Move LSP semantics into typed analysis

examples/generics.gt

@@ -0,0 +1,15 @@
+package main
+
+data class Box<T>(var value: T) {
+    fun get(): T { return value }
+}
+
+fun identity<T>(value: T): T { return value }
+
+fun main() {
+    val number = identity(42)
+    val text = identity<String>("value")
+    val box = Box(text)
+    println(number)
+    println(box.get())
+}