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-rw-r--r--src/go/printer/nodes.go1844
1 files changed, 1844 insertions, 0 deletions
diff --git a/src/go/printer/nodes.go b/src/go/printer/nodes.go
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+// 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.
+
+// This file implements printing of AST nodes; specifically
+// expressions, statements, declarations, and files. It uses
+// the print functionality implemented in printer.go.
+
+package printer
+
+import (
+ "bytes"
+ "go/ast"
+ "go/token"
+ "math"
+ "strconv"
+ "strings"
+ "unicode"
+ "unicode/utf8"
+)
+
+// Formatting issues:
+// - better comment formatting for /*-style comments at the end of a line (e.g. a declaration)
+// when the comment spans multiple lines; if such a comment is just two lines, formatting is
+// not idempotent
+// - formatting of expression lists
+// - should use blank instead of tab to separate one-line function bodies from
+// the function header unless there is a group of consecutive one-liners
+
+// ----------------------------------------------------------------------------
+// Common AST nodes.
+
+// Print as many newlines as necessary (but at least min newlines) to get to
+// the current line. ws is printed before the first line break. If newSection
+// is set, the first line break is printed as formfeed. Returns 0 if no line
+// breaks were printed, returns 1 if there was exactly one newline printed,
+// and returns a value > 1 if there was a formfeed or more than one newline
+// printed.
+//
+// TODO(gri): linebreak may add too many lines if the next statement at "line"
+// is preceded by comments because the computation of n assumes
+// the current position before the comment and the target position
+// after the comment. Thus, after interspersing such comments, the
+// space taken up by them is not considered to reduce the number of
+// linebreaks. At the moment there is no easy way to know about
+// future (not yet interspersed) comments in this function.
+//
+func (p *printer) linebreak(line, min int, ws whiteSpace, newSection bool) (nbreaks int) {
+ n := nlimit(line - p.pos.Line)
+ if n < min {
+ n = min
+ }
+ if n > 0 {
+ p.print(ws)
+ if newSection {
+ p.print(formfeed)
+ n--
+ nbreaks = 2
+ }
+ nbreaks += n
+ for ; n > 0; n-- {
+ p.print(newline)
+ }
+ }
+ return
+}
+
+// setComment sets g as the next comment if g != nil and if node comments
+// are enabled - this mode is used when printing source code fragments such
+// as exports only. It assumes that there is no pending comment in p.comments
+// and at most one pending comment in the p.comment cache.
+func (p *printer) setComment(g *ast.CommentGroup) {
+ if g == nil || !p.useNodeComments {
+ return
+ }
+ if p.comments == nil {
+ // initialize p.comments lazily
+ p.comments = make([]*ast.CommentGroup, 1)
+ } else if p.cindex < len(p.comments) {
+ // for some reason there are pending comments; this
+ // should never happen - handle gracefully and flush
+ // all comments up to g, ignore anything after that
+ p.flush(p.posFor(g.List[0].Pos()), token.ILLEGAL)
+ p.comments = p.comments[0:1]
+ // in debug mode, report error
+ p.internalError("setComment found pending comments")
+ }
+ p.comments[0] = g
+ p.cindex = 0
+ // don't overwrite any pending comment in the p.comment cache
+ // (there may be a pending comment when a line comment is
+ // immediately followed by a lead comment with no other
+ // tokens between)
+ if p.commentOffset == infinity {
+ p.nextComment() // get comment ready for use
+ }
+}
+
+type exprListMode uint
+
+const (
+ commaTerm exprListMode = 1 << iota // list is optionally terminated by a comma
+ noIndent // no extra indentation in multi-line lists
+)
+
+// If indent is set, a multi-line identifier list is indented after the
+// first linebreak encountered.
+func (p *printer) identList(list []*ast.Ident, indent bool) {
+ // convert into an expression list so we can re-use exprList formatting
+ xlist := make([]ast.Expr, len(list))
+ for i, x := range list {
+ xlist[i] = x
+ }
+ var mode exprListMode
+ if !indent {
+ mode = noIndent
+ }
+ p.exprList(token.NoPos, xlist, 1, mode, token.NoPos, false)
+}
+
+const filteredMsg = "contains filtered or unexported fields"
+
+// Print a list of expressions. If the list spans multiple
+// source lines, the original line breaks are respected between
+// expressions.
+//
+// TODO(gri) Consider rewriting this to be independent of []ast.Expr
+// so that we can use the algorithm for any kind of list
+// (e.g., pass list via a channel over which to range).
+func (p *printer) exprList(prev0 token.Pos, list []ast.Expr, depth int, mode exprListMode, next0 token.Pos, isIncomplete bool) {
+ if len(list) == 0 {
+ if isIncomplete {
+ prev := p.posFor(prev0)
+ next := p.posFor(next0)
+ if prev.IsValid() && prev.Line == next.Line {
+ p.print("/* " + filteredMsg + " */")
+ } else {
+ p.print(newline)
+ p.print(indent, "// "+filteredMsg, unindent, newline)
+ }
+ }
+ return
+ }
+
+ prev := p.posFor(prev0)
+ next := p.posFor(next0)
+ line := p.lineFor(list[0].Pos())
+ endLine := p.lineFor(list[len(list)-1].End())
+
+ if prev.IsValid() && prev.Line == line && line == endLine {
+ // all list entries on a single line
+ for i, x := range list {
+ if i > 0 {
+ // use position of expression following the comma as
+ // comma position for correct comment placement
+ p.print(x.Pos(), token.COMMA, blank)
+ }
+ p.expr0(x, depth)
+ }
+ if isIncomplete {
+ p.print(token.COMMA, blank, "/* "+filteredMsg+" */")
+ }
+ return
+ }
+
+ // list entries span multiple lines;
+ // use source code positions to guide line breaks
+
+ // Don't add extra indentation if noIndent is set;
+ // i.e., pretend that the first line is already indented.
+ ws := ignore
+ if mode&noIndent == 0 {
+ ws = indent
+ }
+
+ // The first linebreak is always a formfeed since this section must not
+ // depend on any previous formatting.
+ prevBreak := -1 // index of last expression that was followed by a linebreak
+ if prev.IsValid() && prev.Line < line && p.linebreak(line, 0, ws, true) > 0 {
+ ws = ignore
+ prevBreak = 0
+ }
+
+ // initialize expression/key size: a zero value indicates expr/key doesn't fit on a single line
+ size := 0
+
+ // We use the ratio between the geometric mean of the previous key sizes and
+ // the current size to determine if there should be a break in the alignment.
+ // To compute the geometric mean we accumulate the ln(size) values (lnsum)
+ // and the number of sizes included (count).
+ lnsum := 0.0
+ count := 0
+
+ // print all list elements
+ prevLine := prev.Line
+ for i, x := range list {
+ line = p.lineFor(x.Pos())
+
+ // Determine if the next linebreak, if any, needs to use formfeed:
+ // in general, use the entire node size to make the decision; for
+ // key:value expressions, use the key size.
+ // TODO(gri) for a better result, should probably incorporate both
+ // the key and the node size into the decision process
+ useFF := true
+
+ // Determine element size: All bets are off if we don't have
+ // position information for the previous and next token (likely
+ // generated code - simply ignore the size in this case by setting
+ // it to 0).
+ prevSize := size
+ const infinity = 1e6 // larger than any source line
+ size = p.nodeSize(x, infinity)
+ pair, isPair := x.(*ast.KeyValueExpr)
+ if size <= infinity && prev.IsValid() && next.IsValid() {
+ // x fits on a single line
+ if isPair {
+ size = p.nodeSize(pair.Key, infinity) // size <= infinity
+ }
+ } else {
+ // size too large or we don't have good layout information
+ size = 0
+ }
+
+ // If the previous line and the current line had single-
+ // line-expressions and the key sizes are small or the
+ // ratio between the current key and the geometric mean
+ // if the previous key sizes does not exceed a threshold,
+ // align columns and do not use formfeed.
+ if prevSize > 0 && size > 0 {
+ const smallSize = 40
+ if count == 0 || prevSize <= smallSize && size <= smallSize {
+ useFF = false
+ } else {
+ const r = 2.5 // threshold
+ geomean := math.Exp(lnsum / float64(count)) // count > 0
+ ratio := float64(size) / geomean
+ useFF = r*ratio <= 1 || r <= ratio
+ }
+ }
+
+ needsLinebreak := 0 < prevLine && prevLine < line
+ if i > 0 {
+ // Use position of expression following the comma as
+ // comma position for correct comment placement, but
+ // only if the expression is on the same line.
+ if !needsLinebreak {
+ p.print(x.Pos())
+ }
+ p.print(token.COMMA)
+ needsBlank := true
+ if needsLinebreak {
+ // Lines are broken using newlines so comments remain aligned
+ // unless useFF is set or there are multiple expressions on
+ // the same line in which case formfeed is used.
+ nbreaks := p.linebreak(line, 0, ws, useFF || prevBreak+1 < i)
+ if nbreaks > 0 {
+ ws = ignore
+ prevBreak = i
+ needsBlank = false // we got a line break instead
+ }
+ // If there was a new section or more than one new line
+ // (which means that the tabwriter will implicitly break
+ // the section), reset the geomean variables since we are
+ // starting a new group of elements with the next element.
+ if nbreaks > 1 {
+ lnsum = 0
+ count = 0
+ }
+ }
+ if needsBlank {
+ p.print(blank)
+ }
+ }
+
+ if len(list) > 1 && isPair && size > 0 && needsLinebreak {
+ // We have a key:value expression that fits onto one line
+ // and it's not on the same line as the prior expression:
+ // Use a column for the key such that consecutive entries
+ // can align if possible.
+ // (needsLinebreak is set if we started a new line before)
+ p.expr(pair.Key)
+ p.print(pair.Colon, token.COLON, vtab)
+ p.expr(pair.Value)
+ } else {
+ p.expr0(x, depth)
+ }
+
+ if size > 0 {
+ lnsum += math.Log(float64(size))
+ count++
+ }
+
+ prevLine = line
+ }
+
+ if mode&commaTerm != 0 && next.IsValid() && p.pos.Line < next.Line {
+ // Print a terminating comma if the next token is on a new line.
+ p.print(token.COMMA)
+ if isIncomplete {
+ p.print(newline)
+ p.print("// " + filteredMsg)
+ }
+ if ws == ignore && mode&noIndent == 0 {
+ // unindent if we indented
+ p.print(unindent)
+ }
+ p.print(formfeed) // terminating comma needs a line break to look good
+ return
+ }
+
+ if isIncomplete {
+ p.print(token.COMMA, newline)
+ p.print("// "+filteredMsg, newline)
+ }
+
+ if ws == ignore && mode&noIndent == 0 {
+ // unindent if we indented
+ p.print(unindent)
+ }
+}
+
+func (p *printer) parameters(fields *ast.FieldList) {
+ p.print(fields.Opening, token.LPAREN)
+ if len(fields.List) > 0 {
+ prevLine := p.lineFor(fields.Opening)
+ ws := indent
+ for i, par := range fields.List {
+ // determine par begin and end line (may be different
+ // if there are multiple parameter names for this par
+ // or the type is on a separate line)
+ var parLineBeg int
+ if len(par.Names) > 0 {
+ parLineBeg = p.lineFor(par.Names[0].Pos())
+ } else {
+ parLineBeg = p.lineFor(par.Type.Pos())
+ }
+ var parLineEnd = p.lineFor(par.Type.End())
+ // separating "," if needed
+ needsLinebreak := 0 < prevLine && prevLine < parLineBeg
+ if i > 0 {
+ // use position of parameter following the comma as
+ // comma position for correct comma placement, but
+ // only if the next parameter is on the same line
+ if !needsLinebreak {
+ p.print(par.Pos())
+ }
+ p.print(token.COMMA)
+ }
+ // separator if needed (linebreak or blank)
+ if needsLinebreak && p.linebreak(parLineBeg, 0, ws, true) > 0 {
+ // break line if the opening "(" or previous parameter ended on a different line
+ ws = ignore
+ } else if i > 0 {
+ p.print(blank)
+ }
+ // parameter names
+ if len(par.Names) > 0 {
+ // Very subtle: If we indented before (ws == ignore), identList
+ // won't indent again. If we didn't (ws == indent), identList will
+ // indent if the identList spans multiple lines, and it will outdent
+ // again at the end (and still ws == indent). Thus, a subsequent indent
+ // by a linebreak call after a type, or in the next multi-line identList
+ // will do the right thing.
+ p.identList(par.Names, ws == indent)
+ p.print(blank)
+ }
+ // parameter type
+ p.expr(stripParensAlways(par.Type))
+ prevLine = parLineEnd
+ }
+ // if the closing ")" is on a separate line from the last parameter,
+ // print an additional "," and line break
+ if closing := p.lineFor(fields.Closing); 0 < prevLine && prevLine < closing {
+ p.print(token.COMMA)
+ p.linebreak(closing, 0, ignore, true)
+ }
+ // unindent if we indented
+ if ws == ignore {
+ p.print(unindent)
+ }
+ }
+ p.print(fields.Closing, token.RPAREN)
+}
+
+func (p *printer) signature(params, result *ast.FieldList) {
+ if params != nil {
+ p.parameters(params)
+ } else {
+ p.print(token.LPAREN, token.RPAREN)
+ }
+ n := result.NumFields()
+ if n > 0 {
+ // result != nil
+ p.print(blank)
+ if n == 1 && result.List[0].Names == nil {
+ // single anonymous result; no ()'s
+ p.expr(stripParensAlways(result.List[0].Type))
+ return
+ }
+ p.parameters(result)
+ }
+}
+
+func identListSize(list []*ast.Ident, maxSize int) (size int) {
+ for i, x := range list {
+ if i > 0 {
+ size += len(", ")
+ }
+ size += utf8.RuneCountInString(x.Name)
+ if size >= maxSize {
+ break
+ }
+ }
+ return
+}
+
+func (p *printer) isOneLineFieldList(list []*ast.Field) bool {
+ if len(list) != 1 {
+ return false // allow only one field
+ }
+ f := list[0]
+ if f.Tag != nil || f.Comment != nil {
+ return false // don't allow tags or comments
+ }
+ // only name(s) and type
+ const maxSize = 30 // adjust as appropriate, this is an approximate value
+ namesSize := identListSize(f.Names, maxSize)
+ if namesSize > 0 {
+ namesSize = 1 // blank between names and types
+ }
+ typeSize := p.nodeSize(f.Type, maxSize)
+ return namesSize+typeSize <= maxSize
+}
+
+func (p *printer) setLineComment(text string) {
+ p.setComment(&ast.CommentGroup{List: []*ast.Comment{{Slash: token.NoPos, Text: text}}})
+}
+
+func (p *printer) fieldList(fields *ast.FieldList, isStruct, isIncomplete bool) {
+ lbrace := fields.Opening
+ list := fields.List
+ rbrace := fields.Closing
+ hasComments := isIncomplete || p.commentBefore(p.posFor(rbrace))
+ srcIsOneLine := lbrace.IsValid() && rbrace.IsValid() && p.lineFor(lbrace) == p.lineFor(rbrace)
+
+ if !hasComments && srcIsOneLine {
+ // possibly a one-line struct/interface
+ if len(list) == 0 {
+ // no blank between keyword and {} in this case
+ p.print(lbrace, token.LBRACE, rbrace, token.RBRACE)
+ return
+ } else if p.isOneLineFieldList(list) {
+ // small enough - print on one line
+ // (don't use identList and ignore source line breaks)
+ p.print(lbrace, token.LBRACE, blank)
+ f := list[0]
+ if isStruct {
+ for i, x := range f.Names {
+ if i > 0 {
+ // no comments so no need for comma position
+ p.print(token.COMMA, blank)
+ }
+ p.expr(x)
+ }
+ if len(f.Names) > 0 {
+ p.print(blank)
+ }
+ p.expr(f.Type)
+ } else { // interface
+ if ftyp, isFtyp := f.Type.(*ast.FuncType); isFtyp {
+ // method
+ p.expr(f.Names[0])
+ p.signature(ftyp.Params, ftyp.Results)
+ } else {
+ // embedded interface
+ p.expr(f.Type)
+ }
+ }
+ p.print(blank, rbrace, token.RBRACE)
+ return
+ }
+ }
+ // hasComments || !srcIsOneLine
+
+ p.print(blank, lbrace, token.LBRACE, indent)
+ if hasComments || len(list) > 0 {
+ p.print(formfeed)
+ }
+
+ if isStruct {
+
+ sep := vtab
+ if len(list) == 1 {
+ sep = blank
+ }
+ var line int
+ for i, f := range list {
+ if i > 0 {
+ p.linebreak(p.lineFor(f.Pos()), 1, ignore, p.linesFrom(line) > 0)
+ }
+ extraTabs := 0
+ p.setComment(f.Doc)
+ p.recordLine(&line)
+ if len(f.Names) > 0 {
+ // named fields
+ p.identList(f.Names, false)
+ p.print(sep)
+ p.expr(f.Type)
+ extraTabs = 1
+ } else {
+ // anonymous field
+ p.expr(f.Type)
+ extraTabs = 2
+ }
+ if f.Tag != nil {
+ if len(f.Names) > 0 && sep == vtab {
+ p.print(sep)
+ }
+ p.print(sep)
+ p.expr(f.Tag)
+ extraTabs = 0
+ }
+ if f.Comment != nil {
+ for ; extraTabs > 0; extraTabs-- {
+ p.print(sep)
+ }
+ p.setComment(f.Comment)
+ }
+ }
+ if isIncomplete {
+ if len(list) > 0 {
+ p.print(formfeed)
+ }
+ p.flush(p.posFor(rbrace), token.RBRACE) // make sure we don't lose the last line comment
+ p.setLineComment("// " + filteredMsg)
+ }
+
+ } else { // interface
+
+ var line int
+ for i, f := range list {
+ if i > 0 {
+ p.linebreak(p.lineFor(f.Pos()), 1, ignore, p.linesFrom(line) > 0)
+ }
+ p.setComment(f.Doc)
+ p.recordLine(&line)
+ if ftyp, isFtyp := f.Type.(*ast.FuncType); isFtyp {
+ // method
+ p.expr(f.Names[0])
+ p.signature(ftyp.Params, ftyp.Results)
+ } else {
+ // embedded interface
+ p.expr(f.Type)
+ }
+ p.setComment(f.Comment)
+ }
+ if isIncomplete {
+ if len(list) > 0 {
+ p.print(formfeed)
+ }
+ p.flush(p.posFor(rbrace), token.RBRACE) // make sure we don't lose the last line comment
+ p.setLineComment("// contains filtered or unexported methods")
+ }
+
+ }
+ p.print(unindent, formfeed, rbrace, token.RBRACE)
+}
+
+// ----------------------------------------------------------------------------
+// Expressions
+
+func walkBinary(e *ast.BinaryExpr) (has4, has5 bool, maxProblem int) {
+ switch e.Op.Precedence() {
+ case 4:
+ has4 = true
+ case 5:
+ has5 = true
+ }
+
+ switch l := e.X.(type) {
+ case *ast.BinaryExpr:
+ if l.Op.Precedence() < e.Op.Precedence() {
+ // parens will be inserted.
+ // pretend this is an *ast.ParenExpr and do nothing.
+ break
+ }
+ h4, h5, mp := walkBinary(l)
+ has4 = has4 || h4
+ has5 = has5 || h5
+ if maxProblem < mp {
+ maxProblem = mp
+ }
+ }
+
+ switch r := e.Y.(type) {
+ case *ast.BinaryExpr:
+ if r.Op.Precedence() <= e.Op.Precedence() {
+ // parens will be inserted.
+ // pretend this is an *ast.ParenExpr and do nothing.
+ break
+ }
+ h4, h5, mp := walkBinary(r)
+ has4 = has4 || h4
+ has5 = has5 || h5
+ if maxProblem < mp {
+ maxProblem = mp
+ }
+
+ case *ast.StarExpr:
+ if e.Op == token.QUO { // `*/`
+ maxProblem = 5
+ }
+
+ case *ast.UnaryExpr:
+ switch e.Op.String() + r.Op.String() {
+ case "/*", "&&", "&^":
+ maxProblem = 5
+ case "++", "--":
+ if maxProblem < 4 {
+ maxProblem = 4
+ }
+ }
+ }
+ return
+}
+
+func cutoff(e *ast.BinaryExpr, depth int) int {
+ has4, has5, maxProblem := walkBinary(e)
+ if maxProblem > 0 {
+ return maxProblem + 1
+ }
+ if has4 && has5 {
+ if depth == 1 {
+ return 5
+ }
+ return 4
+ }
+ if depth == 1 {
+ return 6
+ }
+ return 4
+}
+
+func diffPrec(expr ast.Expr, prec int) int {
+ x, ok := expr.(*ast.BinaryExpr)
+ if !ok || prec != x.Op.Precedence() {
+ return 1
+ }
+ return 0
+}
+
+func reduceDepth(depth int) int {
+ depth--
+ if depth < 1 {
+ depth = 1
+ }
+ return depth
+}
+
+// Format the binary expression: decide the cutoff and then format.
+// Let's call depth == 1 Normal mode, and depth > 1 Compact mode.
+// (Algorithm suggestion by Russ Cox.)
+//
+// The precedences are:
+// 5 * / % << >> & &^
+// 4 + - | ^
+// 3 == != < <= > >=
+// 2 &&
+// 1 ||
+//
+// The only decision is whether there will be spaces around levels 4 and 5.
+// There are never spaces at level 6 (unary), and always spaces at levels 3 and below.
+//
+// To choose the cutoff, look at the whole expression but excluding primary
+// expressions (function calls, parenthesized exprs), and apply these rules:
+//
+// 1) If there is a binary operator with a right side unary operand
+// that would clash without a space, the cutoff must be (in order):
+//
+// /* 6
+// && 6
+// &^ 6
+// ++ 5
+// -- 5
+//
+// (Comparison operators always have spaces around them.)
+//
+// 2) If there is a mix of level 5 and level 4 operators, then the cutoff
+// is 5 (use spaces to distinguish precedence) in Normal mode
+// and 4 (never use spaces) in Compact mode.
+//
+// 3) If there are no level 4 operators or no level 5 operators, then the
+// cutoff is 6 (always use spaces) in Normal mode
+// and 4 (never use spaces) in Compact mode.
+//
+func (p *printer) binaryExpr(x *ast.BinaryExpr, prec1, cutoff, depth int) {
+ prec := x.Op.Precedence()
+ if prec < prec1 {
+ // parenthesis needed
+ // Note: The parser inserts an ast.ParenExpr node; thus this case
+ // can only occur if the AST is created in a different way.
+ p.print(token.LPAREN)
+ p.expr0(x, reduceDepth(depth)) // parentheses undo one level of depth
+ p.print(token.RPAREN)
+ return
+ }
+
+ printBlank := prec < cutoff
+
+ ws := indent
+ p.expr1(x.X, prec, depth+diffPrec(x.X, prec))
+ if printBlank {
+ p.print(blank)
+ }
+ xline := p.pos.Line // before the operator (it may be on the next line!)
+ yline := p.lineFor(x.Y.Pos())
+ p.print(x.OpPos, x.Op)
+ if xline != yline && xline > 0 && yline > 0 {
+ // at least one line break, but respect an extra empty line
+ // in the source
+ if p.linebreak(yline, 1, ws, true) > 0 {
+ ws = ignore
+ printBlank = false // no blank after line break
+ }
+ }
+ if printBlank {
+ p.print(blank)
+ }
+ p.expr1(x.Y, prec+1, depth+1)
+ if ws == ignore {
+ p.print(unindent)
+ }
+}
+
+func isBinary(expr ast.Expr) bool {
+ _, ok := expr.(*ast.BinaryExpr)
+ return ok
+}
+
+func (p *printer) expr1(expr ast.Expr, prec1, depth int) {
+ p.print(expr.Pos())
+
+ switch x := expr.(type) {
+ case *ast.BadExpr:
+ p.print("BadExpr")
+
+ case *ast.Ident:
+ p.print(x)
+
+ case *ast.BinaryExpr:
+ if depth < 1 {
+ p.internalError("depth < 1:", depth)
+ depth = 1
+ }
+ p.binaryExpr(x, prec1, cutoff(x, depth), depth)
+
+ case *ast.KeyValueExpr:
+ p.expr(x.Key)
+ p.print(x.Colon, token.COLON, blank)
+ p.expr(x.Value)
+
+ case *ast.StarExpr:
+ const prec = token.UnaryPrec
+ if prec < prec1 {
+ // parenthesis needed
+ p.print(token.LPAREN)
+ p.print(token.MUL)
+ p.expr(x.X)
+ p.print(token.RPAREN)
+ } else {
+ // no parenthesis needed
+ p.print(token.MUL)
+ p.expr(x.X)
+ }
+
+ case *ast.UnaryExpr:
+ const prec = token.UnaryPrec
+ if prec < prec1 {
+ // parenthesis needed
+ p.print(token.LPAREN)
+ p.expr(x)
+ p.print(token.RPAREN)
+ } else {
+ // no parenthesis needed
+ p.print(x.Op)
+ if x.Op == token.RANGE {
+ // TODO(gri) Remove this code if it cannot be reached.
+ p.print(blank)
+ }
+ p.expr1(x.X, prec, depth)
+ }
+
+ case *ast.BasicLit:
+ if p.Config.Mode&normalizeNumbers != 0 {
+ x = normalizedNumber(x)
+ }
+ p.print(x)
+
+ case *ast.FuncLit:
+ p.print(x.Type.Pos(), token.FUNC)
+ // See the comment in funcDecl about how the header size is computed.
+ startCol := p.out.Column - len("func")
+ p.signature(x.Type.Params, x.Type.Results)
+ p.funcBody(p.distanceFrom(x.Type.Pos(), startCol), blank, x.Body)
+
+ case *ast.ParenExpr:
+ if _, hasParens := x.X.(*ast.ParenExpr); hasParens {
+ // don't print parentheses around an already parenthesized expression
+ // TODO(gri) consider making this more general and incorporate precedence levels
+ p.expr0(x.X, depth)
+ } else {
+ p.print(token.LPAREN)
+ p.expr0(x.X, reduceDepth(depth)) // parentheses undo one level of depth
+ p.print(x.Rparen, token.RPAREN)
+ }
+
+ case *ast.SelectorExpr:
+ p.selectorExpr(x, depth, false)
+
+ case *ast.TypeAssertExpr:
+ p.expr1(x.X, token.HighestPrec, depth)
+ p.print(token.PERIOD, x.Lparen, token.LPAREN)
+ if x.Type != nil {
+ p.expr(x.Type)
+ } else {
+ p.print(token.TYPE)
+ }
+ p.print(x.Rparen, token.RPAREN)
+
+ case *ast.IndexExpr:
+ // TODO(gri): should treat[] like parentheses and undo one level of depth
+ p.expr1(x.X, token.HighestPrec, 1)
+ p.print(x.Lbrack, token.LBRACK)
+ p.expr0(x.Index, depth+1)
+ p.print(x.Rbrack, token.RBRACK)
+
+ case *ast.SliceExpr:
+ // TODO(gri): should treat[] like parentheses and undo one level of depth
+ p.expr1(x.X, token.HighestPrec, 1)
+ p.print(x.Lbrack, token.LBRACK)
+ indices := []ast.Expr{x.Low, x.High}
+ if x.Max != nil {
+ indices = append(indices, x.Max)
+ }
+ // determine if we need extra blanks around ':'
+ var needsBlanks bool
+ if depth <= 1 {
+ var indexCount int
+ var hasBinaries bool
+ for _, x := range indices {
+ if x != nil {
+ indexCount++
+ if isBinary(x) {
+ hasBinaries = true
+ }
+ }
+ }
+ if indexCount > 1 && hasBinaries {
+ needsBlanks = true
+ }
+ }
+ for i, x := range indices {
+ if i > 0 {
+ if indices[i-1] != nil && needsBlanks {
+ p.print(blank)
+ }
+ p.print(token.COLON)
+ if x != nil && needsBlanks {
+ p.print(blank)
+ }
+ }
+ if x != nil {
+ p.expr0(x, depth+1)
+ }
+ }
+ p.print(x.Rbrack, token.RBRACK)
+
+ case *ast.CallExpr:
+ if len(x.Args) > 1 {
+ depth++
+ }
+ var wasIndented bool
+ if _, ok := x.Fun.(*ast.FuncType); ok {
+ // conversions to literal function types require parentheses around the type
+ p.print(token.LPAREN)
+ wasIndented = p.possibleSelectorExpr(x.Fun, token.HighestPrec, depth)
+ p.print(token.RPAREN)
+ } else {
+ wasIndented = p.possibleSelectorExpr(x.Fun, token.HighestPrec, depth)
+ }
+ p.print(x.Lparen, token.LPAREN)
+ if x.Ellipsis.IsValid() {
+ p.exprList(x.Lparen, x.Args, depth, 0, x.Ellipsis, false)
+ p.print(x.Ellipsis, token.ELLIPSIS)
+ if x.Rparen.IsValid() && p.lineFor(x.Ellipsis) < p.lineFor(x.Rparen) {
+ p.print(token.COMMA, formfeed)
+ }
+ } else {
+ p.exprList(x.Lparen, x.Args, depth, commaTerm, x.Rparen, false)
+ }
+ p.print(x.Rparen, token.RPAREN)
+ if wasIndented {
+ p.print(unindent)
+ }
+
+ case *ast.CompositeLit:
+ // composite literal elements that are composite literals themselves may have the type omitted
+ if x.Type != nil {
+ p.expr1(x.Type, token.HighestPrec, depth)
+ }
+ p.level++
+ p.print(x.Lbrace, token.LBRACE)
+ p.exprList(x.Lbrace, x.Elts, 1, commaTerm, x.Rbrace, x.Incomplete)
+ // do not insert extra line break following a /*-style comment
+ // before the closing '}' as it might break the code if there
+ // is no trailing ','
+ mode := noExtraLinebreak
+ // do not insert extra blank following a /*-style comment
+ // before the closing '}' unless the literal is empty
+ if len(x.Elts) > 0 {
+ mode |= noExtraBlank
+ }
+ // need the initial indent to print lone comments with
+ // the proper level of indentation
+ p.print(indent, unindent, mode, x.Rbrace, token.RBRACE, mode)
+ p.level--
+
+ case *ast.Ellipsis:
+ p.print(token.ELLIPSIS)
+ if x.Elt != nil {
+ p.expr(x.Elt)
+ }
+
+ case *ast.ArrayType:
+ p.print(token.LBRACK)
+ if x.Len != nil {
+ p.expr(x.Len)
+ }
+ p.print(token.RBRACK)
+ p.expr(x.Elt)
+
+ case *ast.StructType:
+ p.print(token.STRUCT)
+ p.fieldList(x.Fields, true, x.Incomplete)
+
+ case *ast.FuncType:
+ p.print(token.FUNC)
+ p.signature(x.Params, x.Results)
+
+ case *ast.InterfaceType:
+ p.print(token.INTERFACE)
+ p.fieldList(x.Methods, false, x.Incomplete)
+
+ case *ast.MapType:
+ p.print(token.MAP, token.LBRACK)
+ p.expr(x.Key)
+ p.print(token.RBRACK)
+ p.expr(x.Value)
+
+ case *ast.ChanType:
+ switch x.Dir {
+ case ast.SEND | ast.RECV:
+ p.print(token.CHAN)
+ case ast.RECV:
+ p.print(token.ARROW, token.CHAN) // x.Arrow and x.Pos() are the same
+ case ast.SEND:
+ p.print(token.CHAN, x.Arrow, token.ARROW)
+ }
+ p.print(blank)
+ p.expr(x.Value)
+
+ default:
+ panic("unreachable")
+ }
+}
+
+// normalizedNumber rewrites base prefixes and exponents
+// of numbers to use lower-case letters (0X123 to 0x123 and 1.2E3 to 1.2e3),
+// and removes leading 0's from integer imaginary literals (0765i to 765i).
+// It leaves hexadecimal digits alone.
+//
+// normalizedNumber doesn't modify the ast.BasicLit value lit points to.
+// If lit is not a number or a number in canonical format already,
+// lit is returned as is. Otherwise a new ast.BasicLit is created.
+func normalizedNumber(lit *ast.BasicLit) *ast.BasicLit {
+ if lit.Kind != token.INT && lit.Kind != token.FLOAT && lit.Kind != token.IMAG {
+ return lit // not a number - nothing to do
+ }
+ if len(lit.Value) < 2 {
+ return lit // only one digit (common case) - nothing to do
+ }
+ // len(lit.Value) >= 2
+
+ // We ignore lit.Kind because for lit.Kind == token.IMAG the literal may be an integer
+ // or floating-point value, decimal or not. Instead, just consider the literal pattern.
+ x := lit.Value
+ switch x[:2] {
+ default:
+ // 0-prefix octal, decimal int, or float (possibly with 'i' suffix)
+ if i := strings.LastIndexByte(x, 'E'); i >= 0 {
+ x = x[:i] + "e" + x[i+1:]
+ break
+ }
+ // remove leading 0's from integer (but not floating-point) imaginary literals
+ if x[len(x)-1] == 'i' && strings.IndexByte(x, '.') < 0 && strings.IndexByte(x, 'e') < 0 {
+ x = strings.TrimLeft(x, "0_")
+ if x == "i" {
+ x = "0i"
+ }
+ }
+ case "0X":
+ x = "0x" + x[2:]
+ // possibly a hexadecimal float
+ if i := strings.LastIndexByte(x, 'P'); i >= 0 {
+ x = x[:i] + "p" + x[i+1:]
+ }
+ case "0x":
+ // possibly a hexadecimal float
+ i := strings.LastIndexByte(x, 'P')
+ if i == -1 {
+ return lit // nothing to do
+ }
+ x = x[:i] + "p" + x[i+1:]
+ case "0O":
+ x = "0o" + x[2:]
+ case "0o":
+ return lit // nothing to do
+ case "0B":
+ x = "0b" + x[2:]
+ case "0b":
+ return lit // nothing to do
+ }
+
+ return &ast.BasicLit{ValuePos: lit.ValuePos, Kind: lit.Kind, Value: x}
+}
+
+func (p *printer) possibleSelectorExpr(expr ast.Expr, prec1, depth int) bool {
+ if x, ok := expr.(*ast.SelectorExpr); ok {
+ return p.selectorExpr(x, depth, true)
+ }
+ p.expr1(expr, prec1, depth)
+ return false
+}
+
+// selectorExpr handles an *ast.SelectorExpr node and reports whether x spans
+// multiple lines.
+func (p *printer) selectorExpr(x *ast.SelectorExpr, depth int, isMethod bool) bool {
+ p.expr1(x.X, token.HighestPrec, depth)
+ p.print(token.PERIOD)
+ if line := p.lineFor(x.Sel.Pos()); p.pos.IsValid() && p.pos.Line < line {
+ p.print(indent, newline, x.Sel.Pos(), x.Sel)
+ if !isMethod {
+ p.print(unindent)
+ }
+ return true
+ }
+ p.print(x.Sel.Pos(), x.Sel)
+ return false
+}
+
+func (p *printer) expr0(x ast.Expr, depth int) {
+ p.expr1(x, token.LowestPrec, depth)
+}
+
+func (p *printer) expr(x ast.Expr) {
+ const depth = 1
+ p.expr1(x, token.LowestPrec, depth)
+}
+
+// ----------------------------------------------------------------------------
+// Statements
+
+// Print the statement list indented, but without a newline after the last statement.
+// Extra line breaks between statements in the source are respected but at most one
+// empty line is printed between statements.
+func (p *printer) stmtList(list []ast.Stmt, nindent int, nextIsRBrace bool) {
+ if nindent > 0 {
+ p.print(indent)
+ }
+ var line int
+ i := 0
+ for _, s := range list {
+ // ignore empty statements (was issue 3466)
+ if _, isEmpty := s.(*ast.EmptyStmt); !isEmpty {
+ // nindent == 0 only for lists of switch/select case clauses;
+ // in those cases each clause is a new section
+ if len(p.output) > 0 {
+ // only print line break if we are not at the beginning of the output
+ // (i.e., we are not printing only a partial program)
+ p.linebreak(p.lineFor(s.Pos()), 1, ignore, i == 0 || nindent == 0 || p.linesFrom(line) > 0)
+ }
+ p.recordLine(&line)
+ p.stmt(s, nextIsRBrace && i == len(list)-1)
+ // labeled statements put labels on a separate line, but here
+ // we only care about the start line of the actual statement
+ // without label - correct line for each label
+ for t := s; ; {
+ lt, _ := t.(*ast.LabeledStmt)
+ if lt == nil {
+ break
+ }
+ line++
+ t = lt.Stmt
+ }
+ i++
+ }
+ }
+ if nindent > 0 {
+ p.print(unindent)
+ }
+}
+
+// block prints an *ast.BlockStmt; it always spans at least two lines.
+func (p *printer) block(b *ast.BlockStmt, nindent int) {
+ p.print(b.Lbrace, token.LBRACE)
+ p.stmtList(b.List, nindent, true)
+ p.linebreak(p.lineFor(b.Rbrace), 1, ignore, true)
+ p.print(b.Rbrace, token.RBRACE)
+}
+
+func isTypeName(x ast.Expr) bool {
+ switch t := x.(type) {
+ case *ast.Ident:
+ return true
+ case *ast.SelectorExpr:
+ return isTypeName(t.X)
+ }
+ return false
+}
+
+func stripParens(x ast.Expr) ast.Expr {
+ if px, strip := x.(*ast.ParenExpr); strip {
+ // parentheses must not be stripped if there are any
+ // unparenthesized composite literals starting with
+ // a type name
+ ast.Inspect(px.X, func(node ast.Node) bool {
+ switch x := node.(type) {
+ case *ast.ParenExpr:
+ // parentheses protect enclosed composite literals
+ return false
+ case *ast.CompositeLit:
+ if isTypeName(x.Type) {
+ strip = false // do not strip parentheses
+ }
+ return false
+ }
+ // in all other cases, keep inspecting
+ return true
+ })
+ if strip {
+ return stripParens(px.X)
+ }
+ }
+ return x
+}
+
+func stripParensAlways(x ast.Expr) ast.Expr {
+ if x, ok := x.(*ast.ParenExpr); ok {
+ return stripParensAlways(x.X)
+ }
+ return x
+}
+
+func (p *printer) controlClause(isForStmt bool, init ast.Stmt, expr ast.Expr, post ast.Stmt) {
+ p.print(blank)
+ needsBlank := false
+ if init == nil && post == nil {
+ // no semicolons required
+ if expr != nil {
+ p.expr(stripParens(expr))
+ needsBlank = true
+ }
+ } else {
+ // all semicolons required
+ // (they are not separators, print them explicitly)
+ if init != nil {
+ p.stmt(init, false)
+ }
+ p.print(token.SEMICOLON, blank)
+ if expr != nil {
+ p.expr(stripParens(expr))
+ needsBlank = true
+ }
+ if isForStmt {
+ p.print(token.SEMICOLON, blank)
+ needsBlank = false
+ if post != nil {
+ p.stmt(post, false)
+ needsBlank = true
+ }
+ }
+ }
+ if needsBlank {
+ p.print(blank)
+ }
+}
+
+// indentList reports whether an expression list would look better if it
+// were indented wholesale (starting with the very first element, rather
+// than starting at the first line break).
+//
+func (p *printer) indentList(list []ast.Expr) bool {
+ // Heuristic: indentList reports whether there are more than one multi-
+ // line element in the list, or if there is any element that is not
+ // starting on the same line as the previous one ends.
+ if len(list) >= 2 {
+ var b = p.lineFor(list[0].Pos())
+ var e = p.lineFor(list[len(list)-1].End())
+ if 0 < b && b < e {
+ // list spans multiple lines
+ n := 0 // multi-line element count
+ line := b
+ for _, x := range list {
+ xb := p.lineFor(x.Pos())
+ xe := p.lineFor(x.End())
+ if line < xb {
+ // x is not starting on the same
+ // line as the previous one ended
+ return true
+ }
+ if xb < xe {
+ // x is a multi-line element
+ n++
+ }
+ line = xe
+ }
+ return n > 1
+ }
+ }
+ return false
+}
+
+func (p *printer) stmt(stmt ast.Stmt, nextIsRBrace bool) {
+ p.print(stmt.Pos())
+
+ switch s := stmt.(type) {
+ case *ast.BadStmt:
+ p.print("BadStmt")
+
+ case *ast.DeclStmt:
+ p.decl(s.Decl)
+
+ case *ast.EmptyStmt:
+ // nothing to do
+
+ case *ast.LabeledStmt:
+ // a "correcting" unindent immediately following a line break
+ // is applied before the line break if there is no comment
+ // between (see writeWhitespace)
+ p.print(unindent)
+ p.expr(s.Label)
+ p.print(s.Colon, token.COLON, indent)
+ if e, isEmpty := s.Stmt.(*ast.EmptyStmt); isEmpty {
+ if !nextIsRBrace {
+ p.print(newline, e.Pos(), token.SEMICOLON)
+ break
+ }
+ } else {
+ p.linebreak(p.lineFor(s.Stmt.Pos()), 1, ignore, true)
+ }
+ p.stmt(s.Stmt, nextIsRBrace)
+
+ case *ast.ExprStmt:
+ const depth = 1
+ p.expr0(s.X, depth)
+
+ case *ast.SendStmt:
+ const depth = 1
+ p.expr0(s.Chan, depth)
+ p.print(blank, s.Arrow, token.ARROW, blank)
+ p.expr0(s.Value, depth)
+
+ case *ast.IncDecStmt:
+ const depth = 1
+ p.expr0(s.X, depth+1)
+ p.print(s.TokPos, s.Tok)
+
+ case *ast.AssignStmt:
+ var depth = 1
+ if len(s.Lhs) > 1 && len(s.Rhs) > 1 {
+ depth++
+ }
+ p.exprList(s.Pos(), s.Lhs, depth, 0, s.TokPos, false)
+ p.print(blank, s.TokPos, s.Tok, blank)
+ p.exprList(s.TokPos, s.Rhs, depth, 0, token.NoPos, false)
+
+ case *ast.GoStmt:
+ p.print(token.GO, blank)
+ p.expr(s.Call)
+
+ case *ast.DeferStmt:
+ p.print(token.DEFER, blank)
+ p.expr(s.Call)
+
+ case *ast.ReturnStmt:
+ p.print(token.RETURN)
+ if s.Results != nil {
+ p.print(blank)
+ // Use indentList heuristic to make corner cases look
+ // better (issue 1207). A more systematic approach would
+ // always indent, but this would cause significant
+ // reformatting of the code base and not necessarily
+ // lead to more nicely formatted code in general.
+ if p.indentList(s.Results) {
+ p.print(indent)
+ // Use NoPos so that a newline never goes before
+ // the results (see issue #32854).
+ p.exprList(token.NoPos, s.Results, 1, noIndent, token.NoPos, false)
+ p.print(unindent)
+ } else {
+ p.exprList(token.NoPos, s.Results, 1, 0, token.NoPos, false)
+ }
+ }
+
+ case *ast.BranchStmt:
+ p.print(s.Tok)
+ if s.Label != nil {
+ p.print(blank)
+ p.expr(s.Label)
+ }
+
+ case *ast.BlockStmt:
+ p.block(s, 1)
+
+ case *ast.IfStmt:
+ p.print(token.IF)
+ p.controlClause(false, s.Init, s.Cond, nil)
+ p.block(s.Body, 1)
+ if s.Else != nil {
+ p.print(blank, token.ELSE, blank)
+ switch s.Else.(type) {
+ case *ast.BlockStmt, *ast.IfStmt:
+ p.stmt(s.Else, nextIsRBrace)
+ default:
+ // This can only happen with an incorrectly
+ // constructed AST. Permit it but print so
+ // that it can be parsed without errors.
+ p.print(token.LBRACE, indent, formfeed)
+ p.stmt(s.Else, true)
+ p.print(unindent, formfeed, token.RBRACE)
+ }
+ }
+
+ case *ast.CaseClause:
+ if s.List != nil {
+ p.print(token.CASE, blank)
+ p.exprList(s.Pos(), s.List, 1, 0, s.Colon, false)
+ } else {
+ p.print(token.DEFAULT)
+ }
+ p.print(s.Colon, token.COLON)
+ p.stmtList(s.Body, 1, nextIsRBrace)
+
+ case *ast.SwitchStmt:
+ p.print(token.SWITCH)
+ p.controlClause(false, s.Init, s.Tag, nil)
+ p.block(s.Body, 0)
+
+ case *ast.TypeSwitchStmt:
+ p.print(token.SWITCH)
+ if s.Init != nil {
+ p.print(blank)
+ p.stmt(s.Init, false)
+ p.print(token.SEMICOLON)
+ }
+ p.print(blank)
+ p.stmt(s.Assign, false)
+ p.print(blank)
+ p.block(s.Body, 0)
+
+ case *ast.CommClause:
+ if s.Comm != nil {
+ p.print(token.CASE, blank)
+ p.stmt(s.Comm, false)
+ } else {
+ p.print(token.DEFAULT)
+ }
+ p.print(s.Colon, token.COLON)
+ p.stmtList(s.Body, 1, nextIsRBrace)
+
+ case *ast.SelectStmt:
+ p.print(token.SELECT, blank)
+ body := s.Body
+ if len(body.List) == 0 && !p.commentBefore(p.posFor(body.Rbrace)) {
+ // print empty select statement w/o comments on one line
+ p.print(body.Lbrace, token.LBRACE, body.Rbrace, token.RBRACE)
+ } else {
+ p.block(body, 0)
+ }
+
+ case *ast.ForStmt:
+ p.print(token.FOR)
+ p.controlClause(true, s.Init, s.Cond, s.Post)
+ p.block(s.Body, 1)
+
+ case *ast.RangeStmt:
+ p.print(token.FOR, blank)
+ if s.Key != nil {
+ p.expr(s.Key)
+ if s.Value != nil {
+ // use position of value following the comma as
+ // comma position for correct comment placement
+ p.print(s.Value.Pos(), token.COMMA, blank)
+ p.expr(s.Value)
+ }
+ p.print(blank, s.TokPos, s.Tok, blank)
+ }
+ p.print(token.RANGE, blank)
+ p.expr(stripParens(s.X))
+ p.print(blank)
+ p.block(s.Body, 1)
+
+ default:
+ panic("unreachable")
+ }
+}
+
+// ----------------------------------------------------------------------------
+// Declarations
+
+// The keepTypeColumn function determines if the type column of a series of
+// consecutive const or var declarations must be kept, or if initialization
+// values (V) can be placed in the type column (T) instead. The i'th entry
+// in the result slice is true if the type column in spec[i] must be kept.
+//
+// For example, the declaration:
+//
+// const (
+// foobar int = 42 // comment
+// x = 7 // comment
+// foo
+// bar = 991
+// )
+//
+// leads to the type/values matrix below. A run of value columns (V) can
+// be moved into the type column if there is no type for any of the values
+// in that column (we only move entire columns so that they align properly).
+//
+// matrix formatted result
+// matrix
+// T V -> T V -> true there is a T and so the type
+// - V - V true column must be kept
+// - - - - false
+// - V V - false V is moved into T column
+//
+func keepTypeColumn(specs []ast.Spec) []bool {
+ m := make([]bool, len(specs))
+
+ populate := func(i, j int, keepType bool) {
+ if keepType {
+ for ; i < j; i++ {
+ m[i] = true
+ }
+ }
+ }
+
+ i0 := -1 // if i0 >= 0 we are in a run and i0 is the start of the run
+ var keepType bool
+ for i, s := range specs {
+ t := s.(*ast.ValueSpec)
+ if t.Values != nil {
+ if i0 < 0 {
+ // start of a run of ValueSpecs with non-nil Values
+ i0 = i
+ keepType = false
+ }
+ } else {
+ if i0 >= 0 {
+ // end of a run
+ populate(i0, i, keepType)
+ i0 = -1
+ }
+ }
+ if t.Type != nil {
+ keepType = true
+ }
+ }
+ if i0 >= 0 {
+ // end of a run
+ populate(i0, len(specs), keepType)
+ }
+
+ return m
+}
+
+func (p *printer) valueSpec(s *ast.ValueSpec, keepType bool) {
+ p.setComment(s.Doc)
+ p.identList(s.Names, false) // always present
+ extraTabs := 3
+ if s.Type != nil || keepType {
+ p.print(vtab)
+ extraTabs--
+ }
+ if s.Type != nil {
+ p.expr(s.Type)
+ }
+ if s.Values != nil {
+ p.print(vtab, token.ASSIGN, blank)
+ p.exprList(token.NoPos, s.Values, 1, 0, token.NoPos, false)
+ extraTabs--
+ }
+ if s.Comment != nil {
+ for ; extraTabs > 0; extraTabs-- {
+ p.print(vtab)
+ }
+ p.setComment(s.Comment)
+ }
+}
+
+func sanitizeImportPath(lit *ast.BasicLit) *ast.BasicLit {
+ // Note: An unmodified AST generated by go/parser will already
+ // contain a backward- or double-quoted path string that does
+ // not contain any invalid characters, and most of the work
+ // here is not needed. However, a modified or generated AST
+ // may possibly contain non-canonical paths. Do the work in
+ // all cases since it's not too hard and not speed-critical.
+
+ // if we don't have a proper string, be conservative and return whatever we have
+ if lit.Kind != token.STRING {
+ return lit
+ }
+ s, err := strconv.Unquote(lit.Value)
+ if err != nil {
+ return lit
+ }
+
+ // if the string is an invalid path, return whatever we have
+ //
+ // spec: "Implementation restriction: A compiler may restrict
+ // ImportPaths to non-empty strings using only characters belonging
+ // to Unicode's L, M, N, P, and S general categories (the Graphic
+ // characters without spaces) and may also exclude the characters
+ // !"#$%&'()*,:;<=>?[\]^`{|} and the Unicode replacement character
+ // U+FFFD."
+ if s == "" {
+ return lit
+ }
+ const illegalChars = `!"#$%&'()*,:;<=>?[\]^{|}` + "`\uFFFD"
+ for _, r := range s {
+ if !unicode.IsGraphic(r) || unicode.IsSpace(r) || strings.ContainsRune(illegalChars, r) {
+ return lit
+ }
+ }
+
+ // otherwise, return the double-quoted path
+ s = strconv.Quote(s)
+ if s == lit.Value {
+ return lit // nothing wrong with lit
+ }
+ return &ast.BasicLit{ValuePos: lit.ValuePos, Kind: token.STRING, Value: s}
+}
+
+// The parameter n is the number of specs in the group. If doIndent is set,
+// multi-line identifier lists in the spec are indented when the first
+// linebreak is encountered.
+//
+func (p *printer) spec(spec ast.Spec, n int, doIndent bool) {
+ switch s := spec.(type) {
+ case *ast.ImportSpec:
+ p.setComment(s.Doc)
+ if s.Name != nil {
+ p.expr(s.Name)
+ p.print(blank)
+ }
+ p.expr(sanitizeImportPath(s.Path))
+ p.setComment(s.Comment)
+ p.print(s.EndPos)
+
+ case *ast.ValueSpec:
+ if n != 1 {
+ p.internalError("expected n = 1; got", n)
+ }
+ p.setComment(s.Doc)
+ p.identList(s.Names, doIndent) // always present
+ if s.Type != nil {
+ p.print(blank)
+ p.expr(s.Type)
+ }
+ if s.Values != nil {
+ p.print(blank, token.ASSIGN, blank)
+ p.exprList(token.NoPos, s.Values, 1, 0, token.NoPos, false)
+ }
+ p.setComment(s.Comment)
+
+ case *ast.TypeSpec:
+ p.setComment(s.Doc)
+ p.expr(s.Name)
+ if n == 1 {
+ p.print(blank)
+ } else {
+ p.print(vtab)
+ }
+ if s.Assign.IsValid() {
+ p.print(token.ASSIGN, blank)
+ }
+ p.expr(s.Type)
+ p.setComment(s.Comment)
+
+ default:
+ panic("unreachable")
+ }
+}
+
+func (p *printer) genDecl(d *ast.GenDecl) {
+ p.setComment(d.Doc)
+ p.print(d.Pos(), d.Tok, blank)
+
+ if d.Lparen.IsValid() || len(d.Specs) > 1 {
+ // group of parenthesized declarations
+ p.print(d.Lparen, token.LPAREN)
+ if n := len(d.Specs); n > 0 {
+ p.print(indent, formfeed)
+ if n > 1 && (d.Tok == token.CONST || d.Tok == token.VAR) {
+ // two or more grouped const/var declarations:
+ // determine if the type column must be kept
+ keepType := keepTypeColumn(d.Specs)
+ var line int
+ for i, s := range d.Specs {
+ if i > 0 {
+ p.linebreak(p.lineFor(s.Pos()), 1, ignore, p.linesFrom(line) > 0)
+ }
+ p.recordLine(&line)
+ p.valueSpec(s.(*ast.ValueSpec), keepType[i])
+ }
+ } else {
+ var line int
+ for i, s := range d.Specs {
+ if i > 0 {
+ p.linebreak(p.lineFor(s.Pos()), 1, ignore, p.linesFrom(line) > 0)
+ }
+ p.recordLine(&line)
+ p.spec(s, n, false)
+ }
+ }
+ p.print(unindent, formfeed)
+ }
+ p.print(d.Rparen, token.RPAREN)
+
+ } else if len(d.Specs) > 0 {
+ // single declaration
+ p.spec(d.Specs[0], 1, true)
+ }
+}
+
+// nodeSize determines the size of n in chars after formatting.
+// The result is <= maxSize if the node fits on one line with at
+// most maxSize chars and the formatted output doesn't contain
+// any control chars. Otherwise, the result is > maxSize.
+//
+func (p *printer) nodeSize(n ast.Node, maxSize int) (size int) {
+ // nodeSize invokes the printer, which may invoke nodeSize
+ // recursively. For deep composite literal nests, this can
+ // lead to an exponential algorithm. Remember previous
+ // results to prune the recursion (was issue 1628).
+ if size, found := p.nodeSizes[n]; found {
+ return size
+ }
+
+ size = maxSize + 1 // assume n doesn't fit
+ p.nodeSizes[n] = size
+
+ // nodeSize computation must be independent of particular
+ // style so that we always get the same decision; print
+ // in RawFormat
+ cfg := Config{Mode: RawFormat}
+ var buf bytes.Buffer
+ if err := cfg.fprint(&buf, p.fset, n, p.nodeSizes); err != nil {
+ return
+ }
+ if buf.Len() <= maxSize {
+ for _, ch := range buf.Bytes() {
+ if ch < ' ' {
+ return
+ }
+ }
+ size = buf.Len() // n fits
+ p.nodeSizes[n] = size
+ }
+ return
+}
+
+// numLines returns the number of lines spanned by node n in the original source.
+func (p *printer) numLines(n ast.Node) int {
+ if from := n.Pos(); from.IsValid() {
+ if to := n.End(); to.IsValid() {
+ return p.lineFor(to) - p.lineFor(from) + 1
+ }
+ }
+ return infinity
+}
+
+// bodySize is like nodeSize but it is specialized for *ast.BlockStmt's.
+func (p *printer) bodySize(b *ast.BlockStmt, maxSize int) int {
+ pos1 := b.Pos()
+ pos2 := b.Rbrace
+ if pos1.IsValid() && pos2.IsValid() && p.lineFor(pos1) != p.lineFor(pos2) {
+ // opening and closing brace are on different lines - don't make it a one-liner
+ return maxSize + 1
+ }
+ if len(b.List) > 5 {
+ // too many statements - don't make it a one-liner
+ return maxSize + 1
+ }
+ // otherwise, estimate body size
+ bodySize := p.commentSizeBefore(p.posFor(pos2))
+ for i, s := range b.List {
+ if bodySize > maxSize {
+ break // no need to continue
+ }
+ if i > 0 {
+ bodySize += 2 // space for a semicolon and blank
+ }
+ bodySize += p.nodeSize(s, maxSize)
+ }
+ return bodySize
+}
+
+// funcBody prints a function body following a function header of given headerSize.
+// If the header's and block's size are "small enough" and the block is "simple enough",
+// the block is printed on the current line, without line breaks, spaced from the header
+// by sep. Otherwise the block's opening "{" is printed on the current line, followed by
+// lines for the block's statements and its closing "}".
+//
+func (p *printer) funcBody(headerSize int, sep whiteSpace, b *ast.BlockStmt) {
+ if b == nil {
+ return
+ }
+
+ // save/restore composite literal nesting level
+ defer func(level int) {
+ p.level = level
+ }(p.level)
+ p.level = 0
+
+ const maxSize = 100
+ if headerSize+p.bodySize(b, maxSize) <= maxSize {
+ p.print(sep, b.Lbrace, token.LBRACE)
+ if len(b.List) > 0 {
+ p.print(blank)
+ for i, s := range b.List {
+ if i > 0 {
+ p.print(token.SEMICOLON, blank)
+ }
+ p.stmt(s, i == len(b.List)-1)
+ }
+ p.print(blank)
+ }
+ p.print(noExtraLinebreak, b.Rbrace, token.RBRACE, noExtraLinebreak)
+ return
+ }
+
+ if sep != ignore {
+ p.print(blank) // always use blank
+ }
+ p.block(b, 1)
+}
+
+// distanceFrom returns the column difference between p.out (the current output
+// position) and startOutCol. If the start position is on a different line from
+// the current position (or either is unknown), the result is infinity.
+func (p *printer) distanceFrom(startPos token.Pos, startOutCol int) int {
+ if startPos.IsValid() && p.pos.IsValid() && p.posFor(startPos).Line == p.pos.Line {
+ return p.out.Column - startOutCol
+ }
+ return infinity
+}
+
+func (p *printer) funcDecl(d *ast.FuncDecl) {
+ p.setComment(d.Doc)
+ p.print(d.Pos(), token.FUNC, blank)
+ // We have to save startCol only after emitting FUNC; otherwise it can be on a
+ // different line (all whitespace preceding the FUNC is emitted only when the
+ // FUNC is emitted).
+ startCol := p.out.Column - len("func ")
+ if d.Recv != nil {
+ p.parameters(d.Recv) // method: print receiver
+ p.print(blank)
+ }
+ p.expr(d.Name)
+ p.signature(d.Type.Params, d.Type.Results)
+ p.funcBody(p.distanceFrom(d.Pos(), startCol), vtab, d.Body)
+}
+
+func (p *printer) decl(decl ast.Decl) {
+ switch d := decl.(type) {
+ case *ast.BadDecl:
+ p.print(d.Pos(), "BadDecl")
+ case *ast.GenDecl:
+ p.genDecl(d)
+ case *ast.FuncDecl:
+ p.funcDecl(d)
+ default:
+ panic("unreachable")
+ }
+}
+
+// ----------------------------------------------------------------------------
+// Files
+
+func declToken(decl ast.Decl) (tok token.Token) {
+ tok = token.ILLEGAL
+ switch d := decl.(type) {
+ case *ast.GenDecl:
+ tok = d.Tok
+ case *ast.FuncDecl:
+ tok = token.FUNC
+ }
+ return
+}
+
+func (p *printer) declList(list []ast.Decl) {
+ tok := token.ILLEGAL
+ for _, d := range list {
+ prev := tok
+ tok = declToken(d)
+ // If the declaration token changed (e.g., from CONST to TYPE)
+ // or the next declaration has documentation associated with it,
+ // print an empty line between top-level declarations.
+ // (because p.linebreak is called with the position of d, which
+ // is past any documentation, the minimum requirement is satisfied
+ // even w/o the extra getDoc(d) nil-check - leave it in case the
+ // linebreak logic improves - there's already a TODO).
+ if len(p.output) > 0 {
+ // only print line break if we are not at the beginning of the output
+ // (i.e., we are not printing only a partial program)
+ min := 1
+ if prev != tok || getDoc(d) != nil {
+ min = 2
+ }
+ // start a new section if the next declaration is a function
+ // that spans multiple lines (see also issue #19544)
+ p.linebreak(p.lineFor(d.Pos()), min, ignore, tok == token.FUNC && p.numLines(d) > 1)
+ }
+ p.decl(d)
+ }
+}
+
+func (p *printer) file(src *ast.File) {
+ p.setComment(src.Doc)
+ p.print(src.Pos(), token.PACKAGE, blank)
+ p.expr(src.Name)
+ p.declList(src.Decls)
+ p.print(newline)
+}
generated by cgit v1.2.3 (git 2.39.1) at 2024-09-26 21:47:05 +0000