1 files changed, 212 insertions, 0 deletions
diff --git a/src/cmd/compile/internal/syntax/dumper.go b/src/cmd/compile/internal/syntax/dumper.go
new file mode 100644
index 0000000..d524788
--- /dev/null
+++ b/src/cmd/compile/internal/syntax/dumper.go
@@ -0,0 +1,212 @@
+// Copyright 2016 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 syntax tree structures.
+
+package syntax
+
+import (
+	"fmt"
+	"io"
+	"reflect"
+	"unicode"
+	"unicode/utf8"
+)
+
+// Fdump dumps the structure of the syntax tree rooted at n to w.
+// It is intended for debugging purposes; no specific output format
+// is guaranteed.
+func Fdump(w io.Writer, n Node) (err error) {
+	p := dumper{
+		output: w,
+		ptrmap: make(map[Node]int),
+		last:   '\n', // force printing of line number on first line
+	}
+
+	defer func() {
+		if e := recover(); e != nil {
+			err = e.(writeError).err // re-panics if it's not a writeError
+		}
+	}()
+
+	if n == nil {
+		p.printf("nil\n")
+		return
+	}
+	p.dump(reflect.ValueOf(n), n)
+	p.printf("\n")
+
+	return
+}
+
+type dumper struct {
+	output io.Writer
+	ptrmap map[Node]int // node -> dump line number
+	indent int          // current indentation level
+	last   byte         // last byte processed by Write
+	line   int          // current line number
+}
+
+var indentBytes = []byte(".  ")
+
+func (p *dumper) Write(data []byte) (n int, err error) {
+	var m int
+	for i, b := range data {
+		// invariant: data[0:n] has been written
+		if b == '\n' {
+			m, err = p.output.Write(data[n : i+1])
+			n += m
+			if err != nil {
+				return
+			}
+		} else if p.last == '\n' {
+			p.line++
+			_, err = fmt.Fprintf(p.output, "%6d  ", p.line)
+			if err != nil {
+				return
+			}
+			for j := p.indent; j > 0; j-- {
+				_, err = p.output.Write(indentBytes)
+				if err != nil {
+					return
+				}
+			}
+		}
+		p.last = b
+	}
+	if len(data) > n {
+		m, err = p.output.Write(data[n:])
+		n += m
+	}
+	return
+}
+
+// writeError wraps locally caught write errors so we can distinguish
+// them from genuine panics which we don't want to return as errors.
+type writeError struct {
+	err error
+}
+
+// printf is a convenience wrapper that takes care of print errors.
+func (p *dumper) printf(format string, args ...interface{}) {
+	if _, err := fmt.Fprintf(p, format, args...); err != nil {
+		panic(writeError{err})
+	}
+}
+
+// dump prints the contents of x.
+// If x is the reflect.Value of a struct s, where &s
+// implements Node, then &s should be passed for n -
+// this permits printing of the unexported span and
+// comments fields of the embedded isNode field by
+// calling the Span() and Comment() instead of using
+// reflection.
+func (p *dumper) dump(x reflect.Value, n Node) {
+	switch x.Kind() {
+	case reflect.Interface:
+		if x.IsNil() {
+			p.printf("nil")
+			return
+		}
+		p.dump(x.Elem(), nil)
+
+	case reflect.Ptr:
+		if x.IsNil() {
+			p.printf("nil")
+			return
+		}
+
+		// special cases for identifiers w/o attached comments (common case)
+		if x, ok := x.Interface().(*Name); ok {
+			p.printf("%s @ %v", x.Value, x.Pos())
+			return
+		}
+
+		p.printf("*")
+		// Fields may share type expressions, and declarations
+		// may share the same group - use ptrmap to keep track
+		// of nodes that have been printed already.
+		if ptr, ok := x.Interface().(Node); ok {
+			if line, exists := p.ptrmap[ptr]; exists {
+				p.printf("(Node @ %d)", line)
+				return
+			}
+			p.ptrmap[ptr] = p.line
+			n = ptr
+		}
+		p.dump(x.Elem(), n)
+
+	case reflect.Slice:
+		if x.IsNil() {
+			p.printf("nil")
+			return
+		}
+		p.printf("%s (%d entries) {", x.Type(), x.Len())
+		if x.Len() > 0 {
+			p.indent++
+			p.printf("\n")
+			for i, n := 0, x.Len(); i < n; i++ {
+				p.printf("%d: ", i)
+				p.dump(x.Index(i), nil)
+				p.printf("\n")
+			}
+			p.indent--
+		}
+		p.printf("}")
+
+	case reflect.Struct:
+		typ := x.Type()
+
+		// if span, ok := x.Interface().(lexical.Span); ok {
+		// 	p.printf("%s", &span)
+		// 	return
+		// }
+
+		p.printf("%s {", typ)
+		p.indent++
+
+		first := true
+		if n != nil {
+			p.printf("\n")
+			first = false
+			// p.printf("Span: %s\n", n.Span())
+			// if c := *n.Comments(); c != nil {
+			// 	p.printf("Comments: ")
+			// 	p.dump(reflect.ValueOf(c), nil) // a Comment is not a Node
+			// 	p.printf("\n")
+			// }
+		}
+
+		for i, n := 0, typ.NumField(); i < n; i++ {
+			// Exclude non-exported fields because their
+			// values cannot be accessed via reflection.
+			if name := typ.Field(i).Name; isExported(name) {
+				if first {
+					p.printf("\n")
+					first = false
+				}
+				p.printf("%s: ", name)
+				p.dump(x.Field(i), nil)
+				p.printf("\n")
+			}
+		}
+
+		p.indent--
+		p.printf("}")
+
+	default:
+		switch x := x.Interface().(type) {
+		case string:
+			// print strings in quotes
+			p.printf("%q", x)
+		default:
+			p.printf("%v", x)
+		}
+	}
+}
+
+func isExported(name string) bool {
+	ch, _ := utf8.DecodeRuneInString(name)
+	return unicode.IsUpper(ch)
+}