ABOUT ME

• @felixmulder
• github.com/felixmulder
• Built the 2.12 Scaladoc
• Research fellow LAMP EPFL
• Dotty Compiler Engineer

A LANGUAGE IS ONLY AS

GOOD AS ITS TOOLING

ROUGH EDGES

trait Super {
def x: String
println(s"initialized with: $x")
}

class Tester extends Super {
val x = "hello!"
}

"initialized with: null"

DON’T WORRY SCALA, I STILL LOVE YOU

WE CAN WORK AROUND THIS

Newbie “Solutions”

• Compromised Immutability
• Lazification hell
• Refactor, maybe dump the trait

TYPE INFERENCE

型推論

TYPE INFERENCE

def ap1[A,B](a: A, f: A => B): B = f(a)

ap1(1, x => x * 2) // error: missing parameter type

TYPE INFERENCE

def ap2[A,B](a: A)(f: A => B): B = f(a)

ap2(1)(x => x * 2) // 2

class Foo { def bar: Int = ??? }
val foo = new Foo
// ...
foo.barr

AWESOME ERROR MESSAGES

SLOW COMPILE TIMES

長いコンパイル時間

Compilers crash course

• Tokenize Source
• Build Trees (AST)
• Typecheck
• Simplify
• Bytecode!

Compiler Phases

FUSED PHASES

SCALADOC

LANGUAGE SERVER

TASTY

• Pickling format
• Typed Trees
• Efficiently stored in bytecode
• Interop between binary incompatible compilers

Developer Usability

Get involved today!

Thank you!