Add check for number of type variables in type signature (#512)

* Fix tvar string generation

* Add check for number of tvars in a single type signature

The number of tvars is limited by serialization (u8) to 255

* Added a comment in CHANGELOG

* Docs fixes

* Adding docs about the limitation on number of tvars

* Limit is 256, not 255

* Update CHANGELOG.md

Co-authored-by: Gaith Hallak <gaithhallak@gmail.com>

---------

Co-authored-by: Gaith Hallak <gaithhallak@gmail.com>

docs/sophia_features.md

@@ -295,6 +295,11 @@ of `A`.
 - When a user-defined type `t('a)` is invariant in `'a`, then `t(A)` can never be
 a subtype of `t(B)`.
 
+#### Type variable limitation
+
+Because of how FATE represents types as values there is a fixed upper limit (256)
+of type variables that can be used in a single type signature.
+
 ## Mutable state
 
 Sophia does not have arbitrary mutable state, but only a limited form of state

docs/sophia_syntax.md

@@ -267,11 +267,11 @@ UnOp  ::= '-' | '!' | 'bnot'
 | Operators | Type
 | --- | ---
 | `-` `+` `*` `/` `mod` `^` | arithmetic operators
-| `!` `&&` `||` | logical operators
+| `!` `&&` `\|\|` | logical operators
 | `band` `bor` `bxor` `bnot` `<<` `>>` | bitwise operators
 | `==` `!=` `<` `>` `=<` `>=` | comparison operators
 | `::` `++` | list operators
-| `|>` | functional operators
+| `\|>` | functional operators
 
 ## Operator precedence
 
@@ -291,5 +291,5 @@ In order of highest to lowest precedence.
 | `bxor` | left
 | `bor` | left
 | `&&` | right
-| `||` | right
-| `|>` | left
+| `\|\|` | right
+| `\|>` | left