object.go

     1  // Copyright 2013 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 types2
     6  
     7  import (
     8  	"bytes"
     9  	"cmd/compile/internal/syntax"
    10  	"fmt"
    11  	"go/constant"
    12  	"unicode"
    13  	"unicode/utf8"
    14  )
    15  
    16  // An Object describes a named language entity such as a package,
    17  // constant, type, variable, function (incl. methods), or label.
    18  // All objects implement the Object interface.
    19  type Object interface {
    20  	Parent() *Scope  // scope in which this object is declared; nil for methods and struct fields
    21  	Pos() syntax.Pos // position of object identifier in declaration
    22  	Pkg() *Package   // package to which this object belongs; nil for labels and objects in the Universe scope
    23  	Name() string    // package local object name
    24  	Type() Type      // object type
    25  	Exported() bool  // reports whether the name starts with a capital letter
    26  	Id() string      // object name if exported, qualified name if not exported (see func Id)
    27  
    28  	// String returns a human-readable string of the object.
    29  	String() string
    30  
    31  	// order reflects a package-level object's source order: if object
    32  	// a is before object b in the source, then a.order() < b.order().
    33  	// order returns a value > 0 for package-level objects; it returns
    34  	// 0 for all other objects (including objects in file scopes).
    35  	order() uint32
    36  
    37  	// color returns the object's color.
    38  	color() color
    39  
    40  	// setType sets the type of the object.
    41  	setType(Type)
    42  
    43  	// setOrder sets the order number of the object. It must be > 0.
    44  	setOrder(uint32)
    45  
    46  	// setColor sets the object's color. It must not be white.
    47  	setColor(color color)
    48  
    49  	// setParent sets the parent scope of the object.
    50  	setParent(*Scope)
    51  
    52  	// sameId reports whether obj.Id() and Id(pkg, name) are the same.
    53  	sameId(pkg *Package, name string) bool
    54  
    55  	// scopePos returns the start position of the scope of this Object
    56  	scopePos() syntax.Pos
    57  
    58  	// setScopePos sets the start position of the scope for this Object.
    59  	setScopePos(pos syntax.Pos)
    60  }
    61  
    62  func isExported(name string) bool {
    63  	ch, _ := utf8.DecodeRuneInString(name)
    64  	return unicode.IsUpper(ch)
    65  }
    66  
    67  // Id returns name if it is exported, otherwise it
    68  // returns the name qualified with the package path.
    69  func Id(pkg *Package, name string) string {
    70  	if isExported(name) {
    71  		return name
    72  	}
    73  	// unexported names need the package path for differentiation
    74  	// (if there's no package, make sure we don't start with '.'
    75  	// as that may change the order of methods between a setup
    76  	// inside a package and outside a package - which breaks some
    77  	// tests)
    78  	path := "_"
    79  	// pkg is nil for objects in Universe scope and possibly types
    80  	// introduced via Eval (see also comment in object.sameId)
    81  	if pkg != nil && pkg.path != "" {
    82  		path = pkg.path
    83  	}
    84  	return path + "." + name
    85  }
    86  
    87  // An object implements the common parts of an Object.
    88  type object struct {
    89  	parent    *Scope
    90  	pos       syntax.Pos
    91  	pkg       *Package
    92  	name      string
    93  	typ       Type
    94  	order_    uint32
    95  	color_    color
    96  	scopePos_ syntax.Pos
    97  }
    98  
    99  // color encodes the color of an object (see Checker.objDecl for details).
   100  type color uint32
   101  
   102  // An object may be painted in one of three colors.
   103  // Color values other than white or black are considered grey.
   104  const (
   105  	white color = iota
   106  	black
   107  	grey // must be > white and black
   108  )
   109  
   110  func (c color) String() string {
   111  	switch c {
   112  	case white:
   113  		return "white"
   114  	case black:
   115  		return "black"
   116  	default:
   117  		return "grey"
   118  	}
   119  }
   120  
   121  // colorFor returns the (initial) color for an object depending on
   122  // whether its type t is known or not.
   123  func colorFor(t Type) color {
   124  	if t != nil {
   125  		return black
   126  	}
   127  	return white
   128  }
   129  
   130  // Parent returns the scope in which the object is declared.
   131  // The result is nil for methods and struct fields.
   132  func (obj *object) Parent() *Scope { return obj.parent }
   133  
   134  // Pos returns the declaration position of the object's identifier.
   135  func (obj *object) Pos() syntax.Pos { return obj.pos }
   136  
   137  // Pkg returns the package to which the object belongs.
   138  // The result is nil for labels and objects in the Universe scope.
   139  func (obj *object) Pkg() *Package { return obj.pkg }
   140  
   141  // Name returns the object's (package-local, unqualified) name.
   142  func (obj *object) Name() string { return obj.name }
   143  
   144  // Type returns the object's type.
   145  func (obj *object) Type() Type { return obj.typ }
   146  
   147  // Exported reports whether the object is exported (starts with a capital letter).
   148  // It doesn't take into account whether the object is in a local (function) scope
   149  // or not.
   150  func (obj *object) Exported() bool { return isExported(obj.name) }
   151  
   152  // Id is a wrapper for Id(obj.Pkg(), obj.Name()).
   153  func (obj *object) Id() string { return Id(obj.pkg, obj.name) }
   154  
   155  func (obj *object) String() string       { panic("abstract") }
   156  func (obj *object) order() uint32        { return obj.order_ }
   157  func (obj *object) color() color         { return obj.color_ }
   158  func (obj *object) scopePos() syntax.Pos { return obj.scopePos_ }
   159  
   160  func (obj *object) setParent(parent *Scope)    { obj.parent = parent }
   161  func (obj *object) setType(typ Type)           { obj.typ = typ }
   162  func (obj *object) setOrder(order uint32)      { assert(order > 0); obj.order_ = order }
   163  func (obj *object) setColor(color color)       { assert(color != white); obj.color_ = color }
   164  func (obj *object) setScopePos(pos syntax.Pos) { obj.scopePos_ = pos }
   165  
   166  func (obj *object) sameId(pkg *Package, name string) bool {
   167  	// spec:
   168  	// "Two identifiers are different if they are spelled differently,
   169  	// or if they appear in different packages and are not exported.
   170  	// Otherwise, they are the same."
   171  	if name != obj.name {
   172  		return false
   173  	}
   174  	// obj.Name == name
   175  	if obj.Exported() {
   176  		return true
   177  	}
   178  	// not exported, so packages must be the same (pkg == nil for
   179  	// fields in Universe scope; this can only happen for types
   180  	// introduced via Eval)
   181  	if pkg == nil || obj.pkg == nil {
   182  		return pkg == obj.pkg
   183  	}
   184  	// pkg != nil && obj.pkg != nil
   185  	return pkg.path == obj.pkg.path
   186  }
   187  
   188  // less reports whether object a is ordered before object b.
   189  //
   190  // Objects are ordered nil before non-nil, exported before
   191  // non-exported, then by name, and finally (for non-exported
   192  // functions) by package path.
   193  func (a *object) less(b *object) bool {
   194  	if a == b {
   195  		return false
   196  	}
   197  
   198  	// Nil before non-nil.
   199  	if a == nil {
   200  		return true
   201  	}
   202  	if b == nil {
   203  		return false
   204  	}
   205  
   206  	// Exported functions before non-exported.
   207  	ea := isExported(a.name)
   208  	eb := isExported(b.name)
   209  	if ea != eb {
   210  		return ea
   211  	}
   212  
   213  	// Order by name and then (for non-exported names) by package.
   214  	if a.name != b.name {
   215  		return a.name < b.name
   216  	}
   217  	if !ea {
   218  		return a.pkg.path < b.pkg.path
   219  	}
   220  
   221  	return false
   222  }
   223  
   224  // A PkgName represents an imported Go package.
   225  // PkgNames don't have a type.
   226  type PkgName struct {
   227  	object
   228  	imported *Package
   229  	used     bool // set if the package was used
   230  }
   231  
   232  // NewPkgName returns a new PkgName object representing an imported package.
   233  // The remaining arguments set the attributes found with all Objects.
   234  func NewPkgName(pos syntax.Pos, pkg *Package, name string, imported *Package) *PkgName {
   235  	return &PkgName{object{nil, pos, pkg, name, Typ[Invalid], 0, black, nopos}, imported, false}
   236  }
   237  
   238  // Imported returns the package that was imported.
   239  // It is distinct from Pkg(), which is the package containing the import statement.
   240  func (obj *PkgName) Imported() *Package { return obj.imported }
   241  
   242  // A Const represents a declared constant.
   243  type Const struct {
   244  	object
   245  	val constant.Value
   246  }
   247  
   248  // NewConst returns a new constant with value val.
   249  // The remaining arguments set the attributes found with all Objects.
   250  func NewConst(pos syntax.Pos, pkg *Package, name string, typ Type, val constant.Value) *Const {
   251  	return &Const{object{nil, pos, pkg, name, typ, 0, colorFor(typ), nopos}, val}
   252  }
   253  
   254  // Val returns the constant's value.
   255  func (obj *Const) Val() constant.Value { return obj.val }
   256  
   257  func (*Const) isDependency() {} // a constant may be a dependency of an initialization expression
   258  
   259  // A TypeName represents a name for a (defined or alias) type.
   260  type TypeName struct {
   261  	object
   262  }
   263  
   264  // NewTypeName returns a new type name denoting the given typ.
   265  // The remaining arguments set the attributes found with all Objects.
   266  //
   267  // The typ argument may be a defined (Named) type or an alias type.
   268  // It may also be nil such that the returned TypeName can be used as
   269  // argument for NewNamed, which will set the TypeName's type as a side-
   270  // effect.
   271  func NewTypeName(pos syntax.Pos, pkg *Package, name string, typ Type) *TypeName {
   272  	return &TypeName{object{nil, pos, pkg, name, typ, 0, colorFor(typ), nopos}}
   273  }
   274  
   275  // NewTypeNameLazy returns a new defined type like NewTypeName, but it
   276  // lazily calls resolve to finish constructing the Named object.
   277  func NewTypeNameLazy(pos syntax.Pos, pkg *Package, name string, load func(named *Named) (tparams []*TypeParam, underlying Type, methods []*Func)) *TypeName {
   278  	obj := NewTypeName(pos, pkg, name, nil)
   279  	NewNamed(obj, nil, nil).loader = load
   280  	return obj
   281  }
   282  
   283  // IsAlias reports whether obj is an alias name for a type.
   284  func (obj *TypeName) IsAlias() bool {
   285  	switch t := obj.typ.(type) {
   286  	case nil:
   287  		return false
   288  	// case *Alias:
   289  	//	handled by default case
   290  	case *Basic:
   291  		// unsafe.Pointer is not an alias.
   292  		if obj.pkg == Unsafe {
   293  			return false
   294  		}
   295  		// Any user-defined type name for a basic type is an alias for a
   296  		// basic type (because basic types are pre-declared in the Universe
   297  		// scope, outside any package scope), and so is any type name with
   298  		// a different name than the name of the basic type it refers to.
   299  		// Additionally, we need to look for "byte" and "rune" because they
   300  		// are aliases but have the same names (for better error messages).
   301  		return obj.pkg != nil || t.name != obj.name || t == universeByte || t == universeRune
   302  	case *Named:
   303  		return obj != t.obj
   304  	case *TypeParam:
   305  		return obj != t.obj
   306  	default:
   307  		return true
   308  	}
   309  }
   310  
   311  // A Variable represents a declared variable (including function parameters and results, and struct fields).
   312  type Var struct {
   313  	object
   314  	embedded bool // if set, the variable is an embedded struct field, and name is the type name
   315  	isField  bool // var is struct field
   316  	used     bool // set if the variable was used
   317  	origin   *Var // if non-nil, the Var from which this one was instantiated
   318  }
   319  
   320  // NewVar returns a new variable.
   321  // The arguments set the attributes found with all Objects.
   322  func NewVar(pos syntax.Pos, pkg *Package, name string, typ Type) *Var {
   323  	return &Var{object: object{nil, pos, pkg, name, typ, 0, colorFor(typ), nopos}}
   324  }
   325  
   326  // NewParam returns a new variable representing a function parameter.
   327  func NewParam(pos syntax.Pos, pkg *Package, name string, typ Type) *Var {
   328  	return &Var{object: object{nil, pos, pkg, name, typ, 0, colorFor(typ), nopos}, used: true} // parameters are always 'used'
   329  }
   330  
   331  // NewField returns a new variable representing a struct field.
   332  // For embedded fields, the name is the unqualified type name
   333  // under which the field is accessible.
   334  func NewField(pos syntax.Pos, pkg *Package, name string, typ Type, embedded bool) *Var {
   335  	return &Var{object: object{nil, pos, pkg, name, typ, 0, colorFor(typ), nopos}, embedded: embedded, isField: true}
   336  }
   337  
   338  // Anonymous reports whether the variable is an embedded field.
   339  // Same as Embedded; only present for backward-compatibility.
   340  func (obj *Var) Anonymous() bool { return obj.embedded }
   341  
   342  // Embedded reports whether the variable is an embedded field.
   343  func (obj *Var) Embedded() bool { return obj.embedded }
   344  
   345  // IsField reports whether the variable is a struct field.
   346  func (obj *Var) IsField() bool { return obj.isField }
   347  
   348  // Origin returns the canonical Var for its receiver, i.e. the Var object
   349  // recorded in Info.Defs.
   350  //
   351  // For synthetic Vars created during instantiation (such as struct fields or
   352  // function parameters that depend on type arguments), this will be the
   353  // corresponding Var on the generic (uninstantiated) type. For all other Vars
   354  // Origin returns the receiver.
   355  func (obj *Var) Origin() *Var {
   356  	if obj.origin != nil {
   357  		return obj.origin
   358  	}
   359  	return obj
   360  }
   361  
   362  func (*Var) isDependency() {} // a variable may be a dependency of an initialization expression
   363  
   364  // A Func represents a declared function, concrete method, or abstract
   365  // (interface) method. Its Type() is always a *Signature.
   366  // An abstract method may belong to many interfaces due to embedding.
   367  type Func struct {
   368  	object
   369  	hasPtrRecv_ bool  // only valid for methods that don't have a type yet; use hasPtrRecv() to read
   370  	origin      *Func // if non-nil, the Func from which this one was instantiated
   371  }
   372  
   373  // NewFunc returns a new function with the given signature, representing
   374  // the function's type.
   375  func NewFunc(pos syntax.Pos, pkg *Package, name string, sig *Signature) *Func {
   376  	// don't store a (typed) nil signature
   377  	var typ Type
   378  	if sig != nil {
   379  		typ = sig
   380  	}
   381  	return &Func{object{nil, pos, pkg, name, typ, 0, colorFor(typ), nopos}, false, nil}
   382  }
   383  
   384  // FullName returns the package- or receiver-type-qualified name of
   385  // function or method obj.
   386  func (obj *Func) FullName() string {
   387  	var buf bytes.Buffer
   388  	writeFuncName(&buf, obj, nil)
   389  	return buf.String()
   390  }
   391  
   392  // Scope returns the scope of the function's body block.
   393  // The result is nil for imported or instantiated functions and methods
   394  // (but there is also no mechanism to get to an instantiated function).
   395  func (obj *Func) Scope() *Scope { return obj.typ.(*Signature).scope }
   396  
   397  // Origin returns the canonical Func for its receiver, i.e. the Func object
   398  // recorded in Info.Defs.
   399  //
   400  // For synthetic functions created during instantiation (such as methods on an
   401  // instantiated Named type or interface methods that depend on type arguments),
   402  // this will be the corresponding Func on the generic (uninstantiated) type.
   403  // For all other Funcs Origin returns the receiver.
   404  func (obj *Func) Origin() *Func {
   405  	if obj.origin != nil {
   406  		return obj.origin
   407  	}
   408  	return obj
   409  }
   410  
   411  // Pkg returns the package to which the function belongs.
   412  //
   413  // The result is nil for methods of types in the Universe scope,
   414  // like method Error of the error built-in interface type.
   415  func (obj *Func) Pkg() *Package { return obj.object.Pkg() }
   416  
   417  // hasPtrRecv reports whether the receiver is of the form *T for the given method obj.
   418  func (obj *Func) hasPtrRecv() bool {
   419  	// If a method's receiver type is set, use that as the source of truth for the receiver.
   420  	// Caution: Checker.funcDecl (decl.go) marks a function by setting its type to an empty
   421  	// signature. We may reach here before the signature is fully set up: we must explicitly
   422  	// check if the receiver is set (we cannot just look for non-nil obj.typ).
   423  	if sig, _ := obj.typ.(*Signature); sig != nil && sig.recv != nil {
   424  		_, isPtr := deref(sig.recv.typ)
   425  		return isPtr
   426  	}
   427  
   428  	// If a method's type is not set it may be a method/function that is:
   429  	// 1) client-supplied (via NewFunc with no signature), or
   430  	// 2) internally created but not yet type-checked.
   431  	// For case 1) we can't do anything; the client must know what they are doing.
   432  	// For case 2) we can use the information gathered by the resolver.
   433  	return obj.hasPtrRecv_
   434  }
   435  
   436  func (*Func) isDependency() {} // a function may be a dependency of an initialization expression
   437  
   438  // A Label represents a declared label.
   439  // Labels don't have a type.
   440  type Label struct {
   441  	object
   442  	used bool // set if the label was used
   443  }
   444  
   445  // NewLabel returns a new label.
   446  func NewLabel(pos syntax.Pos, pkg *Package, name string) *Label {
   447  	return &Label{object{pos: pos, pkg: pkg, name: name, typ: Typ[Invalid], color_: black}, false}
   448  }
   449  
   450  // A Builtin represents a built-in function.
   451  // Builtins don't have a valid type.
   452  type Builtin struct {
   453  	object
   454  	id builtinId
   455  }
   456  
   457  func newBuiltin(id builtinId) *Builtin {
   458  	return &Builtin{object{name: predeclaredFuncs[id].name, typ: Typ[Invalid], color_: black}, id}
   459  }
   460  
   461  // Nil represents the predeclared value nil.
   462  type Nil struct {
   463  	object
   464  }
   465  
   466  func writeObject(buf *bytes.Buffer, obj Object, qf Qualifier) {
   467  	var tname *TypeName
   468  	typ := obj.Type()
   469  
   470  	switch obj := obj.(type) {
   471  	case *PkgName:
   472  		fmt.Fprintf(buf, "package %s", obj.Name())
   473  		if path := obj.imported.path; path != "" && path != obj.name {
   474  			fmt.Fprintf(buf, " (%q)", path)
   475  		}
   476  		return
   477  
   478  	case *Const:
   479  		buf.WriteString("const")
   480  
   481  	case *TypeName:
   482  		tname = obj
   483  		buf.WriteString("type")
   484  		if isTypeParam(typ) {
   485  			buf.WriteString(" parameter")
   486  		}
   487  
   488  	case *Var:
   489  		if obj.isField {
   490  			buf.WriteString("field")
   491  		} else {
   492  			buf.WriteString("var")
   493  		}
   494  
   495  	case *Func:
   496  		buf.WriteString("func ")
   497  		writeFuncName(buf, obj, qf)
   498  		if typ != nil {
   499  			WriteSignature(buf, typ.(*Signature), qf)
   500  		}
   501  		return
   502  
   503  	case *Label:
   504  		buf.WriteString("label")
   505  		typ = nil
   506  
   507  	case *Builtin:
   508  		buf.WriteString("builtin")
   509  		typ = nil
   510  
   511  	case *Nil:
   512  		buf.WriteString("nil")
   513  		return
   514  
   515  	default:
   516  		panic(fmt.Sprintf("writeObject(%T)", obj))
   517  	}
   518  
   519  	buf.WriteByte(' ')
   520  
   521  	// For package-level objects, qualify the name.
   522  	if obj.Pkg() != nil && obj.Pkg().scope.Lookup(obj.Name()) == obj {
   523  		buf.WriteString(packagePrefix(obj.Pkg(), qf))
   524  	}
   525  	buf.WriteString(obj.Name())
   526  
   527  	if typ == nil {
   528  		return
   529  	}
   530  
   531  	if tname != nil {
   532  		switch t := typ.(type) {
   533  		case *Basic:
   534  			// Don't print anything more for basic types since there's
   535  			// no more information.
   536  			return
   537  		case *Named:
   538  			if t.TypeParams().Len() > 0 {
   539  				newTypeWriter(buf, qf).tParamList(t.TypeParams().list())
   540  			}
   541  		}
   542  		if tname.IsAlias() {
   543  			buf.WriteString(" =")
   544  		} else if t, _ := typ.(*TypeParam); t != nil {
   545  			typ = t.bound
   546  		} else {
   547  			// TODO(gri) should this be fromRHS for *Named?
   548  			typ = under(typ)
   549  		}
   550  	}
   551  
   552  	// Special handling for any: because WriteType will format 'any' as 'any',
   553  	// resulting in the object string `type any = any` rather than `type any =
   554  	// interface{}`. To avoid this, swap in a different empty interface.
   555  	if obj == universeAny {
   556  		assert(Identical(typ, &emptyInterface))
   557  		typ = &emptyInterface
   558  	}
   559  
   560  	buf.WriteByte(' ')
   561  	WriteType(buf, typ, qf)
   562  }
   563  
   564  func packagePrefix(pkg *Package, qf Qualifier) string {
   565  	if pkg == nil {
   566  		return ""
   567  	}
   568  	var s string
   569  	if qf != nil {
   570  		s = qf(pkg)
   571  	} else {
   572  		s = pkg.Path()
   573  	}
   574  	if s != "" {
   575  		s += "."
   576  	}
   577  	return s
   578  }
   579  
   580  // ObjectString returns the string form of obj.
   581  // The Qualifier controls the printing of
   582  // package-level objects, and may be nil.
   583  func ObjectString(obj Object, qf Qualifier) string {
   584  	var buf bytes.Buffer
   585  	writeObject(&buf, obj, qf)
   586  	return buf.String()
   587  }
   588  
   589  func (obj *PkgName) String() string  { return ObjectString(obj, nil) }
   590  func (obj *Const) String() string    { return ObjectString(obj, nil) }
   591  func (obj *TypeName) String() string { return ObjectString(obj, nil) }
   592  func (obj *Var) String() string      { return ObjectString(obj, nil) }
   593  func (obj *Func) String() string     { return ObjectString(obj, nil) }
   594  func (obj *Label) String() string    { return ObjectString(obj, nil) }
   595  func (obj *Builtin) String() string  { return ObjectString(obj, nil) }
   596  func (obj *Nil) String() string      { return ObjectString(obj, nil) }
   597  
   598  func writeFuncName(buf *bytes.Buffer, f *Func, qf Qualifier) {
   599  	if f.typ != nil {
   600  		sig := f.typ.(*Signature)
   601  		if recv := sig.Recv(); recv != nil {
   602  			buf.WriteByte('(')
   603  			if _, ok := recv.Type().(*Interface); ok {
   604  				// gcimporter creates abstract methods of
   605  				// named interfaces using the interface type
   606  				// (not the named type) as the receiver.
   607  				// Don't print it in full.
   608  				buf.WriteString("interface")
   609  			} else {
   610  				WriteType(buf, recv.Type(), qf)
   611  			}
   612  			buf.WriteByte(')')
   613  			buf.WriteByte('.')
   614  		} else if f.pkg != nil {
   615  			buf.WriteString(packagePrefix(f.pkg, qf))
   616  		}
   617  	}
   618  	buf.WriteString(f.name)
   619  }
   620
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