Allow for variables with unknown types

Author: adamsol

src/compiler.py

@@ -359,8 +359,6 @@ def unify(self, node, *values):
     def declare(self, node, type, id, redeclare=False, initialize=False, check_only=False):
         if type == tVoid:
             self.throw(node, err.InvalidDeclaration(type))
-        if type.isUnknown():
-            self.throw(node, err.UnknownType())
         if id in self.env and not redeclare:
             self.throw(node, err.RedeclaredIdentifier(id))
         if check_only:

test/bad/arrays/empty01.err

@@ -1 +1 @@
-Cannot settle type of the expression.
+Illegal assignment from `[Int]` to `[<Unknown>]`.

test/bad/arrays/empty01.px

@@ -1,2 +1,3 @@
 
 a = []
+a = [3]

test/bad/arrays/empty02.err

@@ -0,0 +1,2 @@
+0
+6

test/bad/arrays/empty02.px

@@ -0,0 +1,8 @@
+
+func length<T>([T] a) Int def
+    if a.length == 0 do
+        return 0
+    return length(a[1:]) + 1
+
+print length([])
+print length([1, 2] * 3)