PROG ::= (INSTR (EOI+ INSTR)*)?

INSTR ::= EXPR
| assert EXPR
| assert_static_fail INSTR
| return EXPR
| VARDECL
| CONSTDECL
| ASSIGN
| IF

VARDECL ::= let_mut ident assign EXPR
CONSTDECL ::= let ident assign EXPR
ASSIGN ::= ident assign EXPR
IF ::= if EXPR THEN (else (IF | ELSE))?
THEN ::= INSTR*
ELSE ::= INSTR*

EXPR ::= IMP

IMP ::= OR (imp OR)?
OR ::= AND (or AND)*
AND ::= EQ (and EQ)*

EQ ::= CMP ((eq | ne) CMP)?
CMP ::= TERM ((lt | le | gt | ge) TERM)?

TERM ::= FACTOR ((add | sub) FACTOR)*
FACTOR ::= UNOP ((mul | div | mod) UNOP)*

UNOP ::= (add | sub | not)? POW
POW ::= GROUP (pow GROUP)?
GROUP ::= BASE | opar EXPR cpar
BASE ::= int | bool | ident | FUN | CALL

CALL ::= obrace ident expr* cbrace
ARGS ::= expr*

FUN ::= fun opar PARAMS cpar RET BODY end
PARAMS ::= (PARAM (comma PARAM))?
PARAM ::= ident (as TYPE)
RET ::= arrow TYPE |
BODY ::= INSTR*
TYPE ::= type | fun lt (type (arrow type)*)? gt