Keep in mind that Rust was already trying to figure out what the language itself was supposed to be and even if the whole lifetime analysis would work once they landed on it as a possible solution. Making a compiler suitable for an IDE from the beginning is much harder (but can inform language design). If you compare the output from rustc 1.0 to any recent version you will see how much of the work needed for a production compiler is at best tangentially related to what people consider the raison d'être for a compiler.