Update spec.md

spec.md

@@ -409,28 +409,85 @@ Give fuzzy-matched suggestions for at the following things:
 ## Store as much debug in fromation as possible until type checking is done
 
 
+# Compilation units 
+
+Each file is a "compilation unit"
+
+When compiling a compilation unit, the following inputs have to be provided:
+- any amount of files containing signatures of exported definitions.
+  only definitions of the compilation unit that are in one of the signature files will get exported.
+- any amount of other files containing imported definitions
+
+Note that there is no practical difference between signature and source files.
+
+<details>
+<summary>Example</summary>
+
+Export signature file `List.li`:
+```
+type List[t] = 'End | 'Cons {head:t, tail:List[t]}
+
+# not providing a function body makes it a function signature definition
+def [t] `a++b`(a: List[t], b: List[t]) -> List[t]
+```
+
+Import signature file `Option.li`:
+```
+type Option[t] = 'None | 'Some t
+```
+
+Compilation unit `List.lu`:
+```
+def [t] `a++b`(a: List[t], b: List[t]) -> List[t] {
+  # ...
+}
+```
+
+</details>
+
 
 # Syntax
 Note that the order of syntax cases matter!
 ```
 Identifier = { (* ( a-z | A-Z | 0-9 | _ | - | . | # )    TODO: cvt to ebnf *) };
+
 Partial Type = '?', Identifier;
 Union Type Case = '\'', Identifier, [ Type (*default to Unit*) ];
 Union Type = Union Type Case, { '|', Union Type Case};
 Record Type Field = Identifier, ':',  Type;
 Record Type = '{', [Record Type Field, {',' Record Type Field }], [ '...', Partial Type ], '}';
-Type = Partial Type | Identifier | Union Type | Record Type | TODO;
+With Type = 'with', Identifier, {',', Identifier}, ':', Type;
+Recursive Type = '&', Identifier, Type;
+Nested Type = '(', Type, ')';
+Multi Arg Type = '[', Type, {',', Type} ']', Type;
+Auto Type = '_';   (* this only works as return type of signatures of func def, that also contain the impl *)
+Type Part = Auto Type | Identifier | Partial Type | Union Type | Record Type | With Type | Recursive Type | Nested Type;
+Type = {Type Part (* args *)}, Type Part;
+
 ```
 
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 # OLD SPECIFICATION STARTING HERE
-## automatic return types
-```
-def add(a: Num, b: Num) -> _ {
-  a + b
-}
-```
-
 ## pattern matching
 ```
 type Option[t] = 'None | 'Some t
@@ -462,121 +519,7 @@ def example(li: List[Char]) -> {t:Token,rem:List[Char]} {
 }
 ```
 
-## recursive data types
-```
-type List[t] = 'End | 'Cons {head:t, tail:List[t]}
-# now you might notice an issue with this
-# `type` defines non-distinct type alisases
-# so what is the type of this...
-# Introducing: type self references
-# the above example is the same as this:
-type List[t] = &a ('End | 'Cons {head:t, tail:a})
 
-# example 2:
-# a List[List[t]] is just:
-&b ('End | 'Cons {head: &a ('End | 'Cons {head:t, tail:a}), tail: b})
-```
-
-Infinitely sized types are not allowed:
-```
-&a {x:Num, y:a}
-```
-
-However, infinite types without size *are* allowed:
-```
-&a {x:a}
-```
-
-This is *not* allowed:
-```
-&a a
-```
-
-## module system
-Each file is a "compilation unit"
-
-When compiling a compilation unit, the following inputs have to be provided:
-- any amount of files containing signatures of exported definitions.
-  only definitions of the compilation unit that are in one of the signature files will get exported.
-- any amount of other files containing imported definitions
-
-Note that there is no practical difference between signature and source files.
-
-### Example
-Export signature file `List.li`:
-```
-type List[t] = 'End | 'Cons {head:t, tail:List[t]}
-
-# not providing a function body makes it a function signature definition
-def [t] `a++b`(a: List[t], b: List[t]) -> List[t]
-
-def [t] Match.`a++b`(
-  value: List[t],
-  l: List[t],
-  r: MatchUtil.Var[List[t]]
-) -> Option[{ r: List[t] }]
-```
-
-Import signature file `Option.li`:
-```
-type Option[t] = 'None | 'Some t
-```
-
-Compilation unit `List.lu`:
-```
-def [t] `a++b`(a: List[t], b: List[t]) -> List[t] {
-  # ...
-}
-
-def [t] Match.`a++b`(
-  value: List[t],
-  l: List[t],
-  r: MatchUtil.Var[List[t]]
-) -> Option[{ r: List[t] }] {
-  # ...
-}
-```
-
-### Notes
-Each compilation unit gets compiled to implementation-specific bytecode.
-
-Templated functions can only be compiled partially during a compilation unit. This will impact compile speeds.
-
-Avoid templated functions wherever possible.
-
-## Hide record fields in module signatures
-Signatue:
-```
-type User = {name: List[Char], ...}
-  # the ... is used to indicate that this is a partial type definition
-  # User, as given here, can not be constructed, but name can be accessed
-```
-Compilation unit:
-```
-type User = {name: List[Char], password: List[Char]}
-```
-
-## Hide union variants in module signatures
-Signature:
-```
-type DType = 'Int | 'UInt | 'Byte | ...
-  # users of this can never do exhaustive pattern matching on this
-```
-Compilation unit:
-```
-type DType = 'Int | 'UInt | 'Byte
-  # this compilation unit can actually do exhaustive pattern matching on this
-```
-
-## Note on hidden union variants / record fields
-To make these work, the following is legal:
-```
-def example() -> 'Int | 'UInt | ...
-
-def example() -> 'Int | 'UInt | 'Byte | 'Char {
-  # ...
-}
-```
 
 ## Extensible unions
 ```
@@ -589,17 +532,6 @@ extend Plan with 'WritelnPlan Unit
 # can only pattern match with the imported extensions 
 ```
 
-## Any type
-in the stdlib:
-```
-extensible union Any
-
-type Any.LambdaCalc = 'Apply {fn: Any.LambdaCalc, arg: Any.LambdaCalc}
-                    | 'Scope {idx: Uint}
-                    | 'Abstr {inner: Any.LambdaCalc}
-def Any.toLambda(a: Any) -> Any.LambdaCalc
-```
-It gets automatically extended with every type ever used.
 
 ## Lenses
 In the stdlib: