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Diffstat (limited to 'src/go/printer/testdata/parser.go')
| -rw-r--r-- | src/go/printer/testdata/parser.go | 2153 |
1 files changed, 2153 insertions, 0 deletions
diff --git a/src/go/printer/testdata/parser.go b/src/go/printer/testdata/parser.go new file mode 100644 index 0000000..80b476c --- /dev/null +++ b/src/go/printer/testdata/parser.go @@ -0,0 +1,2153 @@ +// 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. + +package parser + +import ( + "fmt" + "go/ast" + "go/scanner" + "go/token" +) + +// The mode parameter to the Parse* functions is a set of flags (or 0). +// They control the amount of source code parsed and other optional +// parser functionality. +// +const ( + PackageClauseOnly uint = 1 << iota // parsing stops after package clause + ImportsOnly // parsing stops after import declarations + ParseComments // parse comments and add them to AST + Trace // print a trace of parsed productions + DeclarationErrors // report declaration errors +) + +// The parser structure holds the parser's internal state. +type parser struct { + file *token.File + scanner.ErrorVector + scanner scanner.Scanner + + // Tracing/debugging + mode uint // parsing mode + trace bool // == (mode & Trace != 0) + indent uint // 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 + + // Non-syntactic parser control + exprLev int // < 0: in control clause, >= 0: in 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 scope + // (maintained by open/close LabelScope) + labelScope *ast.Scope // label scope for current function + targetStack [][]*ast.Ident // stack of unresolved labels +} + +// scannerMode returns the scanner mode bits given the parser's mode bits. +func scannerMode(mode uint) uint { + var m uint = scanner.InsertSemis + if mode&ParseComments != 0 { + m |= scanner.ScanComments + } + return m +} + +func (p *parser) init(fset *token.FileSet, filename string, src []byte, mode uint) { + p.file = fset.AddFile(filename, fset.Base(), len(src)) + p.scanner.Init(p.file, src, p, scannerMode(mode)) + + p.mode = mode + p.trace = mode&Trace != 0 // for convenience (p.trace is used frequently) + + p.next() + + // set up the pkgScope here (as opposed to in parseFile) because + // there are other parser entry points (ParseExpr, etc.) + p.openScope() + p.pkgScope = p.topScope + + // for the same reason, set up a label scope + p.openLabelScope() +} + +// ---------------------------------------------------------------------------- +// 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 interface{}, scope *ast.Scope, kind ast.ObjKind, idents ...*ast.Ident) { + for _, ident := range idents { + assert(ident.Obj == nil, "identifier already declared or resolved") + if ident.Name != "_" { + obj := ast.NewObj(kind, ident.Name) + // remember the corresponding declaration for redeclaration + // errors and global variable resolution/typechecking phase + obj.Decl = decl + 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)) + } + ident.Obj = obj + } + } +} + +func (p *parser) shortVarDecl(idents []*ast.Ident) { + // 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 _, ident := range idents { + assert(ident.Obj == nil, "identifier already declared or resolved") + if ident.Name != "_" { + obj := ast.NewObj(ast.Var, ident.Name) + // short var declarations cannot have redeclaration errors + // and are not global => no need to remember the respective + // declaration + alt := p.topScope.Insert(obj) + if alt == nil { + n++ // new declaration + alt = obj + } + ident.Obj = alt + } + } + if n == 0 && p.mode&DeclarationErrors != 0 { + p.error(idents[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) + +func (p *parser) resolve(x ast.Expr) { + // 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 + ident.Obj = unresolved + p.unresolved = append(p.unresolved, ident) +} + +// ---------------------------------------------------------------------------- +// Parsing support + +func (p *parser) printTrace(a ...interface{}) { + const dots = ". . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . " + + ". . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . " + const n = uint(len(dots)) + pos := p.file.Position(p.pos) + fmt.Printf("%5d:%3d: ", pos.Line, pos.Column) + i := 2 * p.indent + for ; i > n; i -= n { + fmt.Print(dots) + } + 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{p.pos, 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. An empty line or non-comment +// token terminates a comment group. +// +func (p *parser) consumeCommentGroup() (comments *ast.CommentGroup, endline int) { + var list []*ast.Comment + endline = p.file.Line(p.pos) + for p.tok == token.COMMENT && endline+1 >= p.file.Line(p.pos) { + var comment *ast.Comment + comment, endline = p.consumeComment() + list = append(list, comment) + } + + // add comment group to the comments list + comments = &ast.CommentGroup{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 + line := p.file.Line(p.pos) // current line + p.next0() + + if p.tok == token.COMMENT { + var comment *ast.CommentGroup + var endline int + + if p.file.Line(p.pos) == line { + // 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() + if p.file.Line(p.pos) != endline { + // 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() + } + + 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 + } + } +} + +func (p *parser) error(pos token.Pos, msg string) { + p.Error(p.file.Position(pos), 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 + if p.tok == token.SEMICOLON && p.lit[0] == '\n' { + msg += ", found newline" + } else { + msg += ", found '" + p.tok.String() + "'" + if p.tok.IsLiteral() { + msg += " " + p.lit + } + } + } + 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 +} + +func (p *parser) expectSemi() { + if p.tok != token.RPAREN && p.tok != token.RBRACE { + p.expect(token.SEMICOLON) + } +} + +func assert(cond bool, msg string) { + if !cond { + panic("go/parser internal error: " + msg) + } +} + +// ---------------------------------------------------------------------------- +// 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{pos, name, nil} +} + +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.parseExpr(lhs)) + for p.tok == token.COMMA { + p.next() + list = append(list, p.parseExpr(lhs)) + } + + return +} + +func (p *parser) parseLhsList() []ast.Expr { + list := p.parseExprList(true) + switch p.tok { + case token.DEFINE: + // lhs of a short variable declaration + p.shortVarDecl(p.makeIdentList(list)) + 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) + } + } + return list +} + +func (p *parser) parseRhsList() []ast.Expr { + return p.parseExprList(false) +} + +// ---------------------------------------------------------------------------- +// 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.next() // make progress + return &ast.BadExpr{pos, 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{ident, sel} + } + + return ident +} + +func (p *parser) parseArrayType(ellipsisOk bool) ast.Expr { + if p.trace { + defer un(trace(p, "ArrayType")) + } + + lbrack := p.expect(token.LBRACK) + var len ast.Expr + if ellipsisOk && p.tok == token.ELLIPSIS { + len = &ast.Ellipsis{p.pos, nil} + p.next() + } else if p.tok != token.RBRACK { + len = p.parseRhs() + } + p.expect(token.RBRACK) + elt := p.parseType() + + return &ast.ArrayType{lbrack, len, 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 { + pos := x.(ast.Expr).Pos() + p.errorExpected(pos, "identifier") + ident = &ast.Ident{pos, "_", nil} + } + 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 + + // fields + list, typ := p.parseVarList(false) + + // optional tag + var tag *ast.BasicLit + if p.tok == token.STRING { + tag = &ast.BasicLit{p.pos, p.tok, p.lit} + p.next() + } + + // 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 + p.resolve(typ) + if n := len(list); n > 1 || !isTypeName(deref(typ)) { + pos := typ.Pos() + p.errorExpected(pos, "anonymous field") + typ = &ast.BadExpr{pos, list[n-1].End()} + } + } + + p.expectSemi() // call before accessing p.linecomment + + field := &ast.Field{doc, idents, typ, tag, p.lineComment} + p.declare(field, scope, ast.Var, idents...) + + 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) + + // TODO(gri): store struct scope in AST + return &ast.StructType{pos, &ast.FieldList{lbrace, list, rbrace}, false} +} + +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, base} +} + +func (p *parser) tryVarType(isParam bool) ast.Expr { + if isParam && p.tok == token.ELLIPSIS { + pos := p.pos + p.next() + typ := p.tryIdentOrType(isParam) // don't use parseType so we can provide better error message + if typ == nil { + p.error(pos, "'...' parameter is missing type") + typ = &ast.BadExpr{pos, p.pos} + } + if p.tok != token.RPAREN { + p.error(pos, "can use '...' with last parameter type only") + } + return &ast.Ellipsis{pos, typ} + } + return p.tryIdentOrType(false) +} + +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{pos, p.pos} + } + return typ +} + +func (p *parser) parseVarList(isParam bool) (list []ast.Expr, typ ast.Expr) { + if p.trace { + defer un(trace(p, "VarList")) + } + + // a list of identifiers looks like a list of type names + for { + // parseVarType accepts any type (including parenthesized ones) + // even though the syntax does not permit them here: we + // accept them all for more robust parsing and complain + // afterwards + list = append(list, p.parseVarType(isParam)) + if p.tok != token.COMMA { + break + } + p.next() + } + + // if we had a list of identifiers, it must be followed by a type + typ = p.tryVarType(isParam) + if typ != nil { + p.resolve(typ) + } + + return +} + +func (p *parser) parseParameterList(scope *ast.Scope, ellipsisOk bool) (params []*ast.Field) { + if p.trace { + defer un(trace(p, "ParameterList")) + } + + list, typ := p.parseVarList(ellipsisOk) + if typ != nil { + // IdentifierList Type + idents := p.makeIdentList(list) + field := &ast.Field{nil, idents, typ, nil, nil} + 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, scope, ast.Var, idents...) + if p.tok == token.COMMA { + p.next() + } + + for p.tok != token.RPAREN && p.tok != token.EOF { + idents := p.parseIdentList() + typ := p.parseVarType(ellipsisOk) + field := &ast.Field{nil, idents, typ, nil, nil} + 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, scope, ast.Var, idents...) + if p.tok != token.COMMA { + break + } + p.next() + } + + } else { + // Type { "," Type } (anonymous parameters) + params = make([]*ast.Field, len(list)) + for i, x := range list { + p.resolve(x) + params[i] = &ast.Field{Type: x} + } + } + + 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{lparen, params, 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{pos, params, 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{token.NoPos, params, results} + } else { + // embedded interface + typ = x + } + p.expectSemi() // call before accessing p.linecomment + + spec := &ast.Field{doc, idents, typ, nil, p.lineComment} + p.declare(spec, 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) + + // TODO(gri): store interface scope in AST + return &ast.InterfaceType{pos, &ast.FieldList{lbrace, list, rbrace}, false} +} + +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{pos, key, value} +} + +func (p *parser) parseChanType() *ast.ChanType { + if p.trace { + defer un(trace(p, "ChanType")) + } + + pos := p.pos + dir := ast.SEND | ast.RECV + if p.tok == token.CHAN { + p.next() + if p.tok == token.ARROW { + p.next() + dir = ast.SEND + } + } else { + p.expect(token.ARROW) + p.expect(token.CHAN) + dir = ast.RECV + } + value := p.parseType() + + return &ast.ChanType{pos, dir, value} +} + +// If the result is an identifier, it is not resolved. +func (p *parser) tryIdentOrType(ellipsisOk bool) ast.Expr { + switch p.tok { + case token.IDENT: + return p.parseTypeName() + case token.LBRACK: + return p.parseArrayType(ellipsisOk) + 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, typ, rparen} + } + + // no type found + return nil +} + +func (p *parser) tryType() ast.Expr { + typ := p.tryIdentOrType(false) + 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.expect(token.RBRACE) + + return &ast.BlockStmt{lbrace, list, 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.expect(token.RBRACE) + + return &ast.BlockStmt{lbrace, list, 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{typ, 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{p.pos, p.tok, p.lit} + p.next() + return x + + case token.LPAREN: + lparen := p.pos + p.next() + p.exprLev++ + x := p.parseRhs() + p.exprLev-- + rparen := p.expect(token.RPAREN) + return &ast.ParenExpr{lparen, x, rparen} + + case token.FUNC: + return p.parseFuncTypeOrLit() + + default: + if typ := p.tryIdentOrType(true); typ != nil { + // could be type for composite literal or conversion + _, isIdent := typ.(*ast.Ident) + assert(!isIdent, "type cannot be identifier") + return typ + } + } + + pos := p.pos + p.errorExpected(pos, "operand") + p.next() // make progress + return &ast.BadExpr{pos, 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, sel} +} + +func (p *parser) parseTypeAssertion(x ast.Expr) ast.Expr { + if p.trace { + defer un(trace(p, "TypeAssertion")) + } + + p.expect(token.LPAREN) + var typ ast.Expr + if p.tok == token.TYPE { + // type switch: typ == nil + p.next() + } else { + typ = p.parseType() + } + p.expect(token.RPAREN) + + return &ast.TypeAssertExpr{x, typ} +} + +func (p *parser) parseIndexOrSlice(x ast.Expr) ast.Expr { + if p.trace { + defer un(trace(p, "IndexOrSlice")) + } + + lbrack := p.expect(token.LBRACK) + p.exprLev++ + var low, high ast.Expr + isSlice := false + if p.tok != token.COLON { + low = p.parseRhs() + } + if p.tok == token.COLON { + isSlice = true + p.next() + if p.tok != token.RBRACK { + high = p.parseRhs() + } + } + p.exprLev-- + rbrack := p.expect(token.RBRACK) + + if isSlice { + return &ast.SliceExpr{x, lbrack, low, high, rbrack} + } + return &ast.IndexExpr{x, lbrack, low, 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.parseRhs()) + if p.tok == token.ELLIPSIS { + ellipsis = p.pos + p.next() + } + if p.tok != token.COMMA { + break + } + p.next() + } + p.exprLev-- + rparen := p.expect(token.RPAREN) + + return &ast.CallExpr{fun, lparen, list, ellipsis, rparen} +} + +func (p *parser) parseElement(keyOk bool) ast.Expr { + if p.trace { + defer un(trace(p, "Element")) + } + + if p.tok == token.LBRACE { + return p.parseLiteralValue(nil) + } + + x := p.parseExpr(keyOk) // don't resolve if map key + if keyOk { + if p.tok == token.COLON { + colon := p.pos + p.next() + return &ast.KeyValueExpr{x, colon, p.parseElement(false)} + } + p.resolve(x) // not a map key + } + + 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(true)) + if p.tok != token.COMMA { + 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.expect(token.RBRACE) + return &ast.CompositeLit{typ, lbrace, elts, rbrace} +} + +// checkExpr checks that x is an expression (and not a type). +func (p *parser) checkExpr(x ast.Expr) ast.Expr { + switch t := 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 { + // the form X.(type) is only allowed in type switch expressions + p.errorExpected(x.Pos(), "expression") + x = &ast.BadExpr{x.Pos(), x.End()} + } + case *ast.CallExpr: + case *ast.StarExpr: + case *ast.UnaryExpr: + if t.Op == token.RANGE { + // the range operator is only allowed at the top of a for statement + p.errorExpected(x.Pos(), "expression") + x = &ast.BadExpr{x.Pos(), x.End()} + } + case *ast.BinaryExpr: + default: + // all other nodes are not proper expressions + p.errorExpected(x.Pos(), "expression") + x = &ast.BadExpr{x.Pos(), 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.UnaryExpr: + if t.Op == token.RANGE { + // the range operator is only allowed at the top of a for statement + p.errorExpected(x.Pos(), "expression") + x = &ast.BadExpr{x.Pos(), x.End()} + } + case *ast.ArrayType: + if len, isEllipsis := t.Len.(*ast.Ellipsis); isEllipsis { + p.error(len.Pos(), "expected array length, found '...'") + x = &ast.BadExpr{x.Pos(), 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.checkExpr(x)) + case token.LPAREN: + x = p.parseTypeAssertion(p.checkExpr(x)) + default: + pos := p.pos + p.next() // make progress + p.errorExpected(pos, "selector or type assertion") + x = &ast.BadExpr{pos, p.pos} + } + 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, token.RANGE: + pos, op := p.pos, p.tok + p.next() + x := p.parseUnaryExpr(false) + return &ast.UnaryExpr{pos, op, p.checkExpr(x)} + + case token.ARROW: + // channel type or receive expression + pos := p.pos + p.next() + if p.tok == token.CHAN { + p.next() + value := p.parseType() + return &ast.ChanType{pos, ast.RECV, value} + } + + x := p.parseUnaryExpr(false) + return &ast.UnaryExpr{pos, token.ARROW, p.checkExpr(x)} + + case token.MUL: + // pointer type or unary "*" expression + pos := p.pos + p.next() + x := p.parseUnaryExpr(false) + return &ast.StarExpr{pos, p.checkExprOrType(x)} + } + + return p.parsePrimaryExpr(lhs) +} + +// 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 prec := p.tok.Precedence(); prec >= prec1; prec-- { + for p.tok.Precedence() == prec { + pos, op := p.pos, p.tok + p.next() + if lhs { + p.resolve(x) + lhs = false + } + y := p.parseBinaryExpr(false, prec+1) + x = &ast.BinaryExpr{p.checkExpr(x), pos, op, p.checkExpr(y)} + } + } + + return x +} + +// If lhs is set and the result is an identifier, it is not resolved. +// TODO(gri): parseExpr may return a type or even a raw type ([..]int) - +// should reject when a type/raw type is obviously not allowed +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 { + return p.parseExpr(false) +} + +// ---------------------------------------------------------------------------- +// Statements + +func (p *parser) parseSimpleStmt(labelOk bool) ast.Stmt { + 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 + pos, tok := p.pos, p.tok + p.next() + y := p.parseRhsList() + return &ast.AssignStmt{x, pos, tok, y} + } + + 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); 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, colon, p.parseStmt()} + p.declare(stmt, p.labelScope, ast.Lbl, label) + return stmt + } + p.error(x[0].Pos(), "illegal label declaration") + return &ast.BadStmt{x[0].Pos(), colon + 1} + + case token.ARROW: + // send statement + arrow := p.pos + p.next() // consume "<-" + y := p.parseRhs() + return &ast.SendStmt{x[0], arrow, y} + + case token.INC, token.DEC: + // increment or decrement + s := &ast.IncDecStmt{x[0], p.pos, p.tok} + p.next() // consume "++" or "--" + return s + } + + // expression + return &ast.ExprStmt{x[0]} +} + +func (p *parser) parseCallExpr() *ast.CallExpr { + x := p.parseRhs() + if call, isCall := x.(*ast.CallExpr); isCall { + return call + } + p.errorExpected(x.Pos(), "function/method call") + return nil +} + +func (p *parser) parseGoStmt() ast.Stmt { + if p.trace { + defer un(trace(p, "GoStmt")) + } + + pos := p.expect(token.GO) + call := p.parseCallExpr() + p.expectSemi() + if call == nil { + return &ast.BadStmt{pos, pos + 2} // len("go") + } + + return &ast.GoStmt{pos, call} +} + +func (p *parser) parseDeferStmt() ast.Stmt { + if p.trace { + defer un(trace(p, "DeferStmt")) + } + + pos := p.expect(token.DEFER) + call := p.parseCallExpr() + p.expectSemi() + if call == nil { + return &ast.BadStmt{pos, pos + 5} // len("defer") + } + + return &ast.DeferStmt{pos, 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{pos, 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{pos, tok, label} +} + +func (p *parser) makeExpr(s ast.Stmt) ast.Expr { + if s == nil { + return nil + } + if es, isExpr := s.(*ast.ExprStmt); isExpr { + return p.checkExpr(es.X) + } + p.error(s.Pos(), "expected condition, found simple statement") + return &ast.BadExpr{s.Pos(), s.End()} +} + +func (p *parser) parseIfStmt() *ast.IfStmt { + if p.trace { + defer un(trace(p, "IfStmt")) + } + + pos := p.expect(token.IF) + p.openScope() + defer p.closeScope() + + var s ast.Stmt + var x ast.Expr + { + prevLev := p.exprLev + p.exprLev = -1 + if p.tok == token.SEMICOLON { + p.next() + x = p.parseRhs() + } else { + s = p.parseSimpleStmt(false) + if p.tok == token.SEMICOLON { + p.next() + x = p.parseRhs() + } else { + x = p.makeExpr(s) + s = nil + } + } + p.exprLev = prevLev + } + + body := p.parseBlockStmt() + var else_ ast.Stmt + if p.tok == token.ELSE { + p.next() + else_ = p.parseStmt() + } else { + p.expectSemi() + } + + return &ast.IfStmt{pos, s, x, body, 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(exprSwitch 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 exprSwitch { + list = p.parseRhsList() + } else { + list = p.parseTypeList() + } + } else { + p.expect(token.DEFAULT) + } + + colon := p.expect(token.COLON) + p.openScope() + body := p.parseStmtList() + p.closeScope() + + return &ast.CaseClause{pos, list, colon, body} +} + +func isExprSwitch(s ast.Stmt) bool { + if s == nil { + return true + } + if e, ok := s.(*ast.ExprStmt); ok { + if a, ok := e.X.(*ast.TypeAssertExpr); ok { + return a.Type != nil // regular type assertion + } + 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(false) + } + if p.tok == token.SEMICOLON { + p.next() + s1 = s2 + s2 = nil + if p.tok != token.LBRACE { + s2 = p.parseSimpleStmt(false) + } + } + p.exprLev = prevLev + } + + exprSwitch := isExprSwitch(s2) + lbrace := p.expect(token.LBRACE) + var list []ast.Stmt + for p.tok == token.CASE || p.tok == token.DEFAULT { + list = append(list, p.parseCaseClause(exprSwitch)) + } + rbrace := p.expect(token.RBRACE) + p.expectSemi() + body := &ast.BlockStmt{lbrace, list, rbrace} + + if exprSwitch { + return &ast.SwitchStmt{pos, s1, p.makeExpr(s2), body} + } + // type switch + // TODO(gri): do all the checks! + return &ast.TypeSwitchStmt{pos, s1, s2, 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{lhs[0], arrow, rhs} + } else { + // RecvStmt + pos := p.pos + tok := p.tok + var rhs ast.Expr + if 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] + } + p.next() + rhs = p.parseRhs() + } else { + // rhs must be single receive operation + if len(lhs) > 1 { + p.errorExpected(lhs[0].Pos(), "1 expression") + // continue with first expression + } + rhs = lhs[0] + lhs = nil // there is no lhs + } + if x, isUnary := rhs.(*ast.UnaryExpr); !isUnary || x.Op != token.ARROW { + p.errorExpected(rhs.Pos(), "send or receive operation") + rhs = &ast.BadExpr{rhs.Pos(), rhs.End()} + } + if lhs != nil { + comm = &ast.AssignStmt{lhs, pos, tok, []ast.Expr{rhs}} + } else { + comm = &ast.ExprStmt{rhs} + } + } + } else { + p.expect(token.DEFAULT) + } + + colon := p.expect(token.COLON) + body := p.parseStmtList() + p.closeScope() + + return &ast.CommClause{pos, comm, colon, 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, list, rbrace} + + return &ast.SelectStmt{pos, 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 + if p.tok != token.LBRACE { + prevLev := p.exprLev + p.exprLev = -1 + if p.tok != token.SEMICOLON { + s2 = p.parseSimpleStmt(false) + } + if p.tok == token.SEMICOLON { + p.next() + s1 = s2 + s2 = nil + if p.tok != token.SEMICOLON { + s2 = p.parseSimpleStmt(false) + } + p.expectSemi() + if p.tok != token.LBRACE { + s3 = p.parseSimpleStmt(false) + } + } + p.exprLev = prevLev + } + + body := p.parseBlockStmt() + p.expectSemi() + + if as, isAssign := s2.(*ast.AssignStmt); isAssign { + // possibly a for statement with a range clause; check assignment operator + if as.Tok != token.ASSIGN && as.Tok != token.DEFINE { + p.errorExpected(as.TokPos, "'=' or ':='") + return &ast.BadStmt{pos, body.End()} + } + // check lhs + var key, value ast.Expr + switch len(as.Lhs) { + case 2: + key, value = as.Lhs[0], as.Lhs[1] + case 1: + key = as.Lhs[0] + default: + p.errorExpected(as.Lhs[0].Pos(), "1 or 2 expressions") + return &ast.BadStmt{pos, body.End()} + } + // check rhs + if len(as.Rhs) != 1 { + p.errorExpected(as.Rhs[0].Pos(), "1 expression") + return &ast.BadStmt{pos, body.End()} + } + if rhs, isUnary := as.Rhs[0].(*ast.UnaryExpr); isUnary && rhs.Op == token.RANGE { + // rhs is range expression + // (any short variable declaration was handled by parseSimpleStat above) + return &ast.RangeStmt{pos, key, value, as.TokPos, as.Tok, rhs.X, body} + } + p.errorExpected(s2.Pos(), "range clause") + return &ast.BadStmt{pos, body.End()} + } + + // regular for statement + return &ast.ForStmt{pos, s1, p.makeExpr(s2), s3, 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{p.parseDecl()} + case + // tokens that may start a top-level expression + token.IDENT, token.INT, token.FLOAT, token.CHAR, token.STRING, token.FUNC, token.LPAREN, // operand + token.LBRACK, token.STRUCT, // composite type + token.MUL, token.AND, token.ARROW, token.ADD, token.SUB, token.XOR: // unary operators + s = p.parseSimpleStmt(true) + // 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: + s = &ast.EmptyStmt{p.pos} + p.next() + case token.RBRACE: + // a semicolon may be omitted before a closing "}" + s = &ast.EmptyStmt{p.pos} + default: + // no statement found + pos := p.pos + p.errorExpected(pos, "statement") + p.next() // make progress + s = &ast.BadStmt{pos, p.pos} + } + + return +} + +// ---------------------------------------------------------------------------- +// Declarations + +type parseSpecFunction func(p *parser, doc *ast.CommentGroup, iota int) ast.Spec + +func parseImportSpec(p *parser, doc *ast.CommentGroup, _ int) ast.Spec { + if p.trace { + defer un(trace(p, "ImportSpec")) + } + + var ident *ast.Ident + switch p.tok { + case token.PERIOD: + ident = &ast.Ident{p.pos, ".", nil} + p.next() + case token.IDENT: + ident = p.parseIdent() + } + + var path *ast.BasicLit + if p.tok == token.STRING { + path = &ast.BasicLit{p.pos, p.tok, p.lit} + p.next() + } else { + p.expect(token.STRING) // use expect() error handling + } + p.expectSemi() // call before accessing p.linecomment + + // collect imports + spec := &ast.ImportSpec{doc, ident, path, p.lineComment} + p.imports = append(p.imports, spec) + + return spec +} + +func parseConstSpec(p *parser, doc *ast.CommentGroup, iota int) ast.Spec { + if p.trace { + defer un(trace(p, "ConstSpec")) + } + + idents := p.parseIdentList() + typ := p.tryType() + var values []ast.Expr + if typ != nil || p.tok == token.ASSIGN || iota == 0 { + p.expect(token.ASSIGN) + values = p.parseRhsList() + } + p.expectSemi() // call before accessing p.linecomment + + // 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, idents, typ, values, p.lineComment} + p.declare(spec, p.topScope, ast.Con, idents...) + + return spec +} + +func parseTypeSpec(p *parser, doc *ast.CommentGroup, _ 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, ident, nil, nil} + p.declare(spec, p.topScope, ast.Typ, ident) + + spec.Type = p.parseType() + p.expectSemi() // call before accessing p.linecomment + spec.Comment = p.lineComment + + return spec +} + +func parseVarSpec(p *parser, doc *ast.CommentGroup, _ int) ast.Spec { + if p.trace { + defer un(trace(p, "VarSpec")) + } + + idents := p.parseIdentList() + typ := p.tryType() + var values []ast.Expr + if typ == nil || p.tok == token.ASSIGN { + p.expect(token.ASSIGN) + values = p.parseRhsList() + } + p.expectSemi() // call before accessing p.linecomment + + // 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, idents, typ, values, p.lineComment} + p.declare(spec, p.topScope, ast.Var, idents...) + + 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, p.leadComment, iota)) + } + rparen = p.expect(token.RPAREN) + p.expectSemi() + } else { + list = append(list, f(p, nil, 0)) + } + + return &ast.GenDecl{doc, pos, keyword, lparen, list, rparen} +} + +func (p *parser) parseReceiver(scope *ast.Scope) *ast.FieldList { + if p.trace { + defer un(trace(p, "Receiver")) + } + + pos := p.pos + par := p.parseParameters(scope, false) + + // must have exactly one receiver + if par.NumFields() != 1 { + p.errorExpected(pos, "exactly one receiver") + // TODO determine a better range for BadExpr below + par.List = []*ast.Field{{Type: &ast.BadExpr{pos, pos}}} + return par + } + + // recv type must be of the form ["*"] identifier + recv := par.List[0] + base := deref(recv.Type) + if _, isIdent := base.(*ast.Ident); !isIdent { + p.errorExpected(base.Pos(), "(unqualified) identifier") + par.List = []*ast.Field{{Type: &ast.BadExpr{recv.Pos(), recv.End()}}} + } + + return par +} + +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.parseReceiver(scope) + } + + ident := p.parseIdent() + + params, results := p.parseSignature(scope) + + var body *ast.BlockStmt + if p.tok == token.LBRACE { + body = p.parseBody(scope) + } + p.expectSemi() + + decl := &ast.FuncDecl{doc, recv, ident, &ast.FuncType{pos, params, results}, 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, p.pkgScope, ast.Fun, ident) + } + } + + return decl +} + +func (p *parser) parseDecl() ast.Decl { + if p.trace { + defer un(trace(p, "Declaration")) + } + + var f parseSpecFunction + switch p.tok { + case token.CONST: + f = parseConstSpec + + case token.TYPE: + f = parseTypeSpec + + case token.VAR: + f = parseVarSpec + + case token.FUNC: + return p.parseFuncDecl() + + default: + pos := p.pos + p.errorExpected(pos, "declaration") + p.next() // make progress + decl := &ast.BadDecl{pos, p.pos} + return decl + } + + return p.parseGenDecl(p.tok, f) +} + +func (p *parser) parseDeclList() (list []ast.Decl) { + if p.trace { + defer un(trace(p, "DeclList")) + } + + for p.tok != token.EOF { + list = append(list, p.parseDecl()) + } + + return +} + +// ---------------------------------------------------------------------------- +// Source files + +func (p *parser) parseFile() *ast.File { + if p.trace { + defer un(trace(p, "File")) + } + + // 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.error(p.pos, "invalid package name _") + } + p.expectSemi() + + var decls []ast.Decl + + // Don't bother parsing the rest if we had errors already. + // Likely not a Go source file at all. + + if p.ErrorCount() == 0 && p.mode&PackageClauseOnly == 0 { + // import decls + for p.tok == token.IMPORT { + decls = append(decls, p.parseGenDecl(token.IMPORT, parseImportSpec)) + } + + if p.mode&ImportsOnly == 0 { + // rest of package body + for p.tok != token.EOF { + decls = append(decls, p.parseDecl()) + } + } + } + + assert(p.topScope == p.pkgScope, "imbalanced 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++ + } + } + + // TODO(gri): store p.imports in AST + return &ast.File{doc, pos, ident, decls, p.pkgScope, p.imports, p.unresolved[0:i], p.comments} +} |