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// Copyright 2018 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 source
import (
"context"
"fmt"
"go/ast"
"go/parser"
"go/token"
"go/types"
"sort"
"strconv"
"golang.org/x/tools/go/ast/astutil"
"golang.org/x/tools/internal/event"
"golang.org/x/tools/internal/lsp/protocol"
"golang.org/x/tools/internal/span"
"golang.org/x/tools/internal/typeparams"
errors "golang.org/x/xerrors"
)
// IdentifierInfo holds information about an identifier in Go source.
type IdentifierInfo struct {
Name string
Snapshot Snapshot
MappedRange
Type struct {
MappedRange
Object types.Object
}
Inferred *types.Signature
Declaration Declaration
ident *ast.Ident
// enclosing is an expression used to determine the link anchor for an
// identifier. If it's a named type, it should be exported.
enclosing types.Type
pkg Package
qf types.Qualifier
}
func (i *IdentifierInfo) IsImport() bool {
_, ok := i.Declaration.node.(*ast.ImportSpec)
return ok
}
type Declaration struct {
MappedRange []MappedRange
// The typechecked node.
node ast.Node
// Optional: the fully parsed node, to be used for formatting in cases where
// node has missing information. This could be the case when node was parsed
// in ParseExported mode.
fullDecl ast.Decl
// The typechecked object.
obj types.Object
// typeSwitchImplicit indicates that the declaration is in an implicit
// type switch. Its type is the type of the variable on the right-hand
// side of the type switch.
typeSwitchImplicit types.Type
}
// Identifier returns identifier information for a position
// in a file, accounting for a potentially incomplete selector.
func Identifier(ctx context.Context, snapshot Snapshot, fh FileHandle, pos protocol.Position) (*IdentifierInfo, error) {
ctx, done := event.Start(ctx, "source.Identifier")
defer done()
pkgs, err := snapshot.PackagesForFile(ctx, fh.URI(), TypecheckAll, false)
if err != nil {
return nil, err
}
if len(pkgs) == 0 {
return nil, fmt.Errorf("no packages for file %v", fh.URI())
}
sort.Slice(pkgs, func(i, j int) bool {
// Prefer packages with a more complete parse mode.
if pkgs[i].ParseMode() != pkgs[j].ParseMode() {
return pkgs[i].ParseMode() > pkgs[j].ParseMode()
}
return len(pkgs[i].CompiledGoFiles()) < len(pkgs[j].CompiledGoFiles())
})
var findErr error
for _, pkg := range pkgs {
pgf, err := pkg.File(fh.URI())
if err != nil {
return nil, err
}
spn, err := pgf.Mapper.PointSpan(pos)
if err != nil {
return nil, err
}
rng, err := spn.Range(pgf.Mapper.Converter)
if err != nil {
return nil, err
}
var ident *IdentifierInfo
ident, findErr = findIdentifier(ctx, snapshot, pkg, pgf, rng.Start)
if findErr == nil {
return ident, nil
}
}
return nil, findErr
}
// ErrNoIdentFound is error returned when no identifer is found at a particular position
var ErrNoIdentFound = errors.New("no identifier found")
func findIdentifier(ctx context.Context, snapshot Snapshot, pkg Package, pgf *ParsedGoFile, pos token.Pos) (*IdentifierInfo, error) {
file := pgf.File
// Handle import specs separately, as there is no formal position for a
// package declaration.
if result, err := importSpec(snapshot, pkg, file, pos); result != nil || err != nil {
return result, err
}
path := pathEnclosingObjNode(file, pos)
if path == nil {
return nil, ErrNoIdentFound
}
qf := Qualifier(file, pkg.GetTypes(), pkg.GetTypesInfo())
ident, _ := path[0].(*ast.Ident)
if ident == nil {
return nil, ErrNoIdentFound
}
// Special case for package declarations, since they have no
// corresponding types.Object.
if ident == file.Name {
rng, err := posToMappedRange(snapshot, pkg, file.Name.Pos(), file.Name.End())
if err != nil {
return nil, err
}
var declAST *ast.File
for _, pgf := range pkg.CompiledGoFiles() {
if pgf.File.Doc != nil {
declAST = pgf.File
}
}
// If there's no package documentation, just use current file.
if declAST == nil {
declAST = file
}
declRng, err := posToMappedRange(snapshot, pkg, declAST.Name.Pos(), declAST.Name.End())
if err != nil {
return nil, err
}
return &IdentifierInfo{
Name: file.Name.Name,
ident: file.Name,
MappedRange: rng,
pkg: pkg,
qf: qf,
Snapshot: snapshot,
Declaration: Declaration{
node: declAST.Name,
MappedRange: []MappedRange{declRng},
},
}, nil
}
result := &IdentifierInfo{
Snapshot: snapshot,
qf: qf,
pkg: pkg,
ident: ident,
enclosing: searchForEnclosing(pkg.GetTypesInfo(), path),
}
result.Name = result.ident.Name
var err error
if result.MappedRange, err = posToMappedRange(snapshot, pkg, result.ident.Pos(), result.ident.End()); err != nil {
return nil, err
}
result.Declaration.obj = pkg.GetTypesInfo().ObjectOf(result.ident)
if result.Declaration.obj == nil {
// If there was no types.Object for the declaration, there might be an
// implicit local variable declaration in a type switch.
if objs, typ := typeSwitchImplicits(pkg, path); len(objs) > 0 {
// There is no types.Object for the declaration of an implicit local variable,
// but all of the types.Objects associated with the usages of this variable can be
// used to connect it back to the declaration.
// Preserve the first of these objects and treat it as if it were the declaring object.
result.Declaration.obj = objs[0]
result.Declaration.typeSwitchImplicit = typ
} else {
// Probably a type error.
return nil, errors.Errorf("%w for ident %v", errNoObjectFound, result.Name)
}
}
// Handle builtins separately.
if result.Declaration.obj.Parent() == types.Universe {
builtin, err := snapshot.BuiltinFile(ctx)
if err != nil {
return nil, err
}
builtinObj := builtin.File.Scope.Lookup(result.Name)
if builtinObj == nil {
return nil, fmt.Errorf("no builtin object for %s", result.Name)
}
decl, ok := builtinObj.Decl.(ast.Node)
if !ok {
return nil, errors.Errorf("no declaration for %s", result.Name)
}
result.Declaration.node = decl
// The builtin package isn't in the dependency graph, so the usual
// utilities won't work here.
rng := NewMappedRange(snapshot.FileSet(), builtin.Mapper, decl.Pos(), decl.Pos()+token.Pos(len(result.Name)))
result.Declaration.MappedRange = append(result.Declaration.MappedRange, rng)
return result, nil
}
// (error).Error is a special case of builtin. Lots of checks to confirm
// that this is the builtin Error.
if obj := result.Declaration.obj; obj.Parent() == nil && obj.Pkg() == nil && obj.Name() == "Error" {
if _, ok := obj.Type().(*types.Signature); ok {
builtin, err := snapshot.BuiltinFile(ctx)
if err != nil {
return nil, err
}
// Look up "error" and then navigate to its only method.
// The Error method does not appear in the builtin package's scope.log.Pri
const errorName = "error"
builtinObj := builtin.File.Scope.Lookup(errorName)
if builtinObj == nil {
return nil, fmt.Errorf("no builtin object for %s", errorName)
}
decl, ok := builtinObj.Decl.(ast.Node)
if !ok {
return nil, errors.Errorf("no declaration for %s", errorName)
}
spec, ok := decl.(*ast.TypeSpec)
if !ok {
return nil, fmt.Errorf("no type spec for %s", errorName)
}
iface, ok := spec.Type.(*ast.InterfaceType)
if !ok {
return nil, fmt.Errorf("%s is not an interface", errorName)
}
if iface.Methods.NumFields() != 1 {
return nil, fmt.Errorf("expected 1 method for %s, got %v", errorName, iface.Methods.NumFields())
}
method := iface.Methods.List[0]
if len(method.Names) != 1 {
return nil, fmt.Errorf("expected 1 name for %v, got %v", method, len(method.Names))
}
name := method.Names[0].Name
result.Declaration.node = method
rng := NewMappedRange(snapshot.FileSet(), builtin.Mapper, method.Pos(), method.Pos()+token.Pos(len(name)))
result.Declaration.MappedRange = append(result.Declaration.MappedRange, rng)
return result, nil
}
}
// If the original position was an embedded field, we want to jump
// to the field's type definition, not the field's definition.
if v, ok := result.Declaration.obj.(*types.Var); ok && v.Embedded() {
// types.Info.Uses contains the embedded field's *types.TypeName.
if typeName := pkg.GetTypesInfo().Uses[ident]; typeName != nil {
result.Declaration.obj = typeName
}
}
rng, err := objToMappedRange(snapshot, pkg, result.Declaration.obj)
if err != nil {
return nil, err
}
result.Declaration.MappedRange = append(result.Declaration.MappedRange, rng)
declPkg, err := FindPackageFromPos(ctx, snapshot, result.Declaration.obj.Pos())
if err != nil {
return nil, err
}
if result.Declaration.node, err = snapshot.PosToDecl(ctx, declPkg, result.Declaration.obj.Pos()); err != nil {
return nil, err
}
// Ensure that we have the full declaration, in case the declaration was
// parsed in ParseExported and therefore could be missing information.
if result.Declaration.fullDecl, err = fullNode(snapshot, result.Declaration.obj, declPkg); err != nil {
return nil, err
}
typ := pkg.GetTypesInfo().TypeOf(result.ident)
if typ == nil {
return result, nil
}
result.Inferred = inferredSignature(pkg.GetTypesInfo(), path)
result.Type.Object = typeToObject(typ)
if result.Type.Object != nil {
// Identifiers with the type "error" are a special case with no position.
if hasErrorType(result.Type.Object) {
return result, nil
}
if result.Type.MappedRange, err = objToMappedRange(snapshot, pkg, result.Type.Object); err != nil {
return nil, err
}
}
return result, nil
}
// fullNode tries to extract the full spec corresponding to obj's declaration.
// If the package was not parsed in full, the declaration file will be
// re-parsed to ensure it has complete syntax.
func fullNode(snapshot Snapshot, obj types.Object, pkg Package) (ast.Decl, error) {
// declaration in a different package... make sure we have full AST information.
tok := snapshot.FileSet().File(obj.Pos())
uri := span.URIFromPath(tok.Name())
pgf, err := pkg.File(uri)
if err != nil {
return nil, err
}
file := pgf.File
pos := obj.Pos()
if pgf.Mode != ParseFull {
fset := snapshot.FileSet()
file2, _ := parser.ParseFile(fset, tok.Name(), pgf.Src, parser.AllErrors|parser.ParseComments)
if file2 != nil {
offset := tok.Offset(obj.Pos())
file = file2
tok2 := fset.File(file2.Pos())
pos = tok2.Pos(offset)
}
}
path, _ := astutil.PathEnclosingInterval(file, pos, pos)
for _, n := range path {
if decl, ok := n.(ast.Decl); ok {
return decl, nil
}
}
return nil, nil
}
// inferredSignature determines the resolved non-generic signature for an
// identifier with a generic signature that is the operand of an IndexExpr or
// CallExpr.
//
// If no such signature exists, it returns nil.
func inferredSignature(info *types.Info, path []ast.Node) *types.Signature {
if len(path) < 2 {
return nil
}
// There are four ways in which a signature may be resolved:
// 1. It has no explicit type arguments, but the CallExpr can be fully
// inferred from function arguments.
// 2. It has full type arguments, and the IndexExpr has a non-generic type.
// 3. For a partially instantiated IndexExpr representing a function-valued
// expression (i.e. not part of a CallExpr), type arguments may be
// inferred using constraint type inference.
// 4. For a partially instantiated IndexExpr that is part of a CallExpr,
// type arguments may be inferred using both constraint type inference
// and function argument inference.
//
// These branches are handled below.
switch n := path[1].(type) {
case *ast.CallExpr:
_, sig := typeparams.GetInferred(info, n)
return sig
default:
if ix := typeparams.GetIndexExprData(n); ix != nil {
e := n.(ast.Expr)
// If the IndexExpr is fully instantiated, we consider that 'inference' for
// gopls' purposes.
sig, _ := info.TypeOf(e).(*types.Signature)
if sig != nil && len(typeparams.ForSignature(sig)) == 0 {
return sig
}
_, sig = typeparams.GetInferred(info, e)
if sig != nil {
return sig
}
if len(path) >= 2 {
if call, _ := path[2].(*ast.CallExpr); call != nil {
_, sig := typeparams.GetInferred(info, call)
return sig
}
}
}
}
return nil
}
func searchForEnclosing(info *types.Info, path []ast.Node) types.Type {
for _, n := range path {
switch n := n.(type) {
case *ast.SelectorExpr:
if sel, ok := info.Selections[n]; ok {
recv := Deref(sel.Recv())
// Keep track of the last exported type seen.
var exported types.Type
if named, ok := recv.(*types.Named); ok && named.Obj().Exported() {
exported = named
}
// We don't want the last element, as that's the field or
// method itself.
for _, index := range sel.Index()[:len(sel.Index())-1] {
if r, ok := recv.Underlying().(*types.Struct); ok {
recv = Deref(r.Field(index).Type())
if named, ok := recv.(*types.Named); ok && named.Obj().Exported() {
exported = named
}
}
}
return exported
}
case *ast.CompositeLit:
if t, ok := info.Types[n]; ok {
return t.Type
}
case *ast.TypeSpec:
if _, ok := n.Type.(*ast.StructType); ok {
if t, ok := info.Defs[n.Name]; ok {
return t.Type()
}
}
}
}
return nil
}
func typeToObject(typ types.Type) types.Object {
switch typ := typ.(type) {
case *types.Named:
return typ.Obj()
case *types.Pointer:
return typeToObject(typ.Elem())
case *types.Array:
return typeToObject(typ.Elem())
case *types.Slice:
return typeToObject(typ.Elem())
case *types.Chan:
return typeToObject(typ.Elem())
case *types.Signature:
// Try to find a return value of a named type. If there's only one
// such value, jump to its type definition.
var res types.Object
results := typ.Results()
for i := 0; i < results.Len(); i++ {
obj := typeToObject(results.At(i).Type())
if obj == nil || hasErrorType(obj) {
// Skip builtins.
continue
}
if res != nil {
// The function/method must have only one return value of a named type.
return nil
}
res = obj
}
return res
default:
return nil
}
}
func hasErrorType(obj types.Object) bool {
return types.IsInterface(obj.Type()) && obj.Pkg() == nil && obj.Name() == "error"
}
// importSpec handles positions inside of an *ast.ImportSpec.
func importSpec(snapshot Snapshot, pkg Package, file *ast.File, pos token.Pos) (*IdentifierInfo, error) {
var imp *ast.ImportSpec
for _, spec := range file.Imports {
if spec.Path.Pos() <= pos && pos < spec.Path.End() {
imp = spec
}
}
if imp == nil {
return nil, nil
}
importPath, err := strconv.Unquote(imp.Path.Value)
if err != nil {
return nil, errors.Errorf("import path not quoted: %s (%v)", imp.Path.Value, err)
}
result := &IdentifierInfo{
Snapshot: snapshot,
Name: importPath,
pkg: pkg,
}
if result.MappedRange, err = posToMappedRange(snapshot, pkg, imp.Path.Pos(), imp.Path.End()); err != nil {
return nil, err
}
// Consider the "declaration" of an import spec to be the imported package.
importedPkg, err := pkg.GetImport(importPath)
if err != nil {
return nil, err
}
// Return all of the files in the package as the definition of the import spec.
for _, dst := range importedPkg.GetSyntax() {
rng, err := posToMappedRange(snapshot, pkg, dst.Pos(), dst.End())
if err != nil {
return nil, err
}
result.Declaration.MappedRange = append(result.Declaration.MappedRange, rng)
}
result.Declaration.node = imp
return result, nil
}
// typeSwitchImplicits returns all the implicit type switch objects that
// correspond to the leaf *ast.Ident. It also returns the original type
// associated with the identifier (outside of a case clause).
func typeSwitchImplicits(pkg Package, path []ast.Node) ([]types.Object, types.Type) {
ident, _ := path[0].(*ast.Ident)
if ident == nil {
return nil, nil
}
var (
ts *ast.TypeSwitchStmt
assign *ast.AssignStmt
cc *ast.CaseClause
obj = pkg.GetTypesInfo().ObjectOf(ident)
)
// Walk our ancestors to determine if our leaf ident refers to a
// type switch variable, e.g. the "a" from "switch a := b.(type)".
Outer:
for i := 1; i < len(path); i++ {
switch n := path[i].(type) {
case *ast.AssignStmt:
// Check if ident is the "a" in "a := foo.(type)". The "a" in
// this case has no types.Object, so check for ident equality.
if len(n.Lhs) == 1 && n.Lhs[0] == ident {
assign = n
}
case *ast.CaseClause:
// Check if ident is a use of "a" within a case clause. Each
// case clause implicitly maps "a" to a different types.Object,
// so check if ident's object is the case clause's implicit
// object.
if obj != nil && pkg.GetTypesInfo().Implicits[n] == obj {
cc = n
}
case *ast.TypeSwitchStmt:
// Look for the type switch that owns our previously found
// *ast.AssignStmt or *ast.CaseClause.
if n.Assign == assign {
ts = n
break Outer
}
for _, stmt := range n.Body.List {
if stmt == cc {
ts = n
break Outer
}
}
}
}
if ts == nil {
return nil, nil
}
// Our leaf ident refers to a type switch variable. Fan out to the
// type switch's implicit case clause objects.
var objs []types.Object
for _, cc := range ts.Body.List {
if ccObj := pkg.GetTypesInfo().Implicits[cc]; ccObj != nil {
objs = append(objs, ccObj)
}
}
// The right-hand side of a type switch should only have one
// element, and we need to track its type in order to generate
// hover information for implicit type switch variables.
var typ types.Type
if assign, ok := ts.Assign.(*ast.AssignStmt); ok && len(assign.Rhs) == 1 {
if rhs := assign.Rhs[0].(*ast.TypeAssertExpr); ok {
typ = pkg.GetTypesInfo().TypeOf(rhs.X)
}
}
return objs, typ
}