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// Copyright 2013 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 oracle
import (
"fmt"
"go/ast"
"go/token"
"reflect"
"sort"
"strings"
"golang.org/x/tools/go/types"
"golang.org/x/tools/oracle/serial"
)
// Implements displays the "implements" relation as it pertains to the
// selected type.
//
func implements(o *Oracle, qpos *QueryPos) (queryResult, error) {
// Find the selected type.
// TODO(adonovan): fix: make it work on qualified Idents too.
path, action := findInterestingNode(qpos.info, qpos.path)
if action != actionType {
return nil, fmt.Errorf("no type here")
}
T := qpos.info.TypeOf(path[0].(ast.Expr))
if T == nil {
return nil, fmt.Errorf("no type here")
}
// Find all named types, even local types (which can have
// methods via promotion) and the built-in "error".
//
// TODO(adonovan): include all packages in PTA scope too?
// i.e. don't reduceScope?
//
var allNamed []types.Type
for _, info := range o.typeInfo {
for _, obj := range info.Defs {
if obj, ok := obj.(*types.TypeName); ok {
allNamed = append(allNamed, obj.Type())
}
}
}
allNamed = append(allNamed, types.Universe.Lookup("error").Type())
var msets types.MethodSetCache
// Test each named type.
var to, from, fromPtr []types.Type
for _, U := range allNamed {
if isInterface(T) {
if msets.MethodSet(T).Len() == 0 {
continue // empty interface
}
if isInterface(U) {
if msets.MethodSet(U).Len() == 0 {
continue // empty interface
}
// T interface, U interface
if !types.Identical(T, U) {
if types.AssignableTo(U, T) {
to = append(to, U)
}
if types.AssignableTo(T, U) {
from = append(from, U)
}
}
} else {
// T interface, U concrete
if types.AssignableTo(U, T) {
to = append(to, U)
} else if pU := types.NewPointer(U); types.AssignableTo(pU, T) {
to = append(to, pU)
}
}
} else if isInterface(U) {
if msets.MethodSet(U).Len() == 0 {
continue // empty interface
}
// T concrete, U interface
if types.AssignableTo(T, U) {
from = append(from, U)
} else if pT := types.NewPointer(T); types.AssignableTo(pT, U) {
fromPtr = append(fromPtr, U)
}
}
}
var pos interface{} = qpos
if nt, ok := deref(T).(*types.Named); ok {
pos = nt.Obj()
}
// Sort types (arbitrarily) to ensure test determinism.
sort.Sort(typesByString(to))
sort.Sort(typesByString(from))
sort.Sort(typesByString(fromPtr))
return &implementsResult{T, pos, to, from, fromPtr}, nil
}
type implementsResult struct {
t types.Type // queried type (not necessarily named)
pos interface{} // pos of t (*types.Name or *QueryPos)
to []types.Type // named or ptr-to-named types assignable to interface T
from []types.Type // named interfaces assignable from T
fromPtr []types.Type // named interfaces assignable only from *T
}
func (r *implementsResult) display(printf printfFunc) {
if isInterface(r.t) {
if types.NewMethodSet(r.t).Len() == 0 { // TODO(adonovan): cache mset
printf(r.pos, "empty interface type %s", r.t)
return
}
printf(r.pos, "interface type %s", r.t)
// Show concrete types first; use two passes.
for _, sub := range r.to {
if !isInterface(sub) {
printf(deref(sub).(*types.Named).Obj(), "\tis implemented by %s type %s",
typeKind(sub), sub)
}
}
for _, sub := range r.to {
if isInterface(sub) {
printf(deref(sub).(*types.Named).Obj(), "\tis implemented by %s type %s", typeKind(sub), sub)
}
}
for _, super := range r.from {
printf(super.(*types.Named).Obj(), "\timplements %s", super)
}
} else {
if r.from != nil {
printf(r.pos, "%s type %s", typeKind(r.t), r.t)
for _, super := range r.from {
printf(super.(*types.Named).Obj(), "\timplements %s", super)
}
}
if r.fromPtr != nil {
printf(r.pos, "pointer type *%s", r.t)
for _, psuper := range r.fromPtr {
printf(psuper.(*types.Named).Obj(), "\timplements %s", psuper)
}
} else if r.from == nil {
printf(r.pos, "%s type %s implements only interface{}", typeKind(r.t), r.t)
}
}
}
func (r *implementsResult) toSerial(res *serial.Result, fset *token.FileSet) {
res.Implements = &serial.Implements{
T: makeImplementsType(r.t, fset),
AssignableTo: makeImplementsTypes(r.to, fset),
AssignableFrom: makeImplementsTypes(r.from, fset),
AssignableFromPtr: makeImplementsTypes(r.fromPtr, fset),
}
}
func makeImplementsTypes(tt []types.Type, fset *token.FileSet) []serial.ImplementsType {
var r []serial.ImplementsType
for _, t := range tt {
r = append(r, makeImplementsType(t, fset))
}
return r
}
func makeImplementsType(T types.Type, fset *token.FileSet) serial.ImplementsType {
var pos token.Pos
if nt, ok := deref(T).(*types.Named); ok { // implementsResult.t may be non-named
pos = nt.Obj().Pos()
}
return serial.ImplementsType{
Name: T.String(),
Pos: fset.Position(pos).String(),
Kind: typeKind(T),
}
}
// typeKind returns a string describing the underlying kind of type,
// e.g. "slice", "array", "struct".
func typeKind(T types.Type) string {
s := reflect.TypeOf(T.Underlying()).String()
return strings.ToLower(strings.TrimPrefix(s, "*types."))
}
func isInterface(T types.Type) bool { return types.IsInterface(T) }
type typesByString []types.Type
func (p typesByString) Len() int { return len(p) }
func (p typesByString) Less(i, j int) bool { return p[i].String() < p[j].String() }
func (p typesByString) Swap(i, j int) { p[i], p[j] = p[j], p[i] }
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