Assignment : @<Expression, Assignment: Assignment, ext: void> {
    Ident _ '=' _ Expect<Assignment>  ast("assign" + ext)
    Expression  ast("value")
}

# HoldAssignment : Assignment<Int, HoldAssignment>  # fails with endless recursion!
HoldAssignment : Assignment<Int, HoldAssignment> Empty  # workaround!

# ast_print(Assignment<Int>)
ast_print(HoldAssignment)

#---
#a=b=c=42
#---
#assign [start 1:1, end 1:9]
# assign [start 1:3, end 1:9]
#  assign [start 1:5, end 1:9]
#   value [start 1:7, end 1:9] => 42