gopls/internal/lsp/source/completion/util.go - tools - Git at Google

 // Copyright 2020 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 completion

 import (
 	"go/ast"
 	"go/token"
 	"go/types"

 	"golang.org/x/tools/go/types/typeutil"
 	"golang.org/x/tools/gopls/internal/lsp/protocol"
 	"golang.org/x/tools/gopls/internal/lsp/safetoken"
 	"golang.org/x/tools/gopls/internal/lsp/source"
 	"golang.org/x/tools/internal/diff"
 	"golang.org/x/tools/internal/typeparams"
 )

 // exprAtPos returns the index of the expression containing pos.
 func exprAtPos(pos token.Pos, args []ast.Expr) int {
 	for i, expr := range args {
 		if expr.Pos() <= pos && pos <= expr.End() {
 			return i
 		}
 	}
 	return len(args)
 }

 // eachField invokes fn for each field that can be selected from a
 // value of type T.
 func eachField(T types.Type, fn func(*types.Var)) {
 	// TODO(adonovan): this algorithm doesn't exclude ambiguous
 	// selections that match more than one field/method.
 	// types.NewSelectionSet should do that for us.

 	// for termination on recursive types
 	var seen typeutil.Map

 	var visit func(T types.Type)
 	visit = func(T types.Type) {
 		if T, ok := source.Deref(T).Underlying().(*types.Struct); ok {
 			if seen.At(T) != nil {
 				return
 			}

 			for i := 0; i < T.NumFields(); i++ {
 				f := T.Field(i)
 				fn(f)
 				if f.Anonymous() {
 					seen.Set(T, true)
 					visit(f.Type())
 				}
 			}
 		}
 	}
 	visit(T)
 }

 // typeIsValid reports whether typ doesn't contain any Invalid types.
 func typeIsValid(typ types.Type) bool {
 	// Check named types separately, because we don't want
 	// to call Underlying() on them to avoid problems with recursive types.
 	if _, ok := typ.(*types.Named); ok {
 		return true
 	}

 	switch typ := typ.Underlying().(type) {
 	case *types.Basic:
 		return typ.Kind() != types.Invalid
 	case *types.Array:
 		return typeIsValid(typ.Elem())
 	case *types.Slice:
 		return typeIsValid(typ.Elem())
 	case *types.Pointer:
 		return typeIsValid(typ.Elem())
 	case *types.Map:
 		return typeIsValid(typ.Key()) && typeIsValid(typ.Elem())
 	case *types.Chan:
 		return typeIsValid(typ.Elem())
 	case *types.Signature:
 		return typeIsValid(typ.Params()) && typeIsValid(typ.Results())
 	case *types.Tuple:
 		for i := 0; i < typ.Len(); i++ {
 			if !typeIsValid(typ.At(i).Type()) {
 				return false
 			}
 		}
 		return true
 	case *types.Struct, *types.Interface:
 		// Don't bother checking structs, interfaces for validity.
 		return true
 	default:
 		return false
 	}
 }

 // resolveInvalid traverses the node of the AST that defines the scope
 // containing the declaration of obj, and attempts to find a user-friendly
 // name for its invalid type. The resulting Object and its Type are fake.
 func resolveInvalid(fset *token.FileSet, obj types.Object, node ast.Node, info *types.Info) types.Object {
 	var resultExpr ast.Expr
 	ast.Inspect(node, func(node ast.Node) bool {
 		switch n := node.(type) {
 		case *ast.ValueSpec:
 			for _, name := range n.Names {
 				if info.Defs[name] == obj {
 					resultExpr = n.Type
 				}
 			}
 			return false
 		case *ast.Field: // This case handles parameters and results of a FuncDecl or FuncLit.
 			for _, name := range n.Names {
 				if info.Defs[name] == obj {
 					resultExpr = n.Type
 				}
 			}
 			return false
 		default:
 			return true
 		}
 	})
 	// Construct a fake type for the object and return a fake object with this type.
 	typename := source.FormatNode(fset, resultExpr)
 	typ := types.NewNamed(types.NewTypeName(token.NoPos, obj.Pkg(), typename, nil), types.Typ[types.Invalid], nil)
 	return types.NewVar(obj.Pos(), obj.Pkg(), obj.Name(), typ)
 }

 func isPointer(T types.Type) bool {
 	_, ok := T.(*types.Pointer)
 	return ok
 }

 func isVar(obj types.Object) bool {
 	_, ok := obj.(*types.Var)
 	return ok
 }

 func isTypeName(obj types.Object) bool {
 	_, ok := obj.(*types.TypeName)
 	return ok
 }

 func isFunc(obj types.Object) bool {
 	_, ok := obj.(*types.Func)
 	return ok
 }

 func isEmptyInterface(T types.Type) bool {
 	intf, _ := T.(*types.Interface)
 	return intf != nil && intf.NumMethods() == 0 && typeparams.IsMethodSet(intf)
 }

 func isUntyped(T types.Type) bool {
 	if basic, ok := T.(*types.Basic); ok {
 		return basic.Info()&types.IsUntyped > 0
 	}
 	return false
 }

 func isPkgName(obj types.Object) bool {
 	_, ok := obj.(*types.PkgName)
 	return ok
 }

 func isASTFile(n ast.Node) bool {
 	_, ok := n.(*ast.File)
 	return ok
 }

 func deslice(T types.Type) types.Type {
 	if slice, ok := T.Underlying().(*types.Slice); ok {
 		return slice.Elem()
 	}
 	return nil
 }

 // isSelector returns the enclosing *ast.SelectorExpr when pos is in the
 // selector.
 func enclosingSelector(path []ast.Node, pos token.Pos) *ast.SelectorExpr {
 	if len(path) == 0 {
 		return nil
 	}

 	if sel, ok := path[0].(*ast.SelectorExpr); ok {
 		return sel
 	}

 	if _, ok := path[0].(*ast.Ident); ok && len(path) > 1 {
 		if sel, ok := path[1].(*ast.SelectorExpr); ok && pos >= sel.Sel.Pos() {
 			return sel
 		}
 	}

 	return nil
 }

 // enclosingDeclLHS returns LHS idents from containing value spec or
 // assign statement.
 func enclosingDeclLHS(path []ast.Node) []*ast.Ident {
 	for _, n := range path {
 		switch n := n.(type) {
 		case *ast.ValueSpec:
 			return n.Names
 		case *ast.AssignStmt:
 			ids := make([]*ast.Ident, 0, len(n.Lhs))
 			for _, e := range n.Lhs {
 				if id, ok := e.(*ast.Ident); ok {
 					ids = append(ids, id)
 				}
 			}
 			return ids
 		}
 	}

 	return nil
 }

 // exprObj returns the types.Object associated with the *ast.Ident or
 // *ast.SelectorExpr e.
 func exprObj(info *types.Info, e ast.Expr) types.Object {
 	var ident *ast.Ident
 	switch expr := e.(type) {
 	case *ast.Ident:
 		ident = expr
 	case *ast.SelectorExpr:
 		ident = expr.Sel
 	default:
 		return nil
 	}

 	return info.ObjectOf(ident)
 }

 // typeConversion returns the type being converted to if call is a type
 // conversion expression.
 func typeConversion(call *ast.CallExpr, info *types.Info) types.Type {
 	// Type conversion (e.g. "float64(foo)").
 	if fun, _ := exprObj(info, call.Fun).(*types.TypeName); fun != nil {
 		return fun.Type()
 	}

 	return nil
 }

 // fieldsAccessible returns whether s has at least one field accessible by p.
 func fieldsAccessible(s *types.Struct, p *types.Package) bool {
 	for i := 0; i < s.NumFields(); i++ {
 		f := s.Field(i)
 		if f.Exported() || f.Pkg() == p {
 			return true
 		}
 	}
 	return false
 }

 // prevStmt returns the statement that precedes the statement containing pos.
 // For example:
 //
 //	foo := 1
 //	bar(1 + 2<>)
 //
 // If "<>" is pos, prevStmt returns "foo := 1"
 func prevStmt(pos token.Pos, path []ast.Node) ast.Stmt {
 	var blockLines []ast.Stmt
 	for i := 0; i < len(path) && blockLines == nil; i++ {
 		switch n := path[i].(type) {
 		case *ast.BlockStmt:
 			blockLines = n.List
 		case *ast.CommClause:
 			blockLines = n.Body
 		case *ast.CaseClause:
 			blockLines = n.Body
 		}
 	}

 	for i := len(blockLines) - 1; i >= 0; i-- {
 		if blockLines[i].End() < pos {
 			return blockLines[i]
 		}
 	}

 	return nil
 }

 // formatZeroValue produces Go code representing the zero value of T. It
 // returns the empty string if T is invalid.
 func formatZeroValue(T types.Type, qf types.Qualifier) string {
 	switch u := T.Underlying().(type) {
 	case *types.Basic:
 		switch {
 		case u.Info()&types.IsNumeric > 0:
 			return "0"
 		case u.Info()&types.IsString > 0:
 			return `""`
 		case u.Info()&types.IsBoolean > 0:
 			return "false"
 		default:
 			return ""
 		}
 	case *types.Pointer, *types.Interface, *types.Chan, *types.Map, *types.Slice, *types.Signature:
 		return "nil"
 	default:
 		return types.TypeString(T, qf) + "{}"
 	}
 }

 // isBasicKind returns whether t is a basic type of kind k.
 func isBasicKind(t types.Type, k types.BasicInfo) bool {
 	b, _ := t.Underlying().(*types.Basic)
 	return b != nil && b.Info()&k > 0
 }

 func (c *completer) editText(from, to token.Pos, newText string) ([]protocol.TextEdit, error) {
 	start, end, err := safetoken.Offsets(c.tokFile, from, to)
 	if err != nil {
 		return nil, err // can't happen: from/to came from c
 	}
 	return source.ToProtocolEdits(c.mapper, []diff.Edit{{
 		Start: start,
 		End:   end,
 		New:   newText,
 	}})
 }

 // assignableTo is like types.AssignableTo, but returns false if
 // either type is invalid.
 func assignableTo(x, to types.Type) bool {
 	if x == types.Typ[types.Invalid] || to == types.Typ[types.Invalid] {
 		return false
 	}

 	return types.AssignableTo(x, to)
 }

 // convertibleTo is like types.ConvertibleTo, but returns false if
 // either type is invalid.
 func convertibleTo(x, to types.Type) bool {
 	if x == types.Typ[types.Invalid] || to == types.Typ[types.Invalid] {
 		return false
 	}

 	return types.ConvertibleTo(x, to)
 }
	// Copyright 2020 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 completion

	import (
	"go/ast"
	"go/token"
	"go/types"

	"golang.org/x/tools/go/types/typeutil"
	"golang.org/x/tools/gopls/internal/lsp/protocol"
	"golang.org/x/tools/gopls/internal/lsp/safetoken"
	"golang.org/x/tools/gopls/internal/lsp/source"
	"golang.org/x/tools/internal/diff"
	"golang.org/x/tools/internal/typeparams"
	)

	// exprAtPos returns the index of the expression containing pos.
	func exprAtPos(pos token.Pos, args []ast.Expr) int {
	for i, expr := range args {
	if expr.Pos() <= pos && pos <= expr.End() {
	return i
	}
	}
	return len(args)
	}

	// eachField invokes fn for each field that can be selected from a
	// value of type T.
	func eachField(T types.Type, fn func(*types.Var)) {
	// TODO(adonovan): this algorithm doesn't exclude ambiguous
	// selections that match more than one field/method.
	// types.NewSelectionSet should do that for us.

	// for termination on recursive types
	var seen typeutil.Map

	var visit func(T types.Type)
	visit = func(T types.Type) {
	if T, ok := source.Deref(T).Underlying().(*types.Struct); ok {
	if seen.At(T) != nil {
	return
	}

	for i := 0; i < T.NumFields(); i++ {
	f := T.Field(i)
	fn(f)
	if f.Anonymous() {
	seen.Set(T, true)
	visit(f.Type())
	}
	}
	}
	}
	visit(T)
	}

	// typeIsValid reports whether typ doesn't contain any Invalid types.
	func typeIsValid(typ types.Type) bool {
	// Check named types separately, because we don't want
	// to call Underlying() on them to avoid problems with recursive types.
	if _, ok := typ.(*types.Named); ok {
	return true
	}

	switch typ := typ.Underlying().(type) {
	case *types.Basic:
	return typ.Kind() != types.Invalid
	case *types.Array:
	return typeIsValid(typ.Elem())
	case *types.Slice:
	return typeIsValid(typ.Elem())
	case *types.Pointer:
	return typeIsValid(typ.Elem())
	case *types.Map:
	return typeIsValid(typ.Key()) && typeIsValid(typ.Elem())
	case *types.Chan:
	return typeIsValid(typ.Elem())
	case *types.Signature:
	return typeIsValid(typ.Params()) && typeIsValid(typ.Results())
	case *types.Tuple:
	for i := 0; i < typ.Len(); i++ {
	if !typeIsValid(typ.At(i).Type()) {
	return false
	}
	}
	return true
	case types.Struct, types.Interface:
	// Don't bother checking structs, interfaces for validity.
	return true
	default:
	return false
	}
	}

	// resolveInvalid traverses the node of the AST that defines the scope
	// containing the declaration of obj, and attempts to find a user-friendly
	// name for its invalid type. The resulting Object and its Type are fake.
	func resolveInvalid(fset token.FileSet, obj types.Object, node ast.Node, info types.Info) types.Object {
	var resultExpr ast.Expr
	ast.Inspect(node, func(node ast.Node) bool {
	switch n := node.(type) {
	case *ast.ValueSpec:
	for _, name := range n.Names {
	if info.Defs[name] == obj {
	resultExpr = n.Type
	}
	}
	return false
	case *ast.Field: // This case handles parameters and results of a FuncDecl or FuncLit.
	for _, name := range n.Names {
	if info.Defs[name] == obj {
	resultExpr = n.Type
	}
	}
	return false
	default:
	return true
	}
	})
	// Construct a fake type for the object and return a fake object with this type.
	typename := source.FormatNode(fset, resultExpr)
	typ := types.NewNamed(types.NewTypeName(token.NoPos, obj.Pkg(), typename, nil), types.Typ[types.Invalid], nil)
	return types.NewVar(obj.Pos(), obj.Pkg(), obj.Name(), typ)
	}

	func isPointer(T types.Type) bool {
	_, ok := T.(*types.Pointer)
	return ok
	}

	func isVar(obj types.Object) bool {
	_, ok := obj.(*types.Var)
	return ok
	}

	func isTypeName(obj types.Object) bool {
	_, ok := obj.(*types.TypeName)
	return ok
	}

	func isFunc(obj types.Object) bool {
	_, ok := obj.(*types.Func)
	return ok
	}

	func isEmptyInterface(T types.Type) bool {
	intf, _ := T.(*types.Interface)
	return intf != nil && intf.NumMethods() == 0 && typeparams.IsMethodSet(intf)
	}

	func isUntyped(T types.Type) bool {
	if basic, ok := T.(*types.Basic); ok {
	return basic.Info()&types.IsUntyped > 0
	}
	return false
	}

	func isPkgName(obj types.Object) bool {
	_, ok := obj.(*types.PkgName)
	return ok
	}

	func isASTFile(n ast.Node) bool {
	_, ok := n.(*ast.File)
	return ok
	}

	func deslice(T types.Type) types.Type {
	if slice, ok := T.Underlying().(*types.Slice); ok {
	return slice.Elem()
	}
	return nil
	}

	// isSelector returns the enclosing *ast.SelectorExpr when pos is in the
	// selector.
	func enclosingSelector(path []ast.Node, pos token.Pos) *ast.SelectorExpr {
	if len(path) == 0 {
	return nil
	}

	if sel, ok := path[0].(*ast.SelectorExpr); ok {
	return sel
	}

	if _, ok := path[0].(*ast.Ident); ok && len(path) > 1 {
	if sel, ok := path[1].(*ast.SelectorExpr); ok && pos >= sel.Sel.Pos() {
	return sel
	}
	}

	return nil
	}

	// enclosingDeclLHS returns LHS idents from containing value spec or
	// assign statement.
	func enclosingDeclLHS(path []ast.Node) []*ast.Ident {
	for _, n := range path {
	switch n := n.(type) {
	case *ast.ValueSpec:
	return n.Names
	case *ast.AssignStmt:
	ids := make([]*ast.Ident, 0, len(n.Lhs))
	for _, e := range n.Lhs {
	if id, ok := e.(*ast.Ident); ok {
	ids = append(ids, id)
	}
	}
	return ids
	}
	}

	return nil
	}

	// exprObj returns the types.Object associated with the *ast.Ident or
	// *ast.SelectorExpr e.
	func exprObj(info *types.Info, e ast.Expr) types.Object {
	var ident *ast.Ident
	switch expr := e.(type) {
	case *ast.Ident:
	ident = expr
	case *ast.SelectorExpr:
	ident = expr.Sel
	default:
	return nil
	}

	return info.ObjectOf(ident)
	}

	// typeConversion returns the type being converted to if call is a type
	// conversion expression.
	func typeConversion(call ast.CallExpr, info types.Info) types.Type {
	// Type conversion (e.g. "float64(foo)").
	if fun, _ := exprObj(info, call.Fun).(*types.TypeName); fun != nil {
	return fun.Type()
	}

	return nil
	}

	// fieldsAccessible returns whether s has at least one field accessible by p.
	func fieldsAccessible(s types.Struct, p types.Package) bool {
	for i := 0; i < s.NumFields(); i++ {
	f := s.Field(i)
	if f.Exported() \|\| f.Pkg() == p {
	return true
	}
	}
	return false
	}

	// prevStmt returns the statement that precedes the statement containing pos.
	// For example:
	//
	// foo := 1
	// bar(1 + 2<>)
	//
	// If "<>" is pos, prevStmt returns "foo := 1"
	func prevStmt(pos token.Pos, path []ast.Node) ast.Stmt {
	var blockLines []ast.Stmt
	for i := 0; i < len(path) && blockLines == nil; i++ {
	switch n := path[i].(type) {
	case *ast.BlockStmt:
	blockLines = n.List
	case *ast.CommClause:
	blockLines = n.Body
	case *ast.CaseClause:
	blockLines = n.Body
	}
	}

	for i := len(blockLines) - 1; i >= 0; i-- {
	if blockLines[i].End() < pos {
	return blockLines[i]
	}
	}

	return nil
	}

	// formatZeroValue produces Go code representing the zero value of T. It
	// returns the empty string if T is invalid.
	func formatZeroValue(T types.Type, qf types.Qualifier) string {
	switch u := T.Underlying().(type) {
	case *types.Basic:
	switch {
	case u.Info()&types.IsNumeric > 0:
	return "0"
	case u.Info()&types.IsString > 0:
	return `""`
	case u.Info()&types.IsBoolean > 0:
	return "false"
	default:
	return ""
	}
	case types.Pointer, types.Interface, types.Chan, types.Map, types.Slice, types.Signature:
	return "nil"
	default:
	return types.TypeString(T, qf) + "{}"
	}
	}

	// isBasicKind returns whether t is a basic type of kind k.
	func isBasicKind(t types.Type, k types.BasicInfo) bool {
	b, _ := t.Underlying().(*types.Basic)
	return b != nil && b.Info()&k > 0
	}

	func (c *completer) editText(from, to token.Pos, newText string) ([]protocol.TextEdit, error) {
	start, end, err := safetoken.Offsets(c.tokFile, from, to)
	if err != nil {
	return nil, err // can't happen: from/to came from c
	}
	return source.ToProtocolEdits(c.mapper, []diff.Edit{{
	Start: start,
	End: end,
	New: newText,
	}})
	}

	// assignableTo is like types.AssignableTo, but returns false if
	// either type is invalid.
	func assignableTo(x, to types.Type) bool {
	if x == types.Typ[types.Invalid] \|\| to == types.Typ[types.Invalid] {
	return false
	}

	return types.AssignableTo(x, to)
	}

	// convertibleTo is like types.ConvertibleTo, but returns false if
	// either type is invalid.
	func convertibleTo(x, to types.Type) bool {
	if x == types.Typ[types.Invalid] \|\| to == types.Typ[types.Invalid] {
	return false
	}

	return types.ConvertibleTo(x, to)
	}