From d915b961000acdc2fc3f4ad726c540e1fc1e6aa2 Mon Sep 17 00:00:00 2001
From: Ken Thompson <ken@golang.org>
Date: Thu, 3 Jul 2008 16:41:32 -0700
Subject: [PATCH] new iota

SVN=125984
---
 src/cmd/gc/go.h   |  3 +++
 src/cmd/gc/go.y   | 28 +++++++++++++++++++++-------
 src/cmd/gc/subr.c | 34 ++++++++++++++++++++++++++++++++++
 3 files changed, 58 insertions(+), 7 deletions(-)

diff --git a/src/cmd/gc/go.h b/src/cmd/gc/go.h
index 42285550af..828ebbb712 100644
--- a/src/cmd/gc/go.h
+++ b/src/cmd/gc/go.h
@@ -114,6 +114,7 @@ struct	Node
 	uchar	etype;		// op for OASOP, etype for OTYPE, exclam for export
 	uchar	class;		// PPARAM, PAUTO, PEXTERN, PSTATIC
 	uchar	method;		// OCALLMETH name
+	uchar	iota;		// OLITERAL made from iota
 
 	// most nodes
 	Node*	left;
@@ -393,6 +394,7 @@ EXTERN	int	inimportsys;
 EXTERN	Node*	booltrue;
 EXTERN	Node*	boolfalse;
 EXTERN	ulong	iota;
+EXTERN	Node*	lastconst;
 EXTERN	long	vargen;
 EXTERN	long	exportgen;
 EXTERN	long	maxarg;
@@ -479,6 +481,7 @@ void	badtype(int, Type*, Type*);
 Type*	ptrto(Type*);
 Node*	cleanidlist(Node*);
 Node*	syslook(char*, int);
+Node*	treecopy(Node*);
 
 Type**	getthis(Type*);
 Type**	getoutarg(Type*);
diff --git a/src/cmd/gc/go.y b/src/cmd/gc/go.y
index 587486003b..5f223f5056 100644
--- a/src/cmd/gc/go.y
+++ b/src/cmd/gc/go.y
@@ -40,7 +40,7 @@
 %type	<node>		range_header range_body range_stmt
 %type	<node>		simple_stmt osimple_stmt semi_stmt
 %type	<node>		expr uexpr pexpr expr_list oexpr oexpr_list expr_list_r
-%type	<node>		name name_name new_name new_name_list_r
+%type	<node>		name name_name new_name new_name_list_r conexpr
 %type	<node>		vardcl_list_r vardcl Avardcl Bvardcl
 %type	<node>		interfacedcl_list_r interfacedcl
 %type	<node>		structdcl_list_r structdcl
@@ -166,6 +166,7 @@ Acommon_dcl:
 	{
 		$$ = N;
 		iota = 0;
+		lastconst = N;
 	}
 |	LTYPE Atypedcl
 	{
@@ -185,6 +186,7 @@ Bcommon_dcl:
 	{
 		$$ = N;
 		iota = 0;
+		lastconst = N;
 	}
 |	LTYPE Btypedcl
 	{
@@ -224,22 +226,33 @@ Bvardcl:
 		walktype($3, Erv);	// this is a little harry
 		defaultlit($3);
 		dodclvar($1, $3->type);
-
 		$$ = nod(OAS, $1, $3);
 	}
 
 constdcl:
-	new_name '=' expr
+	new_name conexpr
+	{
+		walktype($2, Erv);
+		dodclconst($1, $2);
+	}
+|	new_name type conexpr
 	{
 		walktype($3, Erv);
+		convlit($3, $2);
 		dodclconst($1, $3);
+	}
+
+conexpr:
+	{
+		if(lastconst == N)
+			yyerror("first constant must evaluate an expression");
+		$$ = treecopy(lastconst);
 		iota += 1;
 	}
-|	new_name type '=' expr
+|	'=' expr
 	{
-		walktype($4, Erv);
-		convlit($4, $2);
-		dodclconst($1, $4);
+		$$ = $2;
+		lastconst = treecopy($$);
 		iota += 1;
 	}
 
@@ -653,6 +666,7 @@ pexpr:
 |	LIOTA
 	{
 		$$ = literal(iota);
+		$$->iota = 1;	// flag to reevaluate on copy
 	}
 |	name
 |	'(' expr ')'
diff --git a/src/cmd/gc/subr.c b/src/cmd/gc/subr.c
index 2a2da5b7c3..6bf97911e4 100644
--- a/src/cmd/gc/subr.c
+++ b/src/cmd/gc/subr.c
@@ -1092,6 +1092,40 @@ out:
 	return fmtstrcpy(fp, buf);
 }
 
+Node*
+treecopy(Node *n)
+{
+	Node *m;
+
+	if(n == N)
+		return N;
+
+	switch(n->op) {
+	default:
+		m = nod(OXXX, N, N);
+		*m = *n;
+		m->left = treecopy(n->left);
+		m->right = treecopy(n->right);
+		break;
+
+	case OLITERAL:
+		if(n->iota) {
+			m = literal(iota);
+			m->iota = 1;	// flag to reevaluate on copy
+			break;
+		}
+		m = nod(OXXX, N, N);
+		*m = *n;
+		break;
+
+	case ONAME:
+		m = nod(OXXX, N, N);
+		*m = *n;
+		break;
+	}
+	return m;
+}
+
 int
 Zconv(Fmt *fp)
 {
-- 
2.50.0