func castIfOverflow(ident *ast.Ident) ast.Expr {
c, ok := defs[ident].(*types.Const)
if !ok || c == nil {
return ident
}
v := c.Val()
switch {
case v.Kind() != exact.Int:
return ident
case exact.Compare(v, token.LSS, minInt32):
return &ast.CallExpr{Fun: ast.NewIdent("int64"), Args: []ast.Expr{ident}}
case exact.Compare(v, token.GTR, maxInt32):
return &ast.CallExpr{Fun: ast.NewIdent("uint64"), Args: []ast.Expr{ident}}
default:
return ident
}
}
func (check *Checker) comparison(x, y *operand, op token.Token) {
// spec: "In any comparison, the first operand must be assignable
// to the type of the second operand, or vice versa."
err := ""
if x.assignableTo(check.conf, y.typ) || y.assignableTo(check.conf, x.typ) {
defined := false
switch op {
case token.EQL, token.NEQ:
// spec: "The equality operators == and != apply to operands that are comparable."
defined = Comparable(x.typ) || x.isNil() && hasNil(y.typ) || y.isNil() && hasNil(x.typ)
case token.LSS, token.LEQ, token.GTR, token.GEQ:
// spec: The ordering operators <, <=, >, and >= apply to operands that are ordered."
defined = isOrdered(x.typ)
default:
unreachable()
}
if !defined {
typ := x.typ
if x.isNil() {
typ = y.typ
}
err = check.sprintf("operator %s not defined for %s", op, typ)
}
} else {
err = check.sprintf("mismatched types %s and %s", x.typ, y.typ)
}
if err != "" {
check.errorf(x.pos(), "cannot compare %s %s %s (%s)", x.expr, op, y.expr, err)
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]
}