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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 ssa
// This file defines a number of miscellaneous utility functions.
import (
"fmt"
"go/ast"
"go/token"
"go/types"
"io"
"os"
"sync"
"golang.org/x/tools/go/ast/astutil"
"golang.org/x/tools/go/types/typeutil"
"golang.org/x/tools/internal/aliases"
"golang.org/x/tools/internal/typeparams"
"golang.org/x/tools/internal/typesinternal"
)
type unit struct{}
//// Sanity checking utilities
// assert panics with the mesage msg if p is false.
// Avoid combining with expensive string formatting.
func assert(p bool, msg string) {
if !p {
panic(msg)
}
}
//// AST utilities
func unparen(e ast.Expr) ast.Expr { return astutil.Unparen(e) }
// isBlankIdent returns true iff e is an Ident with name "_".
// They have no associated types.Object, and thus no type.
func isBlankIdent(e ast.Expr) bool {
id, ok := e.(*ast.Ident)
return ok && id.Name == "_"
}
// rangePosition is the position to give for the `range` token in a RangeStmt.
var rangePosition = func(rng *ast.RangeStmt) token.Pos {
// Before 1.20, this is unreachable.
// rng.For is a close, but incorrect position.
return rng.For
}
//// Type utilities. Some of these belong in go/types.
// isNonTypeParamInterface reports whether t is an interface type but not a type parameter.
func isNonTypeParamInterface(t types.Type) bool {
return !typeparams.IsTypeParam(t) && types.IsInterface(t)
}
// isBasic reports whether t is a basic type.
// t is assumed to be an Underlying type (not Named or Alias).
func isBasic(t types.Type) bool {
_, ok := t.(*types.Basic)
return ok
}
// isString reports whether t is exactly a string type.
// t is assumed to be an Underlying type (not Named or Alias).
func isString(t types.Type) bool {
basic, ok := t.(*types.Basic)
return ok && basic.Info()&types.IsString != 0
}
// isByteSlice reports whether t is of the form []~bytes.
// t is assumed to be an Underlying type (not Named or Alias).
func isByteSlice(t types.Type) bool {
if b, ok := t.(*types.Slice); ok {
e, _ := b.Elem().Underlying().(*types.Basic)
return e != nil && e.Kind() == types.Byte
}
return false
}
// isRuneSlice reports whether t is of the form []~runes.
// t is assumed to be an Underlying type (not Named or Alias).
func isRuneSlice(t types.Type) bool {
if b, ok := t.(*types.Slice); ok {
e, _ := b.Elem().Underlying().(*types.Basic)
return e != nil && e.Kind() == types.Rune
}
return false
}
// isBasicConvTypes returns true when a type set can be
// one side of a Convert operation. This is when:
// - All are basic, []byte, or []rune.
// - At least 1 is basic.
// - At most 1 is []byte or []rune.
func isBasicConvTypes(tset termList) bool {
basics := 0
all := underIs(tset, func(t types.Type) bool {
if isBasic(t) {
basics++
return true
}
return isByteSlice(t) || isRuneSlice(t)
})
return all && basics >= 1 && tset.Len()-basics <= 1
}
// isPointer reports whether t's underlying type is a pointer.
func isPointer(t types.Type) bool {
return is[*types.Pointer](t.Underlying())
}
// isPointerCore reports whether t's core type is a pointer.
//
// (Most pointer manipulation is related to receivers, in which case
// isPointer is appropriate. tecallers can use isPointer(t).
func isPointerCore(t types.Type) bool {
return is[*types.Pointer](typeparams.CoreType(t))
}
func is[T any](x any) bool {
_, ok := x.(T)
return ok
}
// recvType returns the receiver type of method obj.
func recvType(obj *types.Func) types.Type {
return obj.Type().(*types.Signature).Recv().Type()
}
// fieldOf returns the index'th field of the (core type of) a struct type;
// otherwise returns nil.
func fieldOf(typ types.Type, index int) *types.Var {
if st, ok := typeparams.CoreType(typ).(*types.Struct); ok {
if 0 <= index && index < st.NumFields() {
return st.Field(index)
}
}
return nil
}
// isUntyped reports whether typ is the type of an untyped constant.
func isUntyped(typ types.Type) bool {
// No Underlying/Unalias: untyped constant types cannot be Named or Alias.
b, ok := typ.(*types.Basic)
return ok && b.Info()&types.IsUntyped != 0
}
// declaredWithin reports whether an object is declared within a function.
//
// obj must not be a method or a field.
func declaredWithin(obj types.Object, fn *types.Func) bool {
if obj.Pos() != token.NoPos {
return fn.Scope().Contains(obj.Pos()) // trust the positions if they exist.
}
if fn.Pkg() != obj.Pkg() {
return false // fast path for different packages
}
// Traverse Parent() scopes for fn.Scope().
for p := obj.Parent(); p != nil; p = p.Parent() {
if p == fn.Scope() {
return true
}
}
return false
}
// logStack prints the formatted "start" message to stderr and
// returns a closure that prints the corresponding "end" message.
// Call using 'defer logStack(...)()' to show builder stack on panic.
// Don't forget trailing parens!
func logStack(format string, args ...interface{}) func() {
msg := fmt.Sprintf(format, args...)
io.WriteString(os.Stderr, msg)
io.WriteString(os.Stderr, "\n")
return func() {
io.WriteString(os.Stderr, msg)
io.WriteString(os.Stderr, " end\n")
}
}
// newVar creates a 'var' for use in a types.Tuple.
func newVar(name string, typ types.Type) *types.Var {
return types.NewParam(token.NoPos, nil, name, typ)
}
// anonVar creates an anonymous 'var' for use in a types.Tuple.
func anonVar(typ types.Type) *types.Var {
return newVar("", typ)
}
var lenResults = types.NewTuple(anonVar(tInt))
// makeLen returns the len builtin specialized to type func(T)int.
func makeLen(T types.Type) *Builtin {
lenParams := types.NewTuple(anonVar(T))
return &Builtin{
name: "len",
sig: types.NewSignature(nil, lenParams, lenResults, false),
}
}
// receiverTypeArgs returns the type arguments to a method's receiver.
// Returns an empty list if the receiver does not have type arguments.
func receiverTypeArgs(method *types.Func) []types.Type {
recv := method.Type().(*types.Signature).Recv()
_, named := typesinternal.ReceiverNamed(recv)
if named == nil {
return nil // recv is anonymous struct/interface
}
ts := named.TypeArgs()
if ts.Len() == 0 {
return nil
}
targs := make([]types.Type, ts.Len())
for i := 0; i < ts.Len(); i++ {
targs[i] = ts.At(i)
}
return targs
}
// recvAsFirstArg takes a method signature and returns a function
// signature with receiver as the first parameter.
func recvAsFirstArg(sig *types.Signature) *types.Signature {
params := make([]*types.Var, 0, 1+sig.Params().Len())
params = append(params, sig.Recv())
for i := 0; i < sig.Params().Len(); i++ {
params = append(params, sig.Params().At(i))
}
return types.NewSignatureType(nil, nil, nil, types.NewTuple(params...), sig.Results(), sig.Variadic())
}
// instance returns whether an expression is a simple or qualified identifier
// that is a generic instantiation.
func instance(info *types.Info, expr ast.Expr) bool {
// Compare the logic here against go/types.instantiatedIdent,
// which also handles *IndexExpr and *IndexListExpr.
var id *ast.Ident
switch x := expr.(type) {
case *ast.Ident:
id = x
case *ast.SelectorExpr:
id = x.Sel
default:
return false
}
_, ok := info.Instances[id]
return ok
}
// instanceArgs returns the Instance[id].TypeArgs as a slice.
func instanceArgs(info *types.Info, id *ast.Ident) []types.Type {
targList := info.Instances[id].TypeArgs
if targList == nil {
return nil
}
targs := make([]types.Type, targList.Len())
for i, n := 0, targList.Len(); i < n; i++ {
targs[i] = targList.At(i)
}
return targs
}
// Mapping of a type T to a canonical instance C s.t. types.Indentical(T, C).
// Thread-safe.
type canonizer struct {
mu sync.Mutex
types typeutil.Map // map from type to a canonical instance
lists typeListMap // map from a list of types to a canonical instance
}
func newCanonizer() *canonizer {
c := &canonizer{}
h := typeutil.MakeHasher()
c.types.SetHasher(h)
c.lists.hasher = h
return c
}
// List returns a canonical representative of a list of types.
// Representative of the empty list is nil.
func (c *canonizer) List(ts []types.Type) *typeList {
if len(ts) == 0 {
return nil
}
unaliasAll := func(ts []types.Type) []types.Type {
// Is there some top level alias?
var found bool
for _, t := range ts {
if _, ok := t.(*aliases.Alias); ok {
found = true
break
}
}
if !found {
return ts // no top level alias
}
cp := make([]types.Type, len(ts)) // copy with top level aliases removed.
for i, t := range ts {
cp[i] = aliases.Unalias(t)
}
return cp
}
l := unaliasAll(ts)
c.mu.Lock()
defer c.mu.Unlock()
return c.lists.rep(l)
}
// Type returns a canonical representative of type T.
// Removes top-level aliases.
//
// For performance, reasons the canonical instance is order-dependent,
// and may contain deeply nested aliases.
func (c *canonizer) Type(T types.Type) types.Type {
T = aliases.Unalias(T) // remove the top level alias.
c.mu.Lock()
defer c.mu.Unlock()
if r := c.types.At(T); r != nil {
return r.(types.Type)
}
c.types.Set(T, T)
return T
}
// A type for representing a canonized list of types.
type typeList []types.Type
func (l *typeList) identical(ts []types.Type) bool {
if l == nil {
return len(ts) == 0
}
n := len(*l)
if len(ts) != n {
return false
}
for i, left := range *l {
right := ts[i]
if !types.Identical(left, right) {
return false
}
}
return true
}
type typeListMap struct {
hasher typeutil.Hasher
buckets map[uint32][]*typeList
}
// rep returns a canonical representative of a slice of types.
func (m *typeListMap) rep(ts []types.Type) *typeList {
if m == nil || len(ts) == 0 {
return nil
}
if m.buckets == nil {
m.buckets = make(map[uint32][]*typeList)
}
h := m.hash(ts)
bucket := m.buckets[h]
for _, l := range bucket {
if l.identical(ts) {
return l
}
}
// not present. create a representative.
cp := make(typeList, len(ts))
copy(cp, ts)
rep := &cp
m.buckets[h] = append(bucket, rep)
return rep
}
func (m *typeListMap) hash(ts []types.Type) uint32 {
if m == nil {
return 0
}
// Some smallish prime far away from typeutil.Hash.
n := len(ts)
h := uint32(13619) + 2*uint32(n)
for i := 0; i < n; i++ {
h += 3 * m.hasher.Hash(ts[i])
}
return h
}
// instantiateMethod instantiates m with targs and returns a canonical representative for this method.
func (canon *canonizer) instantiateMethod(m *types.Func, targs []types.Type, ctxt *types.Context) *types.Func {
recv := recvType(m)
if p, ok := aliases.Unalias(recv).(*types.Pointer); ok {
recv = p.Elem()
}
named := aliases.Unalias(recv).(*types.Named)
inst, err := types.Instantiate(ctxt, named.Origin(), targs, false)
if err != nil {
panic(err)
}
rep := canon.Type(inst)
obj, _, _ := types.LookupFieldOrMethod(rep, true, m.Pkg(), m.Name())
return obj.(*types.Func)
}
// Exposed to ssautil using the linkname hack.
func isSyntactic(pkg *Package) bool { return pkg.syntax }
// mapValues returns a new unordered array of map values.
func mapValues[K comparable, V any](m map[K]V) []V {
vals := make([]V, 0, len(m))
for _, fn := range m {
vals = append(vals, fn)
}
return vals
}
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