From 44898c7b76cf64df61428431706102b47e8829b8 Mon Sep 17 00:00:00 2001
From: Russ Cox <rsc@golang.org>
Date: Mon, 1 Feb 2010 23:58:49 -0800
Subject: [PATCH] gc: bug250, bug251 - recursive interface types

Fixes #287.

R=ken2
CC=golang-dev
https://golang.org/cl/199057
---
 src/cmd/gc/dcl.c         |   5 +-
 src/cmd/gc/walk.c        | 100 ++++++++++++++++++++++++++-------------
 test/fixedbugs/bug195.go |   4 +-
 test/fixedbugs/bug250.go |  19 ++++++++
 test/fixedbugs/bug251.go |  21 ++++++++
 5 files changed, 112 insertions(+), 37 deletions(-)
 create mode 100644 test/fixedbugs/bug250.go
 create mode 100644 test/fixedbugs/bug251.go

diff --git a/src/cmd/gc/dcl.c b/src/cmd/gc/dcl.c
index b0b06f7d322..9aedf4bcceb 100644
--- a/src/cmd/gc/dcl.c
+++ b/src/cmd/gc/dcl.c
@@ -853,7 +853,10 @@ stotype(NodeList *l, int et, Type **t)
 		if(et == TINTER && n->left == N) {
 			// embedded interface - inline the methods
 			if(n->type->etype != TINTER) {
-				yyerror("interface contains embedded non-interface %T", n->type);
+				if(n->type->etype == TFORW)
+					yyerror("interface type loop involving %T", n->type);
+				else
+					yyerror("interface contains embedded non-interface %T", n->type);
 				continue;
 			}
 			for(t1=n->type->type; t1!=T; t1=t1->down) {
diff --git a/src/cmd/gc/walk.c b/src/cmd/gc/walk.c
index ffdd17a95da..31d1e3091e1 100644
--- a/src/cmd/gc/walk.c
+++ b/src/cmd/gc/walk.c
@@ -122,10 +122,61 @@ walkdeflist(NodeList *l)
 		walkdef(l->n);
 }
 
+static NodeList *deftypequeue;
+static int intypedef;
+
+static void
+walkdeftype(Node *n)
+{
+	int maplineno, embedlineno, lno;
+	Type *t;
+
+	lno = lineno;
+	setlineno(n);
+	n->type->sym = n->sym;
+	n->typecheck = 1;
+	typecheck(&n->ntype, Etype);
+	if((t = n->ntype->type) == T) {
+		n->diag = 1;
+		goto ret;
+	}
+
+	// copy new type and clear fields
+	// that don't come along
+	maplineno = n->type->maplineno;
+	embedlineno = n->type->embedlineno;
+	*n->type = *t;
+	t = n->type;
+	t->sym = n->sym;
+	t->local = n->local;
+	t->vargen = n->vargen;
+	t->siggen = 0;
+	t->printed = 0;
+	t->method = nil;
+	t->nod = N;
+	t->printed = 0;
+	t->deferwidth = 0;
+
+	// double-check use of type as map key
+	// TODO(rsc): also use of type as receiver?
+	if(maplineno) {
+		lineno = maplineno;
+		maptype(n->type, types[TBOOL]);
+	}
+	if(embedlineno) {
+		lineno = embedlineno;
+		if(isptr[t->etype])
+			yyerror("embedded type cannot be a pointer");
+	}
+
+ret:
+	lineno = lno;
+}
+
 void
 walkdef(Node *n)
 {
-	int lno, maplineno, embedlineno;
+	int lno;
 	NodeList *init;
 	Node *e;
 	Type *t;
@@ -214,40 +265,21 @@ walkdef(Node *n)
 		n->walkdef = 1;
 		n->type = typ(TFORW);
 		n->type->sym = n->sym;
-		n->typecheck = 1;
-		typecheck(&n->ntype, Etype);
-		if((t = n->ntype->type) == T) {
-			n->diag = 1;
-			goto ret;
-		}
-
-		// copy new type and clear fields
-		// that don't come along
-		maplineno = n->type->maplineno;
-		embedlineno = n->type->embedlineno;
-		*n->type = *t;
-		t = n->type;
-		t->sym = n->sym;
-		t->local = n->local;
-		t->vargen = n->vargen;
-		t->siggen = 0;
-		t->printed = 0;
-		t->method = nil;
-		t->nod = N;
-		t->printed = 0;
-		t->deferwidth = 0;
-
-		// double-check use of type as map key
-		// TODO(rsc): also use of type as receiver?
-		if(maplineno) {
-			lineno = maplineno;
-			maptype(n->type, types[TBOOL]);
-		}
-		if(embedlineno) {
-			lineno = embedlineno;
-			if(isptr[t->etype])
-				yyerror("embedded type cannot be a pointer");
+		intypedef++;
+		if(intypedef > 1)
+			deftypequeue = list(deftypequeue, n);
+		else {
+			walkdeftype(n);
+			while(deftypequeue != nil) {
+				NodeList *l;
+				
+				l = deftypequeue;
+				deftypequeue = nil;
+				for(; l; l=l->next)
+					walkdeftype(l->n);
+			}
 		}
+		intypedef--;
 		break;
 
 	case OPACK:
diff --git a/test/fixedbugs/bug195.go b/test/fixedbugs/bug195.go
index 27bbbd354a6..221a2eb0986 100644
--- a/test/fixedbugs/bug195.go
+++ b/test/fixedbugs/bug195.go
@@ -19,9 +19,9 @@ type I4 interface {
 }
 
 type I5 interface {
-	I6
+	I6	// ERROR "interface"
 }
 
 type I6 interface {
-	I5	// ERROR "interface"
+	I5
 }
diff --git a/test/fixedbugs/bug250.go b/test/fixedbugs/bug250.go
new file mode 100644
index 00000000000..cd28642bfc9
--- /dev/null
+++ b/test/fixedbugs/bug250.go
@@ -0,0 +1,19 @@
+// $G $D/$F.go || echo BUG: bug250
+
+// Copyright 2010 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.
+
+package main
+
+type I1 interface {
+	m() I2
+}
+
+type I2 interface {
+	I1
+}
+
+var i1 I1 = i2
+var i2 I2
+var i2a I2 = i1
diff --git a/test/fixedbugs/bug251.go b/test/fixedbugs/bug251.go
new file mode 100644
index 00000000000..1dc712fa7c3
--- /dev/null
+++ b/test/fixedbugs/bug251.go
@@ -0,0 +1,21 @@
+// errchk $G $D/$F.go
+
+// Copyright 2010 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.
+
+package main
+
+type I1 interface {
+	m() I2
+	I2	// ERROR "loop"
+}
+
+type I2 interface {
+	I1
+}
+
+
+var i1 I1 = i2
+var i2 I2
+var i2a I2 = i1