func val(lit string) exact.Value {
if len(lit) == 0 {
return exact.MakeUnknown()
}
switch lit {
case "?":
return exact.MakeUnknown()
case "true":
return exact.MakeBool(true)
case "false":
return exact.MakeBool(false)
}
tok := token.INT
switch first, last := lit[0], lit[len(lit)-1]; {
case first == '"' || first == '`':
tok = token.STRING
lit = strings.Replace(lit, "_", " ", -1)
case first == '\'':
tok = token.CHAR
case last == 'i':
tok = token.IMAG
default:
if !strings.HasPrefix(lit, "0x") && strings.ContainsAny(lit, "./Ee") {
tok = token.FLOAT
}
}
return exact.MakeFromLiteral(lit, tok)
}
func val(lit string) exact.Value {
if len(lit) == 0 {
return exact.MakeUnknown()
}
switch lit {
case "?":
return exact.MakeUnknown()
case "nil":
return nil
case "true":
return exact.MakeBool(true)
case "false":
return exact.MakeBool(false)
}
tok := token.FLOAT
switch first, last := lit[0], lit[len(lit)-1]; {
case first == '"' || first == '`':
tok = token.STRING
lit = strings.Replace(lit, "_", " ", -1)
case first == '\'':
tok = token.CHAR
case last == 'i':
tok = token.IMAG
}
return exact.MakeFromLiteral(lit, tok)
}
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 = exact.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 (check *checker) initConst(lhs *Const, x *operand) {
lhs.val = exact.MakeUnknown()
if x.mode == invalid || x.typ == Typ[Invalid] || lhs.typ == Typ[Invalid] {
if lhs.typ == nil {
lhs.typ = Typ[Invalid]
}
return // nothing else to check
}
// If the lhs doesn't have a type yet, use the type of x.
if lhs.typ == nil {
lhs.typ = x.typ
}
if !check.assignment(x, lhs.typ) {
if x.mode != invalid {
check.errorf(x.pos(), "cannot define constant %s (type %s) as %s", lhs.Name(), lhs.typ, x)
}
return
}
// rhs must be a constant
if x.mode != constant {
check.errorf(x.pos(), "%s is not constant", x)
return
}
assert(isConstType(x.typ))
lhs.val = x.val
}
func (c *compiler) VisitExpr(expr ast.Expr) Value {
c.setDebugLine(expr.Pos())
// Before all else, check if we've got a constant expression.
// go/types performs constant folding, and we store the value
// alongside the expression's type.
if constval := c.typeinfo.Values[expr]; constval != nil {
return c.NewConstValue(constval, c.typeinfo.Types[expr])
}
// nil-literals are parsed to Ident-nodes for some reason,
// treat them like constant values here.
// TODO nil literals should be represented more appropriately.
if identval, valid := expr.(*ast.Ident); valid && identval.Name == "nil" {
return c.NewConstValue(exact.MakeUnknown(), c.typeinfo.Types[expr])
}
switch x := expr.(type) {
case *ast.BinaryExpr:
return c.VisitBinaryExpr(x)
case *ast.FuncLit:
return c.VisitFuncLit(x)
case *ast.CompositeLit:
return c.VisitCompositeLit(x)
case *ast.UnaryExpr:
return c.VisitUnaryExpr(x)
case *ast.CallExpr:
return c.VisitCallExpr(x)
case *ast.IndexExpr:
return c.VisitIndexExpr(x)
case *ast.SelectorExpr:
return c.VisitSelectorExpr(x)
case *ast.StarExpr:
return c.VisitStarExpr(x)
case *ast.ParenExpr:
return c.VisitExpr(x.X)
case *ast.TypeAssertExpr:
return c.VisitTypeAssertExpr(x)
case *ast.SliceExpr:
return c.VisitSliceExpr(x)
case *ast.Ident:
return c.Resolve(x)
}
panic(fmt.Sprintf("Unhandled Expr node: %s", reflect.TypeOf(expr)))
}
