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Types

primary-type ::= nominal-type |
                 literal-type |
                 boolean-type |
                 integer-type |
                 real-type |
                 atom-type |
                 string-type |
                 reference-type |
                 handle-type |
                 module-type |
                 record-type |
                 error-type |
                 tuple-type |
                 array-type |
                 set-type |
                 map-type |
                 function-type |
                 agent-type
type ::= any-type |
         unknown-type |
         union-type |
         variable-type
type-annotation ::= ':' type

Return Types

return-type ::= regular-return-type |
                none-return-type
regular-return-type ::= type
none-return-type ::= 'none'
return-type-annotation ::= '->' return-type return-type-annotation-raise?
return-type-annotation-raise ::= 'raise' type

Special Types

Any Type

any-type ::= 'any'

any is a special type that, like unk, allows any value. Unlike unk, however, any allows you to perform any operation on the value, even if the type checker would otherwise be able to prove that a given operation is incorrect.

The type of any operation on a value typed as any is also any. A value of type any can be assigned to a location of any other type.

unk should generally be preferred over any wherever possible.

Unknown Type

unknown-type ::= 'unk'

unk is a special type that, like any, allows any value. Unlike any, however, unk only allows a very limited set of operations which are safe on all values. In other words, unk is the type-safe counterpart to any.

A value of type unk can only be assigned to a location of type unk or any.

Union Type

union-type ::= primary-type ('or' primary-type)*

Variable Type

variable-type ::= 'type' lower-identifier variable-type-constraint?
variable-type-constraint ::= ':' union-type

Nominal Type

nominal-type ::= nominal-type-path? lower-identifier nominal-type-argument-list?
nominal-type-path ::= module-path '.'
nominal-type-argument-list ::= '(' nominal-type-argument (',' nominal-type-argument)* ','? ')'
nominal-type-argument ::= type

Literal Type

literal-type ::= nil-literal |
                 boolean-literal |
                 '-'? (integer-literal |
                       real-literal) |
                 atom-literal |
                 string-literal

Boolean Type

Integer Type

integer-type ::= 'int' integer-type-range?
integer-type-range ::= '(' (integer-type-range-bound '..' integer-type-range-bound? |
                            '..' integer-type-range-bound) ')'
integer-type-range-bound ::= '-'? integer-literal

Real Type

real-type ::= 'real'

Atom Type

atom-type ::= 'atom'

String Type

string-type ::= 'str'

Reference Type

reference-type ::= 'ref'

Handle Type

handle-type ::= 'handle'

Module Type

module-type ::= 'mod' '{' (module-type-field (',' module-type-field)* ','?)? '}'
module-type-field ::= code-identifier ':' type

Record Type

record-type ::= 'rec' '{' (record-type-field (',' record-type-field)* ','?)? '}' record-type-meta?
record-type-meta ::= 'meta' type
record-type-field ::= 'mut'? code-identifier ':' type

Error Type

error-type ::= 'err' upper-identifier? '{' (error-type-field (',' error-type-field)* ','?)? '}'
error-type-field ::= 'mut'? code-identifier ':' type

Tuple Type

tuple-type ::= '(' type (',' type)+ ','? ')'

Array Type

array-type ::= 'mut'? '[' type ']'

Set Type

set-type ::= 'mut'? '#' '{' type '}'

Map Type

map-type ::= 'mut'? '#' '[' type ':' type ']'

Function Type

function-type ::= 'fn' |
                  'err'? 'fn' function-type-signature?
function-type-signature ::= '(' function-type-parameter-list return-type-annotation ')'
function-type-parameter-list ::= '(' (function-type-parameter (',' function-type-parameter)* ','?)? ')'
function-type-parameter ::= attribute* type

Agent Type

agent-type ::= 'agent' agent-type-protocol?
agent-type-protocol ::= '{' agent-type-message (',' agent-type-message)* ','? '}'
agent-type-message ::= code-identifier agent-type-message-parameter-list
agent-type-message-parameter-list ::= '(' (agent-type-message-parameter (',' agent-type-message-parameter)* ','?)? ')'
agent-type-message-parameter ::= type