Implement pattern matching

[daniel-p-gonzalez]

Implement Erlang/Prolog/Elixir style pattern matching on complex types, e.g.

x = [1,2,3]
[a,b,c] = x
print(a) # 1
print(c) # 3

obj = {'name': 'Emmett', 'age': 1}
{'age': his_age} = obj
print(his_age)

Tasks:

• Implement pattern match assignment ast in parser

• • arrays
• • dicts

• Use unification in type inference pass to bind targets and types
• Unfold multiple assignments in code gen pass

TODO when structs and anonymous structs / tuples are implemented:

x = ("the", 1720512, true)
(token, count, is_stopword) = x
print(token)

# or using struct
struct MyType(token, count, is_stopword)
x = MyType("the", 1720512, true)
(token, count, is_stopword) = x
print(token)

TODO when exceptions are implemented:

x = [1,2,3]
[a, 2, c] = x # a=1, c=3
[a, 5, c] = x # raises pattern match exception

Keep in mind future usage in match construct:

x = ("the", 1720512, true)
match x:
  case (token, count, true):
      print("Matched stopword: " + token)
  case (token, count, false):
      print("Matched non-stopword: " + token)
end

# and possible an expression flavor:
x = ("the", 1720512, true)
message = match x:
  case (token, count, true):
      "Matched stopword: " + token
  case (token, count, false):
      "Matched non-stopword: " + token
end