go/ast: ast.Print needs a file set to print position values nicely

Also removed a TODO (AST nodes have been restructured a while ago).

R=r
CC=golang-dev
https://golang.org/cl/4245077

diff --git a/src/pkg/go/ast/print.go b/src/pkg/go/ast/print.go
index d71490d4a9ff440bb2c032987894ab0d0c4d50d9..e8194e7fa3a1418e498c40efc7907d6c620a20ab 100644 (file)
--- a/src/pkg/go/ast/print.go
+++ b/src/pkg/go/ast/print.go
@@ -30,15 +30,19 @@ func NotNilFilter(_ string, value reflect.Value) bool {
 
 
 // Fprint prints the (sub-)tree starting at AST node x to w.
+// If fset != nil, position information is interpreted relative
+// to that file set. Otherwise positions are printed as integer
+// values (file set specific offsets).
 //
 // A non-nil FieldFilter f may be provided to control the output:
 // struct fields for which f(fieldname, fieldvalue) is true are
 // are printed; all others are filtered from the output.
 //
-func Fprint(w io.Writer, x interface{}, f FieldFilter) (n int, err os.Error) {
+func Fprint(w io.Writer, fset *token.FileSet, x interface{}, f FieldFilter) (n int, err os.Error) {
        // setup printer
        p := printer{
                output: w,
+               fset:   fset,
                filter: f,
                ptrmap: make(map[interface{}]int),
                last:   '\n', // force printing of line number on first line
@@ -65,14 +69,15 @@ func Fprint(w io.Writer, x interface{}, f FieldFilter) (n int, err os.Error) {
 
 
 // Print prints x to standard output, skipping nil fields.
-// Print(x) is the same as Fprint(os.Stdout, x, NotNilFilter).
-func Print(x interface{}) (int, os.Error) {
-       return Fprint(os.Stdout, x, NotNilFilter)
+// Print(fset, x) is the same as Fprint(os.Stdout, fset, x, NotNilFilter).
+func Print(fset *token.FileSet, x interface{}) (int, os.Error) {
+       return Fprint(os.Stdout, fset, x, NotNilFilter)
 }
 
 
 type printer struct {
        output  io.Writer
+       fset    *token.FileSet
        filter  FieldFilter
        ptrmap  map[interface{}]int // *reflect.PtrValue -> line number
        written int                 // number of bytes written to output
@@ -137,16 +142,6 @@ func (p *printer) printf(format string, args ...interface{}) {
 // probably be in a different package.
 
 func (p *printer) print(x reflect.Value) {
-       // Note: This test is only needed because AST nodes
-       //       embed a token.Position, and thus all of them
-       //       understand the String() method (but it only
-       //       applies to the Position field).
-       // TODO: Should reconsider this AST design decision.
-       if pos, ok := x.Interface().(token.Position); ok {
-               p.printf("%s", pos)
-               return
-       }
-
        if !NotNilFilter("", x) {
                p.printf("nil")
                return
@@ -212,6 +207,11 @@ func (p *printer) print(x reflect.Value) {
                p.printf("}")
 
        default:
-               p.printf("%v", x.Interface())
+               value := x.Interface()
+               // position values can be printed nicely if we have a file set
+               if pos, ok := value.(token.Pos); ok && p.fset != nil {
+                       value = p.fset.Position(pos)
+               }
+               p.printf("%v", value)
        }
 }