Merge pull request #2346 from nxadm/master

Document typing of returns in signature

Author: nxadm

doc/Language/typesystem.pod6

@@ -846,6 +846,13 @@ will be checked against the given code object.
     CATCH { default { put .^name,': ', .Str } }
     # OUTPUT: «X::TypeCheck::Assignment: Type check failed in assignment to $i; expected Positive but got Int (-42)␤»
 
+Subsets can be used in signatures, e.g. by typing the output:
+    subset Foo of List where (Int,Str);
+    sub a($a, $b, --> Foo) { $a, $b }
+    # Only a List with the first element beint an Int and the second a Str will pass the type check.
+    a(1,"foo");  # passes
+    a("foo", 1); # fails
+
 Subsets can be anonymous, allowing inline placements where a subset is required
 but a name is neither needed nor desirable.