Merge pull request #15 from alaviss/features/stringify

union: add a way to stringify unions

tests/tconv.nim

@@ -79,3 +79,9 @@ suite "Union conversions":
     check (10 as union(int | float)) == (10 as union(int | string))
     check ("string" as union(int | float | string | seq[string])) == ("string" as union(int | string))
     check ("string" as union(int | float | string | seq[string])) != (42 as union(int | string))
+
+  test "Auto string representation for unions":
+    check $(10 as union(int | float)) == "int(10)"
+    check $("string" as union(int | string)) == "string(\"string\")"
+    check $([1, 2] as union(int | array[2, int])) == "array[0..1, int]([1, 2])"
+    check $(@[1, 2] as union(string | seq[int])) == "seq[int](@[1, 2])"

union.nim

@@ -706,3 +706,11 @@ func `==`*[U, V: Union](a: U, b: V): bool {.inline.} =
           false
   else:
     false
+
+proc `$`*[T: Union](u: T): string =
+  ## Stringify `u` based on its current type in the format `type(value)`.
+  ## Its main purpose is to enable debugging.
+  unpack(u):
+    result = $typeof(it) & "("
+    result.addQuoted it
+    result.add ")"