a document detailing the design of the ast for my lange fflat

fflat_design

Program is 
    Declaration+

TopLevelDeclaration is
    "type" Ident = '{' FieldDeclaration* '}'
    "enum" Ident = ('|' EnumDeclaration)*
    Declaration
    "for<"(Ident',')+'>' TopLevelDeclaration
    
Declaration is
    "let" "fn"? Ident ArgDeclaration* (':' Type)? = FnBody

FieldDeclaration is
    Ident : Type;

EnumDeclaration is
    Ident
    Ident Type
    Ident '{' FieldDeclaration* '}'

ArgDeclaration is
    Ident
    '('Ident ':' Type')'
    '_'
    "( _ :" Type')'

Type is
    Ident
    Ident'<'Type'>'
    Type -> Type
    '('Type')'
    '['Type;number']'
    '('(Type',')+')'
    "()"

Ident is string that is not op or number

FnBody is 
    Statement;+Expr?
    Expr

Statement is
    "return" Expr
    Declaration
    If
    Match
    FnCall

Op is
    string of '|' | '>' | '<' | '!' | '@' |  '$' | '=' | '&' | '+' | '-' | '\\' | '/' | '*' | '^' | '.'

Expr is
    Literal
    FnCall
    '('Expr')'
    Expr Op Expr
    Op Expr
    If
    Match

If is 
    "if" Expr "then" FnBody
    (else FnBody)?

Match is
    match Expr where
    MatchArm +

MatchArm is
    Condition -> Expr,
    Condition -> 
        (Statement';')+
        Expr?

Condition is 
    '|' Literal ('|'Condition)*
    '|' Ident 
    "| _"

Literal is 
    ArrayLiteral
    number
    '\''char'\''
    '"'string'"'
    '('(Expr',')+')'
    "()"

ArrayLiteral is
    '['Expr';'number']'
    '['(Expr',')+']'