Endless method definition

[mamantoha]

Adds support for endless method definitions:

def square(x) = x * x
def square(x : Int32) : Int32 = x * x
def default_value = nil
def self.foo = 1

This is related to the existing RFC/discussion in #9080

This PR is mostly a just-for-fun experiment. The discussion in #9080 was skeptical, and I am not sure anyone actually wants this feature in Crystal. I wanted to explore what the implementation would look like.

Endless method bodies must start on the same line as =.

Invalid examples:

def foo =
  1

def foo(x) =
  x

def foo =
  1
  2
  3

---

This PR is not really about saving characters.

I also agree with everyone who doesn't like it: I don’t really need this change either 🙂

[yxhuvud]

I for one really want it. I see no examples with a type declaration at the end (or wherever they should be)

[mamantoha]

@yxhuvud

Parser spec:

it_parses "def foo(x) : Int32 = x", Def.new("foo", args: ["x".arg], body: "x".var, return_type: "Int32".path)

Formatter spec:

assert_format "def   foo (  x  :  Int32 ) : Int32 = x", "def foo(x : Int32) : Int32 = x"

[kostya]

def square(x); x * x; end - just 4 symbols longer.

[jneen]

I would use this feature in Crystal.