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// Copyright 2014 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.
// This file implements resolveOrder.
package types
import (
"go/ast"
"sort"
)
// resolveOrder computes the order in which package-level objects
// must be type-checked.
//
// Interface types appear first in the list, sorted topologically
// by dependencies on embedded interfaces that are also declared
// in this package, followed by all other objects sorted in source
// order.
//
// TODO(gri) Consider sorting all types by dependencies here, and
// in the process check _and_ report type cycles. This may simplify
// the full type-checking phase.
//
func (check *Checker) resolveOrder() []Object {
var ifaces, others []Object
// collect interface types with their dependencies, and all other objects
for obj := range check.objMap {
if ityp := check.interfaceFor(obj); ityp != nil {
ifaces = append(ifaces, obj)
// determine dependencies on embedded interfaces
for _, f := range ityp.Methods.List {
if len(f.Names) == 0 {
// Embedded interface: The type must be a (possibly
// qualified) identifier denoting another interface.
// Imported interfaces are already fully resolved,
// so we can ignore qualified identifiers.
if ident, _ := f.Type.(*ast.Ident); ident != nil {
embedded := check.pkg.scope.Lookup(ident.Name)
if check.interfaceFor(embedded) != nil {
check.objMap[obj].addDep(embedded)
}
}
}
}
} else {
others = append(others, obj)
}
}
// final object order
var order []Object
// sort interface types topologically by dependencies,
// and in source order if there are no dependencies
sort.Sort(inSourceOrder(ifaces))
if debug {
for _, obj := range ifaces {
assert(check.objMap[obj].mark == 0)
}
}
for _, obj := range ifaces {
check.appendInPostOrder(&order, obj)
}
// sort everything else in source order
sort.Sort(inSourceOrder(others))
return append(order, others...)
}
// interfaceFor returns the AST interface denoted by obj, or nil.
func (check *Checker) interfaceFor(obj Object) *ast.InterfaceType {
tname, _ := obj.(*TypeName)
if tname == nil {
return nil // not a type
}
d := check.objMap[obj]
if d == nil {
check.dump("%s: %s should have been declared", obj.Pos(), obj.Name())
unreachable()
}
if d.typ == nil {
return nil // invalid AST - ignore (will be handled later)
}
ityp, _ := d.typ.(*ast.InterfaceType)
return ityp
}
func (check *Checker) appendInPostOrder(order *[]Object, obj Object) {
d := check.objMap[obj]
if d.mark != 0 {
// We've already seen this object; either because it's
// already added to order, or because we have a cycle.
// In both cases we stop. Cycle errors are reported
// when type-checking types.
return
}
d.mark = 1
for _, obj := range orderedSetObjects(d.deps) {
check.appendInPostOrder(order, obj)
}
*order = append(*order, obj)
}
func orderedSetObjects(set map[Object]bool) []Object {
list := make([]Object, len(set))
i := 0
for obj := range set {
// we don't care about the map element value
list[i] = obj
i++
}
sort.Sort(inSourceOrder(list))
return list
}
// inSourceOrder implements the sort.Sort interface.
type inSourceOrder []Object
func (a inSourceOrder) Len() int { return len(a) }
func (a inSourceOrder) Less(i, j int) bool { return a[i].order() < a[j].order() }
func (a inSourceOrder) Swap(i, j int) { a[i], a[j] = a[j], a[i] }
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