// zeroLiteral returns a new "zero" literal of the specified type,
// which must not be an array or struct type: the zero values of
// aggregates are well-defined but cannot be represented by Literal.
//
func zeroLiteral(t types.Type) *Literal {
switch t := t.(type) {
case *types.Basic:
switch {
case t.Info&types.IsBoolean != 0:
return newLiteral(exact.MakeBool(false), t)
case t.Info&types.IsNumeric != 0:
return newLiteral(exact.MakeInt64(0), t)
case t.Info&types.IsString != 0:
return newLiteral(exact.MakeString(""), t)
case t.Kind == types.UnsafePointer:
fallthrough
case t.Kind == types.UntypedNil:
return nilLiteral(t)
default:
panic(fmt.Sprint("zeroLiteral for unexpected type:", t))
}
case *types.Pointer, *types.Slice, *types.Interface, *types.Chan, *types.Map, *types.Signature:
return nilLiteral(t)
case *types.NamedType:
return newLiteral(zeroLiteral(t.Underlying).Value, t)
case *types.Array, *types.Struct:
panic(fmt.Sprint("zeroLiteral applied to aggregate:", t))
}
panic(fmt.Sprint("zeroLiteral: unexpected ", t))
}
func (check *checker) comparison(x, y *operand, op token.Token) {
// TODO(gri) deal with interface vs non-interface comparison
valid := false
if x.isAssignable(check.ctxt, y.typ) || y.isAssignable(check.ctxt, x.typ) {
switch op {
case token.EQL, token.NEQ:
valid = isComparable(x.typ) ||
x.isNil() && hasNil(y.typ) ||
y.isNil() && hasNil(x.typ)
case token.LSS, token.LEQ, token.GTR, token.GEQ:
valid = isOrdered(x.typ)
default:
unreachable()
}
}
if !valid {
check.invalidOp(x.pos(), "cannot compare %s %s %s", x, op, y)
x.mode = invalid
return
}
if x.mode == constant && y.mode == constant {
x.val = exact.MakeBool(exact.Compare(x.val, op, y.val))
// The operands are never materialized; no need to update
// their types.
} else {
x.mode = value
// The operands 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.
check.updateExprType(x.expr, defaultType(x.typ), true)
check.updateExprType(y.expr, defaultType(y.typ), true)
}
// spec: "Comparison operators compare two operands and yield
// an untyped boolean value."
x.typ = Typ[UntypedBool]
}
// ConstDecl = "const" ExportedName [ Type ] "=" Literal .
// Literal = bool_lit | int_lit | float_lit | complex_lit | rune_lit | string_lit .
// bool_lit = "true" | "false" .
// complex_lit = "(" float_lit "+" float_lit "i" ")" .
// rune_lit = "(" int_lit "+" int_lit ")" .
// string_lit = `"` { unicode_char } `"` .
//
func (p *gcParser) parseConstDecl() {
p.expectKeyword("const")
pkg, name := p.parseExportedName()
obj := declConst(pkg, name)
var x operand
if p.tok != '=' {
obj.Type = p.parseType()
}
p.expect('=')
switch p.tok {
case scanner.Ident:
// bool_lit
if p.lit != "true" && p.lit != "false" {
p.error("expected true or false")
}
x.typ = Typ[UntypedBool]
x.val = exact.MakeBool(p.lit == "true")
p.next()
case '-', scanner.Int:
// int_lit
x = p.parseNumber()
case '(':
// complex_lit or rune_lit
p.next()
if p.tok == scanner.Char {
p.next()
p.expect('+')
x = p.parseNumber()
x.typ = Typ[UntypedRune]
p.expect(')')
break
}
re := p.parseNumber()
p.expect('+')
im := p.parseNumber()
p.expectKeyword("i")
p.expect(')')
x.typ = Typ[UntypedComplex]
// TODO(gri) fix this
_, _ = re, im
x.val = exact.MakeInt64(0)
case scanner.Char:
// rune_lit
x.setConst(token.CHAR, p.lit)
p.next()
case scanner.String:
// string_lit
x.setConst(token.STRING, p.lit)
p.next()
default:
p.errorf("expected literal got %s", scanner.TokenString(p.tok))
}
if obj.Type == nil {
obj.Type = x.typ
}
assert(x.val != nil)
obj.Val = x.val
}
UntypedBool: {UntypedBool, IsBoolean | IsUntyped, 0, "untyped boolean"},
UntypedInt: {UntypedInt, IsInteger | IsUntyped, 0, "untyped integer"},
UntypedRune: {UntypedRune, IsInteger | IsUntyped, 0, "untyped rune"},
UntypedFloat: {UntypedFloat, IsFloat | IsUntyped, 0, "untyped float"},
UntypedComplex: {UntypedComplex, IsComplex | IsUntyped, 0, "untyped complex"},
UntypedString: {UntypedString, IsString | IsUntyped, 0, "untyped string"},
UntypedNil: {UntypedNil, IsUntyped, 0, "untyped nil"},
}
var aliases = [...]*Basic{
{Byte, IsInteger | IsUnsigned, 1, "byte"},
{Rune, IsInteger, 4, "rune"},
}
var predeclaredConstants = [...]*Const{
{Name: "true", Type: Typ[UntypedBool], Val: exact.MakeBool(true)},
{Name: "false", Type: Typ[UntypedBool], Val: exact.MakeBool(false)},
{Name: "iota", Type: Typ[UntypedInt], Val: exact.MakeInt64(0)},
{Name: "nil", Type: Typ[UntypedNil], Val: exact.MakeNil()},
}
var predeclaredFunctions = [...]*builtin{
{_Append, "append", 1, true, false},
{_Cap, "cap", 1, false, false},
{_Close, "close", 1, false, true},
{_Complex, "complex", 2, false, false},
{_Copy, "copy", 2, false, true},
{_Delete, "delete", 2, false, true},
{_Imag, "imag", 1, false, false},
{_Len, "len", 1, false, false},
{_Make, "make", 1, true, false},