go/printer: output tuning for gofix

If braces don't have position information for a composite
literal, don't assume alignment of key:value pairs under
the (wrong) assumption that there may be multiple lines.

R=rsc
CC=golang-dev
https://golang.org/cl/4297043

diff --git a/src/pkg/go/printer/nodes.go b/src/pkg/go/printer/nodes.go
index 7933c2f182003a0ab631d5c785b005bcf2b9bed1..8ccd63612aaae91622a68daa3a284411dd4556b4 100644 (file)
--- a/src/pkg/go/printer/nodes.go
+++ b/src/pkg/go/printer/nodes.go
@@ -204,17 +204,21 @@ func (p *printer) exprList(prev0 token.Pos, list []ast.Expr, depth int, mode exp
                //           the key and the node size into the decision process
                useFF := true
 
-               // determine size
+               // 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 {
+               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
                }
 
@@ -244,7 +248,6 @@ func (p *printer) exprList(prev0 token.Pos, list []ast.Expr, depth int, mode exp
                                // lines are broken using newlines so comments remain aligned
                                // unless forceFF is set or there are multiple expressions on
                                // the same line in which case formfeed is used
-                               // broken with a formfeed
                                if p.linebreak(line, linebreakMin, ws, useFF || prevBreak+1 < i) {
                                        ws = ignore
                                        *multiLine = true