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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 completion provides core functionality for code completion in Go
// editors and tools.
package completion
import (
"context"
"fmt"
"go/ast"
"go/constant"
"go/scanner"
"go/token"
"go/types"
"math"
"sort"
"strconv"
"strings"
"sync"
"time"
"unicode"
"golang.org/x/tools/go/ast/astutil"
"golang.org/x/tools/internal/event"
"golang.org/x/tools/internal/imports"
"golang.org/x/tools/internal/lsp/fuzzy"
"golang.org/x/tools/internal/lsp/protocol"
"golang.org/x/tools/internal/lsp/snippet"
"golang.org/x/tools/internal/lsp/source"
errors "golang.org/x/xerrors"
)
type CompletionItem struct {
// Label is the primary text the user sees for this completion item.
Label string
// Detail is supplemental information to present to the user.
// This often contains the type or return type of the completion item.
Detail string
// InsertText is the text to insert if this item is selected.
// Any of the prefix that has already been typed is not trimmed.
// The insert text does not contain snippets.
InsertText string
Kind protocol.CompletionItemKind
// An optional array of additional TextEdits that are applied when
// selecting this completion.
//
// Additional text edits should be used to change text unrelated to the current cursor position
// (for example adding an import statement at the top of the file if the completion item will
// insert an unqualified type).
AdditionalTextEdits []protocol.TextEdit
// Depth is how many levels were searched to find this completion.
// For example when completing "foo<>", "fooBar" is depth 0, and
// "fooBar.Baz" is depth 1.
Depth int
// Score is the internal relevance score.
// A higher score indicates that this completion item is more relevant.
Score float64
// snippet is the LSP snippet for the completion item. The LSP
// specification contains details about LSP snippets. For example, a
// snippet for a function with the following signature:
//
// func foo(a, b, c int)
//
// would be:
//
// foo(${1:a int}, ${2: b int}, ${3: c int})
//
// If Placeholders is false in the CompletionOptions, the above
// snippet would instead be:
//
// foo(${1:})
snippet *snippet.Builder
// Documentation is the documentation for the completion item.
Documentation string
// obj is the object from which this candidate was derived, if any.
// obj is for internal use only.
obj types.Object
}
// completionOptions holds completion specific configuration.
type completionOptions struct {
unimported bool
documentation bool
fullDocumentation bool
placeholders bool
literal bool
matcher source.Matcher
budget time.Duration
}
// Snippet is a convenience returns the snippet if available, otherwise
// the InsertText.
// used for an item, depending on if the callee wants placeholders or not.
func (i *CompletionItem) Snippet() string {
if i.snippet != nil {
return i.snippet.String()
}
return i.InsertText
}
// Scoring constants are used for weighting the relevance of different candidates.
const (
// stdScore is the base score for all completion items.
stdScore float64 = 1.0
// highScore indicates a very relevant completion item.
highScore float64 = 10.0
// lowScore indicates an irrelevant or not useful completion item.
lowScore float64 = 0.01
)
// matcher matches a candidate's label against the user input. The
// returned score reflects the quality of the match. A score of zero
// indicates no match, and a score of one means a perfect match.
type matcher interface {
Score(candidateLabel string) (score float32)
}
// prefixMatcher implements case sensitive prefix matching.
type prefixMatcher string
func (pm prefixMatcher) Score(candidateLabel string) float32 {
if strings.HasPrefix(candidateLabel, string(pm)) {
return 1
}
return -1
}
// insensitivePrefixMatcher implements case insensitive prefix matching.
type insensitivePrefixMatcher string
func (ipm insensitivePrefixMatcher) Score(candidateLabel string) float32 {
if strings.HasPrefix(strings.ToLower(candidateLabel), string(ipm)) {
return 1
}
return -1
}
// completer contains the necessary information for a single completion request.
type completer struct {
snapshot source.Snapshot
pkg source.Package
qf types.Qualifier
opts *completionOptions
// completionContext contains information about the trigger for this
// completion request.
completionContext completionContext
// fh is a handle to the file associated with this completion request.
fh source.FileHandle
// filename is the name of the file associated with this completion request.
filename string
// file is the AST of the file associated with this completion request.
file *ast.File
// pos is the position at which the request was triggered.
pos token.Pos
// path is the path of AST nodes enclosing the position.
path []ast.Node
// seen is the map that ensures we do not return duplicate results.
seen map[types.Object]bool
// items is the list of completion items returned.
items []CompletionItem
// completionCallbacks is a list of callbacks to collect completions that
// require expensive operations. This includes operations where we search
// through the entire module cache.
completionCallbacks []func(opts *imports.Options) error
// surrounding describes the identifier surrounding the position.
surrounding *Selection
// inference contains information we've inferred about ideal
// candidates such as the candidate's type.
inference candidateInference
// enclosingFunc contains information about the function enclosing
// the position.
enclosingFunc *funcInfo
// enclosingCompositeLiteral contains information about the composite literal
// enclosing the position.
enclosingCompositeLiteral *compLitInfo
// deepState contains the current state of our deep completion search.
deepState deepCompletionState
// matcher matches the candidates against the surrounding prefix.
matcher matcher
// methodSetCache caches the types.NewMethodSet call, which is relatively
// expensive and can be called many times for the same type while searching
// for deep completions.
methodSetCache map[methodSetKey]*types.MethodSet
// mapper converts the positions in the file from which the completion originated.
mapper *protocol.ColumnMapper
// startTime is when we started processing this completion request. It does
// not include any time the request spent in the queue.
startTime time.Time
}
// funcInfo holds info about a function object.
type funcInfo struct {
// sig is the function declaration enclosing the position.
sig *types.Signature
// body is the function's body.
body *ast.BlockStmt
}
type compLitInfo struct {
// cl is the *ast.CompositeLit enclosing the position.
cl *ast.CompositeLit
// clType is the type of cl.
clType types.Type
// kv is the *ast.KeyValueExpr enclosing the position, if any.
kv *ast.KeyValueExpr
// inKey is true if we are certain the position is in the key side
// of a key-value pair.
inKey bool
// maybeInFieldName is true if inKey is false and it is possible
// we are completing a struct field name. For example,
// "SomeStruct{<>}" will be inKey=false, but maybeInFieldName=true
// because we _could_ be completing a field name.
maybeInFieldName bool
}
type importInfo struct {
importPath string
name string
pkg source.Package
}
type methodSetKey struct {
typ types.Type
addressable bool
}
type completionContext struct {
// triggerCharacter is the character used to trigger completion at current
// position, if any.
triggerCharacter string
// triggerKind is information about how a completion was triggered.
triggerKind protocol.CompletionTriggerKind
// commentCompletion is true if we are completing a comment.
commentCompletion bool
// packageCompletion is true if we are completing a package name.
packageCompletion bool
}
// A Selection represents the cursor position and surrounding identifier.
type Selection struct {
content string
cursor token.Pos
source.MappedRange
}
func (p Selection) Content() string {
return p.content
}
func (p Selection) Start() token.Pos {
return p.MappedRange.SpanRange().Start
}
func (p Selection) End() token.Pos {
return p.MappedRange.SpanRange().End
}
func (p Selection) Prefix() string {
return p.content[:p.cursor-p.SpanRange().Start]
}
func (p Selection) Suffix() string {
return p.content[p.cursor-p.SpanRange().Start:]
}
func (c *completer) setSurrounding(ident *ast.Ident) {
if c.surrounding != nil {
return
}
if !(ident.Pos() <= c.pos && c.pos <= ident.End()) {
return
}
c.surrounding = &Selection{
content: ident.Name,
cursor: c.pos,
// Overwrite the prefix only.
MappedRange: source.NewMappedRange(c.snapshot.FileSet(), c.mapper, ident.Pos(), ident.End()),
}
c.setMatcherFromPrefix(c.surrounding.Prefix())
}
func (c *completer) setMatcherFromPrefix(prefix string) {
switch c.opts.matcher {
case source.Fuzzy:
c.matcher = fuzzy.NewMatcher(prefix)
case source.CaseSensitive:
c.matcher = prefixMatcher(prefix)
default:
c.matcher = insensitivePrefixMatcher(strings.ToLower(prefix))
}
}
func (c *completer) getSurrounding() *Selection {
if c.surrounding == nil {
c.surrounding = &Selection{
content: "",
cursor: c.pos,
MappedRange: source.NewMappedRange(c.snapshot.FileSet(), c.mapper, c.pos, c.pos),
}
}
return c.surrounding
}
// candidate represents a completion candidate.
type candidate struct {
// obj is the types.Object to complete to.
obj types.Object
// score is used to rank candidates.
score float64
// name is the deep object name path, e.g. "foo.bar"
name string
// detail is additional information about this item. If not specified,
// defaults to type string for the object.
detail string
// path holds the path from the search root (excluding the candidate
// itself) for a deep candidate.
path []types.Object
// names tracks the names of objects from search root (excluding the
// candidate itself) for a deep candidate. This also includes
// expanded calls for function invocations.
names []string
// expandFuncCall is true if obj should be invoked in the completion.
// For example, expandFuncCall=true yields "foo()", expandFuncCall=false yields "foo".
expandFuncCall bool
// takeAddress is true if the completion should take a pointer to obj.
// For example, takeAddress=true yields "&foo", takeAddress=false yields "foo".
takeAddress bool
// addressable is true if a pointer can be taken to the candidate.
addressable bool
// makePointer is true if the candidate type name T should be made into *T.
makePointer bool
// dereference is a count of how many times to dereference the candidate obj.
// For example, dereference=2 turns "foo" into "**foo" when formatting.
dereference int
// variadic is true if this candidate fills a variadic param and
// needs "..." appended.
variadic bool
// imp is the import that needs to be added to this package in order
// for this candidate to be valid. nil if no import needed.
imp *importInfo
}
// ErrIsDefinition is an error that informs the user they got no
// completions because they tried to complete the name of a new object
// being defined.
type ErrIsDefinition struct {
objStr string
}
func (e ErrIsDefinition) Error() string {
msg := "this is a definition"
if e.objStr != "" {
msg += " of " + e.objStr
}
return msg
}
// Completion returns a list of possible candidates for completion, given a
// a file and a position.
//
// The selection is computed based on the preceding identifier and can be used by
// the client to score the quality of the completion. For instance, some clients
// may tolerate imperfect matches as valid completion results, since users may make typos.
func Completion(ctx context.Context, snapshot source.Snapshot, fh source.FileHandle, protoPos protocol.Position, protoContext protocol.CompletionContext) ([]CompletionItem, *Selection, error) {
ctx, done := event.Start(ctx, "completion.Completion")
defer done()
startTime := time.Now()
pkg, pgf, err := source.GetParsedFile(ctx, snapshot, fh, source.NarrowestPackage)
if err != nil || pgf.File.Package == token.NoPos {
// If we can't parse this file or find position for the package
// keyword, it may be missing a package declaration. Try offering
// suggestions for the package declaration.
// Note that this would be the case even if the keyword 'package' is
// present but no package name exists.
items, surrounding, innerErr := packageClauseCompletions(ctx, snapshot, fh, protoPos)
if innerErr != nil {
// return the error for GetParsedFile since it's more relevant in this situation.
return nil, nil, errors.Errorf("getting file for Completion: %w (package completions: %v)", err, innerErr)
}
return items, surrounding, nil
}
spn, err := pgf.Mapper.PointSpan(protoPos)
if err != nil {
return nil, nil, err
}
rng, err := spn.Range(pgf.Mapper.Converter)
if err != nil {
return nil, nil, err
}
// Completion is based on what precedes the cursor.
// Find the path to the position before pos.
path, _ := astutil.PathEnclosingInterval(pgf.File, rng.Start-1, rng.Start-1)
if path == nil {
return nil, nil, errors.Errorf("cannot find node enclosing position")
}
pos := rng.Start
// Check if completion at this position is valid. If not, return early.
switch n := path[0].(type) {
case *ast.BasicLit:
// Skip completion inside literals except for ImportSpec
if len(path) > 1 {
if _, ok := path[1].(*ast.ImportSpec); ok {
break
}
}
return nil, nil, nil
case *ast.CallExpr:
if n.Ellipsis.IsValid() && pos > n.Ellipsis && pos <= n.Ellipsis+token.Pos(len("...")) {
// Don't offer completions inside or directly after "...". For
// example, don't offer completions at "<>" in "foo(bar...<>").
return nil, nil, nil
}
case *ast.Ident:
// reject defining identifiers
if obj, ok := pkg.GetTypesInfo().Defs[n]; ok {
if v, ok := obj.(*types.Var); ok && v.IsField() && v.Embedded() {
// An anonymous field is also a reference to a type.
} else if pgf.File.Name == n {
// Don't skip completions if Ident is for package name.
break
} else {
objStr := ""
if obj != nil {
qual := types.RelativeTo(pkg.GetTypes())
objStr = types.ObjectString(obj, qual)
}
return nil, nil, ErrIsDefinition{objStr: objStr}
}
}
}
opts := snapshot.View().Options()
c := &completer{
pkg: pkg,
snapshot: snapshot,
qf: source.Qualifier(pgf.File, pkg.GetTypes(), pkg.GetTypesInfo()),
completionContext: completionContext{
triggerCharacter: protoContext.TriggerCharacter,
triggerKind: protoContext.TriggerKind,
},
fh: fh,
filename: fh.URI().Filename(),
file: pgf.File,
path: path,
pos: pos,
seen: make(map[types.Object]bool),
enclosingFunc: enclosingFunction(path, pkg.GetTypesInfo()),
enclosingCompositeLiteral: enclosingCompositeLiteral(path, rng.Start, pkg.GetTypesInfo()),
deepState: deepCompletionState{
enabled: opts.DeepCompletion,
},
opts: &completionOptions{
matcher: opts.Matcher,
unimported: opts.CompleteUnimported,
documentation: opts.CompletionDocumentation && opts.HoverKind != source.NoDocumentation,
fullDocumentation: opts.HoverKind == source.FullDocumentation,
placeholders: opts.UsePlaceholders,
literal: opts.LiteralCompletions && opts.InsertTextFormat == protocol.SnippetTextFormat,
budget: opts.CompletionBudget,
},
// default to a matcher that always matches
matcher: prefixMatcher(""),
methodSetCache: make(map[methodSetKey]*types.MethodSet),
mapper: pgf.Mapper,
startTime: startTime,
}
var cancel context.CancelFunc
if c.opts.budget == 0 {
ctx, cancel = context.WithCancel(ctx)
} else {
// timeoutDuration is the completion budget remaining. If less than
// 10ms, set to 10ms
timeoutDuration := time.Until(c.startTime.Add(c.opts.budget))
if timeoutDuration < 10*time.Millisecond {
timeoutDuration = 10 * time.Millisecond
}
ctx, cancel = context.WithTimeout(ctx, timeoutDuration)
}
defer cancel()
if surrounding := c.containingIdent(pgf.Src); surrounding != nil {
c.setSurrounding(surrounding)
}
c.inference = expectedCandidate(ctx, c)
err = c.collectCompletions(ctx)
if err != nil {
return nil, nil, err
}
// Deep search collected candidates and their members for more candidates.
c.deepSearch(ctx)
c.deepState.searchQueue = nil
for _, callback := range c.completionCallbacks {
if err := c.snapshot.RunProcessEnvFunc(ctx, callback); err != nil {
return nil, nil, err
}
}
// Search candidates populated by expensive operations like
// unimportedMembers etc. for more completion items.
c.deepSearch(ctx)
// Statement candidates offer an entire statement in certain contexts, as
// opposed to a single object. Add statement candidates last because they
// depend on other candidates having already been collected.
c.addStatementCandidates()
c.sortItems()
return c.items, c.getSurrounding(), nil
}
// collectCompletions adds possible completion candidates to either the deep
// search queue or completion items directly for different completion contexts.
func (c *completer) collectCompletions(ctx context.Context) error {
// Inside import blocks, return completions for unimported packages.
for _, importSpec := range c.file.Imports {
if !(importSpec.Path.Pos() <= c.pos && c.pos <= importSpec.Path.End()) {
continue
}
return c.populateImportCompletions(ctx, importSpec)
}
// Inside comments, offer completions for the name of the relevant symbol.
for _, comment := range c.file.Comments {
if comment.Pos() < c.pos && c.pos <= comment.End() {
c.populateCommentCompletions(ctx, comment)
return nil
}
}
// Struct literals are handled entirely separately.
if c.wantStructFieldCompletions() {
// If we are definitely completing a struct field name, deep completions
// don't make sense.
if c.enclosingCompositeLiteral.inKey {
c.deepState.enabled = false
}
return c.structLiteralFieldName(ctx)
}
if lt := c.wantLabelCompletion(); lt != labelNone {
c.labels(lt)
return nil
}
if c.emptySwitchStmt() {
// Empty switch statements only admit "default" and "case" keywords.
c.addKeywordItems(map[string]bool{}, highScore, CASE, DEFAULT)
return nil
}
switch n := c.path[0].(type) {
case *ast.Ident:
if c.file.Name == n {
return c.packageNameCompletions(ctx, c.fh.URI(), n)
} else if sel, ok := c.path[1].(*ast.SelectorExpr); ok && sel.Sel == n {
// Is this the Sel part of a selector?
return c.selector(ctx, sel)
}
return c.lexical(ctx)
// The function name hasn't been typed yet, but the parens are there:
// recv.‸(arg)
case *ast.TypeAssertExpr:
// Create a fake selector expression.
return c.selector(ctx, &ast.SelectorExpr{X: n.X})
case *ast.SelectorExpr:
return c.selector(ctx, n)
// At the file scope, only keywords are allowed.
case *ast.BadDecl, *ast.File:
c.addKeywordCompletions()
default:
// fallback to lexical completions
return c.lexical(ctx)
}
return nil
}
// containingIdent returns the *ast.Ident containing pos, if any. It
// synthesizes an *ast.Ident to allow completion in the face of
// certain syntax errors.
func (c *completer) containingIdent(src []byte) *ast.Ident {
// In the normal case, our leaf AST node is the identifer being completed.
if ident, ok := c.path[0].(*ast.Ident); ok {
return ident
}
pos, tkn, lit := c.scanToken(src)
if !pos.IsValid() {
return nil
}
fakeIdent := &ast.Ident{Name: lit, NamePos: pos}
if _, isBadDecl := c.path[0].(*ast.BadDecl); isBadDecl {
// You don't get *ast.Idents at the file level, so look for bad
// decls and use the manually extracted token.
return fakeIdent
} else if c.emptySwitchStmt() {
// Only keywords are allowed in empty switch statements.
// *ast.Idents are not parsed, so we must use the manually
// extracted token.
return fakeIdent
} else if tkn.IsKeyword() {
// Otherwise, manually extract the prefix if our containing token
// is a keyword. This improves completion after an "accidental
// keyword", e.g. completing to "variance" in "someFunc(var<>)".
return fakeIdent
}
return nil
}
// scanToken scans pgh's contents for the token containing pos.
func (c *completer) scanToken(contents []byte) (token.Pos, token.Token, string) {
tok := c.snapshot.FileSet().File(c.pos)
var s scanner.Scanner
s.Init(tok, contents, nil, 0)
for {
tknPos, tkn, lit := s.Scan()
if tkn == token.EOF || tknPos >= c.pos {
return token.NoPos, token.ILLEGAL, ""
}
if len(lit) > 0 && tknPos <= c.pos && c.pos <= tknPos+token.Pos(len(lit)) {
return tknPos, tkn, lit
}
}
}
func (c *completer) sortItems() {
sort.SliceStable(c.items, func(i, j int) bool {
// Sort by score first.
if c.items[i].Score != c.items[j].Score {
return c.items[i].Score > c.items[j].Score
}
// Then sort by label so order stays consistent. This also has the
// effect of prefering shorter candidates.
return c.items[i].Label < c.items[j].Label
})
}
// emptySwitchStmt reports whether pos is in an empty switch or select
// statement.
func (c *completer) emptySwitchStmt() bool {
block, ok := c.path[0].(*ast.BlockStmt)
if !ok || len(block.List) > 0 || len(c.path) == 1 {
return false
}
switch c.path[1].(type) {
case *ast.SwitchStmt, *ast.TypeSwitchStmt, *ast.SelectStmt:
return true
default:
return false
}
}
// populateImportCompletions yields completions for an import path around the cursor.
//
// Completions are suggested at the directory depth of the given import path so
// that we don't overwhelm the user with a large list of possibilities. As an
// example, a completion for the prefix "golang" results in "golang.org/".
// Completions for "golang.org/" yield its subdirectories
// (i.e. "golang.org/x/"). The user is meant to accept completion suggestions
// until they reach a complete import path.
func (c *completer) populateImportCompletions(ctx context.Context, searchImport *ast.ImportSpec) error {
// deepSearch is not valuable for import completions.
c.deepState.enabled = false
importPath := searchImport.Path.Value
// Extract the text between the quotes (if any) in an import spec.
// prefix is the part of import path before the cursor.
prefixEnd := c.pos - searchImport.Path.Pos()
prefix := strings.Trim(importPath[:prefixEnd], `"`)
// The number of directories in the import path gives us the depth at
// which to search.
depth := len(strings.Split(prefix, "/")) - 1
content := importPath
start, end := searchImport.Path.Pos(), searchImport.Path.End()
namePrefix, nameSuffix := `"`, `"`
// If a starting quote is present, adjust surrounding to either after the
// cursor or after the first slash (/), except if cursor is at the starting
// quote. Otherwise we provide a completion including the starting quote.
if strings.HasPrefix(importPath, `"`) && c.pos > searchImport.Path.Pos() {
content = content[1:]
start++
if depth > 0 {
// Adjust textEdit start to replacement range. For ex: if current
// path was "golang.or/x/to<>ols/internal/", where <> is the cursor
// position, start of the replacement range would be after
// "golang.org/x/".
path := strings.SplitAfter(prefix, "/")
numChars := len(strings.Join(path[:len(path)-1], ""))
content = content[numChars:]
start += token.Pos(numChars)
}
namePrefix = ""
}
// We won't provide an ending quote if one is already present, except if
// cursor is after the ending quote but still in import spec. This is
// because cursor has to be in our textEdit range.
if strings.HasSuffix(importPath, `"`) && c.pos < searchImport.Path.End() {
end--
content = content[:len(content)-1]
nameSuffix = ""
}
c.surrounding = &Selection{
content: content,
cursor: c.pos,
MappedRange: source.NewMappedRange(c.snapshot.FileSet(), c.mapper, start, end),
}
seenImports := make(map[string]struct{})
for _, importSpec := range c.file.Imports {
if importSpec.Path.Value == importPath {
continue
}
seenImportPath, err := strconv.Unquote(importSpec.Path.Value)
if err != nil {
return err
}
seenImports[seenImportPath] = struct{}{}
}
var mu sync.Mutex // guard c.items locally, since searchImports is called in parallel
seen := make(map[string]struct{})
searchImports := func(pkg imports.ImportFix) {
path := pkg.StmtInfo.ImportPath
if _, ok := seenImports[path]; ok {
return
}
// Any package path containing fewer directories than the search
// prefix is not a match.
pkgDirList := strings.Split(path, "/")
if len(pkgDirList) < depth+1 {
return
}
pkgToConsider := strings.Join(pkgDirList[:depth+1], "/")
name := pkgDirList[depth]
// if we're adding an opening quote to completion too, set name to full
// package path since we'll need to overwrite that range.
if namePrefix == `"` {
name = pkgToConsider
}
score := pkg.Relevance
if len(pkgDirList)-1 == depth {
score *= highScore
} else {
// For incomplete package paths, add a terminal slash to indicate that the
// user should keep triggering completions.
name += "/"
pkgToConsider += "/"
}
if _, ok := seen[pkgToConsider]; ok {
return
}
seen[pkgToConsider] = struct{}{}
mu.Lock()
defer mu.Unlock()
name = namePrefix + name + nameSuffix
obj := types.NewPkgName(0, nil, name, types.NewPackage(pkgToConsider, name))
c.deepState.enqueue(candidate{
obj: obj,
detail: fmt.Sprintf("%q", pkgToConsider),
score: score,
})
}
c.completionCallbacks = append(c.completionCallbacks, func(opts *imports.Options) error {
return imports.GetImportPaths(ctx, searchImports, prefix, c.filename, c.pkg.GetTypes().Name(), opts.Env)
})
return nil
}
// populateCommentCompletions yields completions for comments preceding or in declarations.
func (c *completer) populateCommentCompletions(ctx context.Context, comment *ast.CommentGroup) {
// If the completion was triggered by a period, ignore it. These types of
// completions will not be useful in comments.
if c.completionContext.triggerCharacter == "." {
return
}
// Using the comment position find the line after
file := c.snapshot.FileSet().File(comment.End())
if file == nil {
return
}
// Deep completion doesn't work properly in comments since we don't
// have a type object to complete further.
c.deepState.enabled = false
c.completionContext.commentCompletion = true
// Documentation isn't useful in comments, since it might end up being the
// comment itself.
c.opts.documentation = false
commentLine := file.Line(comment.End())
// comment is valid, set surrounding as word boundaries around cursor
c.setSurroundingForComment(comment)
// Using the next line pos, grab and parse the exported symbol on that line
for _, n := range c.file.Decls {
declLine := file.Line(n.Pos())
// if the comment is not in, directly above or on the same line as a declaration
if declLine != commentLine && declLine != commentLine+1 &&
!(n.Pos() <= comment.Pos() && comment.End() <= n.End()) {
continue
}
switch node := n.(type) {
// handle const, vars, and types
case *ast.GenDecl:
for _, spec := range node.Specs {
switch spec := spec.(type) {
case *ast.ValueSpec:
for _, name := range spec.Names {
if name.String() == "_" {
continue
}
obj := c.pkg.GetTypesInfo().ObjectOf(name)
c.deepState.enqueue(candidate{obj: obj, score: stdScore})
}
case *ast.TypeSpec:
// add TypeSpec fields to completion
switch typeNode := spec.Type.(type) {
case *ast.StructType:
c.addFieldItems(ctx, typeNode.Fields)
case *ast.FuncType:
c.addFieldItems(ctx, typeNode.Params)
c.addFieldItems(ctx, typeNode.Results)
case *ast.InterfaceType:
c.addFieldItems(ctx, typeNode.Methods)
}
if spec.Name.String() == "_" {
continue
}
obj := c.pkg.GetTypesInfo().ObjectOf(spec.Name)
// Type name should get a higher score than fields but not highScore by default
// since field near a comment cursor gets a highScore
score := stdScore * 1.1
// If type declaration is on the line after comment, give it a highScore.
if declLine == commentLine+1 {
score = highScore
}
c.deepState.enqueue(candidate{obj: obj, score: score})
}
}
// handle functions
case *ast.FuncDecl:
c.addFieldItems(ctx, node.Recv)
c.addFieldItems(ctx, node.Type.Params)
c.addFieldItems(ctx, node.Type.Results)
// collect receiver struct fields
if node.Recv != nil {
for _, fields := range node.Recv.List {
for _, name := range fields.Names {
obj := c.pkg.GetTypesInfo().ObjectOf(name)
if obj == nil {
continue
}
recvType := obj.Type().Underlying()
if ptr, ok := recvType.(*types.Pointer); ok {
recvType = ptr.Elem()
}
recvStruct, ok := recvType.Underlying().(*types.Struct)
if !ok {
continue
}
for i := 0; i < recvStruct.NumFields(); i++ {
field := recvStruct.Field(i)
c.deepState.enqueue(candidate{obj: field, score: lowScore})
}
}
}
}
if node.Name.String() == "_" {
continue
}
obj := c.pkg.GetTypesInfo().ObjectOf(node.Name)
if obj == nil || obj.Pkg() != nil && obj.Pkg() != c.pkg.GetTypes() {
continue
}
c.deepState.enqueue(candidate{obj: obj, score: highScore})
}
}
}
// sets word boundaries surrounding a cursor for a comment
func (c *completer) setSurroundingForComment(comments *ast.CommentGroup) {
var cursorComment *ast.Comment
for _, comment := range comments.List {
if c.pos >= comment.Pos() && c.pos <= comment.End() {
cursorComment = comment
break
}
}
// if cursor isn't in the comment
if cursorComment == nil {
return
}
// index of cursor in comment text
cursorOffset := int(c.pos - cursorComment.Pos())
start, end := cursorOffset, cursorOffset
for start > 0 && isValidIdentifierChar(cursorComment.Text[start-1]) {
start--
}
for end < len(cursorComment.Text) && isValidIdentifierChar(cursorComment.Text[end]) {
end++
}
c.surrounding = &Selection{
content: cursorComment.Text[start:end],
cursor: c.pos,
MappedRange: source.NewMappedRange(c.snapshot.FileSet(), c.mapper,
token.Pos(int(cursorComment.Slash)+start), token.Pos(int(cursorComment.Slash)+end)),
}
c.setMatcherFromPrefix(c.surrounding.Prefix())
}
// isValidIdentifierChar returns true if a byte is a valid go identifier character
// i.e unicode letter or digit or undescore
func isValidIdentifierChar(char byte) bool {
charRune := rune(char)
return unicode.In(charRune, unicode.Letter, unicode.Digit) || char == '_'
}
// adds struct fields, interface methods, function declaration fields to completion
func (c *completer) addFieldItems(ctx context.Context, fields *ast.FieldList) {
if fields == nil {
return
}
cursor := c.surrounding.cursor
for _, field := range fields.List {
for _, name := range field.Names {
if name.String() == "_" {
continue
}
obj := c.pkg.GetTypesInfo().ObjectOf(name)
if obj == nil {
continue
}
// if we're in a field comment/doc, score that field as more relevant
score := stdScore
if field.Comment != nil && field.Comment.Pos() <= cursor && cursor <= field.Comment.End() {
score = highScore
} else if field.Doc != nil && field.Doc.Pos() <= cursor && cursor <= field.Doc.End() {
score = highScore
}
c.deepState.enqueue(candidate{obj: obj, score: score})
}
}
}
func (c *completer) wantStructFieldCompletions() bool {
clInfo := c.enclosingCompositeLiteral
if clInfo == nil {
return false
}
return clInfo.isStruct() && (clInfo.inKey || clInfo.maybeInFieldName)
}
func (c *completer) wantTypeName() bool {
return !c.completionContext.commentCompletion && c.inference.typeName.wantTypeName
}
// See https://golang.org/issue/36001. Unimported completions are expensive.
const (
maxUnimportedPackageNames = 5
unimportedMemberTarget = 100
)
// selector finds completions for the specified selector expression.
func (c *completer) selector(ctx context.Context, sel *ast.SelectorExpr) error {
c.inference.objChain = objChain(c.pkg.GetTypesInfo(), sel.X)
// Is sel a qualified identifier?
if id, ok := sel.X.(*ast.Ident); ok {
if pkgName, ok := c.pkg.GetTypesInfo().Uses[id].(*types.PkgName); ok {
candidates := c.packageMembers(pkgName.Imported(), stdScore, nil)
for _, cand := range candidates {
c.deepState.enqueue(cand)
}
return nil
}
}
// Invariant: sel is a true selector.
tv, ok := c.pkg.GetTypesInfo().Types[sel.X]
if ok {
candidates := c.methodsAndFields(tv.Type, tv.Addressable(), nil)
for _, cand := range candidates {
c.deepState.enqueue(cand)
}
return nil
}
// Try unimported packages.
if id, ok := sel.X.(*ast.Ident); ok && c.opts.unimported {
if err := c.unimportedMembers(ctx, id); err != nil {
return err
}
}
return nil
}
func (c *completer) unimportedMembers(ctx context.Context, id *ast.Ident) error {
// Try loaded packages first. They're relevant, fast, and fully typed.
known, err := c.snapshot.CachedImportPaths(ctx)
if err != nil {
return err
}
var paths []string
for path, pkg := range known {
if pkg.GetTypes().Name() != id.Name {
continue
}
paths = append(paths, path)
}
var relevances map[string]float64
if len(paths) != 0 {
if err := c.snapshot.RunProcessEnvFunc(ctx, func(opts *imports.Options) error {
var err error
relevances, err = imports.ScoreImportPaths(ctx, opts.Env, paths)
return err
}); err != nil {
return err
}
}
sort.Slice(paths, func(i, j int) bool {
return relevances[paths[i]] > relevances[paths[j]]
})
for _, path := range paths {
pkg := known[path]
if pkg.GetTypes().Name() != id.Name {
continue
}
imp := &importInfo{
importPath: path,
pkg: pkg,
}
if imports.ImportPathToAssumedName(path) != pkg.GetTypes().Name() {
imp.name = pkg.GetTypes().Name()
}
candidates := c.packageMembers(pkg.GetTypes(), unimportedScore(relevances[path]), imp)
for _, cand := range candidates {
c.deepState.enqueue(cand)
}
if len(c.items) >= unimportedMemberTarget {
return nil
}
}
ctx, cancel := context.WithCancel(ctx)
var mu sync.Mutex
add := func(pkgExport imports.PackageExport) {
mu.Lock()
defer mu.Unlock()
if _, ok := known[pkgExport.Fix.StmtInfo.ImportPath]; ok {
return // We got this one above.
}
// Continue with untyped proposals.
pkg := types.NewPackage(pkgExport.Fix.StmtInfo.ImportPath, pkgExport.Fix.IdentName)
for _, export := range pkgExport.Exports {
score := unimportedScore(pkgExport.Fix.Relevance)
c.deepState.enqueue(candidate{
obj: types.NewVar(0, pkg, export, nil),
score: score,
imp: &importInfo{
importPath: pkgExport.Fix.StmtInfo.ImportPath,
name: pkgExport.Fix.StmtInfo.Name,
},
})
}
if len(c.items) >= unimportedMemberTarget {
cancel()
}
}
c.completionCallbacks = append(c.completionCallbacks, func(opts *imports.Options) error {
defer cancel()
return imports.GetPackageExports(ctx, add, id.Name, c.filename, c.pkg.GetTypes().Name(), opts.Env)
})
return nil
}
// unimportedScore returns a score for an unimported package that is generally
// lower than other candidates.
func unimportedScore(relevance float64) float64 {
return (stdScore + .1*relevance) / 2
}
func (c *completer) packageMembers(pkg *types.Package, score float64, imp *importInfo) []candidate {
var candidates []candidate
scope := pkg.Scope()
for _, name := range scope.Names() {
obj := scope.Lookup(name)
candidates = append(candidates, candidate{
obj: obj,
score: score,
imp: imp,
addressable: isVar(obj),
})
}
return candidates
}
func (c *completer) methodsAndFields(typ types.Type, addressable bool, imp *importInfo) []candidate {
mset := c.methodSetCache[methodSetKey{typ, addressable}]
if mset == nil {
if addressable && !types.IsInterface(typ) && !isPointer(typ) {
// Add methods of *T, which includes methods with receiver T.
mset = types.NewMethodSet(types.NewPointer(typ))
} else {
// Add methods of T.
mset = types.NewMethodSet(typ)
}
c.methodSetCache[methodSetKey{typ, addressable}] = mset
}
var candidates []candidate
for i := 0; i < mset.Len(); i++ {
candidates = append(candidates, candidate{
obj: mset.At(i).Obj(),
score: stdScore,
imp: imp,
addressable: addressable || isPointer(typ),
})
}
// Add fields of T.
eachField(typ, func(v *types.Var) {
candidates = append(candidates, candidate{
obj: v,
score: stdScore - 0.01,
imp: imp,
addressable: addressable || isPointer(typ),
})
})
return candidates
}
// lexical finds completions in the lexical environment.
func (c *completer) lexical(ctx context.Context) error {
scopes := source.CollectScopes(c.pkg.GetTypesInfo(), c.path, c.pos)
scopes = append(scopes, c.pkg.GetTypes().Scope(), types.Universe)
var (
builtinIota = types.Universe.Lookup("iota")
builtinNil = types.Universe.Lookup("nil")
)
// Track seen variables to avoid showing completions for shadowed variables.
// This works since we look at scopes from innermost to outermost.
seen := make(map[string]struct{})
// Process scopes innermost first.
for i, scope := range scopes {
if scope == nil {
continue
}
Names:
for _, name := range scope.Names() {
declScope, obj := scope.LookupParent(name, c.pos)
if declScope != scope {
continue // Name was declared in some enclosing scope, or not at all.
}
// If obj's type is invalid, find the AST node that defines the lexical block
// containing the declaration of obj. Don't resolve types for packages.
if !isPkgName(obj) && !typeIsValid(obj.Type()) {
// Match the scope to its ast.Node. If the scope is the package scope,
// use the *ast.File as the starting node.
var node ast.Node
if i < len(c.path) {
node = c.path[i]
} else if i == len(c.path) { // use the *ast.File for package scope
node = c.path[i-1]
}
if node != nil {
if resolved := resolveInvalid(c.snapshot.FileSet(), obj, node, c.pkg.GetTypesInfo()); resolved != nil {
obj = resolved
}
}
}
// Don't use LHS of value spec in RHS.
if vs := enclosingValueSpec(c.path); vs != nil {
for _, ident := range vs.Names {
if obj.Pos() == ident.Pos() {
continue Names
}
}
}
// Don't suggest "iota" outside of const decls.
if obj == builtinIota && !c.inConstDecl() {
continue
}
// Rank outer scopes lower than inner.
score := stdScore * math.Pow(.99, float64(i))
// Dowrank "nil" a bit so it is ranked below more interesting candidates.
if obj == builtinNil {
score /= 2
}
// If we haven't already added a candidate for an object with this name.
if _, ok := seen[obj.Name()]; !ok {
seen[obj.Name()] = struct{}{}
c.deepState.enqueue(candidate{
obj: obj,
score: score,
addressable: isVar(obj),
})
}
}
}
if c.inference.objType != nil {
if named, _ := source.Deref(c.inference.objType).(*types.Named); named != nil {
// If we expected a named type, check the type's package for
// completion items. This is useful when the current file hasn't
// imported the type's package yet.
if named.Obj() != nil && named.Obj().Pkg() != nil {
pkg := named.Obj().Pkg()
// Make sure the package name isn't already in use by another
// object, and that this file doesn't import the package yet.
if _, ok := seen[pkg.Name()]; !ok && pkg != c.pkg.GetTypes() && !alreadyImports(c.file, pkg.Path()) {
seen[pkg.Name()] = struct{}{}
obj := types.NewPkgName(0, nil, pkg.Name(), pkg)
imp := &importInfo{
importPath: pkg.Path(),
}
if imports.ImportPathToAssumedName(pkg.Path()) != pkg.Name() {
imp.name = pkg.Name()
}
c.deepState.enqueue(candidate{
obj: obj,
score: stdScore,
imp: imp,
})
}
}
}
}
if c.opts.unimported {
if err := c.unimportedPackages(ctx, seen); err != nil {
return err
}
}
if t := c.inference.objType; t != nil {
t = source.Deref(t)
// If we have an expected type and it is _not_ a named type,
// handle it specially. Non-named types like "[]int" will never be
// considered via a lexical search, so we need to directly inject
// them.
if _, named := t.(*types.Named); !named {
// If our expected type is "[]int", this will add a literal
// candidate of "[]int{}".
c.literal(ctx, t, nil)
if _, isBasic := t.(*types.Basic); !isBasic {
// If we expect a non-basic type name (e.g. "[]int"), hack up
// a named type whose name is literally "[]int". This allows
// us to reuse our object based completion machinery.
fakeNamedType := candidate{
obj: types.NewTypeName(token.NoPos, nil, types.TypeString(t, c.qf), t),
score: stdScore,
}
// Make sure the type name matches before considering
// candidate. This cuts down on useless candidates.
if c.matchingTypeName(&fakeNamedType) {
c.deepState.enqueue(fakeNamedType)
}
}
}
}
// Add keyword completion items appropriate in the current context.
c.addKeywordCompletions()
return nil
}
func (c *completer) unimportedPackages(ctx context.Context, seen map[string]struct{}) error {
var prefix string
if c.surrounding != nil {
prefix = c.surrounding.Prefix()
}
count := 0
known, err := c.snapshot.CachedImportPaths(ctx)
if err != nil {
return err
}
var paths []string
for path, pkg := range known {
if !strings.HasPrefix(pkg.GetTypes().Name(), prefix) {
continue
}
paths = append(paths, path)
}
var relevances map[string]float64
if len(paths) != 0 {
if err := c.snapshot.RunProcessEnvFunc(ctx, func(opts *imports.Options) error {
var err error
relevances, err = imports.ScoreImportPaths(ctx, opts.Env, paths)
return err
}); err != nil {
return err
}
}
sort.Slice(paths, func(i, j int) bool {
return relevances[paths[i]] > relevances[paths[j]]
})
for _, path := range paths {
pkg := known[path]
if _, ok := seen[pkg.GetTypes().Name()]; ok {
continue
}
imp := &importInfo{
importPath: path,
pkg: pkg,
}
if imports.ImportPathToAssumedName(path) != pkg.GetTypes().Name() {
imp.name = pkg.GetTypes().Name()
}
if count >= maxUnimportedPackageNames {
return nil
}
c.deepState.enqueue(candidate{
obj: types.NewPkgName(0, nil, pkg.GetTypes().Name(), pkg.GetTypes()),
score: unimportedScore(relevances[path]),
imp: imp,
})
count++
}
ctx, cancel := context.WithCancel(ctx)
var mu sync.Mutex
add := func(pkg imports.ImportFix) {
mu.Lock()
defer mu.Unlock()
if _, ok := seen[pkg.IdentName]; ok {
return
}
if _, ok := relevances[pkg.StmtInfo.ImportPath]; ok {
return
}
if count >= maxUnimportedPackageNames {
cancel()
return
}
// Do not add the unimported packages to seen, since we can have
// multiple packages of the same name as completion suggestions, since
// only one will be chosen.
obj := types.NewPkgName(0, nil, pkg.IdentName, types.NewPackage(pkg.StmtInfo.ImportPath, pkg.IdentName))
c.deepState.enqueue(candidate{
obj: obj,
score: unimportedScore(pkg.Relevance),
imp: &importInfo{
importPath: pkg.StmtInfo.ImportPath,
name: pkg.StmtInfo.Name,
},
})
count++
}
c.completionCallbacks = append(c.completionCallbacks, func(opts *imports.Options) error {
defer cancel()
return imports.GetAllCandidates(ctx, add, prefix, c.filename, c.pkg.GetTypes().Name(), opts.Env)
})
return nil
}
// alreadyImports reports whether f has an import with the specified path.
func alreadyImports(f *ast.File, path string) bool {
for _, s := range f.Imports {
if source.ImportPath(s) == path {
return true
}
}
return false
}
func (c *completer) inConstDecl() bool {
for _, n := range c.path {
if decl, ok := n.(*ast.GenDecl); ok && decl.Tok == token.CONST {
return true
}
}
return false
}
// structLiteralFieldName finds completions for struct field names inside a struct literal.
func (c *completer) structLiteralFieldName(ctx context.Context) error {
clInfo := c.enclosingCompositeLiteral
// Mark fields of the composite literal that have already been set,
// except for the current field.
addedFields := make(map[*types.Var]bool)
for _, el := range clInfo.cl.Elts {
if kvExpr, ok := el.(*ast.KeyValueExpr); ok {
if clInfo.kv == kvExpr {
continue
}
if key, ok := kvExpr.Key.(*ast.Ident); ok {
if used, ok := c.pkg.GetTypesInfo().Uses[key]; ok {
if usedVar, ok := used.(*types.Var); ok {
addedFields[usedVar] = true
}
}
}
}
}
deltaScore := 0.0001
switch t := clInfo.clType.(type) {
case *types.Struct:
for i := 0; i < t.NumFields(); i++ {
field := t.Field(i)
if !addedFields[field] {
c.deepState.enqueue(candidate{
obj: field,
score: highScore - float64(i)*deltaScore,
})
}
}
// Add lexical completions if we aren't certain we are in the key part of a
// key-value pair.
if clInfo.maybeInFieldName {
return c.lexical(ctx)
}
default:
return c.lexical(ctx)
}
return nil
}
func (cl *compLitInfo) isStruct() bool {
_, ok := cl.clType.(*types.Struct)
return ok
}
// enclosingCompositeLiteral returns information about the composite literal enclosing the
// position.
func enclosingCompositeLiteral(path []ast.Node, pos token.Pos, info *types.Info) *compLitInfo {
for _, n := range path {
switch n := n.(type) {
case *ast.CompositeLit:
// The enclosing node will be a composite literal if the user has just
// opened the curly brace (e.g. &x{<>) or the completion request is triggered
// from an already completed composite literal expression (e.g. &x{foo: 1, <>})
//
// The position is not part of the composite literal unless it falls within the
// curly braces (e.g. "foo.Foo<>Struct{}").
if !(n.Lbrace < pos && pos <= n.Rbrace) {
// Keep searching since we may yet be inside a composite literal.
// For example "Foo{B: Ba<>{}}".
break
}
tv, ok := info.Types[n]
if !ok {
return nil
}
clInfo := compLitInfo{
cl: n,
clType: source.Deref(tv.Type).Underlying(),
}
var (
expr ast.Expr
hasKeys bool
)
for _, el := range n.Elts {
// Remember the expression that the position falls in, if any.
if el.Pos() <= pos && pos <= el.End() {
expr = el
}
if kv, ok := el.(*ast.KeyValueExpr); ok {
hasKeys = true
// If expr == el then we know the position falls in this expression,
// so also record kv as the enclosing *ast.KeyValueExpr.
if expr == el {
clInfo.kv = kv
break
}
}
}
if clInfo.kv != nil {
// If in a *ast.KeyValueExpr, we know we are in the key if the position
// is to the left of the colon (e.g. "Foo{F<>: V}".
clInfo.inKey = pos <= clInfo.kv.Colon
} else if hasKeys {
// If we aren't in a *ast.KeyValueExpr but the composite literal has
// other *ast.KeyValueExprs, we must be on the key side of a new
// *ast.KeyValueExpr (e.g. "Foo{F: V, <>}").
clInfo.inKey = true
} else {
switch clInfo.clType.(type) {
case *types.Struct:
if len(n.Elts) == 0 {
// If the struct literal is empty, next could be a struct field
// name or an expression (e.g. "Foo{<>}" could become "Foo{F:}"
// or "Foo{someVar}").
clInfo.maybeInFieldName = true
} else if len(n.Elts) == 1 {
// If there is one expression and the position is in that expression
// and the expression is an identifier, we may be writing a field
// name or an expression (e.g. "Foo{F<>}").
_, clInfo.maybeInFieldName = expr.(*ast.Ident)
}
case *types.Map:
// If we aren't in a *ast.KeyValueExpr we must be adding a new key
// to the map.
clInfo.inKey = true
}
}
return &clInfo
default:
if breaksExpectedTypeInference(n, pos) {
return nil
}
}
}
return nil
}
// enclosingFunction returns the signature and body of the function
// enclosing the given position.
func enclosingFunction(path []ast.Node, info *types.Info) *funcInfo {
for _, node := range path {
switch t := node.(type) {
case *ast.FuncDecl:
if obj, ok := info.Defs[t.Name]; ok {
return &funcInfo{
sig: obj.Type().(*types.Signature),
body: t.Body,
}
}
case *ast.FuncLit:
if typ, ok := info.Types[t]; ok {
return &funcInfo{
sig: typ.Type.(*types.Signature),
body: t.Body,
}
}
}
}
return nil
}
func (c *completer) expectedCompositeLiteralType() types.Type {
clInfo := c.enclosingCompositeLiteral
switch t := clInfo.clType.(type) {
case *types.Slice:
if clInfo.inKey {
return types.Typ[types.Int]
}
return t.Elem()
case *types.Array:
if clInfo.inKey {
return types.Typ[types.Int]
}
return t.Elem()
case *types.Map:
if clInfo.inKey {
return t.Key()
}
return t.Elem()
case *types.Struct:
// If we are completing a key (i.e. field name), there is no expected type.
if clInfo.inKey {
return nil
}
// If we are in a key-value pair, but not in the key, then we must be on the
// value side. The expected type of the value will be determined from the key.
if clInfo.kv != nil {
if key, ok := clInfo.kv.Key.(*ast.Ident); ok {
for i := 0; i < t.NumFields(); i++ {
if field := t.Field(i); field.Name() == key.Name {
return field.Type()
}
}
}
} else {
// If we aren't in a key-value pair and aren't in the key, we must be using
// implicit field names.
// The order of the literal fields must match the order in the struct definition.
// Find the element that the position belongs to and suggest that field's type.
if i := exprAtPos(c.pos, clInfo.cl.Elts); i < t.NumFields() {
return t.Field(i).Type()
}
}
}
return nil
}
// typeModifier represents an operator that changes the expected type.
type typeModifier struct {
mod typeMod
arrayLen int64
}
type typeMod int
const (
dereference typeMod = iota // pointer indirection: "*"
reference // adds level of pointer: "&" for values, "*" for type names
chanRead // channel read operator ("<-")
slice // make a slice type ("[]" in "[]int")
array // make an array type ("[2]" in "[2]int")
)
type objKind int
const (
kindAny objKind = 0
kindArray objKind = 1 << iota
kindSlice
kindChan
kindMap
kindStruct
kindString
kindInt
kindBool
kindBytes
kindPtr
kindFloat
kindComplex
kindError
kindStringer
kindFunc
)
// penalizedObj represents an object that should be disfavored as a
// completion candidate.
type penalizedObj struct {
// objChain is the full "chain", e.g. "foo.bar().baz" becomes
// []types.Object{foo, bar, baz}.
objChain []types.Object
// penalty is score penalty in the range (0, 1).
penalty float64
}
// candidateInference holds information we have inferred about a type that can be
// used at the current position.
type candidateInference struct {
// objType is the desired type of an object used at the query position.
objType types.Type
// objKind is a mask of expected kinds of types such as "map", "slice", etc.
objKind objKind
// variadic is true if we are completing the initial variadic
// parameter. For example:
// append([]T{}, <>) // objType=T variadic=true
// append([]T{}, T{}, <>) // objType=T variadic=false
variadic bool
// modifiers are prefixes such as "*", "&" or "<-" that influence how
// a candidate type relates to the expected type.
modifiers []typeModifier
// convertibleTo is a type our candidate type must be convertible to.
convertibleTo types.Type
// typeName holds information about the expected type name at
// position, if any.
typeName typeNameInference
// assignees are the types that would receive a function call's
// results at the position. For example:
//
// foo := 123
// foo, bar := <>
//
// at "<>", the assignees are [int, <invalid>].
assignees []types.Type
// variadicAssignees is true if we could be completing an inner
// function call that fills out an outer function call's variadic
// params. For example:
//
// func foo(int, ...string) {}
//
// foo(<>) // variadicAssignees=true
// foo(bar<>) // variadicAssignees=true
// foo(bar, baz<>) // variadicAssignees=false
variadicAssignees bool
// penalized holds expressions that should be disfavored as
// candidates. For example, it tracks expressions already used in a
// switch statement's other cases. Each expression is tracked using
// its entire object "chain" allowing differentiation between
// "a.foo" and "b.foo" when "a" and "b" are the same type.
penalized []penalizedObj
// objChain contains the chain of objects representing the
// surrounding *ast.SelectorExpr. For example, if we are completing
// "foo.bar.ba<>", objChain will contain []types.Object{foo, bar}.
objChain []types.Object
}
// typeNameInference holds information about the expected type name at
// position.
type typeNameInference struct {
// wantTypeName is true if we expect the name of a type.
wantTypeName bool
// modifiers are prefixes such as "*", "&" or "<-" that influence how
// a candidate type relates to the expected type.
modifiers []typeModifier
// assertableFrom is a type that must be assertable to our candidate type.
assertableFrom types.Type
// wantComparable is true if we want a comparable type.
wantComparable bool
// seenTypeSwitchCases tracks types that have already been used by
// the containing type switch.
seenTypeSwitchCases []types.Type
// compLitType is true if we are completing a composite literal type
// name, e.g "foo<>{}".
compLitType bool
}
// expectedCandidate returns information about the expected candidate
// for an expression at the query position.
func expectedCandidate(ctx context.Context, c *completer) (inf candidateInference) {
inf.typeName = expectTypeName(c)
if c.enclosingCompositeLiteral != nil {
inf.objType = c.expectedCompositeLiteralType()
}
Nodes:
for i, node := range c.path {
switch node := node.(type) {
case *ast.BinaryExpr:
// Determine if query position comes from left or right of op.
e := node.X
if c.pos < node.OpPos {
e = node.Y
}
if tv, ok := c.pkg.GetTypesInfo().Types[e]; ok {
switch node.Op {
case token.LAND, token.LOR:
// Don't infer "bool" type for "&&" or "||". Often you want
// to compose a boolean expression from non-boolean
// candidates.
default:
inf.objType = tv.Type
}
break Nodes
}
case *ast.AssignStmt:
// Only rank completions if you are on the right side of the token.
if c.pos > node.TokPos {
i := exprAtPos(c.pos, node.Rhs)
if i >= len(node.Lhs) {
i = len(node.Lhs) - 1
}
if tv, ok := c.pkg.GetTypesInfo().Types[node.Lhs[i]]; ok {
inf.objType = tv.Type
}
// If we have a single expression on the RHS, record the LHS
// assignees so we can favor multi-return function calls with
// matching result values.
if len(node.Rhs) <= 1 {
for _, lhs := range node.Lhs {
inf.assignees = append(inf.assignees, c.pkg.GetTypesInfo().TypeOf(lhs))
}
} else {
// Otherwse, record our single assignee, even if its type is
// not available. We use this info to downrank functions
// with the wrong number of result values.
inf.assignees = append(inf.assignees, c.pkg.GetTypesInfo().TypeOf(node.Lhs[i]))
}
}
return inf
case *ast.ValueSpec:
if node.Type != nil && c.pos > node.Type.End() {
inf.objType = c.pkg.GetTypesInfo().TypeOf(node.Type)
}
return inf
case *ast.CallExpr:
// Only consider CallExpr args if position falls between parens.
if node.Lparen < c.pos && c.pos <= node.Rparen {
// For type conversions like "int64(foo)" we can only infer our
// desired type is convertible to int64.
if typ := typeConversion(node, c.pkg.GetTypesInfo()); typ != nil {
inf.convertibleTo = typ
break Nodes
}
if tv, ok := c.pkg.GetTypesInfo().Types[node.Fun]; ok {
if sig, ok := tv.Type.(*types.Signature); ok {
numParams := sig.Params().Len()
if numParams == 0 {
return inf
}
exprIdx := exprAtPos(c.pos, node.Args)
// If we have one or zero arg expressions, we may be
// completing to a function call that returns multiple
// values, in turn getting passed in to the surrounding
// call. Record the assignees so we can favor function
// calls that return matching values.
if len(node.Args) <= 1 && exprIdx == 0 {
for i := 0; i < sig.Params().Len(); i++ {
inf.assignees = append(inf.assignees, sig.Params().At(i).Type())
}
// Record that we may be completing into variadic parameters.
inf.variadicAssignees = sig.Variadic()
}
// Make sure not to run past the end of expected parameters.
if exprIdx >= numParams {
inf.objType = sig.Params().At(numParams - 1).Type()
} else {
inf.objType = sig.Params().At(exprIdx).Type()
}
if sig.Variadic() && exprIdx >= (numParams-1) {
// If we are completing a variadic param, deslice the variadic type.
inf.objType = deslice(inf.objType)
// Record whether we are completing the initial variadic param.
inf.variadic = exprIdx == numParams-1 && len(node.Args) <= numParams
// Check if we can infer object kind from printf verb.
inf.objKind |= printfArgKind(c.pkg.GetTypesInfo(), node, exprIdx)
}
}
}
if funIdent, ok := node.Fun.(*ast.Ident); ok {
obj := c.pkg.GetTypesInfo().ObjectOf(funIdent)
if obj != nil && obj.Parent() == types.Universe {
// Defer call to builtinArgType so we can provide it the
// inferred type from its parent node.
defer func() {
inf = c.builtinArgType(obj, node, inf)
inf.objKind = c.builtinArgKind(ctx, obj, node)
}()
// The expected type of builtin arguments like append() is
// the expected type of the builtin call itself. For
// example:
//
// var foo []int = append(<>)
//
// To find the expected type at <> we "skip" the append()
// node and get the expected type one level up, which is
// []int.
continue Nodes
}
}
return inf
}
case *ast.ReturnStmt:
if c.enclosingFunc != nil {
sig := c.enclosingFunc.sig
// Find signature result that corresponds to our return statement.
if resultIdx := exprAtPos(c.pos, node.Results); resultIdx < len(node.Results) {
if resultIdx < sig.Results().Len() {
inf.objType = sig.Results().At(resultIdx).Type()
}
}
}
return inf
case *ast.CaseClause:
if swtch, ok := findSwitchStmt(c.path[i+1:], c.pos, node).(*ast.SwitchStmt); ok {
if tv, ok := c.pkg.GetTypesInfo().Types[swtch.Tag]; ok {
inf.objType = tv.Type
// Record which objects have already been used in the case
// statements so we don't suggest them again.
for _, cc := range swtch.Body.List {
for _, caseExpr := range cc.(*ast.CaseClause).List {
// Don't record the expression we are currently completing.
if caseExpr.Pos() < c.pos && c.pos <= caseExpr.End() {
continue
}
if objs := objChain(c.pkg.GetTypesInfo(), caseExpr); len(objs) > 0 {
inf.penalized = append(inf.penalized, penalizedObj{objChain: objs, penalty: 0.1})
}
}
}
}
}
return inf
case *ast.SliceExpr:
// Make sure position falls within the brackets (e.g. "foo[a:<>]").
if node.Lbrack < c.pos && c.pos <= node.Rbrack {
inf.objType = types.Typ[types.Int]
}
return inf
case *ast.IndexExpr:
// Make sure position falls within the brackets (e.g. "foo[<>]").
if node.Lbrack < c.pos && c.pos <= node.Rbrack {
if tv, ok := c.pkg.GetTypesInfo().Types[node.X]; ok {
switch t := tv.Type.Underlying().(type) {
case *types.Map:
inf.objType = t.Key()
case *types.Slice, *types.Array:
inf.objType = types.Typ[types.Int]
}
}
}
return inf
case *ast.SendStmt:
// Make sure we are on right side of arrow (e.g. "foo <- <>").
if c.pos > node.Arrow+1 {
if tv, ok := c.pkg.GetTypesInfo().Types[node.Chan]; ok {
if ch, ok := tv.Type.Underlying().(*types.Chan); ok {
inf.objType = ch.Elem()
}
}
}
return inf
case *ast.RangeStmt:
if source.NodeContains(node.X, c.pos) {
inf.objKind |= kindSlice | kindArray | kindMap | kindString
if node.Value == nil {
inf.objKind |= kindChan
}
}
return inf
case *ast.StarExpr:
inf.modifiers = append(inf.modifiers, typeModifier{mod: dereference})
case *ast.UnaryExpr:
switch node.Op {
case token.AND:
inf.modifiers = append(inf.modifiers, typeModifier{mod: reference})
case token.ARROW:
inf.modifiers = append(inf.modifiers, typeModifier{mod: chanRead})
}
case *ast.DeferStmt, *ast.GoStmt:
inf.objKind |= kindFunc
return inf
default:
if breaksExpectedTypeInference(node, c.pos) {
return inf
}
}
}
return inf
}
// objChain decomposes e into a chain of objects if possible. For
// example, "foo.bar().baz" will yield []types.Object{foo, bar, baz}.
// If any part can't be turned into an object, return nil.
func objChain(info *types.Info, e ast.Expr) []types.Object {
var objs []types.Object
for e != nil {
switch n := e.(type) {
case *ast.Ident:
obj := info.ObjectOf(n)
if obj == nil {
return nil
}
objs = append(objs, obj)
e = nil
case *ast.SelectorExpr:
obj := info.ObjectOf(n.Sel)
if obj == nil {
return nil
}
objs = append(objs, obj)
e = n.X
case *ast.CallExpr:
if len(n.Args) > 0 {
return nil
}
e = n.Fun
default:
return nil
}
}
// Reverse order so the layout matches the syntactic order.
for i := 0; i < len(objs)/2; i++ {
objs[i], objs[len(objs)-1-i] = objs[len(objs)-1-i], objs[i]
}
return objs
}
// applyTypeModifiers applies the list of type modifiers to a type.
// It returns nil if the modifiers could not be applied.
func (ci candidateInference) applyTypeModifiers(typ types.Type, addressable bool) types.Type {
for _, mod := range ci.modifiers {
switch mod.mod {
case dereference:
// For every "*" indirection operator, remove a pointer layer
// from candidate type.
if ptr, ok := typ.Underlying().(*types.Pointer); ok {
typ = ptr.Elem()
} else {
return nil
}
case reference:
// For every "&" address operator, add another pointer layer to
// candidate type, if the candidate is addressable.
if addressable {
typ = types.NewPointer(typ)
} else {
return nil
}
case chanRead:
// For every "<-" operator, remove a layer of channelness.
if ch, ok := typ.(*types.Chan); ok {
typ = ch.Elem()
} else {
return nil
}
}
}
return typ
}
// applyTypeNameModifiers applies the list of type modifiers to a type name.
func (ci candidateInference) applyTypeNameModifiers(typ types.Type) types.Type {
for _, mod := range ci.typeName.modifiers {
switch mod.mod {
case reference:
typ = types.NewPointer(typ)
case array:
typ = types.NewArray(typ, mod.arrayLen)
case slice:
typ = types.NewSlice(typ)
}
}
return typ
}
// matchesVariadic returns true if we are completing a variadic
// parameter and candType is a compatible slice type.
func (ci candidateInference) matchesVariadic(candType types.Type) bool {
return ci.variadic && ci.objType != nil && types.AssignableTo(candType, types.NewSlice(ci.objType))
}
// findSwitchStmt returns an *ast.CaseClause's corresponding *ast.SwitchStmt or
// *ast.TypeSwitchStmt. path should start from the case clause's first ancestor.
func findSwitchStmt(path []ast.Node, pos token.Pos, c *ast.CaseClause) ast.Stmt {
// Make sure position falls within a "case <>:" clause.
if exprAtPos(pos, c.List) >= len(c.List) {
return nil
}
// A case clause is always nested within a block statement in a switch statement.
if len(path) < 2 {
return nil
}
if _, ok := path[0].(*ast.BlockStmt); !ok {
return nil
}
switch s := path[1].(type) {
case *ast.SwitchStmt:
return s
case *ast.TypeSwitchStmt:
return s
default:
return nil
}
}
// breaksExpectedTypeInference reports if an expression node's type is unrelated
// to its child expression node types. For example, "Foo{Bar: x.Baz(<>)}" should
// expect a function argument, not a composite literal value.
func breaksExpectedTypeInference(n ast.Node, pos token.Pos) bool {
switch n := n.(type) {
case *ast.CompositeLit:
// Doesn't break inference if pos is in type name.
// For example: "Foo<>{Bar: 123}"
return !source.NodeContains(n.Type, pos)
case *ast.CallExpr:
// Doesn't break inference if pos is in func name.
// For example: "Foo<>(123)"
return !source.NodeContains(n.Fun, pos)
case *ast.FuncLit, *ast.IndexExpr, *ast.SliceExpr:
return true
default:
return false
}
}
// expectTypeName returns information about the expected type name at position.
func expectTypeName(c *completer) typeNameInference {
var inf typeNameInference
Nodes:
for i, p := range c.path {
switch n := p.(type) {
case *ast.FieldList:
// Expect a type name if pos is in a FieldList. This applies to
// FuncType params/results, FuncDecl receiver, StructType, and
// InterfaceType. We don't need to worry about the field name
// because completion bails out early if pos is in an *ast.Ident
// that defines an object.
inf.wantTypeName = true
break Nodes
case *ast.CaseClause:
// Expect type names in type switch case clauses.
if swtch, ok := findSwitchStmt(c.path[i+1:], c.pos, n).(*ast.TypeSwitchStmt); ok {
// The case clause types must be assertable from the type switch parameter.
ast.Inspect(swtch.Assign, func(n ast.Node) bool {
if ta, ok := n.(*ast.TypeAssertExpr); ok {
inf.assertableFrom = c.pkg.GetTypesInfo().TypeOf(ta.X)
return false
}
return true
})
inf.wantTypeName = true
// Track the types that have already been used in this
// switch's case statements so we don't recommend them.
for _, e := range swtch.Body.List {
for _, typeExpr := range e.(*ast.CaseClause).List {
// Skip if type expression contains pos. We don't want to
// count it as already used if the user is completing it.
if typeExpr.Pos() < c.pos && c.pos <= typeExpr.End() {
continue
}
if t := c.pkg.GetTypesInfo().TypeOf(typeExpr); t != nil {
inf.seenTypeSwitchCases = append(inf.seenTypeSwitchCases, t)
}
}
}
break Nodes
}
return typeNameInference{}
case *ast.TypeAssertExpr:
// Expect type names in type assert expressions.
if n.Lparen < c.pos && c.pos <= n.Rparen {
// The type in parens must be assertable from the expression type.
inf.assertableFrom = c.pkg.GetTypesInfo().TypeOf(n.X)
inf.wantTypeName = true
break Nodes
}
return typeNameInference{}
case *ast.StarExpr:
inf.modifiers = append(inf.modifiers, typeModifier{mod: reference})
case *ast.CompositeLit:
// We want a type name if position is in the "Type" part of a
// composite literal (e.g. "Foo<>{}").
if n.Type != nil && n.Type.Pos() <= c.pos && c.pos <= n.Type.End() {
inf.wantTypeName = true
inf.compLitType = true
if i < len(c.path)-1 {
// Track preceding "&" operator. Technically it applies to
// the composite literal and not the type name, but if
// affects our type completion nonetheless.
if u, ok := c.path[i+1].(*ast.UnaryExpr); ok && u.Op == token.AND {
inf.modifiers = append(inf.modifiers, typeModifier{mod: reference})
}
}
}
break Nodes
case *ast.ArrayType:
// If we are inside the "Elt" part of an array type, we want a type name.
if n.Elt.Pos() <= c.pos && c.pos <= n.Elt.End() {
inf.wantTypeName = true
if n.Len == nil {
// No "Len" expression means a slice type.
inf.modifiers = append(inf.modifiers, typeModifier{mod: slice})
} else {
// Try to get the array type using the constant value of "Len".
tv, ok := c.pkg.GetTypesInfo().Types[n.Len]
if ok && tv.Value != nil && tv.Value.Kind() == constant.Int {
if arrayLen, ok := constant.Int64Val(tv.Value); ok {
inf.modifiers = append(inf.modifiers, typeModifier{mod: array, arrayLen: arrayLen})
}
}
}
// ArrayTypes can be nested, so keep going if our parent is an
// ArrayType.
if i < len(c.path)-1 {
if _, ok := c.path[i+1].(*ast.ArrayType); ok {
continue Nodes
}
}
break Nodes
}
case *ast.MapType:
inf.wantTypeName = true
if n.Key != nil {
inf.wantComparable = source.NodeContains(n.Key, c.pos)
} else {
// If the key is empty, assume we are completing the key if
// pos is directly after the "map[".
inf.wantComparable = c.pos == n.Pos()+token.Pos(len("map["))
}
break Nodes
case *ast.ValueSpec:
inf.wantTypeName = source.NodeContains(n.Type, c.pos)
break Nodes
case *ast.TypeSpec:
inf.wantTypeName = source.NodeContains(n.Type, c.pos)
default:
if breaksExpectedTypeInference(p, c.pos) {
return typeNameInference{}
}
}
}
return inf
}
func (c *completer) fakeObj(T types.Type) *types.Var {
return types.NewVar(token.NoPos, c.pkg.GetTypes(), "", T)
}
// anyCandType reports whether f returns true for any candidate type
// derivable from c. For example, from "foo" we might derive "&foo",
// and "foo()".
func (c *candidate) anyCandType(f func(t types.Type, addressable bool) bool) bool {
if c.obj == nil || c.obj.Type() == nil {
return false
}
objType := c.obj.Type()
if f(objType, c.addressable) {
return true
}
// If c is a func type with a single result, offer the result type.
if sig, ok := objType.Underlying().(*types.Signature); ok {
if sig.Results().Len() == 1 && f(sig.Results().At(0).Type(), false) {
// Mark the candidate so we know to append "()" when formatting.
c.expandFuncCall = true
return true
}
}
var (
seenPtrTypes map[types.Type]bool
ptrType = objType
ptrDepth int
)
// Check if dereferencing c would match our type inference. We loop
// since c could have arbitrary levels of pointerness.
for {
ptr, ok := ptrType.Underlying().(*types.Pointer)
if !ok {
break
}
ptrDepth++
// Avoid pointer type cycles.
if seenPtrTypes[ptrType] {
break
}
if _, named := ptrType.(*types.Named); named {
// Lazily allocate "seen" since it isn't used normally.
if seenPtrTypes == nil {
seenPtrTypes = make(map[types.Type]bool)
}
// Track named pointer types we have seen to detect cycles.
seenPtrTypes[ptrType] = true
}
if f(ptr.Elem(), false) {
// Mark the candidate so we know to prepend "*" when formatting.
c.dereference = ptrDepth
return true
}
ptrType = ptr.Elem()
}
// Check if c is addressable and a pointer to c matches our type inference.
if c.addressable && f(types.NewPointer(objType), false) {
// Mark the candidate so we know to prepend "&" when formatting.
c.takeAddress = true
return true
}
return false
}
// matchingCandidate reports whether cand matches our type inferences.
// It mutates cand's score in certain cases.
func (c *completer) matchingCandidate(cand *candidate) bool {
if c.completionContext.commentCompletion {
return false
}
if isTypeName(cand.obj) {
return c.matchingTypeName(cand)
} else if c.wantTypeName() {
// If we want a type, a non-type object never matches.
return false
}
if c.inference.candTypeMatches(cand) {
return true
}
candType := cand.obj.Type()
if candType == nil {
return false
}
if sig, ok := candType.Underlying().(*types.Signature); ok {
if c.inference.assigneesMatch(cand, sig) {
// Invoke the candidate if its results are multi-assignable.
cand.expandFuncCall = true
return true
}
}
// Default to invoking *types.Func candidates. This is so function
// completions in an empty statement (or other cases with no expected type)
// are invoked by default.
cand.expandFuncCall = isFunc(cand.obj)
return false
}
// candTypeMatches reports whether cand makes a good completion
// candidate given the candidate inference. cand's score may be
// mutated to downrank the candidate in certain situations.
func (ci *candidateInference) candTypeMatches(cand *candidate) bool {
var (
expTypes = make([]types.Type, 0, 2)
variadicType types.Type
)
if ci.objType != nil {
expTypes = append(expTypes, ci.objType)
if ci.variadic {
variadicType = types.NewSlice(ci.objType)
expTypes = append(expTypes, variadicType)
}
}
return cand.anyCandType(func(candType types.Type, addressable bool) bool {
// Take into account any type modifiers on the expected type.
candType = ci.applyTypeModifiers(candType, addressable)
if candType == nil {
return false
}
if ci.convertibleTo != nil && types.ConvertibleTo(candType, ci.convertibleTo) {
return true
}
for _, expType := range expTypes {
if isEmptyInterface(expType) {
continue
}
matches, untyped := ci.typeMatches(expType, candType)
if !matches {
continue
}
if expType == variadicType {
cand.variadic = true
}
// Lower candidate score for untyped conversions. This avoids
// ranking untyped constants above candidates with an exact type
// match. Don't lower score of builtin constants, e.g. "true".
if untyped && !types.Identical(candType, expType) && cand.obj.Parent() != types.Universe {
cand.score /= 2
}
return true
}
// If we don't have a specific expected type, fall back to coarser
// object kind checks.
if ci.objType == nil || isEmptyInterface(ci.objType) {
// If we were able to apply type modifiers to our candidate type,
// count that as a match. For example:
//
// var foo chan int
// <-fo<>
//
// We were able to apply the "<-" type modifier to "foo", so "foo"
// matches.
if len(ci.modifiers) > 0 {
return true
}
// If we didn't have an exact type match, check if our object kind
// matches.
if ci.kindMatches(candType) {
if ci.objKind == kindFunc {
cand.expandFuncCall = true
}
return true
}
}
return false
})
}
// typeMatches reports whether an object of candType makes a good
// completion candidate given the expected type expType. It also
// returns a second bool which is true if both types are basic types
// of the same kind, and at least one is untyped.
func (ci *candidateInference) typeMatches(expType, candType types.Type) (bool, bool) {
// Handle untyped values specially since AssignableTo gives false negatives
// for them (see https://golang.org/issue/32146).
if candBasic, ok := candType.Underlying().(*types.Basic); ok {
if wantBasic, ok := expType.Underlying().(*types.Basic); ok {
// Make sure at least one of them is untyped.
if isUntyped(candType) || isUntyped(expType) {
// Check that their constant kind (bool|int|float|complex|string) matches.
// This doesn't take into account the constant value, so there will be some
// false positives due to integer sign and overflow.
if candBasic.Info()&types.IsConstType == wantBasic.Info()&types.IsConstType {
return true, true
}
}
}
}
// AssignableTo covers the case where the types are equal, but also handles
// cases like assigning a concrete type to an interface type.
return types.AssignableTo(candType, expType), false
}
// kindMatches reports whether candType's kind matches our expected
// kind (e.g. slice, map, etc.).
func (ci *candidateInference) kindMatches(candType types.Type) bool {
return ci.objKind > 0 && ci.objKind&candKind(candType) > 0
}
// assigneesMatch reports whether an invocation of sig matches the
// number and type of any assignees.
func (ci *candidateInference) assigneesMatch(cand *candidate, sig *types.Signature) bool {
if len(ci.assignees) == 0 {
return false
}
// Uniresult functions are always usable and are handled by the
// normal, non-assignees type matching logic.
if sig.Results().Len() == 1 {
return false
}
var numberOfResultsCouldMatch bool
if ci.variadicAssignees {
numberOfResultsCouldMatch = sig.Results().Len() >= len(ci.assignees)-1
} else {
numberOfResultsCouldMatch = sig.Results().Len() == len(ci.assignees)
}
// If our signature doesn't return the right number of values, it's
// not a match, so downrank it. For example:
//
// var foo func() (int, int)
// a, b, c := <> // downrank "foo()" since it only returns two values
if !numberOfResultsCouldMatch {
cand.score /= 2
return false
}
// If at least one assignee has a valid type, and all valid
// assignees match the corresponding sig result value, the signature
// is a match.
allMatch := false
for i := 0; i < sig.Results().Len(); i++ {
var assignee types.Type
// If we are completing into variadic parameters, deslice the
// expected variadic type.
if ci.variadicAssignees && i >= len(ci.assignees)-1 {
assignee = ci.assignees[len(ci.assignees)-1]
if elem := deslice(assignee); elem != nil {
assignee = elem
}
} else {
assignee = ci.assignees[i]
}
if assignee == nil {
continue
}
allMatch, _ = ci.typeMatches(assignee, sig.Results().At(i).Type())
if !allMatch {
break
}
}
return allMatch
}
func (c *completer) matchingTypeName(cand *candidate) bool {
if !c.wantTypeName() {
return false
}
typeMatches := func(candType types.Type) bool {
// Take into account any type name modifier prefixes.
candType = c.inference.applyTypeNameModifiers(candType)
if from := c.inference.typeName.assertableFrom; from != nil {
// Don't suggest the starting type in type assertions. For example,
// if "foo" is an io.Writer, don't suggest "foo.(io.Writer)".
if types.Identical(from, candType) {
return false
}
if intf, ok := from.Underlying().(*types.Interface); ok {
if !types.AssertableTo(intf, candType) {
return false
}
}
}
if c.inference.typeName.wantComparable && !types.Comparable(candType) {
return false
}
// Skip this type if it has already been used in another type
// switch case.
for _, seen := range c.inference.typeName.seenTypeSwitchCases {
if types.Identical(candType, seen) {
return false
}
}
// We can expect a type name and have an expected type in cases like:
//
// var foo []int
// foo = []i<>
//
// Where our expected type is "[]int", and we expect a type name.
if c.inference.objType != nil {
return types.AssignableTo(candType, c.inference.objType)
}
// Default to saying any type name is a match.
return true
}
t := cand.obj.Type()
if typeMatches(t) {
return true
}
if !source.IsInterface(t) && typeMatches(types.NewPointer(t)) {
if c.inference.typeName.compLitType {
// If we are completing a composite literal type as in
// "foo<>{}", to make a pointer we must prepend "&".
cand.takeAddress = true
} else {
// If we are completing a normal type name such as "foo<>", to
// make a pointer we must prepend "*".
cand.makePointer = true
}
return true
}
return false
}
var (
// "interface { Error() string }" (i.e. error)
errorIntf = types.Universe.Lookup("error").Type().Underlying().(*types.Interface)
// "interface { String() string }" (i.e. fmt.Stringer)
stringerIntf = types.NewInterfaceType([]*types.Func{
types.NewFunc(token.NoPos, nil, "String", types.NewSignature(
nil,
nil,
types.NewTuple(types.NewParam(token.NoPos, nil, "", types.Typ[types.String])),
false,
)),
}, nil).Complete()
byteType = types.Universe.Lookup("byte").Type()
)
// candKind returns the objKind of candType, if any.
func candKind(candType types.Type) objKind {
var kind objKind
switch t := candType.Underlying().(type) {
case *types.Array:
kind |= kindArray
if t.Elem() == byteType {
kind |= kindBytes
}
case *types.Slice:
kind |= kindSlice
if t.Elem() == byteType {
kind |= kindBytes
}
case *types.Chan:
kind |= kindChan
case *types.Map:
kind |= kindMap
case *types.Pointer:
kind |= kindPtr
// Some builtins handle array pointers as arrays, so just report a pointer
// to an array as an array.
if _, isArray := t.Elem().Underlying().(*types.Array); isArray {
kind |= kindArray
}
case *types.Basic:
switch info := t.Info(); {
case info&types.IsString > 0:
kind |= kindString
case info&types.IsInteger > 0:
kind |= kindInt
case info&types.IsFloat > 0:
kind |= kindFloat
case info&types.IsComplex > 0:
kind |= kindComplex
case info&types.IsBoolean > 0:
kind |= kindBool
}
case *types.Signature:
return kindFunc
}
if types.Implements(candType, errorIntf) {
kind |= kindError
}
if types.Implements(candType, stringerIntf) {
kind |= kindStringer
}
return kind
}