// builtin typechecks a built-in call. The built-in type is bin, and iota is the current
// value of iota or -1 if iota doesn't have a value in the current context. The result
// of the call is returned via x. If the call has type errors, the returned x is marked
// as invalid (x.mode == invalid).
//
func (check *checker) builtin(x *operand, call *ast.CallExpr, bin *builtin, iota int) {
args := call.Args
id := bin.id
// declare before goto's
var arg0 ast.Expr // first argument, if present
// check argument count
n := len(args)
msg := ""
if n < bin.nargs {
msg = "not enough"
} else if !bin.isVariadic && n > bin.nargs {
msg = "too many"
}
if msg != "" {
check.invalidOp(call.Pos(), msg+" arguments for %s (expected %d, found %d)", call, bin.nargs, n)
goto Error
}
// common case: evaluate first argument if present;
// if it is an expression, x has the expression value
if n > 0 {
arg0 = args[0]
switch id {
case _Make, _New, _Print, _Println, _Offsetof, _Trace:
// respective cases below do the work
default:
// argument must be an expression
check.expr(x, arg0, nil, iota)
if x.mode == invalid {
goto Error
}
}
}
switch id {
case _Append:
if _, ok := underlying(x.typ).(*Slice); !ok {
check.invalidArg(x.pos(), "%s is not a typed slice", x)
goto Error
}
resultTyp := x.typ
for _, arg := range args[1:] {
check.expr(x, arg, nil, iota)
if x.mode == invalid {
goto Error
}
// TODO(gri) check assignability
}
x.mode = value
x.typ = resultTyp
case _Cap, _Len:
mode := invalid
var val exact.Value
switch typ := implicitArrayDeref(underlying(x.typ)).(type) {
case *Basic:
if isString(typ) && id == _Len {
if x.mode == constant {
mode = constant
val = exact.MakeInt64(int64(len(exact.StringVal(x.val))))
} else {
mode = value
}
}
case *Array:
mode = value
// spec: "The expressions len(s) and cap(s) are constants
// if the type of s is an array or pointer to an array and
// the expression s does not contain channel receives or
// function calls; in this case s is not evaluated."
if !check.containsCallsOrReceives(arg0) {
mode = constant
val = exact.MakeInt64(typ.Len)
}
case *Slice, *Chan:
mode = value
case *Map:
if id == _Len {
mode = value
}
}
if mode == invalid {
check.invalidArg(x.pos(), "%s for %s", x, bin.name)
goto Error
}
x.mode = mode
x.typ = Typ[Int]
x.val = val
case _Close:
ch, ok := underlying(x.typ).(*Chan)
if !ok {
check.invalidArg(x.pos(), "%s is not a channel", x)
goto Error
}
if ch.Dir&ast.SEND == 0 {
check.invalidArg(x.pos(), "%s must not be a receive-only channel", x)
goto Error
}
x.mode = novalue
case _Complex:
if !check.complexArg(x) {
goto Error
}
var y operand
check.expr(&y, args[1], nil, iota)
if y.mode == invalid {
goto Error
}
if !check.complexArg(&y) {
goto Error
}
check.convertUntyped(x, y.typ)
if x.mode == invalid {
goto Error
}
check.convertUntyped(&y, x.typ)
if y.mode == invalid {
goto Error
}
if !IsIdentical(x.typ, y.typ) {
check.invalidArg(x.pos(), "mismatched types %s and %s", x.typ, y.typ)
goto Error
}
typ := underlying(x.typ).(*Basic)
if x.mode == constant && y.mode == constant {
x.val = exact.BinaryOp(x.val, token.ADD, exact.MakeImag(y.val))
} else {
x.mode = value
}
switch typ.Kind {
case Float32:
x.typ = Typ[Complex64]
case Float64:
x.typ = Typ[Complex128]
case UntypedInt, UntypedRune, UntypedFloat:
if x.mode == constant {
typ = defaultType(typ).(*Basic)
x.typ = Typ[UntypedComplex]
} else {
// untyped but not constant; probably because one
// operand is a non-constant shift of untyped lhs
typ = Typ[Float64]
x.typ = Typ[Complex128]
}
default:
check.invalidArg(x.pos(), "float32 or float64 arguments expected")
goto Error
}
if x.mode != constant {
// The arguments have now their final types, which at run-
// time will be materialized. Update the expression trees.
// If the current types are untyped, the materialized type
// is the respective default type.
// (If the result is constant, the arguments are never
// materialized and there is nothing to do.)
check.updateExprType(args[0], typ, true)
check.updateExprType(args[1], typ, true)
}
case _Copy:
var y operand
check.expr(&y, args[1], nil, iota)
if y.mode == invalid {
goto Error
}
var dst, src Type
if t, ok := underlying(x.typ).(*Slice); ok {
dst = t.Elt
}
switch t := underlying(y.typ).(type) {
case *Basic:
if isString(y.typ) {
src = Typ[Byte]
}
case *Slice:
src = t.Elt
}
if dst == nil || src == nil {
check.invalidArg(x.pos(), "copy expects slice arguments; found %s and %s", x, &y)
goto Error
}
if !IsIdentical(dst, src) {
check.invalidArg(x.pos(), "arguments to copy %s and %s have different element types %s and %s", x, &y, dst, src)
goto Error
}
x.mode = value
x.typ = Typ[Int]
case _Delete:
m, ok := underlying(x.typ).(*Map)
if !ok {
check.invalidArg(x.pos(), "%s is not a map", x)
goto Error
}
check.expr(x, args[1], nil, iota)
if x.mode == invalid {
goto Error
}
if !x.isAssignable(check.ctxt, m.Key) {
check.invalidArg(x.pos(), "%s is not assignable to %s", x, m.Key)
goto Error
}
x.mode = novalue
case _Imag, _Real:
if !isComplex(x.typ) {
check.invalidArg(x.pos(), "%s must be a complex number", x)
goto Error
}
if x.mode == constant {
if id == _Real {
x.val = exact.Real(x.val)
} else {
x.val = exact.Imag(x.val)
}
} else {
x.mode = value
}
k := Invalid
switch underlying(x.typ).(*Basic).Kind {
case Complex64:
k = Float32
case Complex128:
k = Float64
case UntypedComplex:
k = UntypedFloat
default:
unreachable()
}
x.typ = Typ[k]
case _Make:
resultTyp := check.typ(arg0, false)
if resultTyp == Typ[Invalid] {
goto Error
}
var min int // minimum number of arguments
switch underlying(resultTyp).(type) {
case *Slice:
min = 2
case *Map, *Chan:
min = 1
default:
check.invalidArg(arg0.Pos(), "cannot make %s; type must be slice, map, or channel", arg0)
goto Error
}
if n := len(args); n < min || min+1 < n {
check.errorf(call.Pos(), "%s expects %d or %d arguments; found %d", call, min, min+1, n)
goto Error
}
var sizes []int64 // constant integer arguments, if any
for _, arg := range args[1:] {
if s, ok := check.index(arg, -1, iota); ok && s >= 0 {
sizes = append(sizes, s)
}
}
if len(sizes) == 2 && sizes[0] > sizes[1] {
check.invalidArg(args[1].Pos(), "length and capacity swapped")
// safe to continue
}
x.mode = variable
x.typ = resultTyp
case _New:
resultTyp := check.typ(arg0, false)
if resultTyp == Typ[Invalid] {
goto Error
}
x.mode = variable
x.typ = &Pointer{Base: resultTyp}
case _Panic:
x.mode = novalue
case _Print, _Println:
for _, arg := range args {
check.expr(x, arg, nil, -1)
if x.mode == invalid {
goto Error
}
}
x.mode = novalue
case _Recover:
x.mode = value
x.typ = new(Interface)
case _Alignof:
x.mode = constant
x.val = exact.MakeInt64(check.ctxt.alignof(x.typ))
x.typ = Typ[Uintptr]
case _Offsetof:
arg, ok := unparen(arg0).(*ast.SelectorExpr)
if !ok {
check.invalidArg(arg0.Pos(), "%s is not a selector expression", arg0)
goto Error
}
check.expr(x, arg.X, nil, -1)
if x.mode == invalid {
goto Error
}
sel := arg.Sel.Name
res := lookupField(x.typ, QualifiedName{check.pkg, arg.Sel.Name})
if res.index == nil {
check.invalidArg(x.pos(), "%s has no single field %s", x, sel)
goto Error
}
offs := check.ctxt.offsetof(deref(x.typ), res.index)
if offs < 0 {
check.invalidArg(x.pos(), "field %s is embedded via a pointer in %s", sel, x)
goto Error
}
x.mode = constant
x.val = exact.MakeInt64(offs)
x.typ = Typ[Uintptr]
case _Sizeof:
x.mode = constant
x.val = exact.MakeInt64(check.ctxt.sizeof(x.typ))
x.typ = Typ[Uintptr]
case _Assert:
// assert(pred) causes a typechecker error if pred is false.
// The result of assert is the value of pred if there is no error.
// Note: assert is only available in self-test mode.
if x.mode != constant || !isBoolean(x.typ) {
check.invalidArg(x.pos(), "%s is not a boolean constant", x)
goto Error
}
if x.val.Kind() != exact.Bool {
check.errorf(x.pos(), "internal error: value of %s should be a boolean constant", x)
goto Error
}
if !exact.BoolVal(x.val) {
check.errorf(call.Pos(), "%s failed", call)
// compile-time assertion failure - safe to continue
}
case _Trace:
// trace(x, y, z, ...) dumps the positions, expressions, and
// values of its arguments. The result of trace is the value
// of the first argument.
// Note: trace is only available in self-test mode.
if len(args) == 0 {
check.dump("%s: trace() without arguments", call.Pos())
x.mode = novalue
x.expr = call
return
}
var t operand
x1 := x
for _, arg := range args {
check.rawExpr(x1, arg, nil, iota, true) // permit trace for types, e.g.: new(trace(T))
check.dump("%s: %s", x1.pos(), x1)
x1 = &t // use incoming x only for first argument
}
default:
check.invalidAST(call.Pos(), "unknown builtin id %d", id)
goto Error
}
x.expr = call
return
Error:
x.mode = invalid
x.expr = call
}
// Complex128 returns the complex value of this literal truncated to
// fit a complex128.
//
func (l *Literal) Complex128() complex128 {
re, _ := exact.Float64Val(exact.Real(l.Value))
im, _ := exact.Float64Val(exact.Imag(l.Value))
return complex(re, im)
}