({{original}}), {{method.return_type && method.return_type.resolve <= Nil || method.return_type.is_a?(Union) && method.return_type.types.map(&.resolve).includes?(Nil)}})
+          _spectator_cast_stub_value(%stub, %call, typeof({{original}}), {{method.return_type && method.return_type.resolve != NoReturn && method.return_type.resolve <= Nil || method.return_type.is_a?(Union) && method.return_type.types.map(&.resolve).includes?(Nil)}})
         else
           # Delegate missing stub behavior to concrete type.
           _spectator_stub_fallback(%call, typeof({{original}})) do
@@ -241,7 +241,7 @@ module Spectator
           # This is necessary to match the expected return type of the original method.
           {% if method.return_type %}
             # Return type restriction takes priority since it can be a superset of the original implementation.
-            _spectator_cast_stub_value(%stub, %call, {{method.return_type}}, {{method.return_type.resolve <= Nil || method.return_type.is_a?(Union) && method.return_type.types.map(&.resolve).includes?(Nil)}})
+            _spectator_cast_stub_value(%stub, %call, {{method.return_type}}, {{method.return_type.resolve != NoReturn && method.return_type.resolve <= Nil || method.return_type.is_a?(Union) && method.return_type.types.map(&.resolve).includes?(Nil)}})
           {% elsif !method.abstract? %}
             # The method isn't abstract, infer the type it returns without calling it.
             _spectator_cast_stub_value(%stub, %call, typeof({{original}}))