writer.go

}

func (dict *writerDict) methodExprIdx(recvInfo typeInfo, methodInfo selectorInfo) int {
	assert(recvInfo.derived)
	newInfo := methodExprInfo{recvIdx: recvInfo.idx, methodInfo: methodInfo}

	for idx, oldInfo := range dict.methodExprs {
		if oldInfo == newInfo {
			return idx
		}
	}

	idx := len(dict.methodExprs)
	dict.methodExprs = append(dict.methodExprs, newInfo)
	return idx
}

// isInterface reports whether typ is known to be an interface type.
// If typ is a type parameter, then isInterface reports an internal
// compiler error instead.
func isInterface(typ types2.Type) bool {
	if _, ok := typ.(*types2.TypeParam); ok {
		// typ is a type parameter and may be instantiated as either a
		// concrete or interface type, so the writer can't depend on
		// knowing this.
		base.Fatalf("%v is a type parameter", typ)
	}

	_, ok := typ.Underlying().(*types2.Interface)
	return ok
}

// op writes an Op into the bitstream.
func (w *writer) op(op ir.Op) {
	// TODO(mdempsky): Remove in favor of explicit codes? Would make
	// export data more stable against internal refactorings, but low
	// priority at the moment.
	assert(op != 0)
	w.Sync(pkgbits.SyncOp)
	w.Len(int(op))
}

// @@@ Package initialization

// Caution: This code is still clumsy, because toolstash -cmp is
// particularly sensitive to it.

type typeDeclGen struct {
	*syntax.TypeDecl
	gen int

	// Implicit type parameters in scope at this type declaration.
	implicits []*types2.TypeName
}

type fileImports struct {
	importedEmbed, importedUnsafe bool
}

// declCollector is a visitor type that collects compiler-needed
// information about declarations that types2 doesn't track.
//
// Notably, it maps declared types and functions back to their
// declaration statement, keeps track of implicit type parameters, and
// assigns unique type "generation" numbers to local defined types.
type declCollector struct {
	pw         *pkgWriter
	typegen    *int
	file       *fileImports
	withinFunc bool
	implicits  []*types2.TypeName
}

func (c *declCollector) withTParams(obj types2.Object) *declCollector {
	tparams := objTypeParams(obj)
	n := tparams.Len()
	if n == 0 {
		return c
	}

	copy := *c
	copy.implicits = copy.implicits[:len(copy.implicits):len(copy.implicits)]
	for i := 0; i < n; i++ {
		copy.implicits = append(copy.implicits, tparams.At(i).Obj())
	}
	return &copy
}

func (c *declCollector) Visit(n syntax.Node) syntax.Visitor {
	pw := c.pw

	switch n := n.(type) {
	case *syntax.File:
		pw.checkPragmas(n.Pragma, ir.GoBuildPragma, false)

	case *syntax.ImportDecl:
		pw.checkPragmas(n.Pragma, 0, false)

		switch pkgNameOf(pw.info, n).Imported().Path() {
		case "embed":
			c.file.importedEmbed = true
		case "unsafe":
			c.file.importedUnsafe = true
		}

	case *syntax.ConstDecl:
		pw.checkPragmas(n.Pragma, 0, false)

	case *syntax.FuncDecl:
		pw.checkPragmas(n.Pragma, funcPragmas, false)

		obj := pw.info.Defs[n.Name].(*types2.Func)
		pw.funDecls[obj] = n

		return c.withTParams(obj)

	case *syntax.TypeDecl:
		obj := pw.info.Defs[n.Name].(*types2.TypeName)
		d := typeDeclGen{TypeDecl: n, implicits: c.implicits}

		if n.Alias {
			pw.checkPragmas(n.Pragma, 0, false)
		} else {
			pw.checkPragmas(n.Pragma, typePragmas, false)

			// Assign a unique ID to function-scoped defined types.
			if c.withinFunc {
				*c.typegen++
				d.gen = *c.typegen
			}
		}

		pw.typDecls[obj] = d

		// TODO(mdempsky): Omit? Not strictly necessary; only matters for
		// type declarations within function literals within parameterized
		// type declarations, but types2 the function literals will be
		// constant folded away.
		return c.withTParams(obj)

	case *syntax.VarDecl:
		pw.checkPragmas(n.Pragma, 0, true)

		if p, ok := n.Pragma.(*pragmas); ok && len(p.Embeds) > 0 {
			if err := checkEmbed(n, c.file.importedEmbed, c.withinFunc); err != nil {
				pw.errorf(p.Embeds[0].Pos, "%s", err)
			}
		}

	case *syntax.BlockStmt:
		if !c.withinFunc {
			copy := *c
			copy.withinFunc = true
			return &copy
		}
	}

	return c
}

func (pw *pkgWriter) collectDecls(noders []*noder) {
	var typegen int
	for _, p := range noders {
		var file fileImports

		syntax.Walk(p.file, &declCollector{
			pw:      pw,
			typegen: &typegen,
			file:    &file,
		})

		pw.cgoPragmas = append(pw.cgoPragmas, p.pragcgobuf...)

		for _, l := range p.linknames {
			if !file.importedUnsafe {
				pw.errorf(l.pos, "//go:linkname only allowed in Go files that import \"unsafe\"")
				continue
			}

			switch obj := pw.curpkg.Scope().Lookup(l.local).(type) {
			case *types2.Func, *types2.Var:
				if _, ok := pw.linknames[obj]; !ok {
					pw.linknames[obj] = l.remote
				} else {
					pw.errorf(l.pos, "duplicate //go:linkname for %s", l.local)
				}

			default:
				pw.errorf(l.pos, "//go:linkname must refer to declared function or variable")
			}
		}
	}
}

func (pw *pkgWriter) checkPragmas(p syntax.Pragma, allowed ir.PragmaFlag, embedOK bool) {
	if p == nil {
		return
	}
	pragma := p.(*pragmas)

	for _, pos := range pragma.Pos {
		if pos.Flag&^allowed != 0 {
			pw.errorf(pos.Pos, "misplaced compiler directive")
		}
	}

	if !embedOK {
		for _, e := range pragma.Embeds {
			pw.errorf(e.Pos, "misplaced go:embed directive")
		}
	}
}

func (w *writer) pkgInit(noders []*noder) {
	w.Len(len(w.p.cgoPragmas))
	for _, cgoPragma := range w.p.cgoPragmas {
		w.Strings(cgoPragma)
	}

	w.Sync(pkgbits.SyncDecls)
	for _, p := range noders {
		for _, decl := range p.file.DeclList {
			w.pkgDecl(decl)
		}
	}
	w.Code(declEnd)

	w.Sync(pkgbits.SyncEOF)
}

func (w *writer) pkgDecl(decl syntax.Decl) {
	switch decl := decl.(type) {
	default:
		w.p.unexpected("declaration", decl)

	case *syntax.ImportDecl:

	case *syntax.ConstDecl:
		w.Code(declOther)
		w.pkgObjs(decl.NameList...)

	case *syntax.FuncDecl:
		if decl.Name.Value == "_" {
			break // skip blank functions
		}

		obj := w.p.info.Defs[decl.Name].(*types2.Func)
		sig := obj.Type().(*types2.Signature)

		if sig.RecvTypeParams() != nil || sig.TypeParams() != nil {
			break // skip generic functions
		}

		if recv := sig.Recv(); recv != nil {
			w.Code(declMethod)
			w.typ(recvBase(recv))
			w.selector(obj)
			break
		}

		w.Code(declFunc)
		w.pkgObjs(decl.Name)

	case *syntax.TypeDecl:
		if len(decl.TParamList) != 0 {
			break // skip generic type decls
		}

		if decl.Name.Value == "_" {
			break // skip blank type decls
		}

		name := w.p.info.Defs[decl.Name].(*types2.TypeName)
		// Skip type declarations for interfaces that are only usable as
		// type parameter bounds.
		if iface, ok := name.Type().Underlying().(*types2.Interface); ok && !iface.IsMethodSet() {
			break
		}

		w.Code(declOther)
		w.pkgObjs(decl.Name)

	case *syntax.VarDecl:
		w.Code(declVar)
		w.pos(decl)
		w.pkgObjs(decl.NameList...)

		// TODO(mdempsky): It would make sense to use multiExpr here, but
		// that results in IR that confuses pkginit/initorder.go. So we
		// continue using exprList, and let typecheck handle inserting any
		// implicit conversions. That's okay though, because package-scope
		// assignments never require dictionaries.
		w.exprList(decl.Values)

		var embeds []pragmaEmbed
		if p, ok := decl.Pragma.(*pragmas); ok {
			embeds = p.Embeds
		}
		w.Len(len(embeds))
		for _, embed := range embeds {
			w.pos(embed.Pos)
			w.Strings(embed.Patterns)
		}
	}
}

func (w *writer) pkgObjs(names ...*syntax.Name) {
	w.Sync(pkgbits.SyncDeclNames)
	w.Len(len(names))

	for _, name := range names {
		obj, ok := w.p.info.Defs[name]
		assert(ok)

		w.Sync(pkgbits.SyncDeclName)
		w.obj(obj, nil)
	}
}

// @@@ Helpers

// hasImplicitTypeParams reports whether obj is a defined type with
// implicit type parameters (e.g., declared within a generic function
// or method).
func (p *pkgWriter) hasImplicitTypeParams(obj *types2.TypeName) bool {
	if obj.Pkg() == p.curpkg {
		decl, ok := p.typDecls[obj]
		assert(ok)
		if len(decl.implicits) != 0 {
			return true
		}
	}
	return false
}

// isDefinedType reports whether obj is a defined type.
func isDefinedType(obj types2.Object) bool {
	if obj, ok := obj.(*types2.TypeName); ok {
		return !obj.IsAlias()
	}
	return false
}

// isGlobal reports whether obj was declared at package scope.
//
// Caveat: blank objects are not declared.
func isGlobal(obj types2.Object) bool {
	return obj.Parent() == obj.Pkg().Scope()
}

// lookupObj returns the object that expr refers to, if any. If expr
// is an explicit instantiation of a generic object, then the instance
// object is returned as well.
func lookupObj(info *types2.Info, expr syntax.Expr) (obj types2.Object, inst types2.Instance) {
	if index, ok := expr.(*syntax.IndexExpr); ok {
		args := unpackListExpr(index.Index)
		if len(args) == 1 {
			tv, ok := info.Types[args[0]]
			assert(ok)
			if tv.IsValue() {
				return // normal index expression
			}
		}

		expr = index.X
	}

	// Strip package qualifier, if present.
	if sel, ok := expr.(*syntax.SelectorExpr); ok {
		if !isPkgQual(info, sel) {
			return // normal selector expression
		}
		expr = sel.Sel
	}

	if name, ok := expr.(*syntax.Name); ok {
		obj = info.Uses[name]
		inst = info.Instances[name]
	}
	return
}

// isPkgQual reports whether the given selector expression is a
// package-qualified identifier.
func isPkgQual(info *types2.Info, sel *syntax.SelectorExpr) bool {
	if name, ok := sel.X.(*syntax.Name); ok {
		_, isPkgName := info.Uses[name].(*types2.PkgName)
		return isPkgName
	}
	return false
}

// isMultiValueExpr reports whether expr is a function call expression
// that yields multiple values.
func isMultiValueExpr(info *types2.Info, expr syntax.Expr) bool {
	tv, ok := info.Types[expr]
	assert(ok)
	assert(tv.IsValue())
	if tuple, ok := tv.Type.(*types2.Tuple); ok {
		assert(tuple.Len() > 1)
		return true
	}
	return false
}

// isNil reports whether expr is a (possibly parenthesized) reference
// to the predeclared nil value.
func isNil(info *types2.Info, expr syntax.Expr) bool {
	tv, ok := info.Types[expr]
	assert(ok)
	return tv.IsNil()
}

// recvBase returns the base type for the given receiver parameter.
func recvBase(recv *types2.Var) *types2.Named {
	typ := recv.Type()
	if ptr, ok := typ.(*types2.Pointer); ok {
		typ = ptr.Elem()
	}
	return typ.(*types2.Named)
}

// namesAsExpr returns a list of names as a syntax.Expr.
func namesAsExpr(names []*syntax.Name) syntax.Expr {
	if len(names) == 1 {
		return names[0]
	}

	exprs := make([]syntax.Expr, len(names))
	for i, name := range names {
		exprs[i] = name
	}
	return &syntax.ListExpr{ElemList: exprs}
}

// fieldIndex returns the index of the struct field named by key.
func fieldIndex(info *types2.Info, str *types2.Struct, key *syntax.Name) int {
	field := info.Uses[key].(*types2.Var)

	for i := 0; i < str.NumFields(); i++ {
		if str.Field(i) == field {
			return i
		}
	}

	panic(fmt.Sprintf("%s: %v is not a field of %v", key.Pos(), field, str))
}

// objTypeParams returns the type parameters on the given object.
func objTypeParams(obj types2.Object) *types2.TypeParamList {
	switch obj := obj.(type) {
	case *types2.Func:
		sig := obj.Type().(*types2.Signature)
		if sig.Recv() != nil {
			return sig.RecvTypeParams()
		}
		return sig.TypeParams()
	case *types2.TypeName:
		if !obj.IsAlias() {
			return obj.Type().(*types2.Named).TypeParams()
		}
	}
	return nil
}

// splitNamed decomposes a use of a defined type into its original
// type definition and the type arguments used to instantiate it.
func splitNamed(typ *types2.Named) (*types2.TypeName, *types2.TypeList) {
	base.Assertf(typ.TypeParams().Len() == typ.TypeArgs().Len(), "use of uninstantiated type: %v", typ)

	orig := typ.Origin()
	base.Assertf(orig.TypeArgs() == nil, "origin %v of %v has type arguments", orig, typ)
	base.Assertf(typ.Obj() == orig.Obj(), "%v has object %v, but %v has object %v", typ, typ.Obj(), orig, orig.Obj())

	return typ.Obj(), typ.TypeArgs()
}

func asPragmaFlag(p syntax.Pragma) ir.PragmaFlag {
	if p == nil {
		return 0
	}
	return p.(*pragmas).Flag
}