src

util.go (10614B)

---

 // 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"
 	_ "unsafe" // for go:linkname hack
 
 	"golang.org/x/tools/go/types/typeutil"
 	"golang.org/x/tools/internal/typeparams"
 	"golang.org/x/tools/internal/typesinternal"
 )
 
 type unit struct{}
 
 //// Sanity checking utilities
 
 // assert panics with the message msg if p is false.
 // Avoid combining with expensive string formatting.
 func assert(p bool, msg string) {
 	if !p {
 		panic(msg)
 	}
 }
 
 //// AST utilities
 
 // 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 == "_"
 }
 
 //// 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 the type set of a type
 // 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(typ types.Type) bool {
 	basics, cnt := 0, 0
 	ok := underIs(typ, func(t types.Type) bool {
 		cnt++
 		if isBasic(t) {
 			basics++
 			return true
 		}
 		return isByteSlice(t) || isRuneSlice(t)
 	})
 	return ok && basics >= 1 && cnt-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.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 ...any) 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)
 }
 
 var lenResults = typesinternal.TupleOf(tInt)
 
 // makeLen returns the len builtin specialized to type func(T)int.
 func makeLen(T types.Type) *Builtin {
 	return &Builtin{
 		name: "len",
 		sig:  types.NewSignatureType(nil, nil, nil, typesinternal.TupleOf(T), 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.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 v := range sig.Params().Variables() {
 		params = append(params, v)
 	}
 	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.Identical(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.(*types.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] = types.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 = types.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 := range n {
 		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 := types.Unalias(recv).(*types.Pointer); ok {
 		recv = p.Elem()
 	}
 	named := types.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.
 //
 //go:linkname isSyntactic golang.org/x/tools/go/ssa.isSyntactic
 func isSyntactic(pkg *Package) bool { return pkg.syntax }