1 // Copyright 2009 The Go Authors. All rights reserved.
2 // Use of this source code is governed by a BSD-style
3 // license that can be found in the LICENSE file.
5 // This file implements printing of AST nodes; specifically
6 // expressions, statements, declarations, and files. It uses
7 // the print functionality implemented in printer.go.
18 // Other formatting issues:
19 // - better comment formatting for /*-style comments at the end of a line (e.g. a declaration)
20 // when the comment spans multiple lines; if such a comment is just two lines, formatting is
22 // - formatting of expression lists
23 // - should use blank instead of tab to separate one-line function bodies from
24 // the function header unless there is a group of consecutive one-liners
26 // ----------------------------------------------------------------------------
29 // Print as many newlines as necessary (but at least min newlines) to get to
30 // the current line. ws is printed before the first line break. If newSection
31 // is set, the first line break is printed as formfeed. Returns true if any
32 // line break was printed; returns false otherwise.
34 // TODO(gri): linebreak may add too many lines if the next statement at "line"
35 // is preceded by comments because the computation of n assumes
36 // the current position before the comment and the target position
37 // after the comment. Thus, after interspersing such comments, the
38 // space taken up by them is not considered to reduce the number of
39 // linebreaks. At the moment there is no easy way to know about
40 // future (not yet interspersed) comments in this function.
42 func (p *printer) linebreak(line, min int, ws whiteSpace, newSection bool) (printedBreak bool) {
43 n := nlimit(line - p.pos.Line)
61 // setComment sets g as the next comment if g != nil and if node comments
62 // are enabled - this mode is used when printing source code fragments such
63 // as exports only. It assumes that there are no other pending comments to
65 func (p *printer) setComment(g *ast.CommentGroup) {
66 if g == nil || !p.useNodeComments {
69 if p.comments == nil {
70 // initialize p.comments lazily
71 p.comments = make([]*ast.CommentGroup, 1)
72 } else if p.cindex < len(p.comments) {
73 // for some reason there are pending comments; this
74 // should never happen - handle gracefully and flush
75 // all comments up to g, ignore anything after that
76 p.flush(p.posFor(g.List[0].Pos()), token.ILLEGAL)
80 p.nextComment() // get comment ready for use
83 type exprListMode uint
86 commaTerm exprListMode = 1 << iota // list is optionally terminated by a comma
87 noIndent // no extra indentation in multi-line lists
90 // If indent is set, a multi-line identifier list is indented after the
91 // first linebreak encountered.
92 func (p *printer) identList(list []*ast.Ident, indent bool) {
93 // convert into an expression list so we can re-use exprList formatting
94 xlist := make([]ast.Expr, len(list))
95 for i, x := range list {
102 p.exprList(token.NoPos, xlist, 1, mode, token.NoPos)
105 // Print a list of expressions. If the list spans multiple
106 // source lines, the original line breaks are respected between
109 // TODO(gri) Consider rewriting this to be independent of []ast.Expr
110 // so that we can use the algorithm for any kind of list
111 // (e.g., pass list via a channel over which to range).
112 func (p *printer) exprList(prev0 token.Pos, list []ast.Expr, depth int, mode exprListMode, next0 token.Pos) {
117 prev := p.posFor(prev0)
118 next := p.posFor(next0)
119 line := p.lineFor(list[0].Pos())
120 endLine := p.lineFor(list[len(list)-1].End())
122 if prev.IsValid() && prev.Line == line && line == endLine {
123 // all list entries on a single line
124 for i, x := range list {
126 // use position of expression following the comma as
127 // comma position for correct comment placement
128 p.print(x.Pos(), token.COMMA, blank)
135 // list entries span multiple lines;
136 // use source code positions to guide line breaks
138 // don't add extra indentation if noIndent is set;
139 // i.e., pretend that the first line is already indented
141 if mode&noIndent == 0 {
145 // the first linebreak is always a formfeed since this section must not
146 // depend on any previous formatting
147 prevBreak := -1 // index of last expression that was followed by a linebreak
148 if prev.IsValid() && prev.Line < line && p.linebreak(line, 0, ws, true) {
153 // initialize expression/key size: a zero value indicates expr/key doesn't fit on a single line
156 // print all list elements
157 for i, x := range list {
159 line = p.lineFor(x.Pos())
161 // determine if the next linebreak, if any, needs to use formfeed:
162 // in general, use the entire node size to make the decision; for
163 // key:value expressions, use the key size
164 // TODO(gri) for a better result, should probably incorporate both
165 // the key and the node size into the decision process
168 // determine element size: all bets are off if we don't have
169 // position information for the previous and next token (likely
170 // generated code - simply ignore the size in this case by setting
173 const infinity = 1e6 // larger than any source line
174 size = p.nodeSize(x, infinity)
175 pair, isPair := x.(*ast.KeyValueExpr)
176 if size <= infinity && prev.IsValid() && next.IsValid() {
177 // x fits on a single line
179 size = p.nodeSize(pair.Key, infinity) // size <= infinity
182 // size too large or we don't have good layout information
186 // if the previous line and the current line had single-
187 // line-expressions and the key sizes are small or the
188 // the ratio between the key sizes does not exceed a
189 // threshold, align columns and do not use formfeed
190 if prevSize > 0 && size > 0 {
192 if prevSize <= smallSize && size <= smallSize {
195 const r = 4 // threshold
196 ratio := float64(size) / float64(prevSize)
197 useFF = ratio <= 1/r || r <= ratio
202 needsLinebreak := prevLine < line && prevLine > 0 && line > 0
203 // use position of expression following the comma as
204 // comma position for correct comment placement, but
205 // only if the expression is on the same line
212 // lines are broken using newlines so comments remain aligned
213 // unless forceFF is set or there are multiple expressions on
214 // the same line in which case formfeed is used
215 if p.linebreak(line, 0, ws, useFF || prevBreak+1 < i) {
218 needsBlank = false // we got a line break instead
226 if isPair && size > 0 && len(list) > 1 {
227 // we have a key:value expression that fits onto one line and
228 // is in a list with more then one entry: use a column for the
229 // key such that consecutive entries can align if possible
231 p.print(pair.Colon, token.COLON, vtab)
238 if mode&commaTerm != 0 && next.IsValid() && p.pos.Line < next.Line {
239 // print a terminating comma if the next token is on a new line
241 if ws == ignore && mode&noIndent == 0 {
242 // unindent if we indented
245 p.print(formfeed) // terminating comma needs a line break to look good
249 if ws == ignore && mode&noIndent == 0 {
250 // unindent if we indented
255 func (p *printer) parameters(fields *ast.FieldList) {
256 p.print(fields.Opening, token.LPAREN)
257 if len(fields.List) > 0 {
258 prevLine := p.lineFor(fields.Opening)
260 for i, par := range fields.List {
261 // determine par begin and end line (may be different
262 // if there are multiple parameter names for this par
263 // or the type is on a separate line)
265 var parLineEnd = p.lineFor(par.Type.Pos())
266 if len(par.Names) > 0 {
267 parLineBeg = p.lineFor(par.Names[0].Pos())
269 parLineBeg = parLineEnd
271 // separating "," if needed
272 needsLinebreak := 0 < prevLine && prevLine < parLineBeg
274 // use position of parameter following the comma as
275 // comma position for correct comma placement, but
276 // only if the next parameter is on the same line
282 // separator if needed (linebreak or blank)
283 if needsLinebreak && p.linebreak(parLineBeg, 0, ws, true) {
284 // break line if the opening "(" or previous parameter ended on a different line
290 if len(par.Names) > 0 {
291 // Very subtle: If we indented before (ws == ignore), identList
292 // won't indent again. If we didn't (ws == indent), identList will
293 // indent if the identList spans multiple lines, and it will outdent
294 // again at the end (and still ws == indent). Thus, a subsequent indent
295 // by a linebreak call after a type, or in the next multi-line identList
296 // will do the right thing.
297 p.identList(par.Names, ws == indent)
302 prevLine = parLineEnd
304 // if the closing ")" is on a separate line from the last parameter,
305 // print an additional "," and line break
306 if closing := p.lineFor(fields.Closing); 0 < prevLine && prevLine < closing {
308 p.linebreak(closing, 0, ignore, true)
310 // unindent if we indented
315 p.print(fields.Closing, token.RPAREN)
318 func (p *printer) signature(params, result *ast.FieldList) {
320 n := result.NumFields()
323 if n == 1 && result.List[0].Names == nil {
324 // single anonymous result; no ()'s
325 p.expr(result.List[0].Type)
332 func identListSize(list []*ast.Ident, maxSize int) (size int) {
333 for i, x := range list {
337 size += utf8.RuneCountInString(x.Name)
345 func (p *printer) isOneLineFieldList(list []*ast.Field) bool {
347 return false // allow only one field
350 if f.Tag != nil || f.Comment != nil {
351 return false // don't allow tags or comments
353 // only name(s) and type
354 const maxSize = 30 // adjust as appropriate, this is an approximate value
355 namesSize := identListSize(f.Names, maxSize)
357 namesSize = 1 // blank between names and types
359 typeSize := p.nodeSize(f.Type, maxSize)
360 return namesSize+typeSize <= maxSize
363 func (p *printer) setLineComment(text string) {
364 p.setComment(&ast.CommentGroup{List: []*ast.Comment{{Slash: token.NoPos, Text: text}}})
367 func (p *printer) isMultiLine(n ast.Node) bool {
368 return p.lineFor(n.End())-p.lineFor(n.Pos()) > 1
371 func (p *printer) fieldList(fields *ast.FieldList, isStruct, isIncomplete bool) {
372 lbrace := fields.Opening
374 rbrace := fields.Closing
375 hasComments := isIncomplete || p.commentBefore(p.posFor(rbrace))
376 srcIsOneLine := lbrace.IsValid() && rbrace.IsValid() && p.lineFor(lbrace) == p.lineFor(rbrace)
378 if !hasComments && srcIsOneLine {
379 // possibly a one-line struct/interface
381 // no blank between keyword and {} in this case
382 p.print(lbrace, token.LBRACE, rbrace, token.RBRACE)
384 } else if isStruct && p.isOneLineFieldList(list) { // for now ignore interfaces
385 // small enough - print on one line
386 // (don't use identList and ignore source line breaks)
387 p.print(lbrace, token.LBRACE, blank)
389 for i, x := range f.Names {
391 // no comments so no need for comma position
392 p.print(token.COMMA, blank)
396 if len(f.Names) > 0 {
400 p.print(blank, rbrace, token.RBRACE)
404 // hasComments || !srcIsOneLine
406 p.print(blank, lbrace, token.LBRACE, indent)
407 if hasComments || len(list) > 0 {
418 for i, f := range list {
420 p.linebreak(p.lineFor(f.Pos()), 1, ignore, newSection)
424 if len(f.Names) > 0 {
426 p.identList(f.Names, false)
436 if len(f.Names) > 0 && sep == vtab {
443 if f.Comment != nil {
444 for ; extraTabs > 0; extraTabs-- {
447 p.setComment(f.Comment)
449 newSection = p.isMultiLine(f)
455 p.flush(p.posFor(rbrace), token.RBRACE) // make sure we don't lose the last line comment
456 p.setLineComment("// contains filtered or unexported fields")
459 } else { // interface
462 for i, f := range list {
464 p.linebreak(p.lineFor(f.Pos()), 1, ignore, newSection)
467 if ftyp, isFtyp := f.Type.(*ast.FuncType); isFtyp {
470 p.signature(ftyp.Params, ftyp.Results)
472 // embedded interface
475 p.setComment(f.Comment)
476 newSection = p.isMultiLine(f)
482 p.flush(p.posFor(rbrace), token.RBRACE) // make sure we don't lose the last line comment
483 p.setLineComment("// contains filtered or unexported methods")
487 p.print(unindent, formfeed, rbrace, token.RBRACE)
490 // ----------------------------------------------------------------------------
493 func walkBinary(e *ast.BinaryExpr) (has4, has5 bool, maxProblem int) {
494 switch e.Op.Precedence() {
501 switch l := e.X.(type) {
502 case *ast.BinaryExpr:
503 if l.Op.Precedence() < e.Op.Precedence() {
504 // parens will be inserted.
505 // pretend this is an *ast.ParenExpr and do nothing.
508 h4, h5, mp := walkBinary(l)
516 switch r := e.Y.(type) {
517 case *ast.BinaryExpr:
518 if r.Op.Precedence() <= e.Op.Precedence() {
519 // parens will be inserted.
520 // pretend this is an *ast.ParenExpr and do nothing.
523 h4, h5, mp := walkBinary(r)
531 if e.Op == token.QUO { // `*/`
536 switch e.Op.String() + r.Op.String() {
537 case "/*", "&&", "&^":
548 func cutoff(e *ast.BinaryExpr, depth int) int {
549 has4, has5, maxProblem := walkBinary(e)
551 return maxProblem + 1
565 func diffPrec(expr ast.Expr, prec int) int {
566 x, ok := expr.(*ast.BinaryExpr)
567 if !ok || prec != x.Op.Precedence() {
573 func reduceDepth(depth int) int {
581 // Format the binary expression: decide the cutoff and then format.
582 // Let's call depth == 1 Normal mode, and depth > 1 Compact mode.
583 // (Algorithm suggestion by Russ Cox.)
585 // The precedences are:
586 // 5 * / % << >> & &^
592 // The only decision is whether there will be spaces around levels 4 and 5.
593 // There are never spaces at level 6 (unary), and always spaces at levels 3 and below.
595 // To choose the cutoff, look at the whole expression but excluding primary
596 // expressions (function calls, parenthesized exprs), and apply these rules:
598 // 1) If there is a binary operator with a right side unary operand
599 // that would clash without a space, the cutoff must be (in order):
607 // (Comparison operators always have spaces around them.)
609 // 2) If there is a mix of level 5 and level 4 operators, then the cutoff
610 // is 5 (use spaces to distinguish precedence) in Normal mode
611 // and 4 (never use spaces) in Compact mode.
613 // 3) If there are no level 4 operators or no level 5 operators, then the
614 // cutoff is 6 (always use spaces) in Normal mode
615 // and 4 (never use spaces) in Compact mode.
617 func (p *printer) binaryExpr(x *ast.BinaryExpr, prec1, cutoff, depth int) {
618 prec := x.Op.Precedence()
620 // parenthesis needed
621 // Note: The parser inserts an ast.ParenExpr node; thus this case
622 // can only occur if the AST is created in a different way.
623 p.print(token.LPAREN)
624 p.expr0(x, reduceDepth(depth)) // parentheses undo one level of depth
625 p.print(token.RPAREN)
629 printBlank := prec < cutoff
632 p.expr1(x.X, prec, depth+diffPrec(x.X, prec))
636 xline := p.pos.Line // before the operator (it may be on the next line!)
637 yline := p.lineFor(x.Y.Pos())
638 p.print(x.OpPos, x.Op)
639 if xline != yline && xline > 0 && yline > 0 {
640 // at least one line break, but respect an extra empty line
642 if p.linebreak(yline, 1, ws, true) {
644 printBlank = false // no blank after line break
650 p.expr1(x.Y, prec+1, depth+1)
656 func isBinary(expr ast.Expr) bool {
657 _, ok := expr.(*ast.BinaryExpr)
661 func (p *printer) expr1(expr ast.Expr, prec1, depth int) {
664 switch x := expr.(type) {
671 case *ast.BinaryExpr:
673 p.internalError("depth < 1:", depth)
676 p.binaryExpr(x, prec1, cutoff(x, depth), depth)
678 case *ast.KeyValueExpr:
680 p.print(x.Colon, token.COLON, blank)
684 const prec = token.UnaryPrec
686 // parenthesis needed
687 p.print(token.LPAREN)
690 p.print(token.RPAREN)
692 // no parenthesis needed
698 const prec = token.UnaryPrec
700 // parenthesis needed
701 p.print(token.LPAREN)
703 p.print(token.RPAREN)
705 // no parenthesis needed
707 if x.Op == token.RANGE {
708 // TODO(gri) Remove this code if it cannot be reached.
711 p.expr1(x.X, prec, depth)
719 p.funcBody(x.Body, p.distance(x.Type.Pos(), p.pos), true)
722 if _, hasParens := x.X.(*ast.ParenExpr); hasParens {
723 // don't print parentheses around an already parenthesized expression
724 // TODO(gri) consider making this more general and incorporate precedence levels
725 p.expr0(x.X, reduceDepth(depth)) // parentheses undo one level of depth
727 p.print(token.LPAREN)
728 p.expr0(x.X, reduceDepth(depth)) // parentheses undo one level of depth
729 p.print(x.Rparen, token.RPAREN)
732 case *ast.SelectorExpr:
733 p.expr1(x.X, token.HighestPrec, depth)
734 p.print(token.PERIOD)
735 if line := p.lineFor(x.Sel.Pos()); p.pos.IsValid() && p.pos.Line < line {
736 p.print(indent, newline, x.Sel.Pos(), x.Sel, unindent)
738 p.print(x.Sel.Pos(), x.Sel)
741 case *ast.TypeAssertExpr:
742 p.expr1(x.X, token.HighestPrec, depth)
743 p.print(token.PERIOD, token.LPAREN)
749 p.print(token.RPAREN)
752 // TODO(gri): should treat[] like parentheses and undo one level of depth
753 p.expr1(x.X, token.HighestPrec, 1)
754 p.print(x.Lbrack, token.LBRACK)
755 p.expr0(x.Index, depth+1)
756 p.print(x.Rbrack, token.RBRACK)
759 // TODO(gri): should treat[] like parentheses and undo one level of depth
760 p.expr1(x.X, token.HighestPrec, 1)
761 p.print(x.Lbrack, token.LBRACK)
763 p.expr0(x.Low, depth+1)
765 // blanks around ":" if both sides exist and either side is a binary expression
766 if depth <= 1 && x.Low != nil && x.High != nil && (isBinary(x.Low) || isBinary(x.High)) {
767 p.print(blank, token.COLON, blank)
772 p.expr0(x.High, depth+1)
774 p.print(x.Rbrack, token.RBRACK)
780 p.expr1(x.Fun, token.HighestPrec, depth)
781 p.print(x.Lparen, token.LPAREN)
782 if x.Ellipsis.IsValid() {
783 p.exprList(x.Lparen, x.Args, depth, 0, x.Ellipsis)
784 p.print(x.Ellipsis, token.ELLIPSIS)
785 if x.Rparen.IsValid() && p.lineFor(x.Ellipsis) < p.lineFor(x.Rparen) {
786 p.print(token.COMMA, formfeed)
789 p.exprList(x.Lparen, x.Args, depth, commaTerm, x.Rparen)
791 p.print(x.Rparen, token.RPAREN)
793 case *ast.CompositeLit:
794 // composite literal elements that are composite literals themselves may have the type omitted
796 p.expr1(x.Type, token.HighestPrec, depth)
798 p.print(x.Lbrace, token.LBRACE)
799 p.exprList(x.Lbrace, x.Elts, 1, commaTerm, x.Rbrace)
800 // do not insert extra line breaks because of comments before
801 // the closing '}' as it might break the code if there is no
803 p.print(noExtraLinebreak, x.Rbrace, token.RBRACE, noExtraLinebreak)
806 p.print(token.ELLIPSIS)
812 p.print(token.LBRACK)
816 p.print(token.RBRACK)
819 case *ast.StructType:
820 p.print(token.STRUCT)
821 p.fieldList(x.Fields, true, x.Incomplete)
825 p.signature(x.Params, x.Results)
827 case *ast.InterfaceType:
828 p.print(token.INTERFACE)
829 p.fieldList(x.Methods, false, x.Incomplete)
832 p.print(token.MAP, token.LBRACK)
834 p.print(token.RBRACK)
839 case ast.SEND | ast.RECV:
842 p.print(token.ARROW, token.CHAN)
844 p.print(token.CHAN, token.ARROW)
856 func (p *printer) expr0(x ast.Expr, depth int) {
857 p.expr1(x, token.LowestPrec, depth)
860 func (p *printer) expr(x ast.Expr) {
862 p.expr1(x, token.LowestPrec, depth)
865 // ----------------------------------------------------------------------------
868 // Print the statement list indented, but without a newline after the last statement.
869 // Extra line breaks between statements in the source are respected but at most one
870 // empty line is printed between statements.
871 func (p *printer) stmtList(list []ast.Stmt, _indent int, nextIsRBrace bool) {
872 // TODO(gri): fix _indent code
877 for i, s := range list {
878 // _indent == 0 only for lists of switch/select case clauses;
879 // in those cases each clause is a new section
880 p.linebreak(p.lineFor(s.Pos()), 1, ignore, i == 0 || _indent == 0 || multiLine)
881 p.stmt(s, nextIsRBrace && i == len(list)-1)
882 multiLine = p.isMultiLine(s)
889 // block prints an *ast.BlockStmt; it always spans at least two lines.
890 func (p *printer) block(s *ast.BlockStmt, indent int) {
891 p.print(s.Pos(), token.LBRACE)
892 p.stmtList(s.List, indent, true)
893 p.linebreak(p.lineFor(s.Rbrace), 1, ignore, true)
894 p.print(s.Rbrace, token.RBRACE)
897 func isTypeName(x ast.Expr) bool {
898 switch t := x.(type) {
901 case *ast.SelectorExpr:
902 return isTypeName(t.X)
907 func stripParens(x ast.Expr) ast.Expr {
908 if px, strip := x.(*ast.ParenExpr); strip {
909 // parentheses must not be stripped if there are any
910 // unparenthesized composite literals starting with
912 ast.Inspect(px.X, func(node ast.Node) bool {
913 switch x := node.(type) {
915 // parentheses protect enclosed composite literals
917 case *ast.CompositeLit:
918 if isTypeName(x.Type) {
919 strip = false // do not strip parentheses
923 // in all other cases, keep inspecting
927 return stripParens(px.X)
933 func (p *printer) controlClause(isForStmt bool, init ast.Stmt, expr ast.Expr, post ast.Stmt) {
936 if init == nil && post == nil {
937 // no semicolons required
939 p.expr(stripParens(expr))
943 // all semicolons required
944 // (they are not separators, print them explicitly)
948 p.print(token.SEMICOLON, blank)
950 p.expr(stripParens(expr))
954 p.print(token.SEMICOLON, blank)
967 func (p *printer) stmt(stmt ast.Stmt, nextIsRBrace bool) {
970 switch s := stmt.(type) {
980 case *ast.LabeledStmt:
981 // a "correcting" unindent immediately following a line break
982 // is applied before the line break if there is no comment
983 // between (see writeWhitespace)
986 p.print(s.Colon, token.COLON, indent)
987 if e, isEmpty := s.Stmt.(*ast.EmptyStmt); isEmpty {
989 p.print(newline, e.Pos(), token.SEMICOLON)
993 p.linebreak(p.lineFor(s.Stmt.Pos()), 1, ignore, true)
995 p.stmt(s.Stmt, nextIsRBrace)
1003 p.expr0(s.Chan, depth)
1004 p.print(blank, s.Arrow, token.ARROW, blank)
1005 p.expr0(s.Value, depth)
1007 case *ast.IncDecStmt:
1009 p.expr0(s.X, depth+1)
1010 p.print(s.TokPos, s.Tok)
1012 case *ast.AssignStmt:
1014 if len(s.Lhs) > 1 && len(s.Rhs) > 1 {
1017 p.exprList(s.Pos(), s.Lhs, depth, 0, s.TokPos)
1018 p.print(blank, s.TokPos, s.Tok, blank)
1019 p.exprList(s.TokPos, s.Rhs, depth, 0, token.NoPos)
1022 p.print(token.GO, blank)
1025 case *ast.DeferStmt:
1026 p.print(token.DEFER, blank)
1029 case *ast.ReturnStmt:
1030 p.print(token.RETURN)
1031 if s.Results != nil {
1033 p.exprList(s.Pos(), s.Results, 1, 0, token.NoPos)
1036 case *ast.BranchStmt:
1043 case *ast.BlockStmt:
1048 p.controlClause(false, s.Init, s.Cond, nil)
1051 p.print(blank, token.ELSE, blank)
1052 switch s.Else.(type) {
1053 case *ast.BlockStmt, *ast.IfStmt:
1054 p.stmt(s.Else, nextIsRBrace)
1056 p.print(token.LBRACE, indent, formfeed)
1057 p.stmt(s.Else, true)
1058 p.print(unindent, formfeed, token.RBRACE)
1062 case *ast.CaseClause:
1064 p.print(token.CASE, blank)
1065 p.exprList(s.Pos(), s.List, 1, 0, s.Colon)
1067 p.print(token.DEFAULT)
1069 p.print(s.Colon, token.COLON)
1070 p.stmtList(s.Body, 1, nextIsRBrace)
1072 case *ast.SwitchStmt:
1073 p.print(token.SWITCH)
1074 p.controlClause(false, s.Init, s.Tag, nil)
1077 case *ast.TypeSwitchStmt:
1078 p.print(token.SWITCH)
1081 p.stmt(s.Init, false)
1082 p.print(token.SEMICOLON)
1085 p.stmt(s.Assign, false)
1089 case *ast.CommClause:
1091 p.print(token.CASE, blank)
1092 p.stmt(s.Comm, false)
1094 p.print(token.DEFAULT)
1096 p.print(s.Colon, token.COLON)
1097 p.stmtList(s.Body, 1, nextIsRBrace)
1099 case *ast.SelectStmt:
1100 p.print(token.SELECT, blank)
1102 if len(body.List) == 0 && !p.commentBefore(p.posFor(body.Rbrace)) {
1103 // print empty select statement w/o comments on one line
1104 p.print(body.Lbrace, token.LBRACE, body.Rbrace, token.RBRACE)
1111 p.controlClause(true, s.Init, s.Cond, s.Post)
1114 case *ast.RangeStmt:
1115 p.print(token.FOR, blank)
1118 // use position of value following the comma as
1119 // comma position for correct comment placement
1120 p.print(s.Value.Pos(), token.COMMA, blank)
1123 p.print(blank, s.TokPos, s.Tok, blank, token.RANGE, blank)
1124 p.expr(stripParens(s.X))
1129 panic("unreachable")
1135 // ----------------------------------------------------------------------------
1138 // The keepTypeColumn function determines if the type column of a series of
1139 // consecutive const or var declarations must be kept, or if initialization
1140 // values (V) can be placed in the type column (T) instead. The i'th entry
1141 // in the result slice is true if the type column in spec[i] must be kept.
1143 // For example, the declaration:
1146 // foobar int = 42 // comment
1152 // leads to the type/values matrix below. A run of value columns (V) can
1153 // be moved into the type column if there is no type for any of the values
1154 // in that column (we only move entire columns so that they align properly).
1156 // matrix formatted result
1158 // T V -> T V -> true there is a T and so the type
1159 // - V - V true column must be kept
1161 // - V V - false V is moved into T column
1163 func keepTypeColumn(specs []ast.Spec) []bool {
1164 m := make([]bool, len(specs))
1166 populate := func(i, j int, keepType bool) {
1174 i0 := -1 // if i0 >= 0 we are in a run and i0 is the start of the run
1176 for i, s := range specs {
1177 t := s.(*ast.ValueSpec)
1178 if t.Values != nil {
1180 // start of a run of ValueSpecs with non-nil Values
1187 populate(i0, i, keepType)
1197 populate(i0, len(specs), keepType)
1203 func (p *printer) valueSpec(s *ast.ValueSpec, keepType, doIndent bool) {
1205 p.identList(s.Names, doIndent) // always present
1207 if s.Type != nil || keepType {
1214 if s.Values != nil {
1215 p.print(vtab, token.ASSIGN, blank)
1216 p.exprList(token.NoPos, s.Values, 1, 0, token.NoPos)
1219 if s.Comment != nil {
1220 for ; extraTabs > 0; extraTabs-- {
1223 p.setComment(s.Comment)
1227 // The parameter n is the number of specs in the group. If doIndent is set,
1228 // multi-line identifier lists in the spec are indented when the first
1229 // linebreak is encountered.
1231 func (p *printer) spec(spec ast.Spec, n int, doIndent bool) {
1232 switch s := spec.(type) {
1233 case *ast.ImportSpec:
1240 p.setComment(s.Comment)
1243 case *ast.ValueSpec:
1245 p.internalError("expected n = 1; got", n)
1248 p.identList(s.Names, doIndent) // always present
1253 if s.Values != nil {
1254 p.print(blank, token.ASSIGN, blank)
1255 p.exprList(token.NoPos, s.Values, 1, 0, token.NoPos)
1257 p.setComment(s.Comment)
1268 p.setComment(s.Comment)
1271 panic("unreachable")
1275 func (p *printer) genDecl(d *ast.GenDecl) {
1277 p.print(d.Pos(), d.Tok, blank)
1279 if d.Lparen.IsValid() {
1280 // group of parenthesized declarations
1281 p.print(d.Lparen, token.LPAREN)
1282 if n := len(d.Specs); n > 0 {
1283 p.print(indent, formfeed)
1284 if n > 1 && (d.Tok == token.CONST || d.Tok == token.VAR) {
1285 // two or more grouped const/var declarations:
1286 // determine if the type column must be kept
1287 keepType := keepTypeColumn(d.Specs)
1289 for i, s := range d.Specs {
1291 p.linebreak(p.lineFor(s.Pos()), 1, ignore, newSection)
1293 p.valueSpec(s.(*ast.ValueSpec), keepType[i], false)
1294 newSection = p.isMultiLine(s)
1298 for i, s := range d.Specs {
1300 p.linebreak(p.lineFor(s.Pos()), 1, ignore, newSection)
1303 newSection = p.isMultiLine(s)
1306 p.print(unindent, formfeed)
1308 p.print(d.Rparen, token.RPAREN)
1311 // single declaration
1312 p.spec(d.Specs[0], 1, true)
1316 // nodeSize determines the size of n in chars after formatting.
1317 // The result is <= maxSize if the node fits on one line with at
1318 // most maxSize chars and the formatted output doesn't contain
1319 // any control chars. Otherwise, the result is > maxSize.
1321 func (p *printer) nodeSize(n ast.Node, maxSize int) (size int) {
1322 // nodeSize invokes the printer, which may invoke nodeSize
1323 // recursively. For deep composite literal nests, this can
1324 // lead to an exponential algorithm. Remember previous
1325 // results to prune the recursion (was issue 1628).
1326 if size, found := p.nodeSizes[n]; found {
1330 size = maxSize + 1 // assume n doesn't fit
1331 p.nodeSizes[n] = size
1333 // nodeSize computation must be independent of particular
1334 // style so that we always get the same decision; print
1336 cfg := Config{Mode: RawFormat}
1337 var buf bytes.Buffer
1338 if err := cfg.fprint(&buf, p.fset, n, p.nodeSizes); err != nil {
1341 if buf.Len() <= maxSize {
1342 for _, ch := range buf.Bytes() {
1347 size = buf.Len() // n fits
1348 p.nodeSizes[n] = size
1353 func (p *printer) isOneLineFunc(b *ast.BlockStmt, headerSize int) bool {
1356 if pos1.IsValid() && pos2.IsValid() && p.lineFor(pos1) != p.lineFor(pos2) {
1357 // opening and closing brace are on different lines - don't make it a one-liner
1360 if len(b.List) > 5 || p.commentBefore(p.posFor(pos2)) {
1361 // too many statements or there is a comment inside - don't make it a one-liner
1364 // otherwise, estimate body size
1367 for i, s := range b.List {
1369 bodySize += 2 // space for a semicolon and blank
1371 bodySize += p.nodeSize(s, maxSize)
1373 return headerSize+bodySize <= maxSize
1376 func (p *printer) funcBody(b *ast.BlockStmt, headerSize int, isLit bool) {
1381 if p.isOneLineFunc(b, headerSize) {
1386 p.print(sep, b.Lbrace, token.LBRACE)
1387 if len(b.List) > 0 {
1389 for i, s := range b.List {
1391 p.print(token.SEMICOLON, blank)
1393 p.stmt(s, i == len(b.List)-1)
1397 p.print(b.Rbrace, token.RBRACE)
1405 // distance returns the column difference between from and to if both
1406 // are on the same line; if they are on different lines (or unknown)
1407 // the result is infinity.
1408 func (p *printer) distance(from0 token.Pos, to token.Position) int {
1409 from := p.posFor(from0)
1410 if from.IsValid() && to.IsValid() && from.Line == to.Line {
1411 return to.Column - from.Column
1416 func (p *printer) funcDecl(d *ast.FuncDecl) {
1418 p.print(d.Pos(), token.FUNC, blank)
1420 p.parameters(d.Recv) // method: print receiver
1424 p.signature(d.Type.Params, d.Type.Results)
1425 p.funcBody(d.Body, p.distance(d.Pos(), p.pos), false)
1428 func (p *printer) decl(decl ast.Decl) {
1429 switch d := decl.(type) {
1431 p.print(d.Pos(), "BadDecl")
1437 panic("unreachable")
1441 // ----------------------------------------------------------------------------
1444 func declToken(decl ast.Decl) (tok token.Token) {
1446 switch d := decl.(type) {
1455 func (p *printer) file(src *ast.File) {
1456 p.setComment(src.Doc)
1457 p.print(src.Pos(), token.PACKAGE, blank)
1460 if len(src.Decls) > 0 {
1461 tok := token.ILLEGAL
1462 for _, d := range src.Decls {
1465 // if the declaration token changed (e.g., from CONST to TYPE)
1466 // or the next declaration has documentation associated with it,
1467 // print an empty line between top-level declarations
1468 // (because p.linebreak is called with the position of d, which
1469 // is past any documentation, the minimum requirement is satisfied
1470 // even w/o the extra getDoc(d) nil-check - leave it in case the
1471 // linebreak logic improves - there's already a TODO).
1473 if prev != tok || getDoc(d) != nil {
1476 p.linebreak(p.lineFor(d.Pos()), min, ignore, false)