fix fromTasty test

Author: liufengyun

tests/pos/simpleCaseObject.decompiled

@@ -7,7 +7,8 @@ package foo {
 
     override def hashCode(): Int = 1045991777
     override def toString(): String = "Foo"
-    override def canEqual(that: Any): Boolean = that.isInstanceOf[foo.Foo]
+    override def canEqual(that: Any): Boolean =
+      that.isInstanceOf[foo.Foo @unchecked]
     override def productArity: Int = 0
     override def productPrefix: String = "Foo"
     override def productElement(n: Int): Any =
@@ -17,4 +18,4 @@ package foo {
         }
   }
 }
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+--------------------------------------------------------------------------------