func (p *printer) signature(params, result *ast.FieldList) {
if params != nil {
p.parameters(params)
} else {
p.print(token.LPAREN, token.RPAREN)
}
n := result.NumFields()
if result != nil && result.Entangled != nil {
n++
}
if n > 0 {
// result != nil
p.print(blank)
if n == 1 && result.List[0].Names == nil {
// single anonymous result; no ()'s
p.expr(stripParensAlways(result.List[0].Type))
return
}
p.parameters(result)
}
}
// filterFieldList removes unexported fields (field names) from the field list
// in place and reports whether fields were removed. Anonymous fields are
// recorded with the parent type. filterType is called with the types of
// all remaining fields.
//
func (r *reader) filterFieldList(parent *namedType, fields *ast.FieldList, ityp *ast.InterfaceType) (removedFields bool) {
if fields == nil {
return
}
list := fields.List
j := 0
for _, field := range list {
keepField := false
if n := len(field.Names); n == 0 {
// anonymous field
fname := r.recordAnonymousField(parent, field.Type)
if ast.IsExported(fname) {
keepField = true
} else if ityp != nil && fname == "error" {
// possibly the predeclared error interface; keep
// it for now but remember this interface so that
// it can be fixed if error is also defined locally
keepField = true
r.remember(ityp)
}
} else {
field.Names = filterIdentList(field.Names)
if len(field.Names) < n {
removedFields = true
}
if len(field.Names) > 0 {
keepField = true
}
}
if keepField {
r.filterType(nil, field.Type)
list[j] = field
j++
}
}
if j < len(list) {
removedFields = true
}
fields.List = list[0:j]
return
}
func (check *Checker) collectParams(scope *Scope, list *ast.FieldList, variadicOk bool) (params []*Var, entangled *Var, variadic bool) {
if list == nil {
return
}
var named, anonymous bool
for i, field := range append(list.List, list.Entangled) {
isEntangled := i == len(list.List)
if isEntangled && field == nil {
continue
}
ftype := field.Type
if t, _ := ftype.(*ast.Ellipsis); t != nil {
ftype = t.Elt
if variadicOk && i == len(list.List)-1 {
variadic = true
} else {
check.invalidAST(field.Pos(), "... not permitted")
// ignore ... and continue
}
}
typ := check.typ(ftype)
if isEntangled {
if IsOptionable(typ) {
typ = NewOptional(typ)
} else if typ != Typ[Bool] {
check.error(field.Pos(), "entangled type must be interface, map, channel, function, pointer or bool")
}
}
// The parser ensures that f.Tag is nil and we don't
// care if a constructed AST contains a non-nil tag.
if len(field.Names) > 0 {
// named parameter
for _, name := range field.Names {
if name.Name == "" {
check.invalidAST(name.Pos(), "anonymous parameter")
// ok to continue
}
par := NewParam(name.Pos(), check.pkg, name.Name, typ)
check.declare(scope, name, par, scope.pos)
if isEntangled {
entangled = par
} else {
params = append(params, par)
}
}
named = true
} else {
// anonymous parameter
par := NewParam(ftype.Pos(), check.pkg, "", typ)
check.recordImplicit(field, par)
if isEntangled {
entangled = par
} else {
params = append(params, par)
}
anonymous = true
}
}
if named && anonymous {
check.invalidAST(list.Pos(), "list contains both named and anonymous parameters")
// ok to continue
}
// For a variadic function, change the last parameter's type from T to []T.
if variadic && len(params) > 0 {
last := params[len(params)-1]
last.typ = &Slice{elem: last.typ}
}
return
}
// funcType type-checks a function or method type.
func (check *Checker) funcType(sig *Signature, recvPar *ast.FieldList, ftyp *ast.FuncType) {
scope := NewScope(check.scope, token.NoPos, token.NoPos, "function")
check.recordScope(ftyp, scope)
recvList, entangledRecvList, _ := check.collectParams(scope, recvPar, false)
if entangledRecvList != nil {
check.error(entangledRecvList.Pos(), "entangled variable in method receiver")
}
params, entangledParam, variadic := check.collectParams(scope, ftyp.Params, true)
if entangledParam != nil && variadic {
check.error(entangledRecvList.Pos(), "variadic function cannot have entangled parameters")
}
results, entangledResult, _ := check.collectParams(scope, ftyp.Results, false)
if recvPar != nil {
// recv parameter list present (may be empty)
// spec: "The receiver is specified via an extra parameter section preceding the
// method name. That parameter section must declare a single parameter, the receiver."
var recv *Var
switch len(recvList) {
case 0:
check.error(recvPar.Pos(), "method is missing receiver")
recv = NewParam(0, nil, "", Typ[Invalid]) // ignore recv below
default:
// more than one receiver
check.error(recvList[len(recvList)-1].Pos(), "method must have exactly one receiver")
fallthrough // continue with first receiver
case 1:
recv = recvList[0]
}
// spec: "The receiver type must be of the form T, *T or ?*T where T is a type name."
// (ignore invalid types - error was reported before)
t := recv.typ
if isOptional(t) {
t = t.Underlying().(*Optional).Elem()
}
if t, _ := deref(t); t != Typ[Invalid] {
var err string
if T, _ := t.(*Named); T != nil {
// spec: "The type denoted by T is called the receiver base type; it must not
// be a pointer or interface type and it must be declared in the same package
// as the method."
if T.obj.pkg != check.pkg {
err = "type not defined in this package"
} else {
// TODO(gri) This is not correct if the underlying type is unknown yet.
switch u := T.underlying.(type) {
case *Basic:
// unsafe.Pointer is treated like a regular pointer
if u.kind == UnsafePointer {
err = "unsafe.Pointer"
}
case *Pointer, *Interface:
err = "pointer or interface type"
}
}
} else {
err = "basic or unnamed type"
}
if err != "" {
check.errorf(recv.pos, "invalid receiver %s (%s)", recv.typ, err)
// ok to continue
}
}
sig.recv = recv
}
sig.scope = scope
sig.params = NewTupleEntangled(append(params, entangledParam)...)
sig.results = NewTupleEntangled(append(results, entangledResult)...)
sig.variadic = variadic
}