func (check *Checker) constDecl(obj *Const, typ, init ast.Expr) {
assert(obj.typ == nil)
if obj.visited {
obj.typ = Typ[Invalid]
return
}
obj.visited = true
// use the correct value of iota
assert(check.iota == nil)
check.iota = obj.val
defer func() { check.iota = nil }()
// provide valid constant value under all circumstances
obj.val = constant.MakeUnknown()
// determine type, if any
if typ != nil {
t := check.typ(typ)
if !isConstType(t) {
check.errorf(typ.Pos(), "invalid constant type %s", t)
obj.typ = Typ[Invalid]
return
}
obj.typ = t
}
// check initialization
var x operand
if init != nil {
check.expr(&x, init)
}
check.initConst(obj, &x)
}
func (p *importer) value() constant.Value {
switch tag := p.tagOrIndex(); tag {
case falseTag:
return constant.MakeBool(false)
case trueTag:
return constant.MakeBool(true)
case int64Tag:
return constant.MakeInt64(p.int64())
case floatTag:
return p.float()
case complexTag:
re := p.float()
im := p.float()
return constant.BinaryOp(re, token.ADD, constant.MakeImag(im))
case stringTag:
return constant.MakeString(p.string())
case unknownTag:
return constant.MakeUnknown()
default:
panic(fmt.Sprintf("unexpected value tag %d", tag))
}
}