ureader.go

     1  // Copyright 2021 The Go Authors. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  package importer
     6  
     7  import (
     8  	"cmd/compile/internal/base"
     9  	"cmd/compile/internal/syntax"
    10  	"cmd/compile/internal/types2"
    11  	"cmd/internal/src"
    12  	"internal/buildcfg"
    13  	"internal/pkgbits"
    14  )
    15  
    16  type pkgReader struct {
    17  	pkgbits.PkgDecoder
    18  
    19  	ctxt        *types2.Context
    20  	imports     map[string]*types2.Package
    21  	enableAlias bool // whether to use aliases
    22  
    23  	posBases []*syntax.PosBase
    24  	pkgs     []*types2.Package
    25  	typs     []types2.Type
    26  }
    27  
    28  func ReadPackage(ctxt *types2.Context, imports map[string]*types2.Package, input pkgbits.PkgDecoder) *types2.Package {
    29  	pr := pkgReader{
    30  		PkgDecoder: input,
    31  
    32  		ctxt:        ctxt,
    33  		imports:     imports,
    34  		enableAlias: true,
    35  
    36  		posBases: make([]*syntax.PosBase, input.NumElems(pkgbits.RelocPosBase)),
    37  		pkgs:     make([]*types2.Package, input.NumElems(pkgbits.RelocPkg)),
    38  		typs:     make([]types2.Type, input.NumElems(pkgbits.RelocType)),
    39  	}
    40  
    41  	r := pr.newReader(pkgbits.RelocMeta, pkgbits.PublicRootIdx, pkgbits.SyncPublic)
    42  	pkg := r.pkg()
    43  	r.Bool() // TODO(mdempsky): Remove; was "has init"
    44  
    45  	for i, n := 0, r.Len(); i < n; i++ {
    46  		// As if r.obj(), but avoiding the Scope.Lookup call,
    47  		// to avoid eager loading of imports.
    48  		r.Sync(pkgbits.SyncObject)
    49  		assert(!r.Bool())
    50  		r.p.objIdx(r.Reloc(pkgbits.RelocObj))
    51  		assert(r.Len() == 0)
    52  	}
    53  
    54  	r.Sync(pkgbits.SyncEOF)
    55  
    56  	pkg.MarkComplete()
    57  	return pkg
    58  }
    59  
    60  type reader struct {
    61  	pkgbits.Decoder
    62  
    63  	p *pkgReader
    64  
    65  	dict *readerDict
    66  }
    67  
    68  type readerDict struct {
    69  	bounds []typeInfo
    70  
    71  	tparams []*types2.TypeParam
    72  
    73  	derived      []derivedInfo
    74  	derivedTypes []types2.Type
    75  }
    76  
    77  type readerTypeBound struct {
    78  	derived  bool
    79  	boundIdx int
    80  }
    81  
    82  func (pr *pkgReader) newReader(k pkgbits.RelocKind, idx pkgbits.Index, marker pkgbits.SyncMarker) *reader {
    83  	return &reader{
    84  		Decoder: pr.NewDecoder(k, idx, marker),
    85  		p:       pr,
    86  	}
    87  }
    88  
    89  func (pr *pkgReader) tempReader(k pkgbits.RelocKind, idx pkgbits.Index, marker pkgbits.SyncMarker) *reader {
    90  	return &reader{
    91  		Decoder: pr.TempDecoder(k, idx, marker),
    92  		p:       pr,
    93  	}
    94  }
    95  
    96  func (pr *pkgReader) retireReader(r *reader) {
    97  	pr.RetireDecoder(&r.Decoder)
    98  }
    99  
   100  // @@@ Positions
   101  
   102  func (r *reader) pos() syntax.Pos {
   103  	r.Sync(pkgbits.SyncPos)
   104  	if !r.Bool() {
   105  		return syntax.Pos{}
   106  	}
   107  
   108  	// TODO(mdempsky): Delta encoding.
   109  	posBase := r.posBase()
   110  	line := r.Uint()
   111  	col := r.Uint()
   112  	return syntax.MakePos(posBase, line, col)
   113  }
   114  
   115  func (r *reader) posBase() *syntax.PosBase {
   116  	return r.p.posBaseIdx(r.Reloc(pkgbits.RelocPosBase))
   117  }
   118  
   119  func (pr *pkgReader) posBaseIdx(idx pkgbits.Index) *syntax.PosBase {
   120  	if b := pr.posBases[idx]; b != nil {
   121  		return b
   122  	}
   123  	var b *syntax.PosBase
   124  	{
   125  		r := pr.tempReader(pkgbits.RelocPosBase, idx, pkgbits.SyncPosBase)
   126  
   127  		filename := r.String()
   128  
   129  		if r.Bool() {
   130  			b = syntax.NewTrimmedFileBase(filename, true)
   131  		} else {
   132  			pos := r.pos()
   133  			line := r.Uint()
   134  			col := r.Uint()
   135  			b = syntax.NewLineBase(pos, filename, true, line, col)
   136  		}
   137  		pr.retireReader(r)
   138  	}
   139  
   140  	pr.posBases[idx] = b
   141  	return b
   142  }
   143  
   144  // @@@ Packages
   145  
   146  func (r *reader) pkg() *types2.Package {
   147  	r.Sync(pkgbits.SyncPkg)
   148  	return r.p.pkgIdx(r.Reloc(pkgbits.RelocPkg))
   149  }
   150  
   151  func (pr *pkgReader) pkgIdx(idx pkgbits.Index) *types2.Package {
   152  	// TODO(mdempsky): Consider using some non-nil pointer to indicate
   153  	// the universe scope, so we don't need to keep re-reading it.
   154  	if pkg := pr.pkgs[idx]; pkg != nil {
   155  		return pkg
   156  	}
   157  
   158  	pkg := pr.newReader(pkgbits.RelocPkg, idx, pkgbits.SyncPkgDef).doPkg()
   159  	pr.pkgs[idx] = pkg
   160  	return pkg
   161  }
   162  
   163  func (r *reader) doPkg() *types2.Package {
   164  	path := r.String()
   165  	switch path {
   166  	case "":
   167  		path = r.p.PkgPath()
   168  	case "builtin":
   169  		return nil // universe
   170  	case "unsafe":
   171  		return types2.Unsafe
   172  	}
   173  
   174  	if pkg := r.p.imports[path]; pkg != nil {
   175  		return pkg
   176  	}
   177  
   178  	name := r.String()
   179  	pkg := types2.NewPackage(path, name)
   180  	r.p.imports[path] = pkg
   181  
   182  	// TODO(mdempsky): The list of imported packages is important for
   183  	// go/types, but we could probably skip populating it for types2.
   184  	imports := make([]*types2.Package, r.Len())
   185  	for i := range imports {
   186  		imports[i] = r.pkg()
   187  	}
   188  	pkg.SetImports(imports)
   189  
   190  	return pkg
   191  }
   192  
   193  // @@@ Types
   194  
   195  func (r *reader) typ() types2.Type {
   196  	return r.p.typIdx(r.typInfo(), r.dict)
   197  }
   198  
   199  func (r *reader) typInfo() typeInfo {
   200  	r.Sync(pkgbits.SyncType)
   201  	if r.Bool() {
   202  		return typeInfo{idx: pkgbits.Index(r.Len()), derived: true}
   203  	}
   204  	return typeInfo{idx: r.Reloc(pkgbits.RelocType), derived: false}
   205  }
   206  
   207  func (pr *pkgReader) typIdx(info typeInfo, dict *readerDict) types2.Type {
   208  	idx := info.idx
   209  	var where *types2.Type
   210  	if info.derived {
   211  		where = &dict.derivedTypes[idx]
   212  		idx = dict.derived[idx].idx
   213  	} else {
   214  		where = &pr.typs[idx]
   215  	}
   216  
   217  	if typ := *where; typ != nil {
   218  		return typ
   219  	}
   220  
   221  	var typ types2.Type
   222  	{
   223  		r := pr.tempReader(pkgbits.RelocType, idx, pkgbits.SyncTypeIdx)
   224  		r.dict = dict
   225  
   226  		typ = r.doTyp()
   227  		assert(typ != nil)
   228  		pr.retireReader(r)
   229  	}
   230  
   231  	// See comment in pkgReader.typIdx explaining how this happens.
   232  	if prev := *where; prev != nil {
   233  		return prev
   234  	}
   235  
   236  	*where = typ
   237  	return typ
   238  }
   239  
   240  func (r *reader) doTyp() (res types2.Type) {
   241  	switch tag := pkgbits.CodeType(r.Code(pkgbits.SyncType)); tag {
   242  	default:
   243  		base.FatalfAt(src.NoXPos, "unhandled type tag: %v", tag)
   244  		panic("unreachable")
   245  
   246  	case pkgbits.TypeBasic:
   247  		return types2.Typ[r.Len()]
   248  
   249  	case pkgbits.TypeNamed:
   250  		obj, targs := r.obj()
   251  		name := obj.(*types2.TypeName)
   252  		if len(targs) != 0 {
   253  			t, _ := types2.Instantiate(r.p.ctxt, name.Type(), targs, false)
   254  			return t
   255  		}
   256  		return name.Type()
   257  
   258  	case pkgbits.TypeTypeParam:
   259  		return r.dict.tparams[r.Len()]
   260  
   261  	case pkgbits.TypeArray:
   262  		len := int64(r.Uint64())
   263  		return types2.NewArray(r.typ(), len)
   264  	case pkgbits.TypeChan:
   265  		dir := types2.ChanDir(r.Len())
   266  		return types2.NewChan(dir, r.typ())
   267  	case pkgbits.TypeMap:
   268  		return types2.NewMap(r.typ(), r.typ())
   269  	case pkgbits.TypePointer:
   270  		return types2.NewPointer(r.typ())
   271  	case pkgbits.TypeSignature:
   272  		return r.signature(nil, nil, nil)
   273  	case pkgbits.TypeSlice:
   274  		return types2.NewSlice(r.typ())
   275  	case pkgbits.TypeStruct:
   276  		return r.structType()
   277  	case pkgbits.TypeInterface:
   278  		return r.interfaceType()
   279  	case pkgbits.TypeUnion:
   280  		return r.unionType()
   281  	}
   282  }
   283  
   284  func (r *reader) structType() *types2.Struct {
   285  	fields := make([]*types2.Var, r.Len())
   286  	var tags []string
   287  	for i := range fields {
   288  		pos := r.pos()
   289  		pkg, name := r.selector()
   290  		ftyp := r.typ()
   291  		tag := r.String()
   292  		embedded := r.Bool()
   293  
   294  		fields[i] = types2.NewField(pos, pkg, name, ftyp, embedded)
   295  		if tag != "" {
   296  			for len(tags) < i {
   297  				tags = append(tags, "")
   298  			}
   299  			tags = append(tags, tag)
   300  		}
   301  	}
   302  	return types2.NewStruct(fields, tags)
   303  }
   304  
   305  func (r *reader) unionType() *types2.Union {
   306  	terms := make([]*types2.Term, r.Len())
   307  	for i := range terms {
   308  		terms[i] = types2.NewTerm(r.Bool(), r.typ())
   309  	}
   310  	return types2.NewUnion(terms)
   311  }
   312  
   313  func (r *reader) interfaceType() *types2.Interface {
   314  	methods := make([]*types2.Func, r.Len())
   315  	embeddeds := make([]types2.Type, r.Len())
   316  	implicit := len(methods) == 0 && len(embeddeds) == 1 && r.Bool()
   317  
   318  	for i := range methods {
   319  		pos := r.pos()
   320  		pkg, name := r.selector()
   321  		mtyp := r.signature(nil, nil, nil)
   322  		methods[i] = types2.NewFunc(pos, pkg, name, mtyp)
   323  	}
   324  
   325  	for i := range embeddeds {
   326  		embeddeds[i] = r.typ()
   327  	}
   328  
   329  	iface := types2.NewInterfaceType(methods, embeddeds)
   330  	if implicit {
   331  		iface.MarkImplicit()
   332  	}
   333  	return iface
   334  }
   335  
   336  func (r *reader) signature(recv *types2.Var, rtparams, tparams []*types2.TypeParam) *types2.Signature {
   337  	r.Sync(pkgbits.SyncSignature)
   338  
   339  	params := r.params()
   340  	results := r.params()
   341  	variadic := r.Bool()
   342  
   343  	return types2.NewSignatureType(recv, rtparams, tparams, params, results, variadic)
   344  }
   345  
   346  func (r *reader) params() *types2.Tuple {
   347  	r.Sync(pkgbits.SyncParams)
   348  	params := make([]*types2.Var, r.Len())
   349  	for i := range params {
   350  		params[i] = r.param()
   351  	}
   352  	return types2.NewTuple(params...)
   353  }
   354  
   355  func (r *reader) param() *types2.Var {
   356  	r.Sync(pkgbits.SyncParam)
   357  
   358  	pos := r.pos()
   359  	pkg, name := r.localIdent()
   360  	typ := r.typ()
   361  
   362  	return types2.NewParam(pos, pkg, name, typ)
   363  }
   364  
   365  // @@@ Objects
   366  
   367  func (r *reader) obj() (types2.Object, []types2.Type) {
   368  	r.Sync(pkgbits.SyncObject)
   369  
   370  	assert(!r.Bool())
   371  
   372  	pkg, name := r.p.objIdx(r.Reloc(pkgbits.RelocObj))
   373  	obj := pkg.Scope().Lookup(name)
   374  
   375  	targs := make([]types2.Type, r.Len())
   376  	for i := range targs {
   377  		targs[i] = r.typ()
   378  	}
   379  
   380  	return obj, targs
   381  }
   382  
   383  func (pr *pkgReader) objIdx(idx pkgbits.Index) (*types2.Package, string) {
   384  	var objPkg *types2.Package
   385  	var objName string
   386  	var tag pkgbits.CodeObj
   387  	{
   388  		rname := pr.tempReader(pkgbits.RelocName, idx, pkgbits.SyncObject1)
   389  
   390  		objPkg, objName = rname.qualifiedIdent()
   391  		assert(objName != "")
   392  
   393  		tag = pkgbits.CodeObj(rname.Code(pkgbits.SyncCodeObj))
   394  		pr.retireReader(rname)
   395  	}
   396  
   397  	if tag == pkgbits.ObjStub {
   398  		base.Assertf(objPkg == nil || objPkg == types2.Unsafe, "unexpected stub package: %v", objPkg)
   399  		return objPkg, objName
   400  	}
   401  
   402  	objPkg.Scope().InsertLazy(objName, func() types2.Object {
   403  		dict := pr.objDictIdx(idx)
   404  
   405  		r := pr.newReader(pkgbits.RelocObj, idx, pkgbits.SyncObject1)
   406  		r.dict = dict
   407  
   408  		switch tag {
   409  		default:
   410  			panic("weird")
   411  
   412  		case pkgbits.ObjAlias:
   413  			if buildcfg.Experiment.AliasTypeParams && len(r.dict.bounds) > 0 {
   414  				// Temporary work-around for issue #68526: rather than panicking
   415  				// with an non-descriptive index-out-of-bounds panic when trying
   416  				// to access a missing type parameter, instead panic with a more
   417  				// descriptive error. Only needed for Go 1.23; Go 1.24 will have
   418  				// the correct implementation.
   419  				panic("importing generic type aliases is not supported in Go 1.23 (see issue #68526)")
   420  			}
   421  			pos := r.pos()
   422  			typ := r.typ()
   423  			return newAliasTypeName(pr.enableAlias, pos, objPkg, objName, typ)
   424  
   425  		case pkgbits.ObjConst:
   426  			pos := r.pos()
   427  			typ := r.typ()
   428  			val := r.Value()
   429  			return types2.NewConst(pos, objPkg, objName, typ, val)
   430  
   431  		case pkgbits.ObjFunc:
   432  			pos := r.pos()
   433  			tparams := r.typeParamNames()
   434  			sig := r.signature(nil, nil, tparams)
   435  			return types2.NewFunc(pos, objPkg, objName, sig)
   436  
   437  		case pkgbits.ObjType:
   438  			pos := r.pos()
   439  
   440  			return types2.NewTypeNameLazy(pos, objPkg, objName, func(named *types2.Named) (tparams []*types2.TypeParam, underlying types2.Type, methods []*types2.Func) {
   441  				tparams = r.typeParamNames()
   442  
   443  				// TODO(mdempsky): Rewrite receiver types to underlying is an
   444  				// Interface? The go/types importer does this (I think because
   445  				// unit tests expected that), but cmd/compile doesn't care
   446  				// about it, so maybe we can avoid worrying about that here.
   447  				underlying = r.typ().Underlying()
   448  
   449  				methods = make([]*types2.Func, r.Len())
   450  				for i := range methods {
   451  					methods[i] = r.method()
   452  				}
   453  
   454  				return
   455  			})
   456  
   457  		case pkgbits.ObjVar:
   458  			pos := r.pos()
   459  			typ := r.typ()
   460  			return types2.NewVar(pos, objPkg, objName, typ)
   461  		}
   462  	})
   463  
   464  	return objPkg, objName
   465  }
   466  
   467  func (pr *pkgReader) objDictIdx(idx pkgbits.Index) *readerDict {
   468  	var dict readerDict
   469  	{
   470  		r := pr.tempReader(pkgbits.RelocObjDict, idx, pkgbits.SyncObject1)
   471  
   472  		if implicits := r.Len(); implicits != 0 {
   473  			base.Fatalf("unexpected object with %v implicit type parameter(s)", implicits)
   474  		}
   475  
   476  		dict.bounds = make([]typeInfo, r.Len())
   477  		for i := range dict.bounds {
   478  			dict.bounds[i] = r.typInfo()
   479  		}
   480  
   481  		dict.derived = make([]derivedInfo, r.Len())
   482  		dict.derivedTypes = make([]types2.Type, len(dict.derived))
   483  		for i := range dict.derived {
   484  			dict.derived[i] = derivedInfo{r.Reloc(pkgbits.RelocType), r.Bool()}
   485  		}
   486  
   487  		pr.retireReader(r)
   488  	}
   489  	// function references follow, but reader doesn't need those
   490  
   491  	return &dict
   492  }
   493  
   494  func (r *reader) typeParamNames() []*types2.TypeParam {
   495  	r.Sync(pkgbits.SyncTypeParamNames)
   496  
   497  	// Note: This code assumes it only processes objects without
   498  	// implement type parameters. This is currently fine, because
   499  	// reader is only used to read in exported declarations, which are
   500  	// always package scoped.
   501  
   502  	if len(r.dict.bounds) == 0 {
   503  		return nil
   504  	}
   505  
   506  	// Careful: Type parameter lists may have cycles. To allow for this,
   507  	// we construct the type parameter list in two passes: first we
   508  	// create all the TypeNames and TypeParams, then we construct and
   509  	// set the bound type.
   510  
   511  	r.dict.tparams = make([]*types2.TypeParam, len(r.dict.bounds))
   512  	for i := range r.dict.bounds {
   513  		pos := r.pos()
   514  		pkg, name := r.localIdent()
   515  
   516  		tname := types2.NewTypeName(pos, pkg, name, nil)
   517  		r.dict.tparams[i] = types2.NewTypeParam(tname, nil)
   518  	}
   519  
   520  	for i, bound := range r.dict.bounds {
   521  		r.dict.tparams[i].SetConstraint(r.p.typIdx(bound, r.dict))
   522  	}
   523  
   524  	return r.dict.tparams
   525  }
   526  
   527  func (r *reader) method() *types2.Func {
   528  	r.Sync(pkgbits.SyncMethod)
   529  	pos := r.pos()
   530  	pkg, name := r.selector()
   531  
   532  	rtparams := r.typeParamNames()
   533  	sig := r.signature(r.param(), rtparams, nil)
   534  
   535  	_ = r.pos() // TODO(mdempsky): Remove; this is a hacker for linker.go.
   536  	return types2.NewFunc(pos, pkg, name, sig)
   537  }
   538  
   539  func (r *reader) qualifiedIdent() (*types2.Package, string) { return r.ident(pkgbits.SyncSym) }
   540  func (r *reader) localIdent() (*types2.Package, string)     { return r.ident(pkgbits.SyncLocalIdent) }
   541  func (r *reader) selector() (*types2.Package, string)       { return r.ident(pkgbits.SyncSelector) }
   542  
   543  func (r *reader) ident(marker pkgbits.SyncMarker) (*types2.Package, string) {
   544  	r.Sync(marker)
   545  	return r.pkg(), r.String()
   546  }
   547  
   548  // newAliasTypeName returns a new TypeName, with a materialized *types2.Alias if supported.
   549  func newAliasTypeName(aliases bool, pos syntax.Pos, pkg *types2.Package, name string, rhs types2.Type) *types2.TypeName {
   550  	// Copied from x/tools/internal/aliases.NewAlias via
   551  	// GOROOT/src/go/internal/gcimporter/ureader.go.
   552  	if aliases {
   553  		tname := types2.NewTypeName(pos, pkg, name, nil)
   554  		_ = types2.NewAlias(tname, rhs) // form TypeName -> Alias cycle
   555  		return tname
   556  	}
   557  	return types2.NewTypeName(pos, pkg, name, rhs)
   558  }
   559
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