cmd/compile/internal/types2: clearer object string for type parameters

[gostls13.git] / src / cmd / compile / internal / types2 / object.go

// 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 types2

import (
        "bytes"
        "cmd/compile/internal/syntax"
        "fmt"
        "go/constant"
        "unicode"
        "unicode/utf8"
)

// An Object describes a named language entity such as a package,
// constant, type, variable, function (incl. methods), or label.
// All objects implement the Object interface.
//
type Object interface {
        Parent() *Scope  // scope in which this object is declared; nil for methods and struct fields
        Pos() syntax.Pos // position of object identifier in declaration
        Pkg() *Package   // package to which this object belongs; nil for labels and objects in the Universe scope
        Name() string    // package local object name
        Type() Type      // object type
        Exported() bool  // reports whether the name starts with a capital letter
        Id() string      // object name if exported, qualified name if not exported (see func Id)

        // String returns a human-readable string of the object.
        String() string

        // order reflects a package-level object's source order: if object
        // a is before object b in the source, then a.order() < b.order().
        // order returns a value > 0 for package-level objects; it returns
        // 0 for all other objects (including objects in file scopes).
        order() uint32

        // color returns the object's color.
        color() color

        // setType sets the type of the object.
        setType(Type)

        // setOrder sets the order number of the object. It must be > 0.
        setOrder(uint32)

        // setColor sets the object's color. It must not be white.
        setColor(color color)

        // setParent sets the parent scope of the object.
        setParent(*Scope)

        // sameId reports whether obj.Id() and Id(pkg, name) are the same.
        sameId(pkg *Package, name string) bool

        // scopePos returns the start position of the scope of this Object
        scopePos() syntax.Pos

        // setScopePos sets the start position of the scope for this Object.
        setScopePos(pos syntax.Pos)
}

func isExported(name string) bool {
        ch, _ := utf8.DecodeRuneInString(name)
        return unicode.IsUpper(ch)
}

// Id returns name if it is exported, otherwise it
// returns the name qualified with the package path.
func Id(pkg *Package, name string) string {
        if isExported(name) {
                return name
        }
        // unexported names need the package path for differentiation
        // (if there's no package, make sure we don't start with '.'
        // as that may change the order of methods between a setup
        // inside a package and outside a package - which breaks some
        // tests)
        path := "_"
        // pkg is nil for objects in Universe scope and possibly types
        // introduced via Eval (see also comment in object.sameId)
        if pkg != nil && pkg.path != "" {
                path = pkg.path
        }
        return path + "." + name
}

// An object implements the common parts of an Object.
type object struct {
        parent    *Scope
        pos       syntax.Pos
        pkg       *Package
        name      string
        typ       Type
        order_    uint32
        color_    color
        scopePos_ syntax.Pos
}

// color encodes the color of an object (see Checker.objDecl for details).
type color uint32

// An object may be painted in one of three colors.
// Color values other than white or black are considered grey.
const (
        white color = iota
        black
        grey // must be > white and black
)

func (c color) String() string {
        switch c {
        case white:
                return "white"
        case black:
                return "black"
        default:
                return "grey"
        }
}

// colorFor returns the (initial) color for an object depending on
// whether its type t is known or not.
func colorFor(t Type) color {
        if t != nil {
                return black
        }
        return white
}

// Parent returns the scope in which the object is declared.
// The result is nil for methods and struct fields.
func (obj *object) Parent() *Scope { return obj.parent }

// Pos returns the declaration position of the object's identifier.
func (obj *object) Pos() syntax.Pos { return obj.pos }

// Pkg returns the package to which the object belongs.
// The result is nil for labels and objects in the Universe scope.
func (obj *object) Pkg() *Package { return obj.pkg }

// Name returns the object's (package-local, unqualified) name.
func (obj *object) Name() string { return obj.name }

// Type returns the object's type.
func (obj *object) Type() Type { return obj.typ }

// Exported reports whether the object is exported (starts with a capital letter).
// It doesn't take into account whether the object is in a local (function) scope
// or not.
func (obj *object) Exported() bool { return isExported(obj.name) }

// Id is a wrapper for Id(obj.Pkg(), obj.Name()).
func (obj *object) Id() string { return Id(obj.pkg, obj.name) }

func (obj *object) String() string       { panic("abstract") }
func (obj *object) order() uint32        { return obj.order_ }
func (obj *object) color() color         { return obj.color_ }
func (obj *object) scopePos() syntax.Pos { return obj.scopePos_ }

func (obj *object) setParent(parent *Scope)    { obj.parent = parent }
func (obj *object) setType(typ Type)           { obj.typ = typ }
func (obj *object) setOrder(order uint32)      { assert(order > 0); obj.order_ = order }
func (obj *object) setColor(color color)       { assert(color != white); obj.color_ = color }
func (obj *object) setScopePos(pos syntax.Pos) { obj.scopePos_ = pos }

func (obj *object) sameId(pkg *Package, name string) bool {
        // spec:
        // "Two identifiers are different if they are spelled differently,
        // or if they appear in different packages and are not exported.
        // Otherwise, they are the same."
        if name != obj.name {
                return false
        }
        // obj.Name == name
        if obj.Exported() {
                return true
        }
        // not exported, so packages must be the same (pkg == nil for
        // fields in Universe scope; this can only happen for types
        // introduced via Eval)
        if pkg == nil || obj.pkg == nil {
                return pkg == obj.pkg
        }
        // pkg != nil && obj.pkg != nil
        return pkg.path == obj.pkg.path
}

// less reports whether object a is ordered before object b.
//
// Objects are ordered nil before non-nil, exported before
// non-exported, then by name, and finally (for non-exported
// functions) by package height and path.
func (a *object) less(b *object) bool {
        if a == b {
                return false
        }

        // Nil before non-nil.
        if a == nil {
                return true
        }
        if b == nil {
                return false
        }

        // Exported functions before non-exported.
        ea := isExported(a.name)
        eb := isExported(b.name)
        if ea != eb {
                return ea
        }

        // Order by name and then (for non-exported names) by package.
        if a.name != b.name {
                return a.name < b.name
        }
        if !ea {
                if a.pkg.height != b.pkg.height {
                        return a.pkg.height < b.pkg.height
                }
                return a.pkg.path < b.pkg.path
        }

        return false
}

// A PkgName represents an imported Go package.
// PkgNames don't have a type.
type PkgName struct {
        object
        imported *Package
        used     bool // set if the package was used
}

// NewPkgName returns a new PkgName object representing an imported package.
// The remaining arguments set the attributes found with all Objects.
func NewPkgName(pos syntax.Pos, pkg *Package, name string, imported *Package) *PkgName {
        return &PkgName{object{nil, pos, pkg, name, Typ[Invalid], 0, black, nopos}, imported, false}
}

// Imported returns the package that was imported.
// It is distinct from Pkg(), which is the package containing the import statement.
func (obj *PkgName) Imported() *Package { return obj.imported }

// A Const represents a declared constant.
type Const struct {
        object
        val constant.Value
}

// NewConst returns a new constant with value val.
// The remaining arguments set the attributes found with all Objects.
func NewConst(pos syntax.Pos, pkg *Package, name string, typ Type, val constant.Value) *Const {
        return &Const{object{nil, pos, pkg, name, typ, 0, colorFor(typ), nopos}, val}
}

// Val returns the constant's value.
func (obj *Const) Val() constant.Value { return obj.val }

func (*Const) isDependency() {} // a constant may be a dependency of an initialization expression

// A TypeName represents a name for a (defined or alias) type.
type TypeName struct {
        object
}

// NewTypeName returns a new type name denoting the given typ.
// The remaining arguments set the attributes found with all Objects.
//
// The typ argument may be a defined (Named) type or an alias type.
// It may also be nil such that the returned TypeName can be used as
// argument for NewNamed, which will set the TypeName's type as a side-
// effect.
func NewTypeName(pos syntax.Pos, pkg *Package, name string, typ Type) *TypeName {
        return &TypeName{object{nil, pos, pkg, name, typ, 0, colorFor(typ), nopos}}
}

// NewTypeNameLazy returns a new defined type like NewTypeName, but it
// lazily calls resolve to finish constructing the Named object.
func NewTypeNameLazy(pos syntax.Pos, pkg *Package, name string, load func(named *Named) (tparams []*TypeParam, underlying Type, methods []*Func)) *TypeName {
        obj := NewTypeName(pos, pkg, name, nil)

        resolve := func(_ *Context, t *Named) (*TypeParamList, Type, []*Func) {
                tparams, underlying, methods := load(t)

                switch underlying.(type) {
                case nil, *Named:
                        panic(fmt.Sprintf("invalid underlying type %T", t.underlying))
                }

                return bindTParams(tparams), underlying, methods
        }

        NewNamed(obj, nil, nil).resolver = resolve
        return obj
}

// IsAlias reports whether obj is an alias name for a type.
func (obj *TypeName) IsAlias() bool {
        switch t := obj.typ.(type) {
        case nil:
                return false
        case *Basic:
                // unsafe.Pointer is not an alias.
                if obj.pkg == Unsafe {
                        return false
                }
                // Any user-defined type name for a basic type is an alias for a
                // basic type (because basic types are pre-declared in the Universe
                // scope, outside any package scope), and so is any type name with
                // a different name than the name of the basic type it refers to.
                // Additionally, we need to look for "byte" and "rune" because they
                // are aliases but have the same names (for better error messages).
                return obj.pkg != nil || t.name != obj.name || t == universeByte || t == universeRune
        case *Named:
                return obj != t.obj
        case *TypeParam:
                return obj != t.obj
        default:
                return true
        }
}

// A Variable represents a declared variable (including function parameters and results, and struct fields).
type Var struct {
        object
        embedded bool // if set, the variable is an embedded struct field, and name is the type name
        isField  bool // var is struct field
        used     bool // set if the variable was used
}

// NewVar returns a new variable.
// The arguments set the attributes found with all Objects.
func NewVar(pos syntax.Pos, pkg *Package, name string, typ Type) *Var {
        return &Var{object: object{nil, pos, pkg, name, typ, 0, colorFor(typ), nopos}}
}

// NewParam returns a new variable representing a function parameter.
func NewParam(pos syntax.Pos, pkg *Package, name string, typ Type) *Var {
        return &Var{object: object{nil, pos, pkg, name, typ, 0, colorFor(typ), nopos}, used: true} // parameters are always 'used'
}

// NewField returns a new variable representing a struct field.
// For embedded fields, the name is the unqualified type name
/// under which the field is accessible.
func NewField(pos syntax.Pos, pkg *Package, name string, typ Type, embedded bool) *Var {
        return &Var{object: object{nil, pos, pkg, name, typ, 0, colorFor(typ), nopos}, embedded: embedded, isField: true}
}

// Anonymous reports whether the variable is an embedded field.
// Same as Embedded; only present for backward-compatibility.
func (obj *Var) Anonymous() bool { return obj.embedded }

// Embedded reports whether the variable is an embedded field.
func (obj *Var) Embedded() bool { return obj.embedded }

// IsField reports whether the variable is a struct field.
func (obj *Var) IsField() bool { return obj.isField }

func (*Var) isDependency() {} // a variable may be a dependency of an initialization expression

// A Func represents a declared function, concrete method, or abstract
// (interface) method. Its Type() is always a *Signature.
// An abstract method may belong to many interfaces due to embedding.
type Func struct {
        object
        instRecv    *Named // if non-nil, the receiver type for an incomplete instance method
        hasPtrRecv_ bool   // only valid for methods that don't have a type yet; use hasPtrRecv() to read
}

// NewFunc returns a new function with the given signature, representing
// the function's type.
func NewFunc(pos syntax.Pos, pkg *Package, name string, sig *Signature) *Func {
        // don't store a (typed) nil signature
        var typ Type
        if sig != nil {
                typ = sig
        }
        return &Func{object{nil, pos, pkg, name, typ, 0, colorFor(typ), nopos}, nil, false}
}

// FullName returns the package- or receiver-type-qualified name of
// function or method obj.
func (obj *Func) FullName() string {
        var buf bytes.Buffer
        writeFuncName(&buf, obj, nil)
        return buf.String()
}

// Scope returns the scope of the function's body block.
func (obj *Func) Scope() *Scope { return obj.typ.(*Signature).scope }

// hasPtrRecv reports whether the receiver is of the form *T for the given method obj.
func (obj *Func) hasPtrRecv() bool {
        // If a method's receiver type is set, use that as the source of truth for the receiver.
        // Caution: Checker.funcDecl (decl.go) marks a function by setting its type to an empty
        // signature. We may reach here before the signature is fully set up: we must explicitly
        // check if the receiver is set (we cannot just look for non-nil obj.typ).
        if sig, _ := obj.typ.(*Signature); sig != nil && sig.recv != nil {
                _, isPtr := deref(sig.recv.typ)
                return isPtr
        }

        // If a method's type is not set it may be a method/function that is:
        // 1) client-supplied (via NewFunc with no signature), or
        // 2) internally created but not yet type-checked.
        // For case 1) we can't do anything; the client must know what they are doing.
        // For case 2) we can use the information gathered by the resolver.
        return obj.hasPtrRecv_
}

func (*Func) isDependency() {} // a function may be a dependency of an initialization expression

// A Label represents a declared label.
// Labels don't have a type.
type Label struct {
        object
        used bool // set if the label was used
}

// NewLabel returns a new label.
func NewLabel(pos syntax.Pos, pkg *Package, name string) *Label {
        return &Label{object{pos: pos, pkg: pkg, name: name, typ: Typ[Invalid], color_: black}, false}
}

// A Builtin represents a built-in function.
// Builtins don't have a valid type.
type Builtin struct {
        object
        id builtinId
}

func newBuiltin(id builtinId) *Builtin {
        return &Builtin{object{name: predeclaredFuncs[id].name, typ: Typ[Invalid], color_: black}, id}
}

// Nil represents the predeclared value nil.
type Nil struct {
        object
}

func writeObject(buf *bytes.Buffer, obj Object, qf Qualifier) {
        var tname *TypeName
        typ := obj.Type()

        switch obj := obj.(type) {
        case *PkgName:
                fmt.Fprintf(buf, "package %s", obj.Name())
                if path := obj.imported.path; path != "" && path != obj.name {
                        fmt.Fprintf(buf, " (%q)", path)
                }
                return

        case *Const:
                buf.WriteString("const")

        case *TypeName:
                tname = obj
                buf.WriteString("type")
                if isTypeParam(typ) {
                        buf.WriteString(" parameter")
                }

        case *Var:
                if obj.isField {
                        buf.WriteString("field")
                } else {
                        buf.WriteString("var")
                }

        case *Func:
                buf.WriteString("func ")
                writeFuncName(buf, obj, qf)
                if typ != nil {
                        WriteSignature(buf, typ.(*Signature), qf)
                }
                return

        case *Label:
                buf.WriteString("label")
                typ = nil

        case *Builtin:
                buf.WriteString("builtin")
                typ = nil

        case *Nil:
                buf.WriteString("nil")
                return

        default:
                panic(fmt.Sprintf("writeObject(%T)", obj))
        }

        buf.WriteByte(' ')

        // For package-level objects, qualify the name.
        if obj.Pkg() != nil && obj.Pkg().scope.Lookup(obj.Name()) == obj {
                writePackage(buf, obj.Pkg(), qf)
        }
        buf.WriteString(obj.Name())

        if typ == nil {
                return
        }

        if tname != nil {
                switch t := typ.(type) {
                case *Basic:
                        // Don't print anything more for basic types since there's
                        // no more information.
                        return
                case *Named:
                        if t.TypeParams().Len() > 0 {
                                newTypeWriter(buf, qf).tParamList(t.TypeParams().list())
                        }
                }
                if tname.IsAlias() {
                        buf.WriteString(" =")
                } else if t, _ := typ.(*TypeParam); t != nil {
                        typ = t.bound
                } else {
                        // TODO(gri) should this be fromRHS for *Named?
                        typ = under(typ)
                }
        }

        buf.WriteByte(' ')
        WriteType(buf, typ, qf)
}

func writePackage(buf *bytes.Buffer, pkg *Package, qf Qualifier) {
        if pkg == nil {
                return
        }
        var s string
        if qf != nil {
                s = qf(pkg)
        } else {
                s = pkg.Path()
        }
        if s != "" {
                buf.WriteString(s)
                buf.WriteByte('.')
        }
}

// ObjectString returns the string form of obj.
// The Qualifier controls the printing of
// package-level objects, and may be nil.
func ObjectString(obj Object, qf Qualifier) string {
        var buf bytes.Buffer
        writeObject(&buf, obj, qf)
        return buf.String()
}

func (obj *PkgName) String() string  { return ObjectString(obj, nil) }
func (obj *Const) String() string    { return ObjectString(obj, nil) }
func (obj *TypeName) String() string { return ObjectString(obj, nil) }
func (obj *Var) String() string      { return ObjectString(obj, nil) }
func (obj *Func) String() string     { return ObjectString(obj, nil) }
func (obj *Label) String() string    { return ObjectString(obj, nil) }
func (obj *Builtin) String() string  { return ObjectString(obj, nil) }
func (obj *Nil) String() string      { return ObjectString(obj, nil) }

func writeFuncName(buf *bytes.Buffer, f *Func, qf Qualifier) {
        if f.typ != nil {
                sig := f.typ.(*Signature)
                if recv := sig.Recv(); recv != nil {
                        buf.WriteByte('(')
                        if _, ok := recv.Type().(*Interface); ok {
                                // gcimporter creates abstract methods of
                                // named interfaces using the interface type
                                // (not the named type) as the receiver.
                                // Don't print it in full.
                                buf.WriteString("interface")
                        } else {
                                WriteType(buf, recv.Type(), qf)
                        }
                        buf.WriteByte(')')
                        buf.WriteByte('.')
                } else if f.pkg != nil {
                        writePackage(buf, f.pkg, qf)
                }
        }
        buf.WriteString(f.name)
}