Compiler: incorrect codegen code for casting a nilable type to a virtual type. Fixes #3512

Ary Borenszweig · Ary Borenszweig · commit 2ce8c2450b53 · 2016-11-08T10:24:41.000+01:00
diff --git a/spec/compiler/codegen/cast_spec.cr b/spec/compiler/codegen/cast_spec.cr
@@ -389,4 +389,26 @@ describe "Code gen: cast" do
       end
       )).to_string.should eq("A")
   end
+
+  it "casts from nilable type to virtual type (#3512)" do
+    run(%(
+      require "prelude"
+
+      class Foo
+        def foo
+          1
+        end
+      end
+
+      class Bar < Foo
+        def foo
+          2
+        end
+      end
+
+      foo = 1 == 2 ? nil : Foo.new
+      x = foo.as(Foo)
+      x.foo
+      )).to_i.should eq(1)
+  end
 end
diff --git a/src/compiler/crystal/codegen/cast.cr b/src/compiler/crystal/codegen/cast.cr
@@ -325,6 +325,10 @@ class Crystal::CodeGenVisitor
     cast_to value, to_type
   end
 
+  def downcast_distinct(value, to_type : VirtualType, from_type : NilableType)
+    cast_to value, to_type
+  end
+
   def downcast_distinct(value, to_type : Type, from_type : NilableType)
     value
   end
