From 573afbcdb6bf11e1fc7ed176b07a04719c1e9a26 Mon Sep 17 00:00:00 2001
From: Robert Griesemer <gri@golang.org>
Date: Wed, 8 Jun 2016 17:45:16 -0700
Subject: cmd/compile/internal/syntax: export ImplicitOne and use to identify
 x++/x--

+ minor documentation improvements
---
 src/cmd/compile/internal/syntax/nodes.go   | 8 ++++----
 src/cmd/compile/internal/syntax/parser.go  | 7 ++++---
 src/cmd/compile/internal/syntax/printer.go | 2 +-
 src/cmd/compile/internal/syntax/tokens.go  | 8 +++++---
 4 files changed, 14 insertions(+), 11 deletions(-)

diff --git a/src/cmd/compile/internal/syntax/nodes.go b/src/cmd/compile/internal/syntax/nodes.go
index f426a5ef47..de677a847a 100644
--- a/src/cmd/compile/internal/syntax/nodes.go
+++ b/src/cmd/compile/internal/syntax/nodes.go
@@ -317,24 +317,24 @@ type (
 
 	AssignStmt struct {
 		Op       Operator // 0 means no operation
-		Lhs, Rhs Expr
+		Lhs, Rhs Expr     // Rhs == ImplicitOne means Lhs++ (Op == Add) or Lhs-- (Op == Sub)
 		simpleStmt
 	}
 
 	BranchStmt struct {
-		Tok   token // TODO(gri) token values are not yet exported
+		Tok   token // Break, Continue, Fallthrough, or Goto
 		Label *Name
 		stmt
 	}
 
 	CallStmt struct {
-		Tok  token // _Go, or _Defer -- TODO(gri) token values are not yet exported
+		Tok  token // Go or Defer
 		Call *CallExpr
 		stmt
 	}
 
 	ReturnStmt struct {
-		Results Expr // nil means no (explicit) results
+		Results Expr // nil means no explicit return values
 		stmt
 	}
 
diff --git a/src/cmd/compile/internal/syntax/parser.go b/src/cmd/compile/internal/syntax/parser.go
index 6419998ff1..903a89c2ff 100644
--- a/src/cmd/compile/internal/syntax/parser.go
+++ b/src/cmd/compile/internal/syntax/parser.go
@@ -1367,8 +1367,9 @@ func (p *parser) paramList() (list []*Field) {
 // ----------------------------------------------------------------------------
 // Statements
 
-// We represent x++, x-- as assignments x += one, x -= one.
-var one = &BasicLit{Value: "1"}
+// We represent x++, x-- as assignments x += ImplicitOne, x -= ImplicitOne.
+// ImplicitOne should not be used elsewhere.
+var ImplicitOne = &BasicLit{Value: "1"}
 
 // SimpleStmt = EmptyStmt | ExpressionStmt | SendStmt | IncDecStmt | Assignment | ShortVarDecl .
 //
@@ -1403,7 +1404,7 @@ func (p *parser) simpleStmt(lhs Expr, rangeOk bool) SimpleStmt {
 			// lhs++ or lhs--
 			op := p.op
 			p.next()
-			return p.newAssignStmt(op, lhs, one)
+			return p.newAssignStmt(op, lhs, ImplicitOne)
 
 		case _Arrow:
 			// lhs <- rhs
diff --git a/src/cmd/compile/internal/syntax/printer.go b/src/cmd/compile/internal/syntax/printer.go
index ce3377afc1..0cacf1e5d4 100644
--- a/src/cmd/compile/internal/syntax/printer.go
+++ b/src/cmd/compile/internal/syntax/printer.go
@@ -499,7 +499,7 @@ func (p *printer) printRawNode(n Node) {
 
 	case *AssignStmt:
 		p.print(n.Lhs)
-		if n.Rhs == one {
+		if n.Rhs == ImplicitOne {
 			// TODO(gri) This is going to break the mayCombine
 			//           check once we enable that again.
 			p.print(n.Op, n.Op) // ++ or --
diff --git a/src/cmd/compile/internal/syntax/tokens.go b/src/cmd/compile/internal/syntax/tokens.go
index ed7a643a97..91a217655f 100644
--- a/src/cmd/compile/internal/syntax/tokens.go
+++ b/src/cmd/compile/internal/syntax/tokens.go
@@ -69,13 +69,15 @@ const (
 )
 
 const (
-	Go    = _Go
-	Defer = _Defer
-
+	// for BranchStmt
 	Break       = _Break
 	Continue    = _Continue
 	Fallthrough = _Fallthrough
 	Goto        = _Goto
+
+	// for CallStmt
+	Go    = _Go
+	Defer = _Defer
 )
 
 var tokstrings = [...]string{
-- 
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