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-rw-r--r--src/go/parser/parser.go2591
1 files changed, 2591 insertions, 0 deletions
diff --git a/src/go/parser/parser.go b/src/go/parser/parser.go
new file mode 100644
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--- /dev/null
+++ b/src/go/parser/parser.go
@@ -0,0 +1,2591 @@
+// Copyright 2009 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 parser implements a parser for Go source files. Input may be
+// provided in a variety of forms (see the various Parse* functions); the
+// output is an abstract syntax tree (AST) representing the Go source. The
+// parser is invoked through one of the Parse* functions.
+//
+// The parser accepts a larger language than is syntactically permitted by
+// the Go spec, for simplicity, and for improved robustness in the presence
+// of syntax errors. For instance, in method declarations, the receiver is
+// treated like an ordinary parameter list and thus may contain multiple
+// entries where the spec permits exactly one. Consequently, the corresponding
+// field in the AST (ast.FuncDecl.Recv) field is not restricted to one entry.
+//
+package parser
+
+import (
+ "fmt"
+ "go/ast"
+ "go/scanner"
+ "go/token"
+ "strconv"
+ "strings"
+ "unicode"
+)
+
+// The parser structure holds the parser's internal state.
+type parser struct {
+ file *token.File
+ errors scanner.ErrorList
+ scanner scanner.Scanner
+
+ // Tracing/debugging
+ mode Mode // parsing mode
+ trace bool // == (mode & Trace != 0)
+ indent int // indentation used for tracing output
+
+ // Comments
+ comments []*ast.CommentGroup
+ leadComment *ast.CommentGroup // last lead comment
+ lineComment *ast.CommentGroup // last line comment
+
+ // Next token
+ pos token.Pos // token position
+ tok token.Token // one token look-ahead
+ lit string // token literal
+
+ // Error recovery
+ // (used to limit the number of calls to parser.advance
+ // w/o making scanning progress - avoids potential endless
+ // loops across multiple parser functions during error recovery)
+ syncPos token.Pos // last synchronization position
+ syncCnt int // number of parser.advance calls without progress
+
+ // Non-syntactic parser control
+ exprLev int // < 0: in control clause, >= 0: in expression
+ inRhs bool // if set, the parser is parsing a rhs expression
+
+ // Ordinary identifier scopes
+ pkgScope *ast.Scope // pkgScope.Outer == nil
+ topScope *ast.Scope // top-most scope; may be pkgScope
+ unresolved []*ast.Ident // unresolved identifiers
+ imports []*ast.ImportSpec // list of imports
+
+ // Label scopes
+ // (maintained by open/close LabelScope)
+ labelScope *ast.Scope // label scope for current function
+ targetStack [][]*ast.Ident // stack of unresolved labels
+}
+
+func (p *parser) init(fset *token.FileSet, filename string, src []byte, mode Mode) {
+ p.file = fset.AddFile(filename, -1, len(src))
+ var m scanner.Mode
+ if mode&ParseComments != 0 {
+ m = scanner.ScanComments
+ }
+ eh := func(pos token.Position, msg string) { p.errors.Add(pos, msg) }
+ p.scanner.Init(p.file, src, eh, m)
+
+ p.mode = mode
+ p.trace = mode&Trace != 0 // for convenience (p.trace is used frequently)
+
+ p.next()
+}
+
+// ----------------------------------------------------------------------------
+// Scoping support
+
+func (p *parser) openScope() {
+ p.topScope = ast.NewScope(p.topScope)
+}
+
+func (p *parser) closeScope() {
+ p.topScope = p.topScope.Outer
+}
+
+func (p *parser) openLabelScope() {
+ p.labelScope = ast.NewScope(p.labelScope)
+ p.targetStack = append(p.targetStack, nil)
+}
+
+func (p *parser) closeLabelScope() {
+ // resolve labels
+ n := len(p.targetStack) - 1
+ scope := p.labelScope
+ for _, ident := range p.targetStack[n] {
+ ident.Obj = scope.Lookup(ident.Name)
+ if ident.Obj == nil && p.mode&DeclarationErrors != 0 {
+ p.error(ident.Pos(), fmt.Sprintf("label %s undefined", ident.Name))
+ }
+ }
+ // pop label scope
+ p.targetStack = p.targetStack[0:n]
+ p.labelScope = p.labelScope.Outer
+}
+
+func (p *parser) declare(decl, data interface{}, scope *ast.Scope, kind ast.ObjKind, idents ...*ast.Ident) {
+ for _, ident := range idents {
+ assert(ident.Obj == nil, "identifier already declared or resolved")
+ obj := ast.NewObj(kind, ident.Name)
+ // remember the corresponding declaration for redeclaration
+ // errors and global variable resolution/typechecking phase
+ obj.Decl = decl
+ obj.Data = data
+ ident.Obj = obj
+ if ident.Name != "_" {
+ if alt := scope.Insert(obj); alt != nil && p.mode&DeclarationErrors != 0 {
+ prevDecl := ""
+ if pos := alt.Pos(); pos.IsValid() {
+ prevDecl = fmt.Sprintf("\n\tprevious declaration at %s", p.file.Position(pos))
+ }
+ p.error(ident.Pos(), fmt.Sprintf("%s redeclared in this block%s", ident.Name, prevDecl))
+ }
+ }
+ }
+}
+
+func (p *parser) shortVarDecl(decl *ast.AssignStmt, list []ast.Expr) {
+ // Go spec: A short variable declaration may redeclare variables
+ // provided they were originally declared in the same block with
+ // the same type, and at least one of the non-blank variables is new.
+ n := 0 // number of new variables
+ for _, x := range list {
+ if ident, isIdent := x.(*ast.Ident); isIdent {
+ assert(ident.Obj == nil, "identifier already declared or resolved")
+ obj := ast.NewObj(ast.Var, ident.Name)
+ // remember corresponding assignment for other tools
+ obj.Decl = decl
+ ident.Obj = obj
+ if ident.Name != "_" {
+ if alt := p.topScope.Insert(obj); alt != nil {
+ ident.Obj = alt // redeclaration
+ } else {
+ n++ // new declaration
+ }
+ }
+ } else {
+ p.errorExpected(x.Pos(), "identifier on left side of :=")
+ }
+ }
+ if n == 0 && p.mode&DeclarationErrors != 0 {
+ p.error(list[0].Pos(), "no new variables on left side of :=")
+ }
+}
+
+// The unresolved object is a sentinel to mark identifiers that have been added
+// to the list of unresolved identifiers. The sentinel is only used for verifying
+// internal consistency.
+var unresolved = new(ast.Object)
+
+// If x is an identifier, tryResolve attempts to resolve x by looking up
+// the object it denotes. If no object is found and collectUnresolved is
+// set, x is marked as unresolved and collected in the list of unresolved
+// identifiers.
+//
+func (p *parser) tryResolve(x ast.Expr, collectUnresolved bool) {
+ // nothing to do if x is not an identifier or the blank identifier
+ ident, _ := x.(*ast.Ident)
+ if ident == nil {
+ return
+ }
+ assert(ident.Obj == nil, "identifier already declared or resolved")
+ if ident.Name == "_" {
+ return
+ }
+ // try to resolve the identifier
+ for s := p.topScope; s != nil; s = s.Outer {
+ if obj := s.Lookup(ident.Name); obj != nil {
+ ident.Obj = obj
+ return
+ }
+ }
+ // all local scopes are known, so any unresolved identifier
+ // must be found either in the file scope, package scope
+ // (perhaps in another file), or universe scope --- collect
+ // them so that they can be resolved later
+ if collectUnresolved {
+ ident.Obj = unresolved
+ p.unresolved = append(p.unresolved, ident)
+ }
+}
+
+func (p *parser) resolve(x ast.Expr) {
+ p.tryResolve(x, true)
+}
+
+// ----------------------------------------------------------------------------
+// Parsing support
+
+func (p *parser) printTrace(a ...interface{}) {
+ const dots = ". . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . "
+ const n = len(dots)
+ pos := p.file.Position(p.pos)
+ fmt.Printf("%5d:%3d: ", pos.Line, pos.Column)
+ i := 2 * p.indent
+ for i > n {
+ fmt.Print(dots)
+ i -= n
+ }
+ // i <= n
+ fmt.Print(dots[0:i])
+ fmt.Println(a...)
+}
+
+func trace(p *parser, msg string) *parser {
+ p.printTrace(msg, "(")
+ p.indent++
+ return p
+}
+
+// Usage pattern: defer un(trace(p, "..."))
+func un(p *parser) {
+ p.indent--
+ p.printTrace(")")
+}
+
+// Advance to the next token.
+func (p *parser) next0() {
+ // Because of one-token look-ahead, print the previous token
+ // when tracing as it provides a more readable output. The
+ // very first token (!p.pos.IsValid()) is not initialized
+ // (it is token.ILLEGAL), so don't print it .
+ if p.trace && p.pos.IsValid() {
+ s := p.tok.String()
+ switch {
+ case p.tok.IsLiteral():
+ p.printTrace(s, p.lit)
+ case p.tok.IsOperator(), p.tok.IsKeyword():
+ p.printTrace("\"" + s + "\"")
+ default:
+ p.printTrace(s)
+ }
+ }
+
+ p.pos, p.tok, p.lit = p.scanner.Scan()
+}
+
+// Consume a comment and return it and the line on which it ends.
+func (p *parser) consumeComment() (comment *ast.Comment, endline int) {
+ // /*-style comments may end on a different line than where they start.
+ // Scan the comment for '\n' chars and adjust endline accordingly.
+ endline = p.file.Line(p.pos)
+ if p.lit[1] == '*' {
+ // don't use range here - no need to decode Unicode code points
+ for i := 0; i < len(p.lit); i++ {
+ if p.lit[i] == '\n' {
+ endline++
+ }
+ }
+ }
+
+ comment = &ast.Comment{Slash: p.pos, Text: p.lit}
+ p.next0()
+
+ return
+}
+
+// Consume a group of adjacent comments, add it to the parser's
+// comments list, and return it together with the line at which
+// the last comment in the group ends. A non-comment token or n
+// empty lines terminate a comment group.
+//
+func (p *parser) consumeCommentGroup(n int) (comments *ast.CommentGroup, endline int) {
+ var list []*ast.Comment
+ endline = p.file.Line(p.pos)
+ for p.tok == token.COMMENT && p.file.Line(p.pos) <= endline+n {
+ var comment *ast.Comment
+ comment, endline = p.consumeComment()
+ list = append(list, comment)
+ }
+
+ // add comment group to the comments list
+ comments = &ast.CommentGroup{List: list}
+ p.comments = append(p.comments, comments)
+
+ return
+}
+
+// Advance to the next non-comment token. In the process, collect
+// any comment groups encountered, and remember the last lead and
+// line comments.
+//
+// A lead comment is a comment group that starts and ends in a
+// line without any other tokens and that is followed by a non-comment
+// token on the line immediately after the comment group.
+//
+// A line comment is a comment group that follows a non-comment
+// token on the same line, and that has no tokens after it on the line
+// where it ends.
+//
+// Lead and line comments may be considered documentation that is
+// stored in the AST.
+//
+func (p *parser) next() {
+ p.leadComment = nil
+ p.lineComment = nil
+ prev := p.pos
+ p.next0()
+
+ if p.tok == token.COMMENT {
+ var comment *ast.CommentGroup
+ var endline int
+
+ if p.file.Line(p.pos) == p.file.Line(prev) {
+ // The comment is on same line as the previous token; it
+ // cannot be a lead comment but may be a line comment.
+ comment, endline = p.consumeCommentGroup(0)
+ if p.file.Line(p.pos) != endline || p.tok == token.EOF {
+ // The next token is on a different line, thus
+ // the last comment group is a line comment.
+ p.lineComment = comment
+ }
+ }
+
+ // consume successor comments, if any
+ endline = -1
+ for p.tok == token.COMMENT {
+ comment, endline = p.consumeCommentGroup(1)
+ }
+
+ if endline+1 == p.file.Line(p.pos) {
+ // The next token is following on the line immediately after the
+ // comment group, thus the last comment group is a lead comment.
+ p.leadComment = comment
+ }
+ }
+}
+
+// A bailout panic is raised to indicate early termination.
+type bailout struct{}
+
+func (p *parser) error(pos token.Pos, msg string) {
+ epos := p.file.Position(pos)
+
+ // If AllErrors is not set, discard errors reported on the same line
+ // as the last recorded error and stop parsing if there are more than
+ // 10 errors.
+ if p.mode&AllErrors == 0 {
+ n := len(p.errors)
+ if n > 0 && p.errors[n-1].Pos.Line == epos.Line {
+ return // discard - likely a spurious error
+ }
+ if n > 10 {
+ panic(bailout{})
+ }
+ }
+
+ p.errors.Add(epos, msg)
+}
+
+func (p *parser) errorExpected(pos token.Pos, msg string) {
+ msg = "expected " + msg
+ if pos == p.pos {
+ // the error happened at the current position;
+ // make the error message more specific
+ switch {
+ case p.tok == token.SEMICOLON && p.lit == "\n":
+ msg += ", found newline"
+ case p.tok.IsLiteral():
+ // print 123 rather than 'INT', etc.
+ msg += ", found " + p.lit
+ default:
+ msg += ", found '" + p.tok.String() + "'"
+ }
+ }
+ p.error(pos, msg)
+}
+
+func (p *parser) expect(tok token.Token) token.Pos {
+ pos := p.pos
+ if p.tok != tok {
+ p.errorExpected(pos, "'"+tok.String()+"'")
+ }
+ p.next() // make progress
+ return pos
+}
+
+// expect2 is like expect, but it returns an invalid position
+// if the expected token is not found.
+func (p *parser) expect2(tok token.Token) (pos token.Pos) {
+ if p.tok == tok {
+ pos = p.pos
+ } else {
+ p.errorExpected(p.pos, "'"+tok.String()+"'")
+ }
+ p.next() // make progress
+ return
+}
+
+// expectClosing is like expect but provides a better error message
+// for the common case of a missing comma before a newline.
+//
+func (p *parser) expectClosing(tok token.Token, context string) token.Pos {
+ if p.tok != tok && p.tok == token.SEMICOLON && p.lit == "\n" {
+ p.error(p.pos, "missing ',' before newline in "+context)
+ p.next()
+ }
+ return p.expect(tok)
+}
+
+func (p *parser) expectSemi() {
+ // semicolon is optional before a closing ')' or '}'
+ if p.tok != token.RPAREN && p.tok != token.RBRACE {
+ switch p.tok {
+ case token.COMMA:
+ // permit a ',' instead of a ';' but complain
+ p.errorExpected(p.pos, "';'")
+ fallthrough
+ case token.SEMICOLON:
+ p.next()
+ default:
+ p.errorExpected(p.pos, "';'")
+ p.advance(stmtStart)
+ }
+ }
+}
+
+func (p *parser) atComma(context string, follow token.Token) bool {
+ if p.tok == token.COMMA {
+ return true
+ }
+ if p.tok != follow {
+ msg := "missing ','"
+ if p.tok == token.SEMICOLON && p.lit == "\n" {
+ msg += " before newline"
+ }
+ p.error(p.pos, msg+" in "+context)
+ return true // "insert" comma and continue
+ }
+ return false
+}
+
+func assert(cond bool, msg string) {
+ if !cond {
+ panic("go/parser internal error: " + msg)
+ }
+}
+
+// advance consumes tokens until the current token p.tok
+// is in the 'to' set, or token.EOF. For error recovery.
+func (p *parser) advance(to map[token.Token]bool) {
+ for ; p.tok != token.EOF; p.next() {
+ if to[p.tok] {
+ // Return only if parser made some progress since last
+ // sync or if it has not reached 10 advance calls without
+ // progress. Otherwise consume at least one token to
+ // avoid an endless parser loop (it is possible that
+ // both parseOperand and parseStmt call advance and
+ // correctly do not advance, thus the need for the
+ // invocation limit p.syncCnt).
+ if p.pos == p.syncPos && p.syncCnt < 10 {
+ p.syncCnt++
+ return
+ }
+ if p.pos > p.syncPos {
+ p.syncPos = p.pos
+ p.syncCnt = 0
+ return
+ }
+ // Reaching here indicates a parser bug, likely an
+ // incorrect token list in this function, but it only
+ // leads to skipping of possibly correct code if a
+ // previous error is present, and thus is preferred
+ // over a non-terminating parse.
+ }
+ }
+}
+
+var stmtStart = map[token.Token]bool{
+ token.BREAK: true,
+ token.CONST: true,
+ token.CONTINUE: true,
+ token.DEFER: true,
+ token.FALLTHROUGH: true,
+ token.FOR: true,
+ token.GO: true,
+ token.GOTO: true,
+ token.IF: true,
+ token.RETURN: true,
+ token.SELECT: true,
+ token.SWITCH: true,
+ token.TYPE: true,
+ token.VAR: true,
+}
+
+var declStart = map[token.Token]bool{
+ token.CONST: true,
+ token.TYPE: true,
+ token.VAR: true,
+}
+
+var exprEnd = map[token.Token]bool{
+ token.COMMA: true,
+ token.COLON: true,
+ token.SEMICOLON: true,
+ token.RPAREN: true,
+ token.RBRACK: true,
+ token.RBRACE: true,
+}
+
+// safePos returns a valid file position for a given position: If pos
+// is valid to begin with, safePos returns pos. If pos is out-of-range,
+// safePos returns the EOF position.
+//
+// This is hack to work around "artificial" end positions in the AST which
+// are computed by adding 1 to (presumably valid) token positions. If the
+// token positions are invalid due to parse errors, the resulting end position
+// may be past the file's EOF position, which would lead to panics if used
+// later on.
+//
+func (p *parser) safePos(pos token.Pos) (res token.Pos) {
+ defer func() {
+ if recover() != nil {
+ res = token.Pos(p.file.Base() + p.file.Size()) // EOF position
+ }
+ }()
+ _ = p.file.Offset(pos) // trigger a panic if position is out-of-range
+ return pos
+}
+
+// ----------------------------------------------------------------------------
+// Identifiers
+
+func (p *parser) parseIdent() *ast.Ident {
+ pos := p.pos
+ name := "_"
+ if p.tok == token.IDENT {
+ name = p.lit
+ p.next()
+ } else {
+ p.expect(token.IDENT) // use expect() error handling
+ }
+ return &ast.Ident{NamePos: pos, Name: name}
+}
+
+func (p *parser) parseIdentList() (list []*ast.Ident) {
+ if p.trace {
+ defer un(trace(p, "IdentList"))
+ }
+
+ list = append(list, p.parseIdent())
+ for p.tok == token.COMMA {
+ p.next()
+ list = append(list, p.parseIdent())
+ }
+
+ return
+}
+
+// ----------------------------------------------------------------------------
+// Common productions
+
+// If lhs is set, result list elements which are identifiers are not resolved.
+func (p *parser) parseExprList(lhs bool) (list []ast.Expr) {
+ if p.trace {
+ defer un(trace(p, "ExpressionList"))
+ }
+
+ list = append(list, p.checkExpr(p.parseExpr(lhs)))
+ for p.tok == token.COMMA {
+ p.next()
+ list = append(list, p.checkExpr(p.parseExpr(lhs)))
+ }
+
+ return
+}
+
+func (p *parser) parseLhsList() []ast.Expr {
+ old := p.inRhs
+ p.inRhs = false
+ list := p.parseExprList(true)
+ switch p.tok {
+ case token.DEFINE:
+ // lhs of a short variable declaration
+ // but doesn't enter scope until later:
+ // caller must call p.shortVarDecl(p.makeIdentList(list))
+ // at appropriate time.
+ case token.COLON:
+ // lhs of a label declaration or a communication clause of a select
+ // statement (parseLhsList is not called when parsing the case clause
+ // of a switch statement):
+ // - labels are declared by the caller of parseLhsList
+ // - for communication clauses, if there is a stand-alone identifier
+ // followed by a colon, we have a syntax error; there is no need
+ // to resolve the identifier in that case
+ default:
+ // identifiers must be declared elsewhere
+ for _, x := range list {
+ p.resolve(x)
+ }
+ }
+ p.inRhs = old
+ return list
+}
+
+func (p *parser) parseRhsList() []ast.Expr {
+ old := p.inRhs
+ p.inRhs = true
+ list := p.parseExprList(false)
+ p.inRhs = old
+ return list
+}
+
+// ----------------------------------------------------------------------------
+// Types
+
+func (p *parser) parseType() ast.Expr {
+ if p.trace {
+ defer un(trace(p, "Type"))
+ }
+
+ typ := p.tryType()
+
+ if typ == nil {
+ pos := p.pos
+ p.errorExpected(pos, "type")
+ p.advance(exprEnd)
+ return &ast.BadExpr{From: pos, To: p.pos}
+ }
+
+ return typ
+}
+
+// If the result is an identifier, it is not resolved.
+func (p *parser) parseTypeName() ast.Expr {
+ if p.trace {
+ defer un(trace(p, "TypeName"))
+ }
+
+ ident := p.parseIdent()
+ // don't resolve ident yet - it may be a parameter or field name
+
+ if p.tok == token.PERIOD {
+ // ident is a package name
+ p.next()
+ p.resolve(ident)
+ sel := p.parseIdent()
+ return &ast.SelectorExpr{X: ident, Sel: sel}
+ }
+
+ return ident
+}
+
+func (p *parser) parseArrayType() ast.Expr {
+ if p.trace {
+ defer un(trace(p, "ArrayType"))
+ }
+
+ lbrack := p.expect(token.LBRACK)
+ p.exprLev++
+ var len ast.Expr
+ // always permit ellipsis for more fault-tolerant parsing
+ if p.tok == token.ELLIPSIS {
+ len = &ast.Ellipsis{Ellipsis: p.pos}
+ p.next()
+ } else if p.tok != token.RBRACK {
+ len = p.parseRhs()
+ }
+ p.exprLev--
+ p.expect(token.RBRACK)
+ elt := p.parseType()
+
+ return &ast.ArrayType{Lbrack: lbrack, Len: len, Elt: elt}
+}
+
+func (p *parser) makeIdentList(list []ast.Expr) []*ast.Ident {
+ idents := make([]*ast.Ident, len(list))
+ for i, x := range list {
+ ident, isIdent := x.(*ast.Ident)
+ if !isIdent {
+ if _, isBad := x.(*ast.BadExpr); !isBad {
+ // only report error if it's a new one
+ p.errorExpected(x.Pos(), "identifier")
+ }
+ ident = &ast.Ident{NamePos: x.Pos(), Name: "_"}
+ }
+ idents[i] = ident
+ }
+ return idents
+}
+
+func (p *parser) parseFieldDecl(scope *ast.Scope) *ast.Field {
+ if p.trace {
+ defer un(trace(p, "FieldDecl"))
+ }
+
+ doc := p.leadComment
+
+ // 1st FieldDecl
+ // A type name used as an anonymous field looks like a field identifier.
+ var list []ast.Expr
+ for {
+ list = append(list, p.parseVarType(false))
+ if p.tok != token.COMMA {
+ break
+ }
+ p.next()
+ }
+
+ typ := p.tryVarType(false)
+
+ // analyze case
+ var idents []*ast.Ident
+ if typ != nil {
+ // IdentifierList Type
+ idents = p.makeIdentList(list)
+ } else {
+ // ["*"] TypeName (AnonymousField)
+ typ = list[0] // we always have at least one element
+ if n := len(list); n > 1 {
+ p.errorExpected(p.pos, "type")
+ typ = &ast.BadExpr{From: p.pos, To: p.pos}
+ } else if !isTypeName(deref(typ)) {
+ p.errorExpected(typ.Pos(), "anonymous field")
+ typ = &ast.BadExpr{From: typ.Pos(), To: p.safePos(typ.End())}
+ }
+ }
+
+ // Tag
+ var tag *ast.BasicLit
+ if p.tok == token.STRING {
+ tag = &ast.BasicLit{ValuePos: p.pos, Kind: p.tok, Value: p.lit}
+ p.next()
+ }
+
+ p.expectSemi() // call before accessing p.linecomment
+
+ field := &ast.Field{Doc: doc, Names: idents, Type: typ, Tag: tag, Comment: p.lineComment}
+ p.declare(field, nil, scope, ast.Var, idents...)
+ p.resolve(typ)
+
+ return field
+}
+
+func (p *parser) parseStructType() *ast.StructType {
+ if p.trace {
+ defer un(trace(p, "StructType"))
+ }
+
+ pos := p.expect(token.STRUCT)
+ lbrace := p.expect(token.LBRACE)
+ scope := ast.NewScope(nil) // struct scope
+ var list []*ast.Field
+ for p.tok == token.IDENT || p.tok == token.MUL || p.tok == token.LPAREN {
+ // a field declaration cannot start with a '(' but we accept
+ // it here for more robust parsing and better error messages
+ // (parseFieldDecl will check and complain if necessary)
+ list = append(list, p.parseFieldDecl(scope))
+ }
+ rbrace := p.expect(token.RBRACE)
+
+ return &ast.StructType{
+ Struct: pos,
+ Fields: &ast.FieldList{
+ Opening: lbrace,
+ List: list,
+ Closing: rbrace,
+ },
+ }
+}
+
+func (p *parser) parsePointerType() *ast.StarExpr {
+ if p.trace {
+ defer un(trace(p, "PointerType"))
+ }
+
+ star := p.expect(token.MUL)
+ base := p.parseType()
+
+ return &ast.StarExpr{Star: star, X: base}
+}
+
+// If the result is an identifier, it is not resolved.
+func (p *parser) tryVarType(isParam bool) ast.Expr {
+ if isParam && p.tok == token.ELLIPSIS {
+ pos := p.pos
+ p.next()
+ typ := p.tryIdentOrType() // don't use parseType so we can provide better error message
+ if typ != nil {
+ p.resolve(typ)
+ } else {
+ p.error(pos, "'...' parameter is missing type")
+ typ = &ast.BadExpr{From: pos, To: p.pos}
+ }
+ return &ast.Ellipsis{Ellipsis: pos, Elt: typ}
+ }
+ return p.tryIdentOrType()
+}
+
+// If the result is an identifier, it is not resolved.
+func (p *parser) parseVarType(isParam bool) ast.Expr {
+ typ := p.tryVarType(isParam)
+ if typ == nil {
+ pos := p.pos
+ p.errorExpected(pos, "type")
+ p.next() // make progress
+ typ = &ast.BadExpr{From: pos, To: p.pos}
+ }
+ return typ
+}
+
+func (p *parser) parseParameterList(scope *ast.Scope, ellipsisOk bool) (params []*ast.Field) {
+ if p.trace {
+ defer un(trace(p, "ParameterList"))
+ }
+
+ // 1st ParameterDecl
+ // A list of identifiers looks like a list of type names.
+ var list []ast.Expr
+ for {
+ list = append(list, p.parseVarType(ellipsisOk))
+ if p.tok != token.COMMA {
+ break
+ }
+ p.next()
+ if p.tok == token.RPAREN {
+ break
+ }
+ }
+
+ // analyze case
+ if typ := p.tryVarType(ellipsisOk); typ != nil {
+ // IdentifierList Type
+ idents := p.makeIdentList(list)
+ field := &ast.Field{Names: idents, Type: typ}
+ params = append(params, field)
+ // Go spec: The scope of an identifier denoting a function
+ // parameter or result variable is the function body.
+ p.declare(field, nil, scope, ast.Var, idents...)
+ p.resolve(typ)
+ if !p.atComma("parameter list", token.RPAREN) {
+ return
+ }
+ p.next()
+ for p.tok != token.RPAREN && p.tok != token.EOF {
+ idents := p.parseIdentList()
+ typ := p.parseVarType(ellipsisOk)
+ field := &ast.Field{Names: idents, Type: typ}
+ params = append(params, field)
+ // Go spec: The scope of an identifier denoting a function
+ // parameter or result variable is the function body.
+ p.declare(field, nil, scope, ast.Var, idents...)
+ p.resolve(typ)
+ if !p.atComma("parameter list", token.RPAREN) {
+ break
+ }
+ p.next()
+ }
+ return
+ }
+
+ // Type { "," Type } (anonymous parameters)
+ params = make([]*ast.Field, len(list))
+ for i, typ := range list {
+ p.resolve(typ)
+ params[i] = &ast.Field{Type: typ}
+ }
+ return
+}
+
+func (p *parser) parseParameters(scope *ast.Scope, ellipsisOk bool) *ast.FieldList {
+ if p.trace {
+ defer un(trace(p, "Parameters"))
+ }
+
+ var params []*ast.Field
+ lparen := p.expect(token.LPAREN)
+ if p.tok != token.RPAREN {
+ params = p.parseParameterList(scope, ellipsisOk)
+ }
+ rparen := p.expect(token.RPAREN)
+
+ return &ast.FieldList{Opening: lparen, List: params, Closing: rparen}
+}
+
+func (p *parser) parseResult(scope *ast.Scope) *ast.FieldList {
+ if p.trace {
+ defer un(trace(p, "Result"))
+ }
+
+ if p.tok == token.LPAREN {
+ return p.parseParameters(scope, false)
+ }
+
+ typ := p.tryType()
+ if typ != nil {
+ list := make([]*ast.Field, 1)
+ list[0] = &ast.Field{Type: typ}
+ return &ast.FieldList{List: list}
+ }
+
+ return nil
+}
+
+func (p *parser) parseSignature(scope *ast.Scope) (params, results *ast.FieldList) {
+ if p.trace {
+ defer un(trace(p, "Signature"))
+ }
+
+ params = p.parseParameters(scope, true)
+ results = p.parseResult(scope)
+
+ return
+}
+
+func (p *parser) parseFuncType() (*ast.FuncType, *ast.Scope) {
+ if p.trace {
+ defer un(trace(p, "FuncType"))
+ }
+
+ pos := p.expect(token.FUNC)
+ scope := ast.NewScope(p.topScope) // function scope
+ params, results := p.parseSignature(scope)
+
+ return &ast.FuncType{Func: pos, Params: params, Results: results}, scope
+}
+
+func (p *parser) parseMethodSpec(scope *ast.Scope) *ast.Field {
+ if p.trace {
+ defer un(trace(p, "MethodSpec"))
+ }
+
+ doc := p.leadComment
+ var idents []*ast.Ident
+ var typ ast.Expr
+ x := p.parseTypeName()
+ if ident, isIdent := x.(*ast.Ident); isIdent && p.tok == token.LPAREN {
+ // method
+ idents = []*ast.Ident{ident}
+ scope := ast.NewScope(nil) // method scope
+ params, results := p.parseSignature(scope)
+ typ = &ast.FuncType{Func: token.NoPos, Params: params, Results: results}
+ } else {
+ // embedded interface
+ typ = x
+ p.resolve(typ)
+ }
+ p.expectSemi() // call before accessing p.linecomment
+
+ spec := &ast.Field{Doc: doc, Names: idents, Type: typ, Comment: p.lineComment}
+ p.declare(spec, nil, scope, ast.Fun, idents...)
+
+ return spec
+}
+
+func (p *parser) parseInterfaceType() *ast.InterfaceType {
+ if p.trace {
+ defer un(trace(p, "InterfaceType"))
+ }
+
+ pos := p.expect(token.INTERFACE)
+ lbrace := p.expect(token.LBRACE)
+ scope := ast.NewScope(nil) // interface scope
+ var list []*ast.Field
+ for p.tok == token.IDENT {
+ list = append(list, p.parseMethodSpec(scope))
+ }
+ rbrace := p.expect(token.RBRACE)
+
+ return &ast.InterfaceType{
+ Interface: pos,
+ Methods: &ast.FieldList{
+ Opening: lbrace,
+ List: list,
+ Closing: rbrace,
+ },
+ }
+}
+
+func (p *parser) parseMapType() *ast.MapType {
+ if p.trace {
+ defer un(trace(p, "MapType"))
+ }
+
+ pos := p.expect(token.MAP)
+ p.expect(token.LBRACK)
+ key := p.parseType()
+ p.expect(token.RBRACK)
+ value := p.parseType()
+
+ return &ast.MapType{Map: pos, Key: key, Value: value}
+}
+
+func (p *parser) parseChanType() *ast.ChanType {
+ if p.trace {
+ defer un(trace(p, "ChanType"))
+ }
+
+ pos := p.pos
+ dir := ast.SEND | ast.RECV
+ var arrow token.Pos
+ if p.tok == token.CHAN {
+ p.next()
+ if p.tok == token.ARROW {
+ arrow = p.pos
+ p.next()
+ dir = ast.SEND
+ }
+ } else {
+ arrow = p.expect(token.ARROW)
+ p.expect(token.CHAN)
+ dir = ast.RECV
+ }
+ value := p.parseType()
+
+ return &ast.ChanType{Begin: pos, Arrow: arrow, Dir: dir, Value: value}
+}
+
+// If the result is an identifier, it is not resolved.
+func (p *parser) tryIdentOrType() ast.Expr {
+ switch p.tok {
+ case token.IDENT:
+ return p.parseTypeName()
+ case token.LBRACK:
+ return p.parseArrayType()
+ case token.STRUCT:
+ return p.parseStructType()
+ case token.MUL:
+ return p.parsePointerType()
+ case token.FUNC:
+ typ, _ := p.parseFuncType()
+ return typ
+ case token.INTERFACE:
+ return p.parseInterfaceType()
+ case token.MAP:
+ return p.parseMapType()
+ case token.CHAN, token.ARROW:
+ return p.parseChanType()
+ case token.LPAREN:
+ lparen := p.pos
+ p.next()
+ typ := p.parseType()
+ rparen := p.expect(token.RPAREN)
+ return &ast.ParenExpr{Lparen: lparen, X: typ, Rparen: rparen}
+ }
+
+ // no type found
+ return nil
+}
+
+func (p *parser) tryType() ast.Expr {
+ typ := p.tryIdentOrType()
+ if typ != nil {
+ p.resolve(typ)
+ }
+ return typ
+}
+
+// ----------------------------------------------------------------------------
+// Blocks
+
+func (p *parser) parseStmtList() (list []ast.Stmt) {
+ if p.trace {
+ defer un(trace(p, "StatementList"))
+ }
+
+ for p.tok != token.CASE && p.tok != token.DEFAULT && p.tok != token.RBRACE && p.tok != token.EOF {
+ list = append(list, p.parseStmt())
+ }
+
+ return
+}
+
+func (p *parser) parseBody(scope *ast.Scope) *ast.BlockStmt {
+ if p.trace {
+ defer un(trace(p, "Body"))
+ }
+
+ lbrace := p.expect(token.LBRACE)
+ p.topScope = scope // open function scope
+ p.openLabelScope()
+ list := p.parseStmtList()
+ p.closeLabelScope()
+ p.closeScope()
+ rbrace := p.expect2(token.RBRACE)
+
+ return &ast.BlockStmt{Lbrace: lbrace, List: list, Rbrace: rbrace}
+}
+
+func (p *parser) parseBlockStmt() *ast.BlockStmt {
+ if p.trace {
+ defer un(trace(p, "BlockStmt"))
+ }
+
+ lbrace := p.expect(token.LBRACE)
+ p.openScope()
+ list := p.parseStmtList()
+ p.closeScope()
+ rbrace := p.expect2(token.RBRACE)
+
+ return &ast.BlockStmt{Lbrace: lbrace, List: list, Rbrace: rbrace}
+}
+
+// ----------------------------------------------------------------------------
+// Expressions
+
+func (p *parser) parseFuncTypeOrLit() ast.Expr {
+ if p.trace {
+ defer un(trace(p, "FuncTypeOrLit"))
+ }
+
+ typ, scope := p.parseFuncType()
+ if p.tok != token.LBRACE {
+ // function type only
+ return typ
+ }
+
+ p.exprLev++
+ body := p.parseBody(scope)
+ p.exprLev--
+
+ return &ast.FuncLit{Type: typ, Body: body}
+}
+
+// parseOperand may return an expression or a raw type (incl. array
+// types of the form [...]T. Callers must verify the result.
+// If lhs is set and the result is an identifier, it is not resolved.
+//
+func (p *parser) parseOperand(lhs bool) ast.Expr {
+ if p.trace {
+ defer un(trace(p, "Operand"))
+ }
+
+ switch p.tok {
+ case token.IDENT:
+ x := p.parseIdent()
+ if !lhs {
+ p.resolve(x)
+ }
+ return x
+
+ case token.INT, token.FLOAT, token.IMAG, token.CHAR, token.STRING:
+ x := &ast.BasicLit{ValuePos: p.pos, Kind: p.tok, Value: p.lit}
+ p.next()
+ return x
+
+ case token.LPAREN:
+ lparen := p.pos
+ p.next()
+ p.exprLev++
+ x := p.parseRhsOrType() // types may be parenthesized: (some type)
+ p.exprLev--
+ rparen := p.expect(token.RPAREN)
+ return &ast.ParenExpr{Lparen: lparen, X: x, Rparen: rparen}
+
+ case token.FUNC:
+ return p.parseFuncTypeOrLit()
+ }
+
+ if typ := p.tryIdentOrType(); typ != nil {
+ // could be type for composite literal or conversion
+ _, isIdent := typ.(*ast.Ident)
+ assert(!isIdent, "type cannot be identifier")
+ return typ
+ }
+
+ // we have an error
+ pos := p.pos
+ p.errorExpected(pos, "operand")
+ p.advance(stmtStart)
+ return &ast.BadExpr{From: pos, To: p.pos}
+}
+
+func (p *parser) parseSelector(x ast.Expr) ast.Expr {
+ if p.trace {
+ defer un(trace(p, "Selector"))
+ }
+
+ sel := p.parseIdent()
+
+ return &ast.SelectorExpr{X: x, Sel: sel}
+}
+
+func (p *parser) parseTypeAssertion(x ast.Expr) ast.Expr {
+ if p.trace {
+ defer un(trace(p, "TypeAssertion"))
+ }
+
+ lparen := p.expect(token.LPAREN)
+ var typ ast.Expr
+ if p.tok == token.TYPE {
+ // type switch: typ == nil
+ p.next()
+ } else {
+ typ = p.parseType()
+ }
+ rparen := p.expect(token.RPAREN)
+
+ return &ast.TypeAssertExpr{X: x, Type: typ, Lparen: lparen, Rparen: rparen}
+}
+
+func (p *parser) parseIndexOrSlice(x ast.Expr) ast.Expr {
+ if p.trace {
+ defer un(trace(p, "IndexOrSlice"))
+ }
+
+ const N = 3 // change the 3 to 2 to disable 3-index slices
+ lbrack := p.expect(token.LBRACK)
+ p.exprLev++
+ var index [N]ast.Expr
+ var colons [N - 1]token.Pos
+ if p.tok != token.COLON {
+ index[0] = p.parseRhs()
+ }
+ ncolons := 0
+ for p.tok == token.COLON && ncolons < len(colons) {
+ colons[ncolons] = p.pos
+ ncolons++
+ p.next()
+ if p.tok != token.COLON && p.tok != token.RBRACK && p.tok != token.EOF {
+ index[ncolons] = p.parseRhs()
+ }
+ }
+ p.exprLev--
+ rbrack := p.expect(token.RBRACK)
+
+ if ncolons > 0 {
+ // slice expression
+ slice3 := false
+ if ncolons == 2 {
+ slice3 = true
+ // Check presence of 2nd and 3rd index here rather than during type-checking
+ // to prevent erroneous programs from passing through gofmt (was issue 7305).
+ if index[1] == nil {
+ p.error(colons[0], "2nd index required in 3-index slice")
+ index[1] = &ast.BadExpr{From: colons[0] + 1, To: colons[1]}
+ }
+ if index[2] == nil {
+ p.error(colons[1], "3rd index required in 3-index slice")
+ index[2] = &ast.BadExpr{From: colons[1] + 1, To: rbrack}
+ }
+ }
+ return &ast.SliceExpr{X: x, Lbrack: lbrack, Low: index[0], High: index[1], Max: index[2], Slice3: slice3, Rbrack: rbrack}
+ }
+
+ return &ast.IndexExpr{X: x, Lbrack: lbrack, Index: index[0], Rbrack: rbrack}
+}
+
+func (p *parser) parseCallOrConversion(fun ast.Expr) *ast.CallExpr {
+ if p.trace {
+ defer un(trace(p, "CallOrConversion"))
+ }
+
+ lparen := p.expect(token.LPAREN)
+ p.exprLev++
+ var list []ast.Expr
+ var ellipsis token.Pos
+ for p.tok != token.RPAREN && p.tok != token.EOF && !ellipsis.IsValid() {
+ list = append(list, p.parseRhsOrType()) // builtins may expect a type: make(some type, ...)
+ if p.tok == token.ELLIPSIS {
+ ellipsis = p.pos
+ p.next()
+ }
+ if !p.atComma("argument list", token.RPAREN) {
+ break
+ }
+ p.next()
+ }
+ p.exprLev--
+ rparen := p.expectClosing(token.RPAREN, "argument list")
+
+ return &ast.CallExpr{Fun: fun, Lparen: lparen, Args: list, Ellipsis: ellipsis, Rparen: rparen}
+}
+
+func (p *parser) parseValue(keyOk bool) ast.Expr {
+ if p.trace {
+ defer un(trace(p, "Element"))
+ }
+
+ if p.tok == token.LBRACE {
+ return p.parseLiteralValue(nil)
+ }
+
+ // Because the parser doesn't know the composite literal type, it cannot
+ // know if a key that's an identifier is a struct field name or a name
+ // denoting a value. The former is not resolved by the parser or the
+ // resolver.
+ //
+ // Instead, _try_ to resolve such a key if possible. If it resolves,
+ // it a) has correctly resolved, or b) incorrectly resolved because
+ // the key is a struct field with a name matching another identifier.
+ // In the former case we are done, and in the latter case we don't
+ // care because the type checker will do a separate field lookup.
+ //
+ // If the key does not resolve, it a) must be defined at the top
+ // level in another file of the same package, the universe scope, or be
+ // undeclared; or b) it is a struct field. In the former case, the type
+ // checker can do a top-level lookup, and in the latter case it will do
+ // a separate field lookup.
+ x := p.checkExpr(p.parseExpr(keyOk))
+ if keyOk {
+ if p.tok == token.COLON {
+ // Try to resolve the key but don't collect it
+ // as unresolved identifier if it fails so that
+ // we don't get (possibly false) errors about
+ // undeclared names.
+ p.tryResolve(x, false)
+ } else {
+ // not a key
+ p.resolve(x)
+ }
+ }
+
+ return x
+}
+
+func (p *parser) parseElement() ast.Expr {
+ if p.trace {
+ defer un(trace(p, "Element"))
+ }
+
+ x := p.parseValue(true)
+ if p.tok == token.COLON {
+ colon := p.pos
+ p.next()
+ x = &ast.KeyValueExpr{Key: x, Colon: colon, Value: p.parseValue(false)}
+ }
+
+ return x
+}
+
+func (p *parser) parseElementList() (list []ast.Expr) {
+ if p.trace {
+ defer un(trace(p, "ElementList"))
+ }
+
+ for p.tok != token.RBRACE && p.tok != token.EOF {
+ list = append(list, p.parseElement())
+ if !p.atComma("composite literal", token.RBRACE) {
+ break
+ }
+ p.next()
+ }
+
+ return
+}
+
+func (p *parser) parseLiteralValue(typ ast.Expr) ast.Expr {
+ if p.trace {
+ defer un(trace(p, "LiteralValue"))
+ }
+
+ lbrace := p.expect(token.LBRACE)
+ var elts []ast.Expr
+ p.exprLev++
+ if p.tok != token.RBRACE {
+ elts = p.parseElementList()
+ }
+ p.exprLev--
+ rbrace := p.expectClosing(token.RBRACE, "composite literal")
+ return &ast.CompositeLit{Type: typ, Lbrace: lbrace, Elts: elts, Rbrace: rbrace}
+}
+
+// checkExpr checks that x is an expression (and not a type).
+func (p *parser) checkExpr(x ast.Expr) ast.Expr {
+ switch unparen(x).(type) {
+ case *ast.BadExpr:
+ case *ast.Ident:
+ case *ast.BasicLit:
+ case *ast.FuncLit:
+ case *ast.CompositeLit:
+ case *ast.ParenExpr:
+ panic("unreachable")
+ case *ast.SelectorExpr:
+ case *ast.IndexExpr:
+ case *ast.SliceExpr:
+ case *ast.TypeAssertExpr:
+ // If t.Type == nil we have a type assertion of the form
+ // y.(type), which is only allowed in type switch expressions.
+ // It's hard to exclude those but for the case where we are in
+ // a type switch. Instead be lenient and test this in the type
+ // checker.
+ case *ast.CallExpr:
+ case *ast.StarExpr:
+ case *ast.UnaryExpr:
+ case *ast.BinaryExpr:
+ default:
+ // all other nodes are not proper expressions
+ p.errorExpected(x.Pos(), "expression")
+ x = &ast.BadExpr{From: x.Pos(), To: p.safePos(x.End())}
+ }
+ return x
+}
+
+// isTypeName reports whether x is a (qualified) TypeName.
+func isTypeName(x ast.Expr) bool {
+ switch t := x.(type) {
+ case *ast.BadExpr:
+ case *ast.Ident:
+ case *ast.SelectorExpr:
+ _, isIdent := t.X.(*ast.Ident)
+ return isIdent
+ default:
+ return false // all other nodes are not type names
+ }
+ return true
+}
+
+// isLiteralType reports whether x is a legal composite literal type.
+func isLiteralType(x ast.Expr) bool {
+ switch t := x.(type) {
+ case *ast.BadExpr:
+ case *ast.Ident:
+ case *ast.SelectorExpr:
+ _, isIdent := t.X.(*ast.Ident)
+ return isIdent
+ case *ast.ArrayType:
+ case *ast.StructType:
+ case *ast.MapType:
+ default:
+ return false // all other nodes are not legal composite literal types
+ }
+ return true
+}
+
+// If x is of the form *T, deref returns T, otherwise it returns x.
+func deref(x ast.Expr) ast.Expr {
+ if p, isPtr := x.(*ast.StarExpr); isPtr {
+ x = p.X
+ }
+ return x
+}
+
+// If x is of the form (T), unparen returns unparen(T), otherwise it returns x.
+func unparen(x ast.Expr) ast.Expr {
+ if p, isParen := x.(*ast.ParenExpr); isParen {
+ x = unparen(p.X)
+ }
+ return x
+}
+
+// checkExprOrType checks that x is an expression or a type
+// (and not a raw type such as [...]T).
+//
+func (p *parser) checkExprOrType(x ast.Expr) ast.Expr {
+ switch t := unparen(x).(type) {
+ case *ast.ParenExpr:
+ panic("unreachable")
+ case *ast.ArrayType:
+ if len, isEllipsis := t.Len.(*ast.Ellipsis); isEllipsis {
+ p.error(len.Pos(), "expected array length, found '...'")
+ x = &ast.BadExpr{From: x.Pos(), To: p.safePos(x.End())}
+ }
+ }
+
+ // all other nodes are expressions or types
+ return x
+}
+
+// If lhs is set and the result is an identifier, it is not resolved.
+func (p *parser) parsePrimaryExpr(lhs bool) ast.Expr {
+ if p.trace {
+ defer un(trace(p, "PrimaryExpr"))
+ }
+
+ x := p.parseOperand(lhs)
+L:
+ for {
+ switch p.tok {
+ case token.PERIOD:
+ p.next()
+ if lhs {
+ p.resolve(x)
+ }
+ switch p.tok {
+ case token.IDENT:
+ x = p.parseSelector(p.checkExprOrType(x))
+ case token.LPAREN:
+ x = p.parseTypeAssertion(p.checkExpr(x))
+ default:
+ pos := p.pos
+ p.errorExpected(pos, "selector or type assertion")
+ p.next() // make progress
+ sel := &ast.Ident{NamePos: pos, Name: "_"}
+ x = &ast.SelectorExpr{X: x, Sel: sel}
+ }
+ case token.LBRACK:
+ if lhs {
+ p.resolve(x)
+ }
+ x = p.parseIndexOrSlice(p.checkExpr(x))
+ case token.LPAREN:
+ if lhs {
+ p.resolve(x)
+ }
+ x = p.parseCallOrConversion(p.checkExprOrType(x))
+ case token.LBRACE:
+ if isLiteralType(x) && (p.exprLev >= 0 || !isTypeName(x)) {
+ if lhs {
+ p.resolve(x)
+ }
+ x = p.parseLiteralValue(x)
+ } else {
+ break L
+ }
+ default:
+ break L
+ }
+ lhs = false // no need to try to resolve again
+ }
+
+ return x
+}
+
+// If lhs is set and the result is an identifier, it is not resolved.
+func (p *parser) parseUnaryExpr(lhs bool) ast.Expr {
+ if p.trace {
+ defer un(trace(p, "UnaryExpr"))
+ }
+
+ switch p.tok {
+ case token.ADD, token.SUB, token.NOT, token.XOR, token.AND:
+ pos, op := p.pos, p.tok
+ p.next()
+ x := p.parseUnaryExpr(false)
+ return &ast.UnaryExpr{OpPos: pos, Op: op, X: p.checkExpr(x)}
+
+ case token.ARROW:
+ // channel type or receive expression
+ arrow := p.pos
+ p.next()
+
+ // If the next token is token.CHAN we still don't know if it
+ // is a channel type or a receive operation - we only know
+ // once we have found the end of the unary expression. There
+ // are two cases:
+ //
+ // <- type => (<-type) must be channel type
+ // <- expr => <-(expr) is a receive from an expression
+ //
+ // In the first case, the arrow must be re-associated with
+ // the channel type parsed already:
+ //
+ // <- (chan type) => (<-chan type)
+ // <- (chan<- type) => (<-chan (<-type))
+
+ x := p.parseUnaryExpr(false)
+
+ // determine which case we have
+ if typ, ok := x.(*ast.ChanType); ok {
+ // (<-type)
+
+ // re-associate position info and <-
+ dir := ast.SEND
+ for ok && dir == ast.SEND {
+ if typ.Dir == ast.RECV {
+ // error: (<-type) is (<-(<-chan T))
+ p.errorExpected(typ.Arrow, "'chan'")
+ }
+ arrow, typ.Begin, typ.Arrow = typ.Arrow, arrow, arrow
+ dir, typ.Dir = typ.Dir, ast.RECV
+ typ, ok = typ.Value.(*ast.ChanType)
+ }
+ if dir == ast.SEND {
+ p.errorExpected(arrow, "channel type")
+ }
+
+ return x
+ }
+
+ // <-(expr)
+ return &ast.UnaryExpr{OpPos: arrow, Op: token.ARROW, X: p.checkExpr(x)}
+
+ case token.MUL:
+ // pointer type or unary "*" expression
+ pos := p.pos
+ p.next()
+ x := p.parseUnaryExpr(false)
+ return &ast.StarExpr{Star: pos, X: p.checkExprOrType(x)}
+ }
+
+ return p.parsePrimaryExpr(lhs)
+}
+
+func (p *parser) tokPrec() (token.Token, int) {
+ tok := p.tok
+ if p.inRhs && tok == token.ASSIGN {
+ tok = token.EQL
+ }
+ return tok, tok.Precedence()
+}
+
+// If lhs is set and the result is an identifier, it is not resolved.
+func (p *parser) parseBinaryExpr(lhs bool, prec1 int) ast.Expr {
+ if p.trace {
+ defer un(trace(p, "BinaryExpr"))
+ }
+
+ x := p.parseUnaryExpr(lhs)
+ for {
+ op, oprec := p.tokPrec()
+ if oprec < prec1 {
+ return x
+ }
+ pos := p.expect(op)
+ if lhs {
+ p.resolve(x)
+ lhs = false
+ }
+ y := p.parseBinaryExpr(false, oprec+1)
+ x = &ast.BinaryExpr{X: p.checkExpr(x), OpPos: pos, Op: op, Y: p.checkExpr(y)}
+ }
+}
+
+// If lhs is set and the result is an identifier, it is not resolved.
+// The result may be a type or even a raw type ([...]int). Callers must
+// check the result (using checkExpr or checkExprOrType), depending on
+// context.
+func (p *parser) parseExpr(lhs bool) ast.Expr {
+ if p.trace {
+ defer un(trace(p, "Expression"))
+ }
+
+ return p.parseBinaryExpr(lhs, token.LowestPrec+1)
+}
+
+func (p *parser) parseRhs() ast.Expr {
+ old := p.inRhs
+ p.inRhs = true
+ x := p.checkExpr(p.parseExpr(false))
+ p.inRhs = old
+ return x
+}
+
+func (p *parser) parseRhsOrType() ast.Expr {
+ old := p.inRhs
+ p.inRhs = true
+ x := p.checkExprOrType(p.parseExpr(false))
+ p.inRhs = old
+ return x
+}
+
+// ----------------------------------------------------------------------------
+// Statements
+
+// Parsing modes for parseSimpleStmt.
+const (
+ basic = iota
+ labelOk
+ rangeOk
+)
+
+// parseSimpleStmt returns true as 2nd result if it parsed the assignment
+// of a range clause (with mode == rangeOk). The returned statement is an
+// assignment with a right-hand side that is a single unary expression of
+// the form "range x". No guarantees are given for the left-hand side.
+func (p *parser) parseSimpleStmt(mode int) (ast.Stmt, bool) {
+ if p.trace {
+ defer un(trace(p, "SimpleStmt"))
+ }
+
+ x := p.parseLhsList()
+
+ switch p.tok {
+ case
+ token.DEFINE, token.ASSIGN, token.ADD_ASSIGN,
+ token.SUB_ASSIGN, token.MUL_ASSIGN, token.QUO_ASSIGN,
+ token.REM_ASSIGN, token.AND_ASSIGN, token.OR_ASSIGN,
+ token.XOR_ASSIGN, token.SHL_ASSIGN, token.SHR_ASSIGN, token.AND_NOT_ASSIGN:
+ // assignment statement, possibly part of a range clause
+ pos, tok := p.pos, p.tok
+ p.next()
+ var y []ast.Expr
+ isRange := false
+ if mode == rangeOk && p.tok == token.RANGE && (tok == token.DEFINE || tok == token.ASSIGN) {
+ pos := p.pos
+ p.next()
+ y = []ast.Expr{&ast.UnaryExpr{OpPos: pos, Op: token.RANGE, X: p.parseRhs()}}
+ isRange = true
+ } else {
+ y = p.parseRhsList()
+ }
+ as := &ast.AssignStmt{Lhs: x, TokPos: pos, Tok: tok, Rhs: y}
+ if tok == token.DEFINE {
+ p.shortVarDecl(as, x)
+ }
+ return as, isRange
+ }
+
+ if len(x) > 1 {
+ p.errorExpected(x[0].Pos(), "1 expression")
+ // continue with first expression
+ }
+
+ switch p.tok {
+ case token.COLON:
+ // labeled statement
+ colon := p.pos
+ p.next()
+ if label, isIdent := x[0].(*ast.Ident); mode == labelOk && isIdent {
+ // Go spec: The scope of a label is the body of the function
+ // in which it is declared and excludes the body of any nested
+ // function.
+ stmt := &ast.LabeledStmt{Label: label, Colon: colon, Stmt: p.parseStmt()}
+ p.declare(stmt, nil, p.labelScope, ast.Lbl, label)
+ return stmt, false
+ }
+ // The label declaration typically starts at x[0].Pos(), but the label
+ // declaration may be erroneous due to a token after that position (and
+ // before the ':'). If SpuriousErrors is not set, the (only) error
+ // reported for the line is the illegal label error instead of the token
+ // before the ':' that caused the problem. Thus, use the (latest) colon
+ // position for error reporting.
+ p.error(colon, "illegal label declaration")
+ return &ast.BadStmt{From: x[0].Pos(), To: colon + 1}, false
+
+ case token.ARROW:
+ // send statement
+ arrow := p.pos
+ p.next()
+ y := p.parseRhs()
+ return &ast.SendStmt{Chan: x[0], Arrow: arrow, Value: y}, false
+
+ case token.INC, token.DEC:
+ // increment or decrement
+ s := &ast.IncDecStmt{X: x[0], TokPos: p.pos, Tok: p.tok}
+ p.next()
+ return s, false
+ }
+
+ // expression
+ return &ast.ExprStmt{X: x[0]}, false
+}
+
+func (p *parser) parseCallExpr(callType string) *ast.CallExpr {
+ x := p.parseRhsOrType() // could be a conversion: (some type)(x)
+ if call, isCall := x.(*ast.CallExpr); isCall {
+ return call
+ }
+ if _, isBad := x.(*ast.BadExpr); !isBad {
+ // only report error if it's a new one
+ p.error(p.safePos(x.End()), fmt.Sprintf("function must be invoked in %s statement", callType))
+ }
+ return nil
+}
+
+func (p *parser) parseGoStmt() ast.Stmt {
+ if p.trace {
+ defer un(trace(p, "GoStmt"))
+ }
+
+ pos := p.expect(token.GO)
+ call := p.parseCallExpr("go")
+ p.expectSemi()
+ if call == nil {
+ return &ast.BadStmt{From: pos, To: pos + 2} // len("go")
+ }
+
+ return &ast.GoStmt{Go: pos, Call: call}
+}
+
+func (p *parser) parseDeferStmt() ast.Stmt {
+ if p.trace {
+ defer un(trace(p, "DeferStmt"))
+ }
+
+ pos := p.expect(token.DEFER)
+ call := p.parseCallExpr("defer")
+ p.expectSemi()
+ if call == nil {
+ return &ast.BadStmt{From: pos, To: pos + 5} // len("defer")
+ }
+
+ return &ast.DeferStmt{Defer: pos, Call: call}
+}
+
+func (p *parser) parseReturnStmt() *ast.ReturnStmt {
+ if p.trace {
+ defer un(trace(p, "ReturnStmt"))
+ }
+
+ pos := p.pos
+ p.expect(token.RETURN)
+ var x []ast.Expr
+ if p.tok != token.SEMICOLON && p.tok != token.RBRACE {
+ x = p.parseRhsList()
+ }
+ p.expectSemi()
+
+ return &ast.ReturnStmt{Return: pos, Results: x}
+}
+
+func (p *parser) parseBranchStmt(tok token.Token) *ast.BranchStmt {
+ if p.trace {
+ defer un(trace(p, "BranchStmt"))
+ }
+
+ pos := p.expect(tok)
+ var label *ast.Ident
+ if tok != token.FALLTHROUGH && p.tok == token.IDENT {
+ label = p.parseIdent()
+ // add to list of unresolved targets
+ n := len(p.targetStack) - 1
+ p.targetStack[n] = append(p.targetStack[n], label)
+ }
+ p.expectSemi()
+
+ return &ast.BranchStmt{TokPos: pos, Tok: tok, Label: label}
+}
+
+func (p *parser) makeExpr(s ast.Stmt, want string) ast.Expr {
+ if s == nil {
+ return nil
+ }
+ if es, isExpr := s.(*ast.ExprStmt); isExpr {
+ return p.checkExpr(es.X)
+ }
+ found := "simple statement"
+ if _, isAss := s.(*ast.AssignStmt); isAss {
+ found = "assignment"
+ }
+ p.error(s.Pos(), fmt.Sprintf("expected %s, found %s (missing parentheses around composite literal?)", want, found))
+ return &ast.BadExpr{From: s.Pos(), To: p.safePos(s.End())}
+}
+
+// parseIfHeader is an adjusted version of parser.header
+// in cmd/compile/internal/syntax/parser.go, which has
+// been tuned for better error handling.
+func (p *parser) parseIfHeader() (init ast.Stmt, cond ast.Expr) {
+ if p.tok == token.LBRACE {
+ p.error(p.pos, "missing condition in if statement")
+ cond = &ast.BadExpr{From: p.pos, To: p.pos}
+ return
+ }
+ // p.tok != token.LBRACE
+
+ outer := p.exprLev
+ p.exprLev = -1
+
+ if p.tok != token.SEMICOLON {
+ // accept potential variable declaration but complain
+ if p.tok == token.VAR {
+ p.next()
+ p.error(p.pos, fmt.Sprintf("var declaration not allowed in 'IF' initializer"))
+ }
+ init, _ = p.parseSimpleStmt(basic)
+ }
+
+ var condStmt ast.Stmt
+ var semi struct {
+ pos token.Pos
+ lit string // ";" or "\n"; valid if pos.IsValid()
+ }
+ if p.tok != token.LBRACE {
+ if p.tok == token.SEMICOLON {
+ semi.pos = p.pos
+ semi.lit = p.lit
+ p.next()
+ } else {
+ p.expect(token.SEMICOLON)
+ }
+ if p.tok != token.LBRACE {
+ condStmt, _ = p.parseSimpleStmt(basic)
+ }
+ } else {
+ condStmt = init
+ init = nil
+ }
+
+ if condStmt != nil {
+ cond = p.makeExpr(condStmt, "boolean expression")
+ } else if semi.pos.IsValid() {
+ if semi.lit == "\n" {
+ p.error(semi.pos, "unexpected newline, expecting { after if clause")
+ } else {
+ p.error(semi.pos, "missing condition in if statement")
+ }
+ }
+
+ // make sure we have a valid AST
+ if cond == nil {
+ cond = &ast.BadExpr{From: p.pos, To: p.pos}
+ }
+
+ p.exprLev = outer
+ return
+}
+
+func (p *parser) parseIfStmt() *ast.IfStmt {
+ if p.trace {
+ defer un(trace(p, "IfStmt"))
+ }
+
+ pos := p.expect(token.IF)
+ p.openScope()
+ defer p.closeScope()
+
+ init, cond := p.parseIfHeader()
+ body := p.parseBlockStmt()
+
+ var else_ ast.Stmt
+ if p.tok == token.ELSE {
+ p.next()
+ switch p.tok {
+ case token.IF:
+ else_ = p.parseIfStmt()
+ case token.LBRACE:
+ else_ = p.parseBlockStmt()
+ p.expectSemi()
+ default:
+ p.errorExpected(p.pos, "if statement or block")
+ else_ = &ast.BadStmt{From: p.pos, To: p.pos}
+ }
+ } else {
+ p.expectSemi()
+ }
+
+ return &ast.IfStmt{If: pos, Init: init, Cond: cond, Body: body, Else: else_}
+}
+
+func (p *parser) parseTypeList() (list []ast.Expr) {
+ if p.trace {
+ defer un(trace(p, "TypeList"))
+ }
+
+ list = append(list, p.parseType())
+ for p.tok == token.COMMA {
+ p.next()
+ list = append(list, p.parseType())
+ }
+
+ return
+}
+
+func (p *parser) parseCaseClause(typeSwitch bool) *ast.CaseClause {
+ if p.trace {
+ defer un(trace(p, "CaseClause"))
+ }
+
+ pos := p.pos
+ var list []ast.Expr
+ if p.tok == token.CASE {
+ p.next()
+ if typeSwitch {
+ list = p.parseTypeList()
+ } else {
+ list = p.parseRhsList()
+ }
+ } else {
+ p.expect(token.DEFAULT)
+ }
+
+ colon := p.expect(token.COLON)
+ p.openScope()
+ body := p.parseStmtList()
+ p.closeScope()
+
+ return &ast.CaseClause{Case: pos, List: list, Colon: colon, Body: body}
+}
+
+func isTypeSwitchAssert(x ast.Expr) bool {
+ a, ok := x.(*ast.TypeAssertExpr)
+ return ok && a.Type == nil
+}
+
+func (p *parser) isTypeSwitchGuard(s ast.Stmt) bool {
+ switch t := s.(type) {
+ case *ast.ExprStmt:
+ // x.(type)
+ return isTypeSwitchAssert(t.X)
+ case *ast.AssignStmt:
+ // v := x.(type)
+ if len(t.Lhs) == 1 && len(t.Rhs) == 1 && isTypeSwitchAssert(t.Rhs[0]) {
+ switch t.Tok {
+ case token.ASSIGN:
+ // permit v = x.(type) but complain
+ p.error(t.TokPos, "expected ':=', found '='")
+ fallthrough
+ case token.DEFINE:
+ return true
+ }
+ }
+ }
+ return false
+}
+
+func (p *parser) parseSwitchStmt() ast.Stmt {
+ if p.trace {
+ defer un(trace(p, "SwitchStmt"))
+ }
+
+ pos := p.expect(token.SWITCH)
+ p.openScope()
+ defer p.closeScope()
+
+ var s1, s2 ast.Stmt
+ if p.tok != token.LBRACE {
+ prevLev := p.exprLev
+ p.exprLev = -1
+ if p.tok != token.SEMICOLON {
+ s2, _ = p.parseSimpleStmt(basic)
+ }
+ if p.tok == token.SEMICOLON {
+ p.next()
+ s1 = s2
+ s2 = nil
+ if p.tok != token.LBRACE {
+ // A TypeSwitchGuard may declare a variable in addition
+ // to the variable declared in the initial SimpleStmt.
+ // Introduce extra scope to avoid redeclaration errors:
+ //
+ // switch t := 0; t := x.(T) { ... }
+ //
+ // (this code is not valid Go because the first t
+ // cannot be accessed and thus is never used, the extra
+ // scope is needed for the correct error message).
+ //
+ // If we don't have a type switch, s2 must be an expression.
+ // Having the extra nested but empty scope won't affect it.
+ p.openScope()
+ defer p.closeScope()
+ s2, _ = p.parseSimpleStmt(basic)
+ }
+ }
+ p.exprLev = prevLev
+ }
+
+ typeSwitch := p.isTypeSwitchGuard(s2)
+ lbrace := p.expect(token.LBRACE)
+ var list []ast.Stmt
+ for p.tok == token.CASE || p.tok == token.DEFAULT {
+ list = append(list, p.parseCaseClause(typeSwitch))
+ }
+ rbrace := p.expect(token.RBRACE)
+ p.expectSemi()
+ body := &ast.BlockStmt{Lbrace: lbrace, List: list, Rbrace: rbrace}
+
+ if typeSwitch {
+ return &ast.TypeSwitchStmt{Switch: pos, Init: s1, Assign: s2, Body: body}
+ }
+
+ return &ast.SwitchStmt{Switch: pos, Init: s1, Tag: p.makeExpr(s2, "switch expression"), Body: body}
+}
+
+func (p *parser) parseCommClause() *ast.CommClause {
+ if p.trace {
+ defer un(trace(p, "CommClause"))
+ }
+
+ p.openScope()
+ pos := p.pos
+ var comm ast.Stmt
+ if p.tok == token.CASE {
+ p.next()
+ lhs := p.parseLhsList()
+ if p.tok == token.ARROW {
+ // SendStmt
+ if len(lhs) > 1 {
+ p.errorExpected(lhs[0].Pos(), "1 expression")
+ // continue with first expression
+ }
+ arrow := p.pos
+ p.next()
+ rhs := p.parseRhs()
+ comm = &ast.SendStmt{Chan: lhs[0], Arrow: arrow, Value: rhs}
+ } else {
+ // RecvStmt
+ if tok := p.tok; tok == token.ASSIGN || tok == token.DEFINE {
+ // RecvStmt with assignment
+ if len(lhs) > 2 {
+ p.errorExpected(lhs[0].Pos(), "1 or 2 expressions")
+ // continue with first two expressions
+ lhs = lhs[0:2]
+ }
+ pos := p.pos
+ p.next()
+ rhs := p.parseRhs()
+ as := &ast.AssignStmt{Lhs: lhs, TokPos: pos, Tok: tok, Rhs: []ast.Expr{rhs}}
+ if tok == token.DEFINE {
+ p.shortVarDecl(as, lhs)
+ }
+ comm = as
+ } else {
+ // lhs must be single receive operation
+ if len(lhs) > 1 {
+ p.errorExpected(lhs[0].Pos(), "1 expression")
+ // continue with first expression
+ }
+ comm = &ast.ExprStmt{X: lhs[0]}
+ }
+ }
+ } else {
+ p.expect(token.DEFAULT)
+ }
+
+ colon := p.expect(token.COLON)
+ body := p.parseStmtList()
+ p.closeScope()
+
+ return &ast.CommClause{Case: pos, Comm: comm, Colon: colon, Body: body}
+}
+
+func (p *parser) parseSelectStmt() *ast.SelectStmt {
+ if p.trace {
+ defer un(trace(p, "SelectStmt"))
+ }
+
+ pos := p.expect(token.SELECT)
+ lbrace := p.expect(token.LBRACE)
+ var list []ast.Stmt
+ for p.tok == token.CASE || p.tok == token.DEFAULT {
+ list = append(list, p.parseCommClause())
+ }
+ rbrace := p.expect(token.RBRACE)
+ p.expectSemi()
+ body := &ast.BlockStmt{Lbrace: lbrace, List: list, Rbrace: rbrace}
+
+ return &ast.SelectStmt{Select: pos, Body: body}
+}
+
+func (p *parser) parseForStmt() ast.Stmt {
+ if p.trace {
+ defer un(trace(p, "ForStmt"))
+ }
+
+ pos := p.expect(token.FOR)
+ p.openScope()
+ defer p.closeScope()
+
+ var s1, s2, s3 ast.Stmt
+ var isRange bool
+ if p.tok != token.LBRACE {
+ prevLev := p.exprLev
+ p.exprLev = -1
+ if p.tok != token.SEMICOLON {
+ if p.tok == token.RANGE {
+ // "for range x" (nil lhs in assignment)
+ pos := p.pos
+ p.next()
+ y := []ast.Expr{&ast.UnaryExpr{OpPos: pos, Op: token.RANGE, X: p.parseRhs()}}
+ s2 = &ast.AssignStmt{Rhs: y}
+ isRange = true
+ } else {
+ s2, isRange = p.parseSimpleStmt(rangeOk)
+ }
+ }
+ if !isRange && p.tok == token.SEMICOLON {
+ p.next()
+ s1 = s2
+ s2 = nil
+ if p.tok != token.SEMICOLON {
+ s2, _ = p.parseSimpleStmt(basic)
+ }
+ p.expectSemi()
+ if p.tok != token.LBRACE {
+ s3, _ = p.parseSimpleStmt(basic)
+ }
+ }
+ p.exprLev = prevLev
+ }
+
+ body := p.parseBlockStmt()
+ p.expectSemi()
+
+ if isRange {
+ as := s2.(*ast.AssignStmt)
+ // check lhs
+ var key, value ast.Expr
+ switch len(as.Lhs) {
+ case 0:
+ // nothing to do
+ case 1:
+ key = as.Lhs[0]
+ case 2:
+ key, value = as.Lhs[0], as.Lhs[1]
+ default:
+ p.errorExpected(as.Lhs[len(as.Lhs)-1].Pos(), "at most 2 expressions")
+ return &ast.BadStmt{From: pos, To: p.safePos(body.End())}
+ }
+ // parseSimpleStmt returned a right-hand side that
+ // is a single unary expression of the form "range x"
+ x := as.Rhs[0].(*ast.UnaryExpr).X
+ return &ast.RangeStmt{
+ For: pos,
+ Key: key,
+ Value: value,
+ TokPos: as.TokPos,
+ Tok: as.Tok,
+ X: x,
+ Body: body,
+ }
+ }
+
+ // regular for statement
+ return &ast.ForStmt{
+ For: pos,
+ Init: s1,
+ Cond: p.makeExpr(s2, "boolean or range expression"),
+ Post: s3,
+ Body: body,
+ }
+}
+
+func (p *parser) parseStmt() (s ast.Stmt) {
+ if p.trace {
+ defer un(trace(p, "Statement"))
+ }
+
+ switch p.tok {
+ case token.CONST, token.TYPE, token.VAR:
+ s = &ast.DeclStmt{Decl: p.parseDecl(stmtStart)}
+ case
+ // tokens that may start an expression
+ token.IDENT, token.INT, token.FLOAT, token.IMAG, token.CHAR, token.STRING, token.FUNC, token.LPAREN, // operands
+ token.LBRACK, token.STRUCT, token.MAP, token.CHAN, token.INTERFACE, // composite types
+ token.ADD, token.SUB, token.MUL, token.AND, token.XOR, token.ARROW, token.NOT: // unary operators
+ s, _ = p.parseSimpleStmt(labelOk)
+ // because of the required look-ahead, labeled statements are
+ // parsed by parseSimpleStmt - don't expect a semicolon after
+ // them
+ if _, isLabeledStmt := s.(*ast.LabeledStmt); !isLabeledStmt {
+ p.expectSemi()
+ }
+ case token.GO:
+ s = p.parseGoStmt()
+ case token.DEFER:
+ s = p.parseDeferStmt()
+ case token.RETURN:
+ s = p.parseReturnStmt()
+ case token.BREAK, token.CONTINUE, token.GOTO, token.FALLTHROUGH:
+ s = p.parseBranchStmt(p.tok)
+ case token.LBRACE:
+ s = p.parseBlockStmt()
+ p.expectSemi()
+ case token.IF:
+ s = p.parseIfStmt()
+ case token.SWITCH:
+ s = p.parseSwitchStmt()
+ case token.SELECT:
+ s = p.parseSelectStmt()
+ case token.FOR:
+ s = p.parseForStmt()
+ case token.SEMICOLON:
+ // Is it ever possible to have an implicit semicolon
+ // producing an empty statement in a valid program?
+ // (handle correctly anyway)
+ s = &ast.EmptyStmt{Semicolon: p.pos, Implicit: p.lit == "\n"}
+ p.next()
+ case token.RBRACE:
+ // a semicolon may be omitted before a closing "}"
+ s = &ast.EmptyStmt{Semicolon: p.pos, Implicit: true}
+ default:
+ // no statement found
+ pos := p.pos
+ p.errorExpected(pos, "statement")
+ p.advance(stmtStart)
+ s = &ast.BadStmt{From: pos, To: p.pos}
+ }
+
+ return
+}
+
+// ----------------------------------------------------------------------------
+// Declarations
+
+type parseSpecFunction func(doc *ast.CommentGroup, keyword token.Token, iota int) ast.Spec
+
+func isValidImport(lit string) bool {
+ const illegalChars = `!"#$%&'()*,:;<=>?[\]^{|}` + "`\uFFFD"
+ s, _ := strconv.Unquote(lit) // go/scanner returns a legal string literal
+ for _, r := range s {
+ if !unicode.IsGraphic(r) || unicode.IsSpace(r) || strings.ContainsRune(illegalChars, r) {
+ return false
+ }
+ }
+ return s != ""
+}
+
+func (p *parser) parseImportSpec(doc *ast.CommentGroup, _ token.Token, _ int) ast.Spec {
+ if p.trace {
+ defer un(trace(p, "ImportSpec"))
+ }
+
+ var ident *ast.Ident
+ switch p.tok {
+ case token.PERIOD:
+ ident = &ast.Ident{NamePos: p.pos, Name: "."}
+ p.next()
+ case token.IDENT:
+ ident = p.parseIdent()
+ }
+
+ pos := p.pos
+ var path string
+ if p.tok == token.STRING {
+ path = p.lit
+ if !isValidImport(path) {
+ p.error(pos, "invalid import path: "+path)
+ }
+ p.next()
+ } else {
+ p.expect(token.STRING) // use expect() error handling
+ }
+ p.expectSemi() // call before accessing p.linecomment
+
+ // collect imports
+ spec := &ast.ImportSpec{
+ Doc: doc,
+ Name: ident,
+ Path: &ast.BasicLit{ValuePos: pos, Kind: token.STRING, Value: path},
+ Comment: p.lineComment,
+ }
+ p.imports = append(p.imports, spec)
+
+ return spec
+}
+
+func (p *parser) parseValueSpec(doc *ast.CommentGroup, keyword token.Token, iota int) ast.Spec {
+ if p.trace {
+ defer un(trace(p, keyword.String()+"Spec"))
+ }
+
+ pos := p.pos
+ idents := p.parseIdentList()
+ typ := p.tryType()
+ var values []ast.Expr
+ // always permit optional initialization for more tolerant parsing
+ if p.tok == token.ASSIGN {
+ p.next()
+ values = p.parseRhsList()
+ }
+ p.expectSemi() // call before accessing p.linecomment
+
+ switch keyword {
+ case token.VAR:
+ if typ == nil && values == nil {
+ p.error(pos, "missing variable type or initialization")
+ }
+ case token.CONST:
+ if values == nil && (iota == 0 || typ != nil) {
+ p.error(pos, "missing constant value")
+ }
+ }
+
+ // Go spec: The scope of a constant or variable identifier declared inside
+ // a function begins at the end of the ConstSpec or VarSpec and ends at
+ // the end of the innermost containing block.
+ // (Global identifiers are resolved in a separate phase after parsing.)
+ spec := &ast.ValueSpec{
+ Doc: doc,
+ Names: idents,
+ Type: typ,
+ Values: values,
+ Comment: p.lineComment,
+ }
+ kind := ast.Con
+ if keyword == token.VAR {
+ kind = ast.Var
+ }
+ p.declare(spec, iota, p.topScope, kind, idents...)
+
+ return spec
+}
+
+func (p *parser) parseTypeSpec(doc *ast.CommentGroup, _ token.Token, _ int) ast.Spec {
+ if p.trace {
+ defer un(trace(p, "TypeSpec"))
+ }
+
+ ident := p.parseIdent()
+
+ // Go spec: The scope of a type identifier declared inside a function begins
+ // at the identifier in the TypeSpec and ends at the end of the innermost
+ // containing block.
+ // (Global identifiers are resolved in a separate phase after parsing.)
+ spec := &ast.TypeSpec{Doc: doc, Name: ident}
+ p.declare(spec, nil, p.topScope, ast.Typ, ident)
+ if p.tok == token.ASSIGN {
+ spec.Assign = p.pos
+ p.next()
+ }
+ spec.Type = p.parseType()
+ p.expectSemi() // call before accessing p.linecomment
+ spec.Comment = p.lineComment
+
+ return spec
+}
+
+func (p *parser) parseGenDecl(keyword token.Token, f parseSpecFunction) *ast.GenDecl {
+ if p.trace {
+ defer un(trace(p, "GenDecl("+keyword.String()+")"))
+ }
+
+ doc := p.leadComment
+ pos := p.expect(keyword)
+ var lparen, rparen token.Pos
+ var list []ast.Spec
+ if p.tok == token.LPAREN {
+ lparen = p.pos
+ p.next()
+ for iota := 0; p.tok != token.RPAREN && p.tok != token.EOF; iota++ {
+ list = append(list, f(p.leadComment, keyword, iota))
+ }
+ rparen = p.expect(token.RPAREN)
+ p.expectSemi()
+ } else {
+ list = append(list, f(nil, keyword, 0))
+ }
+
+ return &ast.GenDecl{
+ Doc: doc,
+ TokPos: pos,
+ Tok: keyword,
+ Lparen: lparen,
+ Specs: list,
+ Rparen: rparen,
+ }
+}
+
+func (p *parser) parseFuncDecl() *ast.FuncDecl {
+ if p.trace {
+ defer un(trace(p, "FunctionDecl"))
+ }
+
+ doc := p.leadComment
+ pos := p.expect(token.FUNC)
+ scope := ast.NewScope(p.topScope) // function scope
+
+ var recv *ast.FieldList
+ if p.tok == token.LPAREN {
+ recv = p.parseParameters(scope, false)
+ }
+
+ ident := p.parseIdent()
+
+ params, results := p.parseSignature(scope)
+
+ var body *ast.BlockStmt
+ if p.tok == token.LBRACE {
+ body = p.parseBody(scope)
+ p.expectSemi()
+ } else if p.tok == token.SEMICOLON {
+ p.next()
+ if p.tok == token.LBRACE {
+ // opening { of function declaration on next line
+ p.error(p.pos, "unexpected semicolon or newline before {")
+ body = p.parseBody(scope)
+ p.expectSemi()
+ }
+ } else {
+ p.expectSemi()
+ }
+
+ decl := &ast.FuncDecl{
+ Doc: doc,
+ Recv: recv,
+ Name: ident,
+ Type: &ast.FuncType{
+ Func: pos,
+ Params: params,
+ Results: results,
+ },
+ Body: body,
+ }
+ if recv == nil {
+ // Go spec: The scope of an identifier denoting a constant, type,
+ // variable, or function (but not method) declared at top level
+ // (outside any function) is the package block.
+ //
+ // init() functions cannot be referred to and there may
+ // be more than one - don't put them in the pkgScope
+ if ident.Name != "init" {
+ p.declare(decl, nil, p.pkgScope, ast.Fun, ident)
+ }
+ }
+
+ return decl
+}
+
+func (p *parser) parseDecl(sync map[token.Token]bool) ast.Decl {
+ if p.trace {
+ defer un(trace(p, "Declaration"))
+ }
+
+ var f parseSpecFunction
+ switch p.tok {
+ case token.CONST, token.VAR:
+ f = p.parseValueSpec
+
+ case token.TYPE:
+ f = p.parseTypeSpec
+
+ case token.FUNC:
+ return p.parseFuncDecl()
+
+ default:
+ pos := p.pos
+ p.errorExpected(pos, "declaration")
+ p.advance(sync)
+ return &ast.BadDecl{From: pos, To: p.pos}
+ }
+
+ return p.parseGenDecl(p.tok, f)
+}
+
+// ----------------------------------------------------------------------------
+// Source files
+
+func (p *parser) parseFile() *ast.File {
+ if p.trace {
+ defer un(trace(p, "File"))
+ }
+
+ // Don't bother parsing the rest if we had errors scanning the first token.
+ // Likely not a Go source file at all.
+ if p.errors.Len() != 0 {
+ return nil
+ }
+
+ // package clause
+ doc := p.leadComment
+ pos := p.expect(token.PACKAGE)
+ // Go spec: The package clause is not a declaration;
+ // the package name does not appear in any scope.
+ ident := p.parseIdent()
+ if ident.Name == "_" && p.mode&DeclarationErrors != 0 {
+ p.error(p.pos, "invalid package name _")
+ }
+ p.expectSemi()
+
+ // Don't bother parsing the rest if we had errors parsing the package clause.
+ // Likely not a Go source file at all.
+ if p.errors.Len() != 0 {
+ return nil
+ }
+
+ p.openScope()
+ p.pkgScope = p.topScope
+ var decls []ast.Decl
+ if p.mode&PackageClauseOnly == 0 {
+ // import decls
+ for p.tok == token.IMPORT {
+ decls = append(decls, p.parseGenDecl(token.IMPORT, p.parseImportSpec))
+ }
+
+ if p.mode&ImportsOnly == 0 {
+ // rest of package body
+ for p.tok != token.EOF {
+ decls = append(decls, p.parseDecl(declStart))
+ }
+ }
+ }
+ p.closeScope()
+ assert(p.topScope == nil, "unbalanced scopes")
+ assert(p.labelScope == nil, "unbalanced label scopes")
+
+ // resolve global identifiers within the same file
+ i := 0
+ for _, ident := range p.unresolved {
+ // i <= index for current ident
+ assert(ident.Obj == unresolved, "object already resolved")
+ ident.Obj = p.pkgScope.Lookup(ident.Name) // also removes unresolved sentinel
+ if ident.Obj == nil {
+ p.unresolved[i] = ident
+ i++
+ }
+ }
+
+ return &ast.File{
+ Doc: doc,
+ Package: pos,
+ Name: ident,
+ Decls: decls,
+ Scope: p.pkgScope,
+ Imports: p.imports,
+ Unresolved: p.unresolved[0:i],
+ Comments: p.comments,
+ }
+}
generated by cgit v1.2.3 (git 2.39.1) at 2024-11-15 14:15:43 +0000