Move LSP semantics into typed analysis

internal/lang/go_interop_test.go

@@ -12,7 +12,7 @@ package demo
 import http net.http
 import json encoding.json
 
-fun main() {
+fun main(handler: (http.ResponseWriter, *http.Request) -> Unit, body: ByteSlice, target: Any) {
     http.handleFunc("/health", handler)
     json.unmarshal(body, &target)
 }