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// Copyright 2021 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package types2
import (
"cmd/compile/internal/syntax"
"strconv"
)
// ----------------------------------------------------------------------------
// API
// A Struct represents a struct type.
type Struct struct {
fields []*Var
tags []string // field tags; nil if there are no tags
}
// NewStruct returns a new struct with the given fields and corresponding field tags.
// If a field with index i has a tag, tags[i] must be that tag, but len(tags) may be
// only as long as required to hold the tag with the largest index i. Consequently,
// if no field has a tag, tags may be nil.
func NewStruct(fields []*Var, tags []string) *Struct {
var fset objset
for _, f := range fields {
if f.name != "_" && fset.insert(f) != nil {
panic("multiple fields with the same name")
}
}
if len(tags) > len(fields) {
panic("more tags than fields")
}
return &Struct{fields: fields, tags: tags}
}
// NumFields returns the number of fields in the struct (including blank and embedded fields).
func (s *Struct) NumFields() int { return len(s.fields) }
// Field returns the i'th field for 0 <= i < NumFields().
func (s *Struct) Field(i int) *Var { return s.fields[i] }
// Tag returns the i'th field tag for 0 <= i < NumFields().
func (s *Struct) Tag(i int) string {
if i < len(s.tags) {
return s.tags[i]
}
return ""
}
func (s *Struct) Underlying() Type { return s }
func (s *Struct) String() string { return TypeString(s, nil) }
// ----------------------------------------------------------------------------
// Implementation
func (check *Checker) structType(styp *Struct, e *syntax.StructType) {
if e.FieldList == nil {
return
}
// struct fields and tags
var fields []*Var
var tags []string
// for double-declaration checks
var fset objset
// current field typ and tag
var typ Type
var tag string
add := func(ident *syntax.Name, embedded bool, pos syntax.Pos) {
if tag != "" && tags == nil {
tags = make([]string, len(fields))
}
if tags != nil {
tags = append(tags, tag)
}
name := ident.Value
fld := NewField(pos, check.pkg, name, typ, embedded)
// spec: "Within a struct, non-blank field names must be unique."
if name == "_" || check.declareInSet(&fset, pos, fld) {
fields = append(fields, fld)
check.recordDef(ident, fld)
}
}
// addInvalid adds an embedded field of invalid type to the struct for
// fields with errors; this keeps the number of struct fields in sync
// with the source as long as the fields are _ or have different names
// (issue #25627).
addInvalid := func(ident *syntax.Name, pos syntax.Pos) {
typ = Typ[Invalid]
tag = ""
add(ident, true, pos)
}
var prev syntax.Expr
for i, f := range e.FieldList {
// Fields declared syntactically with the same type (e.g.: a, b, c T)
// share the same type expression. Only check type if it's a new type.
if i == 0 || f.Type != prev {
typ = check.varType(f.Type)
prev = f.Type
}
tag = ""
if i < len(e.TagList) {
tag = check.tag(e.TagList[i])
}
if f.Name != nil {
// named field
add(f.Name, false, f.Name.Pos())
} else {
// embedded field
// spec: "An embedded type must be specified as a type name T or as a
// pointer to a non-interface type name *T, and T itself may not be a
// pointer type."
pos := syntax.StartPos(f.Type)
name := embeddedFieldIdent(f.Type)
if name == nil {
check.errorf(pos, "invalid embedded field type %s", f.Type)
name = &syntax.Name{Value: "_"} // TODO(gri) need to set position to pos
addInvalid(name, pos)
continue
}
add(name, true, pos)
// Because we have a name, typ must be of the form T or *T, where T is the name
// of a (named or alias) type, and t (= deref(typ)) must be the type of T.
// We must delay this check to the end because we don't want to instantiate
// (via under(t)) a possibly incomplete type.
embeddedTyp := typ // for closure below
embeddedPos := pos
check.later(func() {
t, isPtr := deref(embeddedTyp)
switch t := under(t).(type) {
case *Basic:
if t == Typ[Invalid] {
// error was reported before
return
}
// unsafe.Pointer is treated like a regular pointer
if t.kind == UnsafePointer {
check.error(embeddedPos, "embedded field type cannot be unsafe.Pointer")
}
case *Pointer:
check.error(embeddedPos, "embedded field type cannot be a pointer")
case *TypeParam:
check.error(embeddedPos, "embedded field type cannot be a (pointer to a) type parameter")
case *Interface:
if isPtr {
check.error(embeddedPos, "embedded field type cannot be a pointer to an interface")
}
}
})
}
}
styp.fields = fields
styp.tags = tags
}
func embeddedFieldIdent(e syntax.Expr) *syntax.Name {
switch e := e.(type) {
case *syntax.Name:
return e
case *syntax.Operation:
if base := ptrBase(e); base != nil {
// *T is valid, but **T is not
if op, _ := base.(*syntax.Operation); op == nil || ptrBase(op) == nil {
return embeddedFieldIdent(e.X)
}
}
case *syntax.SelectorExpr:
return e.Sel
case *syntax.IndexExpr:
return embeddedFieldIdent(e.X)
}
return nil // invalid embedded field
}
func (check *Checker) declareInSet(oset *objset, pos syntax.Pos, obj Object) bool {
if alt := oset.insert(obj); alt != nil {
var err error_
err.errorf(pos, "%s redeclared", obj.Name())
err.recordAltDecl(alt)
check.report(&err)
return false
}
return true
}
func (check *Checker) tag(t *syntax.BasicLit) string {
// If t.Bad, an error was reported during parsing.
if t != nil && !t.Bad {
if t.Kind == syntax.StringLit {
if val, err := strconv.Unquote(t.Value); err == nil {
return val
}
}
check.errorf(t, invalidAST+"incorrect tag syntax: %q", t.Value)
}
return ""
}
func ptrBase(x *syntax.Operation) syntax.Expr {
if x.Op == syntax.Mul && x.Y == nil {
return x.X
}
return nil
}
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